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Inactivity Induces Resistance to the Metabolic Benefits Following Acute Exercise
Abstract
Acute exercise improves postprandial lipemia, glucose tolerance, and insulin sensitivity, all of which are risk factors for cardiovascular disease. However, recent research suggests that prolonged sedentary behavior might abolish these healthy metabolic benefits. Accordingly, this study aimed to elucidate the impact of an acute bout of exercise on postprandial plasma triglyceride, glucose, and insulin concentrations after 4 days of prolonged sitting (~13.5 h/day). Ten untrained to recreationally active men ( n = 5) and women ( n = 5) completed a counterbalanced, crossover study. Four days of prolonged sitting without exercise (SIT) were compared with 4 days of prolonged sitting with a 1-h bout of treadmill exercise (SIT + EX; 63.1 ± 5.2% V̇o 2max ) on the evening of the fourth day. The following morning, participants completed a high-fat/glucose tolerance test (HFGTT), during which plasma was collected over a 6-h period and analyzed for triglycerides, glucose, and insulin. No differences between trials ( P > 0.05) were found in the overall plasma triglyceride, glucose, or insulin responses during the HFGTT. This lack of difference between trials comes with similarly low physical activity (~3,500–4,000 steps/day) on each day except for the 1-h bout of exercise during SIT + EX the day before the HFGTT. These data indicate that physical inactivity (e.g., sitting ~13.5 h/day and <4,000 steps/day) creates a condition whereby people become “resistant” to the metabolic improvements that are typically derived from an acute bout of aerobic exercise (i.e., exercise resistance).
NEW & NOTEWORTHY In people who are physically inactive and sitting for a majority of the day, a 1-h bout of vigorous exercise failed to improve lipid, glucose, and insulin metabolism measured the next day. It seems that something inherent to inactivity and/or prolonged sitting makes the body resistant to the 1 h of exercise preventing the normally derived metabolic improvements following exercise.
... This assumption appears flawed, as sedentary habits during off-training times can directly hinder sports outcomes. Evidence shows that inactivity (i.e., < 5000 steps per day) and prolonged sitting (i.e., ~ 13.5 hours per day) preclude metabolic improvements following exercise (Akins et al., 2019;H. Burton et al., 2021). ...
... However, epidemiological studies are increasingly acknowledging resistance to exercise. For instance, H. Burton et al. (2021) and Akins et al. (2019) demonstrated that physical inactivity (i.e., < 5000 steps per day) and prolonged sitting (i.e., ~ 13.5 hours per day) diminish the metabolic improvements elicited by acute exercise and short-term training. Furthermore, Maylor et al. (2018) suggested that acute exercise does not fully counteract the negative cardiovascular effects of prolonged SB and extended sitting time. ...
... Although SED players showed slight performance differences across SSG conditions, the detrimental impact of their inactive off-training lifestyle should not be underestimated. Evidence about exercise resistance suggests that football practice may not fully compensate for the health risks associated with prolonged SB (Akins et al., 2019;H. Burton et al., 2021;Maylor et al., 2018). ...
... To verify our previous report of exercise resistance and that prolonged inactivity prevents a bout of exercise from up-regulating fat metabolism, we directly compared the PPTG responses when subjects remained inactive by taking 3500-4000 steps·d −1 of background activity. They either did no exercise or ran for 1 h at~62% VȮ 2max the evening before measurements (24). The addition of the 1-h bout of running when having a low step count had absolutely no effect on improving the next morning's PPTG response or fat oxidation (Fig. 2B). ...
... Typically, as discussed, a 1-h bout of exercise results in subsequent robust improvement in PPTG and fat oxidation (25) in subjects who are active and presumably above the threshold number of steps for maintaining a healthy fat metabolism. However, it seems that if activity throughout the day is low (e.g., <4000 steps in this study), even a 1-h run does not improve fat metabolism (24). Thus, Figure 2A demonstrates that a 1-h run is not effective for improving fat metabolism when the background steps per day are low (i.e., 1700 steps·d −1 ), and Figure 2B demonstrates that when the background steps per day are low (i.e.,~4000 steps·d −1 ), a 1-h run does not improve fat metabolism. ...
... Ekelund et al. (23) hypothesized that 60-75 min·d −1 of moderate-intensity physical activity might be needed to offset the cardiovascular disease risk and increased mortality associated with prolonged sitting. The observation of Akins et al. (24) that 60 min of exercise at~63% V O 2max on a single day did not offset the effects of 13.5 h·d −1 of sitting and 4000 steps·d −1 in terms of fat metabolism, represents a preliminary test of the hypothesis that 60 min·d −1 of moderateintensity exercise as derived by Ekelund et al. (23) may not be able to maintain a healthy fat metabolism. In Akins et al. (24), the end points of acute fat metabolic responses is different from cardiovascular disease and mortality as measured by Ekelund et al. (23). ...
Prolonged sitting prevents a 1-h bout of running from improving fat oxidation and reducing plasma triglycerides. This "Exercise Resistance" can be prevented by taking 8,500 steps/d or by interrupting 8-h of sitting with hourly cycle sprints. We hypothesize that there is an interplay between background physical activity (e.g.; steps/d) and the exercise stimuli in regulating some acute and chronic adaptations to exercise.
... Along these lines, we have reported a phenomenon termed "exercise resistance" to describe the inactivity-induced (e.g., low daily steps) lack of improvement in fat metabolism during the 16-to 22-h period after acute exercise (1 h of running) that normally elicits robust increases in fat oxidation and the postprandial lowering of plasma triglycerides (8,9). The condition that appears to elicit "exercise resistance" in this case is prior physical inactivity as judged by daily step counts of 5000 or less (10). ...
... We have previously reported that postprandial fat metabolism is improved (i.e., lower postprandial plasma triglyceride concentration and higher fat oxidation) acutely the day after a 1-h bout of running when daily step count is high, whereas it does not improve if step count is low and sitting time is long (8,9). This agrees with the present findings, and we have termed this phenomenon by which inactivity impairs acute adaptation as "exercise resistance" (16). ...
... Further investigation is warranted. Evidence has emerged that prolonged inactivity and sedentary time may impede or eliminate some positive effects classically associated with acute exercise (8,16,33). Kim et al. (16) found that people who sat for >14 h·d −1 did not show the "classic" attenuation of postprandial lipemia and increased fat oxidation on the day after exercise (i.e., 1 h running at 67% V O 2max ) when step count was low (i.e., <1675 steps per day) (9,34). This was confirmed by Akins et al. (8) who also observed that 1 h of running failed to improve postprandial metabolism in people who sat for prolonged periods and took 4000 steps per day. ...
Purpose:
This study determined if the level of background physical inactivity (steps per day) influences the acute and short-term adaptations to intense aerobic training.
Methods:
Sixteen untrained participants (23.6 ± 1.7 yr) completed intense (80%-90% V˙O2peak) short-term training (5 bouts of exercise over 9 d) while taking either 4767 ± 377 steps per day (n = 8; low step) or 16,048 ± 725 steps per day (n = 8; high step). At baseline and after 1 d of acute exercise and then after the short-term training (posttraining), resting metabolic responses to a high-fat meal (i.e., plasma triglyceride concentration and fat oxidation) were assessed during a 6-h high-fat tolerance test. In addition, responses during submaximal exercise were recorded both before and after training during 15 min of cycling (~79% of pretraining V˙O2peak).
Results:
High step displayed a reduced incremental area under the curve for postprandial plasma triglyceride concentrations by 31% after acute exercise and by 27% after short-term training compared with baseline (P < 0.05). This was accompanied by increased whole-body fat oxidation (24% and 19%; P < 0.05). Furthermore, stress during submaximal exercise as reflected by heart rate, blood lactate, and deoxygenated hemoglobin were all reduced in high step (P < 0.05), indicating classic training responses. Despite completing the same training regimen, low step showed no significant improvements in postprandial fat metabolism or any markers of stress during submaximal exercise after training (P > 0.05). However, the two groups showed a similar 7% increase in V˙O2peak (P < 0.05).
Conclusion:
When completing an intense short-term exercise training program, decreasing daily background steps from 16,000 to approximately 5000 steps per day blunts some of the classic cardiometabolic adaptations to training. The blunting might be more pronounced regarding metabolic factors (i.e., fat oxidation and blood lactate concentration) compared with cardiovascular factors (i.e., V˙O2peak).
... This phenomenon is called "exercise resistance" (7). A follow-up study in 2019 (8), using additional controls to verify the existence of this phenomenon, found that a group taking~3700 steps per day also exhibited exercise resistance. Therefore, it is important to systematically delineate what level of daily steps causes impairment of the ability of acute exercise to improve the postprandial plasma triglyceride response and fat oxidation. ...
... Participants in these studies were asked to refrain from any planned exercise but their ambulatory activity, and walking was not carefully controlled. Furthermore, very few studies (7,8) have systematically investigated the collective effects of daily step reduction combined with moderate acute exercise. Recent studies (7,8) that drastically reduced daily step number abolished the ability of an acute bout of exercise to increase fat oxidation the next day and attenuate the increase in PPL. ...
... Furthermore, very few studies (7,8) have systematically investigated the collective effects of daily step reduction combined with moderate acute exercise. Recent studies (7,8) that drastically reduced daily step number abolished the ability of an acute bout of exercise to increase fat oxidation the next day and attenuate the increase in PPL. Some other studies seem to suggest that exercise resistance may not occur when taking as little as~7900 steps per day (4). ...
Introduction:
Two benefits of acute exercise are the next day's lowering of the postprandial plasma triglyceride response to a high fat meal and increased fat oxidation. However, if activity levels (daily steps) are very low, these acute adaptations to exercise don't occur. This phenomenon has been termed 'exercise resistance'. This study sought to systematically reduce daily step number and identify the range of step counts that elicit 'exercise resistance'.
Methods:
Ten participants completed three, five-day trials in a randomized, crossover design with differing levels of step reduction. Following two days of controlled activity, participants completed two days of LOW, LIMITED, or NORMAL steps (2,675 ± 314, 4,759 ± 276, and 8,481 ± 581 steps/day, respectively). Participants completed a 1-hour bout of running on the evening of the second day. High fat tolerance tests were performed on the following morning and postprandial responses were compared.
Results:
Following LOW and LIMITED, postprandial incremental area under the curve (AUC) of plasma triglyceride were elevated 22-23%, compared to NORMAL (p<0.05). Whole body fat oxidation was also significantly lower (16-19%, p<0.05, respectively) in LOW and LIMITED, compared to NORMAL. No significant differences were found between LOW and LIMITED.
Conclusion:
Two days of step reduction to approximately 2,500-5,000 steps/day in young healthy individuals impairs the ability of an acute bout of exercise to increase fat oxidation and attenuate postprandial increases in plasma triglycerides. This suggests 'exercise resistance' occurs in individuals taking approximately 5,000 or fewer steps/day while 8,500 steps/day protects against exercise resistance in fat metabolism. It appears that fat metabolism is influenced more by the inhibitory effects of inactivity than by the stimulating effects derived from 1-hour of moderate intensity running.
... A large epidemiological study (3), estimated that in order to counteract the effects of prolonged sitting, a person needs to exercise for 60-75 min·d −1 at moderate intensity. Furthermore, recent work by Kim et al. (7) and Akins et al. (8) reported that 60 min of running (e.g., 63%-67% V O 2max ) failed to improve postprandial lipemia after several days of sitting for 13.5 h·d −1 , a condition termed "exercise resistance." Therefore, it seems impractical to explore exercise bouts of longer than 1 h·d −1 to counteract the cardiometabolic risk of prolonged sitting due to adherence problems in the general population. ...
... During the rest periods between sprints, subjects were seated. RPE was taken after five sprints using the standard Borg Scale (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Food was provided at two times (lunch and dinner) over the duration of the trial, and the caloric content of these meals was such that energy balance was maintained. ...
... This can be considered the healthy "exercise response." However, in people who are largely sedentary (i.e., 2000-4000 steps per day) (15), a 1-h bout of running does not improve the next day's postprandial plasma triglyceride response or fat oxidation (7,8). This has been termed exercise resistance, as it seems that some aspect of the prolonged inactivity is preventing the acute bout of exercise from causing healthy adaptations in fat metabolism (7,8). ...
High postprandial plasma lipids (PPL; i.e., triglycerides) are a risk factor for cardiovascular disease. Physical inactivity, characterized by prolonged sitting and a low step count, elevates PPL and thus risk of disease.
Purpose:
This study determined if the interruption of prolonged sitting (i.e., 8 h of inactivity) with hourly cycling sprints of only 4-s duration each (i.e., 4 s × 5 per hour × 8 h = 160 s·d SPRINTS) improves PPL. The 4-s sprints used an inertial load ergometer and were followed by 45 s of seated rest.
Methods:
Four men and four women participated in two trials. Interventions consisted of an 8-h period of sitting (SIT), or a trial with equal sitting time interrupted with five SPRINTS every hour. The morning after the interventions, PPL and fat oxidation were measured over a 6-h period. Plasma glucose, insulin, and triglyceride concentrations were measured bihourly and incremental area under the curve (AUC) was calculated.
Results:
No differences (P > 0.05) between interventions were found for plasma insulin or glucose AUC. However, SPRINTS displayed a 31% (408 ± 119 vs 593 ± 88 mg·dL per 6 h; P = 0.009) decrease in plasma triglyceride incremental AUC and a 43% increase in whole-body fat oxidation (P = 0.001) when compared with SIT.
Conclusions:
These data indicate that hourly very short bouts (4 s) of maximal intensity cycle sprints interrupting prolonged sitting can significantly lower the next day's postprandial plasma triglyceride response and increase fat oxidation after a high-fat meal in healthy young adults. Given that these improvements were elicited from only 160 s of nonfatiguing exercise per day, it raises the question as to what is the least amount of exercise that can acutely improve fat metabolism and other aspects of health.
... There is a need for larger cohort studies and randomized controlled trials using "omics" approaches (e.g., genomics, epigenomics, transcriptomics, proteomics, and metabolomics) to better understand the molecular mechanisms underlying the effects of SB on heath and disease. (84) demonstrated that acute exposure to prolonged sitting ($13.5 h/day of sitting and <4,000 steps/day) not only prevented the traditional exercise-related benefits in postprandial triglycerides responses but also improvements in postprandial plasma glucose and insulin responses in healthy adults. Furthermore, Burton and Coyle (85) compared postprandial plasma triglycerides responses to an acute exercise bout after 2 days of low ($2,500 steps/ day), limited ($5,000 steps/day), or normal ($8,500 steps/day) daily step count to determine the range of step counts that elicited this blunted postprandial metabolic response to acute exercise. ...
... Independent of diet, there were no changes in fasting glucose and insulin concentrations and postload glucose and insulin responses in healthy adults following step reduction. However, in another study, 10 days of step reduction resulted in reduced insulin sensitivity along with increases in carbohydrate oxidation measured in response to an oral glucose tolerance text (84). Combining step reduction with overfeeding also increased fasting glucose and insulin concentrations, postload 2-h glucose concentrations, and postload glucose responses in healthy male adults (170), thus suggesting that energy surplus exacerbates the metabolic deteriorations triggered by exposures to both SB and physical inactivity. ...
Sedentary behaviors (SB) are characterized by a low energy expenditure while in a sitting or reclining posture. Evidence relevant to understanding the physiology of SB can be derived from studies employing several experimental models: bed rest, immobilization, reduced step count, and reducing/interrupting prolonged SB. We examine the relevant physiological evidence relating to body weight and energy balance, intermediary metabolism, cardiovascular and respiratory systems, the musculoskeletal system, the central nervous system, and immunity and inflammatory responses. Excessive and prolonged SB can lead to insulin resistance, vascular dysfunction, shift in substrate use towards carbohydrate oxidation, shift in muscle fiber from oxidative to glycolytic type, reduced cardiorespiratory fitness, loss of muscle mass and strength, and bone mass, and increased total body fat mass and visceral fat depot, blood lipid concentrations, and inflammation. Despite marked differences across individual studies, longer-term interventions aimed at reducing/interrupting SB have resulted in small, albeit marginally clinically meaningful, benefits on body weight, waist circumference, percent body fat, fasting glucose, insulin, HbA1c and HDL concentrations, systolic blood pressure, and vascular function in adults and older adults. There is more-limited evidence on other health-related outcomes and physiological systems, and for children and adolescents. Future research should focus on the investigation of molecular and cellular mechanisms underpinning adaptations to increasing and reducing/ interrupting SB and the necessary changes in SB and physical activity to impact physiological systems and overall health in diverse population groups.
... 20 Sitting is especially harmful if it is accumulated in lengthy, uninterrupted bouts throughout the day, even in individuals who perform moderate or vigorous exercise on a daily basis. 21 Studies suggest that sitting for 12 or more hours per day can make an individual resistant to the usual benefits of exercise. 18,19,21 The strengths of our study include the random population sample, prospective design, detailed information about potential confounding variables, and nearly 100% complete follow-up. ...
... 21 Studies suggest that sitting for 12 or more hours per day can make an individual resistant to the usual benefits of exercise. 18,19,21 The strengths of our study include the random population sample, prospective design, detailed information about potential confounding variables, and nearly 100% complete follow-up. The limitations include that the information about quantitating PA used in the present analyses was obtained only at the third examination (between 1991 and 1994); repeated assessments during follow-up of the various types and amounts of exercise or leisuretime sports activities would have strengthened the design. ...
Objective
To investigate the association between the duration of weekly leisure-time sports activity and all-cause mortality.
Methods
As part of the prospective Copenhagen City Heart Study, 8697 healthy adults completed a comprehensive questionnaire about leisure-time sports activities. Duration (minutes per week) of leisure-time sports activities was recorded for tennis, badminton, soccer, handball, cycling, swimming, jogging, calisthenics, health club activities, weightlifting, and other sports. The primary end point was all-cause mortality, and the median follow-up was 25.6 years. The association between duration of leisure-time sports activities and all-cause mortality was studied using multivariable Cox proportional hazards regression analysis.
Results
Compared with the reference group of 2.6 to 4.5 hours of weekly leisure-time sports activities, we found an increased risk for all-cause mortality for those with 0 hours (hazard ratio [HR], 1.51; 95% CI, 1.29 to 1.76), for those with 0.1 to 2.5 hours (HR, 1.24; 95% CI, 1.05 to 1.46), and for those with more than 10 hours (HR, 1.18; 95% CI, 1.00 to 1.39) of weekly leisure-time sports activities. These relationships were generally consistent with additional adjustments for potential confounders among subgroups of age, sex, education, smoking, alcohol intake, and body mass index, when the first 5 years of follow-up were excluded, and for cardiovascular disease mortality.
Conclusion
We observed a U-shaped association between weekly duration of leisure sports activities and cardiovascular and all-cause mortality, with lowest risk for those participating in 2.6 to 4.5 weekly hours, being consistent across subgroups. Participation in sport activities should be promoted, but the potential risk of very high weekly hours of sport participation should be considered for inclusion in guidelines and recommendations.
... This threshold has been exceeded by workers during the pandemic, due to the teleworking situation, according to various authors in different countries [2,3,6]. In addition, increased sedentary behavior attenuates the physiological adaptations induced by PA [13,[18][19][20], so even people who maintained their exercise routine have been affected by mobility restrictions and the new lifestyle caused by the pandemic [18]. ...
... This threshold has been exceeded by workers during the pandemic, due to the teleworking situation, according to various authors in different countries [2,3,6]. In addition, increased sedentary behavior attenuates the physiological adaptations induced by PA [13,[18][19][20], so even people who maintained their exercise routine have been affected by mobility restrictions and the new lifestyle caused by the pandemic [18]. ...
Healthy lifestyles should be encouraged in the workplace through the occupational health teams of the companies. The objective of the present study was to evaluate the adherence to a lifestyle intervention carried out in university employees during the COVID-19 pandemic and its impact on health-related quality of life (HrQoL). A randomized controlled trial following the CONSORT guidelines was performed, consisting of three supervised interventions lasting for 18 weeks: an educational intervention on healthy habits, a nutritional intervention, and a telematic aerobic and strength exercise intervention. Lifestyle and HrQoL were analyzed six months post-intervention to assess adherence. Twenty-three middle-aged participants completed the study. The intervention group significantly improved their lifestyle according to the Health Promoting Lifestyle Profile II questionnaire, especially in the categories of Health Responsibility, Physical Activity, and Nutrition, with a large effect size. Sitting time was reduced by 2.5 h per day, with a moderate effect size. Regarding HrQoL, the intervention group showed a clinically significant improvement in the Physical Component Summary. Despite the lockdown and the mobility restrictions caused by the COVID-19 pandemic, this intervention performed on university employees achieved adherence to a healthier lifestyle and improved their HrQoL, which is of great clinical relevance.
... Prolonged, uninterrupted sitting might further increase the risk of cardiovascular disease by promoting the development of sitting-induced 'exercise resistance' , involving reductions in the typical responses observed after acute exercise 84 . Acute exercise lowers plasma glucose, insulin and triglyceride levels. ...
... Acute exercise lowers plasma glucose, insulin and triglyceride levels. However, 4 days of prolonged sitting prevents these expected beneficial postprandial responses to acute exercise 84,85 . Furthermore, despite the known blood pressure-lowering effects of acute exercise, when this activity is followed by prolonged sitting, the benefits are attenuated 52 . ...
Sedentary behaviour — put simply, too much sitting, as a distinct concept from too little exercise — is a novel determinant of cardiovascular risk. This definition provides a perspective that is complementary to the well-understood detrimental effects of physical inactivity. Sitting occupies the majority of the daily waking hours in most adults and has become even more pervasive owing to the COVID-19 pandemic. The potential for a broad cardiovascular health benefit exists through an integrated approach that involves ‘sitting less and moving more’. In this Review, we first consider observational and experimental evidence on the adverse effects of prolonged, uninterrupted sitting and the evidence identifying the possible mechanisms underlying the associated risk. We summarize the results of randomized controlled trials demonstrating the feasibility of changing sedentary behaviour. We also highlight evidence on the deleterious synergies between sedentary behaviour and physical inactivity as the underpinnings of our case for addressing them jointly in mitigating cardiovascular risk. This integrated approach should not only reduce the specific risks of too much sitting but also have a positive effect on the total amount of physical activity, with the potential to more broadly benefit the health of individuals living with or at risk of developing cardiovascular disease.
... In line with this, Gennuso, Gangnon (9) found that total sedentary time associated to with an increase in the odds of metabolic syndrome components, and that moderate to vigorous physical activity modified the magnitude of these associations. Conversely, more recent reports demonstrated that 4 days of prolonged sitting (13,5 h of sitting with ~3,500-4,000 steps/day) mitigated the beneficial effects of a 1-hour bout of exercise on postprandial blood lipid, insulin and glucose in healthy individuals (10). Van der Berg,Stehouwer (11) reported that an extra hour increase in sedentary time increases the odds for contracting type 2 diabetes T2D and metabolic syndrome by 22% and 39% respectively. ...
... In line with this, Gennuso , 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 Gangnon (9) found total sedentary time associated with an increase in the odds of metabolic syndrome components, and that moderate to vigorous physical activity modified the magnitude of these associations. Conversely, more recent reports demonstrated that 4 days of prolonged sitting (13,5 h of sitting with ~3,500-4,000 steps/day) mitigated the beneficial effects of a 1-hour bout of exercise on postprandial blood lipid, insulin and glucose in healthy individuals (10). Van der Berg, Stehouwer (11) reported that an extra hour increase in sedentary time increases the odds for contracting T2D and metabolic syndrome by 22% and 39% respectively. ...
Many reports showed a dramatic decrease in the levels of physical activity during the
current pandemic of SARS-COV-2. This has substantial immune and metabolic implications, especially in those at risk or with metabolic diseases including individuals with obesity and Type 2 diabetes. Here we discuss the route from physical inactivity to immune and metabolic aberrancies; focusing on how insulin resistance could represent an adaptive mechanism to the low physical activity levels and on how such an adaptive mechanism could shift to a pathognomonic feature of metabolic diseases, creating a vicious circle of immune and metabolic aberrancies. We provide a theoretical framework to the severe immunopathology of COVID-19 in patients with metabolic diseases. We finally discuss the idea of exercise as a potential adjuvant against COVID-19 and emphasize how even interrupting prolonged periods of sitting with short time breaks of very light activity could be a feasible strategy to limit the deleterious effects of the outbreak.
... Even brief periods of exposure to these behaviours can be deleterious; for example, a 2-week reduction in daily steps from ~10,000 to ~1,500 steps lead to impaired insulin sensitivity and lipid metabolism, increased visceral fat and decreased fat-free mass and cardiovascular fitness in healthy adults 5 . Interestingly, a bout of moderate-intensity exercise does not counteract the detrimental effects of 4 days of inactivity, suggesting that individuals can become 'resistant' to well-known exercise-induced metabolic adaptations 6 . ...
... Exercise (structured physical activity) is advocated by EULAR as an integral part of standard care for patients with inflammatory arthritis and osteoarthritis 7 Gualano 1,6 ✉ Physical inactivity is common during periods of self-isolation, but for patients with rheumatic diseases, there are crucial benefits to be gained from maintaining an active lifestyle throughout the COVID-19 pandemic. Patients should be provided with support to maintain physical activity and avoid prolonged periods of time spent sitting. ...
Physical inactivity is common during periods of self-isolation, but for patients with rheumatic diseases, there are crucial benefits to be gained from maintaining an active lifestyle throughout the COVID-19 pandemic. Patients should be provided with support to maintain physical activity and avoid prolonged periods of time spent sitting.
... More important, high inactivity times are associated with pro-inflammatory processes and have negative effects on functional capacity [34,89]. High levels of MVPA may reduce the negative effects of sustained inactivity but the current evidence shows that it does not eliminate it completely [90,91]. It is also necessary to change behaviour by interrupting long inactivity times with short periods of any PA intensity (e.g., walking during a phone call, standing) [92,93]. ...
Background
An infection with SARS-CoV-2 can lead to persistent symptoms more than three months after the acute infection and has also an impact on patients’ physical activity behaviour and sleep quality. There is evidence, that inpatient post-COVID rehabilitation can improve physical capacity and mental health impairments, but less is known about the change in physical behaviour and sleep quality.
Methods
This longitudinal observational study used accelerometery to assess the level of physical activity and sleep quality before and after an inpatient rehabilitation program. The study sample consists of 100 post-COVID patients who acquired COVID-19 in the workplace. Group differences related to sex, age, COVID-19 severity, and pre-existing diseases were also analysed.
Results
Level of physical activity and sleep quality didn’t increase after rehabilitation. Overall, there is a high extent of inactivity time and poor sleep quality at both measurement points. Regarding group differences, male patients showed a significantly higher inactivity time before rehabilitation, and younger patients (< 55 years) spend significant more time in vigorous physical activity than older patients. Post-COVID patients with pre-existing cardiovascular, respiratory, and metabolic disease show slightly less physical activity than post-COVID patients without these comorbidities. Female patients and younger patients showed better sleep quality in some sleep parameters at both measurement points. However, no differences could be detected related to COVID-19 severity.
Conclusions
Ongoing strategies should be implemented to address the high amount of inactivity time and the poor sleep quality in post-COVID patients.
... [9][10][11][12][13][14] This association, which was more pronounced in subjects with high levels of physical activity (moderate to vigorous), indicates, however, that regular physical activity does not fully protect against risk when associated with prolonged sedentary behaviour. 15 Therefore, we might hypothesize that prolonged sedentary behavior, regardless of the level of physical activity, even in leisure time, may play a potential role in the development and progression of NAFLD. The purpose of this crosssectional study was to explore the likelihood of developing NAFLD by associating leisure-time physical activity with time spent sitting in a sample of men and women aged 18 to 64 years, from southern Italy. ...
Background
Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the world. The increasingly sedentary lifestyle in recent years may have accelerated the development of NAFLD, independent of the level of physical activity.
Objective
The purpose of this cross-sectional study was to determine the association between leisure-time physical activity (LTPA) and time spent sitting (TSS) and the likelihood of developing NAFLD in a sample of men and women aged 18–64 years, from southern Italy.
Design
The study is based on two cohort studies, a randomized clinical trial and an observational cost-benefit study.
Participants
A total of 1269 participants (51.5% women) drawn from 3992 eligible subjects were enrolled in this study.
Exposures
Leisure-time physical activity (LTPA) and time spent sitting (TSS) were assessed using the Italian long form of the International Physical Activity Questionnaire (IPAQ-LF), designed for administration to adults aged 18 to 65 years.
Main Measures
The association of exposures with the probability of belonging to a certain NAFLD degree of severity.
Key Results
The probability of having mild, moderate, and severe NAFLD tends to decrease with increasing LTPA and decreasing TSS levels. We selected a combination of participants aged 50 years and older stratified by gender. Men had a statistically significant difference in the probability of developing moderate NAFLD if they spent 70 h per week sitting and had low LTPA, while among women there was a statistically significant difference in the probability of developing mild or moderate NAFLD if they had moderate LPTA and spent 35–70 h/week sitting.
Conclusions
The study thus showed that the amount of LTPA and the amount of TSS are associated with development and progression of NAFLD, but this relationship is not a linear one—especially in women aged ≥ 50 years old.
... Furthermore, increasing attention has been given to sitting-associated abnormal glucose metabolism, which could be attenuated by reducing sitting time [31,32]. Importantly, studies have demonstrated that sitting might diminish the function of moderate physical activity, which could explain our results regarding MUI in males [33]. Additional causal studies are needed to evaluate whether physical activity reverses the impairment caused by prolonged sitting in the UI population. ...
Background
Urinary incontinence (UI) is a common health problem that affects the quality of life and health of millions of people in the United States (US). We aimed to investigate the association between sitting time and UI symptoms in the US population.
Methods
A cross-sectional survey of participants aged 20 and above from the National Health and Nutrition Examination Survey 2007–2018 was performed. A self-report questionnaire that reported complete data on UI, sitting time and covariates was included. Weighted multivariable logistic and regression models were used to assess the association between sitting time and UI symptoms.
Results
A total of 22,916 participants were enrolled. Prolonged sitting time was associated with urgency UI (UUI, odds ratio [OR] = 1.2, 95% confidence interval [CI] = 1.1 to 1.3, p = 0.001). Compared with patients with sitting a time shorter than 7 hours (h), moderate recreational activity modified the association between sitting time and mixed UI in males in the fully adjusted model (OR = 2.5, 95% CI = 1.4 to 4.5, p = 0.002). A sitting time over 7 h was related to mixed UI (MUI, OR = 1.6, 95% CI = 1.1 to 2.2, p = 0.01) in males, and stress UI (SUI, OR = 0.9, 95% CI = 0.8 to 0.98, p = 0.03) in females. However, no significant difference was found among the UI, SUI, and MUI groups in fully adjusted model.
Conclusions
A prolonged sitting time (≥7 h) was associated with UUI symptoms in all populations, SUI symptoms in females and MUI symptoms in males compared with sitting time lower than 7 h. Compared with those sit shorter than 7 h, moderate recreational activity may be a modifier between prolonged sitting and MUI symptoms in male participants, which warrants further studies for confirmation.
... Conversely, individuals accumulating only 2 000-4 000 daily steps and engaging in 1 h of running exercise do not experience reductions in postprandial plasma TG levels or increases in fat oxidation on the following day, a phenomenon referred to as 'exercise resistance'. 20,21 Therefore, prolonged sedentary behavior appears to be an obstacle to improving fat metabolism after 1 h running exercise. Remarkably, this 'exercise resistance' can be overcome by accumulating 8 500 daily steps by walking or by interrupting 8 h of sedentary behavior with hourly sprint exercises. ...
Physical inactivity remains a pressing global public health concern. Prolonged periods of sedentary behavior have been linked to heightened risks of non-communicable diseases such as cardiovascular diseases and type 2 diabetes, while engaging in any form of physical activity can elicit favorable effects on health. Nevertheless, epidemiological research indicates that people often struggle to meet recommended physical activity guidelines, citing time constraints, lack of exercise equipment, and environmental limitations as common barriers. Exercise snacks represents a time-efficient approach with the potential to improve physical activity levels in sedentary populations, cultivate exercise routines, and enhance the perception of the health benefits associated with physical activity. We review the existing literature on exercise snacks, and examine the effects of exercise snacks on physical function and exercise capacity, while also delving into the potential underlying mechanisms. The objective is to establish a solid theoretical foundation for the application of exercise snacks as a viable strategy for promoting physical activity and enhancing overall health, particularly in vulnerable populations who are unable to exercise routinely.
... Prolonged, uninterrupted sitting is related to impaired glucose metabolism and increased systemic inflammation, which can be attenuated by physical activities (33, 34). Moreover, sitting may induce exercise resistance and diminish the benefits of physical activity (35). Nevertheless, additional studies are needed to evaluate whether the observed interaction between sedentary behaviors and physical activity on CVD and all-cause mortality is causal. ...
Aim
The aim of this study was to respectively explore the relationships between physical activity and sedentary behaviors and cardiovascular disease (CVD) and all-cause mortality risk in overweight/obese middle-aged and older patients, and also assess the interaction between physical activity and sedentary behaviors.
Methods
Data of middle-aged and older adults with body mass index (BMI) ≥25 kg/m² were extracted from the National Health and Nutrition Examination Surveys (NHANES) database in 2007–2018 in this retrospective cohort study. Weighted univariate and multivariate logistic regression analyses were used to explore the associations between physical activity and sedentary behaviors and CVDs; weighted univariate and multivariate Cox regression analyses were used to explore the relationships between physical activity and sedentary behaviors with the risk of all-cause mortality. The interaction effect between physical activity and sedentary behaviors on CVD and all-cause mortality was also assessed. We further explored this interaction effect in subgroups of age and BMI. The evaluation indexes were odds ratios (ORs), hazard ratios (HRs), and 95% confidence intervals (CIs).
Results
Among 13,699 eligible patients, 1,947 had CVD, and 1,560 died from all-cause mortality. After adjusting for covariates, patients who had high sedentary time seemed to have both high odds of CVD [OR = 1.24, 95% CI: (1.06–1.44)] and a high risk of all-cause mortality [HR = 1.20, 95% CI: (1.06–1.37)]. Furthermore, being insufficiently active was linked to high odds of CVD [OR = 1.24, 95% CI: (1.05–1.46)] as well as a high risk of all-cause mortality [HR = 1.32, 95% CI: (1.15–1.51)]. High sedentary time and being insufficiently active had an interaction effect on both high odds of CVD [OR = 1.44, 95% CI: (1.20–1.73)] and high risk of all-cause mortality [HR = 1.48, 95% CI: (1.24–1.76)]. Individuals of different ages with/without obesity need to focus on the potential CVD/mortality risk of high sedentary time and low physical activity (all P < 0.05).
Conclusion
Reducing sedentary time combined with increasing physical activity may benefit health by reducing both the risk of CVD and all-cause mortality in overweight or obese middle-aged and older adults.
... The concept of prolonged sitting is still relatively novel, but research is rapidly growing [7][8][9][10][11]13,17,18,[24][25][26][27][28]. The initial research on prolonged sitting predominantly includes the impact of interrupting prolonged sitting by various durations, intensities, and types of exercise on metabolic markers, the metabolic implications of chronic prolonged sitting, and prospective cohort studies [11,18,21,31,[55][56][57][58][59]. Still, a more detailed evaluation of the literature reveals several gaps and shortcomings. ...
(1) There is growing concern surrounding the adverse effects of prolonged sitting on health, yet its impact on post-exercise recovery remains relatively unexplored. This study aimed to better understand the potential influence of habitual prolonged sitting on recovery time and the unfavorable impact prolonged sitting may have on time to recovery, as assessed by muscle damage and inflammatory markers and an isokinetic dynamometer. (2) Nine college-age men (mean age ± SD = 22.1 ± 3.1 years, body mass = 80.9 ± 15.7 kg, height = 171 ± 9.0 cm, Body Mass Index (BMI) = 27.6 ± 4.9 kg·m²) participated in an exhaustive exercise protocol. Creatine Kinase (CK), Myoglobin (Mb), C-Reactive Protein (CRP), White Blood Cell Count (WBC), Peak Torque (PT), and muscle soreness were measured at baseline and 0, 24, 48, and 72 h post-exercise. Dietary and exercise logs were maintained during the 5-day testing procedure. (3) No significant differences were observed in muscle damage markers (CK [p = 0.068] and Mb [p = 0.128]), inflammatory markers (CRP [p = 0.814] and WBC [p = 0.140]), or PT [p = 0.255]) at any time point. However, a significant positive correlation was found between daily sitting time and the percent increase in CK concentration from 0 h to 72 h (r = 0.738, p = 0.023). Strong correlations were also noted between prolonged sitting and percent change in Mb concentration at 48 h (r = 0.71, p = 0.033) and 72 h (r = 0.889, p = 0.001). There was a significant two-way interaction for time × velocity (p = 0.043) for PT with a simple main effect for time at 60°·s−1 (p = 0.038). No significant associations were detected between daily carbohydrate or protein intake and recovery markers (p > 0.05). (4) The findings suggest minimizing daily sitting time may expedite and potentially aid muscle recovery after an intense exercise bout, although further research is warranted to validate these findings.
... Further analysis of the data indicates that this is due in part to the negative effect of prolonged uninterrupted ST time bouts (low number and duration of breaks in ST time). Recent studies in adults have shown that these prolonged periods have deleterious effects on health, independent of those produced by physical inactivity (67) because in addition, they affect vascular function, altering systemic blood flow (68) they favor an increase in BP they have been related to the activation of the sympathetic system (69) they raise postprandial glycemia and insulin resistance by reducing consumption by inactive muscles (70) they alter the regulation of cerebral blood flow (71) they favor an increase in systemic inflammation (67,72) and, finally, they could even reduce the beneficial effect of the practice of physical activity (73). Among ST behaviors in children and adolescents, recreational screen time (63, 74) and prolonged uninterrupted ST bouts (75) have shown associations with adverse health outcomes. ...
Childhood obesity has become a worldwide epidemic in the 21st century. Its treatment is challenging and often ineffective, among others due to complex, often not obvious causes. Awareness of the existence and meaning of psychosocial and environmental risk factors seems to be an essential element in the prevention and treatment of obesity and its complications, especially arterial hypertension. In this review, we will discuss the role of that risk factors linking obesity and increased cardiovascular disorders including the role of nutritional factors (including the role of unhealthy diet, inadequate hydration), unhealthy behaviors (e.g. smoking, alcohol and drugs, sedentary behavior, low physical activity, disrupted circadian rhythms, sleep disorders, screen exposure), unfavorable social factors (such as dysfunctional family, bullying, chronic stress, mood disorders, depression, urbanization, noise, and environmental pollution), and finally differences in cardiovascular risk in girls and boys.
... 76 The exercise intervention was effective in counteracting most of the alterations in metabolic function and adipose tissue metabolism that were observed in the control group. 76 Despite this interesting finding, it should be considered that background inactivity (i.e. a low number of daily steps) can blunt metabolic benefits in response to both acute [83][84][85] and chronic 86 exercise (for a recent review on this topic we refer the reader to Coyle et al. 87 ). An additional countermeasure that could be potentially interesting for limiting the metabolic impact of SR without actually increasing the number of the daily steps would be to increase the non-exercise activity thermogenesis (NEAT), 27 employing standing workstations and gymnastic balls. ...
Physical inactivity represents a heavy burden for modern societies and is spreading worldwide, it is a recognised pandemic and is the fourth cause of global mortality. Not surprisingly, there is an increasing interest in longitudinal studies on the impact of reduced physical activity on different physiological systems. This narrative review focuses on the pathophysiological mechanisms of step reduction (SR), an experimental paradigm that involves a sudden decrease in participants' habitual daily steps to a lower level, mimicking the effects of a sedentary lifestyle. Analogous animal models of reduced physical activity, namely the "wheel-lock" and the "cage reduction" models, which can provide the foundation for human studies, are also discussed. The empirical evidence obtained thus far shows that even brief periods of reduced physical activity can lead to substantial alterations in skeletal muscle health and metabolic function. In particular, decrements in lean/muscle mass, muscle function, muscle protein synthesis, cardiorespiratory fitness, endothelial function and insulin sensitivity, together with an increased fat mass and inflammation, have been observed. Exercise interventions seem particularly effective for counteracting these pathophysiological alterations induced by periods of reduced physical activity. A direct comparison of SR with other human models of unloading, such as bed rest and lower limb suspension/immobilisation, is presented. In addition, we propose a conceptual framework aiming to unravel the mechanisms of muscle atrophy and insulin resistance in the specific context of reduced ambulatory activity. Finally, methodological considerations, knowledge gaps and future directions for both animal and human models are also discussed in the review.
... The independence of SB from physical activity (PA) have been progressively explored alongside this issue (van der Velde et al. 2018;Exel et al. 2019;Franssen et al. 2021). Accordingly, there is a wealth body of evidence indicating that high SB impairs the metabolic improvements deriving from exercise and that acute exercise does not attenuate the deleterious impact on cardiometabolic health induced by prolonged sitting (Akins et al. 2019;Simper et al. 2020;Rafiei et al. 2021). In recognition of this evidence, the World Health Organization (WHO) updated its PA guidelines, eliminating the previous condition of accumulating PA in bouts lasting at least ten minutes minimum . ...
Purpose
A cluster-randomized trial examined the effect of activity wristbands on young players’ off-training PA and SB profiles; assessed the added value of wearable wristbands with PA warnings; and investigated whether manipulating off-training PA can affect the players’ training responses.
Methods
Thirty-two adolescent soccer players (16.1 ± 0.9 years old) were monitored during weekdays for two weeks (interspersed with one week). Players were randomly assigned to a reminder to move (REM) and a non-reminder to move group (nREM). The REM wore an activity wristband (Fitbit Charge 2) with PA warnings in the last week of research, while the nREM wore identical monitors without PA feedback. Throughout the study, off-training PA was assessed using tri-axial accelerometers, and training responses were analysed using wearable inertial monitoring units. Gardner-Altman estimation plots and a Fisher’s Exact Test of Independence estimated each group’s off-training PA changes between the monitored weeks. Complementary, an analysis of covariance identified the effect of the activity wristband configuration (REM vs nREM) on players’ off-training PA profiles and soccer training responses.
Results
Interestingly, results showed that different wearable wristbands did not influence the players’ off-training PA profiles (p > 0.05). Concomitantly, no differences were observed in training responses (p > 0.05).
Conclusion
Findings emphasize the importance of health and youth sports organizations in developing newer approaches for promoting healthier lifestyles, beyond training practices, with potentially favourable implications for sports performance.
... However, even shorter periods of prolonged sitting or lying time, such that is commonly observed in day-to-day activity 20 , has been associated with decreased insulin action in acute experimental studies 21 . When accumulated across several days, prolonged sitting can induce resistance to bene ts of physical activity bouts 22 . The importance of local muscle activation is illustrated in rodent and human studies where activation of muscle bers results in improved insulin sensitivity in the activated, but not in the inactive contra-lateral leg 23,24 . ...
Prolonged sedentary behaviour is detrimental to health due to low contractile activity in large lower extremity muscle groups. This muscle inactivity can be measured with electromyography (EMG), but it is unknown how methodological factors affect responsiveness longitudinally. This study aimed to rank 16 different EMG inactivity thresholds based on their responsiveness (absolute and standardized effect size, responsiveness) using data from a randomized controlled trial targeted at reducing and breaking up sedentary time (InPact, ISRCTN28668090). EMG inactivity duration and usual EMG inactivity bout duration (weighted median of bout lengths) were measured from large lower extremity muscle groups (quadriceps, hamstring) with EMG-sensing shorts. The results showed that the EMG inactivity threshold above signal baseline (3 µV) provided overall the best responsiveness indices. At baseline, EMG inactivity duration of 66.8 ± 9.6% was accumulated through 73.9 ± 36.0s usual EMG inactivity bout duration, both of which were reduced following the intervention (-4.8 percentage points, -34.3 seconds). The proposed methodology can reduce variability in longitudinal designs and the detailed results can be used for sample size calculations. EMG inactivity duration and pattern of accumulation can be measured with appropriate responsiveness, and intervening these outcomes has a potential influence on muscle physiology and health.
... Habitual physical activity may be a determinant of the effect of acute exercise on PPL, since recent studies have shown that exercise performed on the evening prior to a high-fat meal failed to reduce PPL when daily step count was low ( < 5000 steps) and/or sitting time was long, as opposed to high daily step count (8500 steps) [90][91][92]. This effect has been termed "exercise resistance" [92]. ...
We review recent findings on the ability of exercise to lower postprandial lipemia (PPL). Specifically, we answer why exercise is important in lowering PPL, when it is most effective to exercise to achieve this, what the preferred exercise is and how exercise reduces PPL. Most findings confirm the power of exercise to lower PPL, which is an independent risk factor for cardiovascular disease. Exercise is most effective when performed on the day preceding a high- or moderate-fat meal. This effect lasts up to approximately two days; therefore, one should exercise frequently to maintain this benefit. However, the time of exercise relative to a meal is not that important in real-life conditions, since one consumes several meals during the day; thus, an exercise bout will inevitably exert its lowering effect on PPL in one or more of the subsequent meals. Although moderate-intensity continuous exercise, high-intensity intermittent exercise (HIIE), resistance exercise and accumulation of short bouts of exercise throughout the day are all effective in lowering PPL, submaximal, high-volume interval exercise seems to be superior, provided it is tolerable. Finally, exercise reduces PPL by both lowering the rate of appearance and increasing the clearance of triacylglycerol-rich lipoproteins from the circulation.
... 8 The growing evidence from experimental studies indicates that prolonged, uninterrupted sitting are associated with impaired glucose metabolism and increased systemic inflammation; 34 however, these can be attenuated by breaking up prolonged sitting. 35 Moreover, sitting may induce exercise resistance and diminish the benefits of physical activity, 36 which could potentially explain the worse survival outcomes observed among cancer survivors who reported no LTPA with concurrent prolonged sitting. Low LTPA and prolonged sitting may also contribute to increased risk of cachexia, thromboembolic events, and fatigue, which all influence survival after cancer. ...
Importance
Sedentary behaviors, particularly prolonged sitting and lack of physical activity, may influence survival after cancer.
Objective
To examine the independent and joint associations of daily sitting time and leisure-time physical activity with mortality outcomes among cancer survivors.
Design, Setting, and Participants
A prospective cohort of a nationally representative sample of cancer survivors, age 40 years or older (n = 1535; weighted population, 14 002 666), from the US National Health and Nutrition Examination Survey from 2007 to 2014. Participants were linked to mortality data from their interview and physical examination date through December 31, 2015. Daily sitting time and leisure-time physical activity (LTPA) were self-reported using the Global Physical Activity Questionnaire. Data analyses were performed from January 1 to May 1, 2021.
Main Outcomes and Measures
All-cause, cancer-specific, and noncancer mortality.
Results
Among 1535 cancer survivors (mean [SE] age, 65.1 [0.4] years; 828 [60.1%] females; 945 [83.1%] non-Hispanic White individuals), 950 (56.8%) reported LTPA of 0 minutes per week (min/wk) during the previous week (inactive); 226 (15.6%) reported LTPA of less than 150 min/wk (insufficiently active); 359 (27.6%) reported LTPA of 150 min/wk or more (active); 553 (35.4%) reported sitting for 6 to 8 hours per day (h/d); and 328 (24.9%) reported sitting for more than 8 h/d. Of note, 574 (35.8%) cancer survivors reported no LTPA with concurrent sitting of more than 6 h/d. During the follow-up period of up to 9 years (median, 4.5 years; 6980 person-years), there were 293 deaths (cancer, 114; heart diseases, 41; other causes, 138). Multivariable models showed that being physically active was associated with lower risks of all-cause (hazard ratio [HR], 0.34; 95% CI, 0.20-0.60) and cancer-specific (HR, 0.32; 95% CI, 0.15-0.70) mortality compared with inactivity. Sitting more than 8 h/d was associated with higher risks of all-cause (HR, 1.81; 95% CI, 1.05-3.14) and cancer-specific (HR, 2.27; 95% CI, 1.08-4.79) mortality compared with those sitting less than 4 h/d. In the joint analyses, prolonged sitting was associated with an increased risk of death among cancer survivors who were not sufficiently active. Specifically, inactive and insufficiently active survivors reported sitting more than 8 h/d had the highest overall (HR, 5.38; 95% CI, 2.99-9.67) and cancer-specific (HR, 4.71; 95% CI, 1.60-13.9) mortality risks.
Conclusions and Relevance
In this cohort study of a nationally representative sample of US cancer survivors, the combination of prolonged sitting with lack of physical activity was highly prevalent and was associated with the highest risks of death from all causes and cancer.
... No entanto, a inatividade física associada ao isolamento social traz uma aceleração ao declínio das capacidades funcionais, redução da força muscular e aptidão cardiorrespiratória, dificultando o processo de reabilitação dos pacientes (WU; MCGOOGAN, 2020;BOWDEN DAVIES et al., 2019). Curiosamente, uma sessão de exercício de intensidade moderada não neutraliza os efeitos prejudiciais de 4 dias de inatividade, sugerindo que os indivíduos podem se tornar resistentes a adaptações metabólicas bem conhecidas induzidas por exercícios (AKINS et al., 2019 ...
O cenário atual da Pandemia do Covid-19 exige cada vez mais a aquisição de um estilo de vida saudável, principalmente quanto à prática de atividade física. Uma das atividades com maior número de adeptos nesse período, devido sua praticidade foi a corrida de rua, que obtiveram mudanças principalmente na dinâmica dos grupos de corrida. Praticar exercícios físicos mesmo com o isolamento social, se tornou o grande desafio da população mundial, tendo em vista que o modelo de entrega dessas atividades passou a ter um novo formato. Dentro desse panorama, nota-se a importância evidenciada da prática de exercício físico para aquisição de níveis ideias de saúde e também formatação adequada do método de treinamento para atividades online. O presente artigo busca apresentar a proposta de intervenção e resultados do alcance do Grupo de corrida Papa-léguas durante a Pandemia do Covid-19. O grupo utilizou as redes sociais Youtube, Plataforma do Google Meet, Facebook e aplicativos WhatsApp e Strava. Por meio de videoaulas, palestras, mensagens e prática de desafio, os professores e bolsistas envolvidos no projeto de extensão mantiveram suas atividades, desenvolveram conhecimento acadêmico e alcançaram um maior público. Youtube apresentou 1473 visualizações nos vídeos, Facebook abrangeu 120 contas alcançadas, plataforma Google Meet apresentou média de 10 participantes no treinamento online e o Strava apresentou 119 participantes do desafio de 120km em 40 dias. O projeto de extensão Papa-léguas apresentou um excelente retrospecto mesmo durante o isolamento social.
... 9 Even exercise after prolonged inactivity provides no metabolic benefit as individual become resistant to it. 10 Due to mandatory homestay, unavoidably people have spent and are still spending long time on watching television, online gaming or social networking. Many pieces of evidence showed that prolonged TV viewing is associated with greater risk of CVD events and all cause of mortality 11 and also increase the risk of obesity, insulin resistance, type 2 diabetes mellitus and hypertension. ...
COVID 19 pandemic has spread around all the corners of the globe. Many countries have adopted social distancing and imposed the nationwide lockdown to prevent human to human transmission. lockdown has proven effective in controlling outbreak but confinement at home is associated with several side effects. lockdown affects the physical, mental and social health of the people. Many chronic diseases and conditions are caused by physical inactivity. Due to mandatory home stay, unavoidably people have spent and are still spending long time on watching television, online gaming or social networking. Eradicating hunger and malnutrition are still a challenge to world. COVID 19 has increased food insecurity and further exposed the people to malnutrition. Prolonged lockdown or prolonged stay at home along with an unhealthy dietary habit of people and sedentary lifestyle will further magnify the risk of obesity. The pandemic and the related containment measures— namely quarantine, social distancing, and self-isolation—can have a detrimental impact on mental health. During this lockdown people are not only dealing with health crisis but also suffering from financial loss. Authorities at global and national level should create awareness among people and also find efficient remedies to prevent the undesirable after-effects of lockdown.
... However, this mindset is flawed as recent evidence has found SB and body fat levels to be independent of the amount of MVPA 28 . Moreover, high physical inactivity can reduce metabolic improvements deriving from exercise 29 . As players were only monitored on weekdays, it is plausible that the PA profiles were shaped by school time and activities. ...
This study aimed to quantify and assess the relationship of young soccer players' off-training physical activity (PA) and training responses on sleep quality. Eleven adolescent soccer players (13 ± 0.5 years old) were monitored during weekdays for four consecutive weeks, throughout soccer practice days. Off-training PA and sleep quality were assessed using 100 Hz tri-axial accelerometers and training responses analyzed using 20 Hz global positioning measurement units. A cluster analysis classified all cases into three different dimensions, (1) off-training PA, (2) training responses and (3) sleep quality. For each dimension, the most important variables for classifying the cases into clusters were sedentary PA and moderate-to-vigorous PA; total distance covered and impacts; and sleep onset latency and sleep fragmentation index, respectively. Afterwards, a correspondence analysis was used to identify whether off-training PA and training responses affected sleep quality. Results exposed that high to medium off-training PA combined with medium to high training responses may have decreased sleep quality. Conversely, no correspondence was observed between off-training PA and training responses, with higher sleep quality. This study emphasizes the importance of sports organizations adopting a holistic approach to youth soccer players' development, that appropriately considers the interrelationship between lifestyle, performance and health-related information.
... any body movement of daily life) were shown to predict individual variation for improvedV O2max after training (Hautala et al. 2012). By contrast, habitual high volumes of sedentary time (too much sitting) and inactivity (not enough exercise) can diminish positive effects of exercise on metabolic health (Akins et al. 2019). These studies suggest that everyday life activity impacts 'trainability' . ...
... sitting) [5]. It is possible that excessive time spent sedentary may attenuate some of the benefits of exercising [6]. ...
Background: Postprandial glucose, insulin, and triglyceride metabolism is impaired by prolonged sitting, but enhanced by exercise. The aim of this study was to assess the effects of a continuous exercise bout with and without intermittent active interruptions to prolonged sitting on postprandial glucose, insulin, and triglycerides.
Methods: Sedentary adults who were overweight to obese (n = 67; mean age 67 yr SD ± 7; BMI 31.2 kg∙m− 2 SD ± 4.1), completed three conditions: SIT: uninterrupted sitting (8-h, control); EX+SIT: sitting (1-h), moderate-intensity walking (30-min), uninterrupted sitting (6.5-h); EX+BR: sitting (1-h), moderate-intensity walking (30- min), sitting interrupted every 30-min with 3-min of light-intensity walking (6.5 h). Participants consumed standardized breakfast and lunch meals and blood was sampled at 13 time-points. Results: When compared to SIT, EX+SIT increased total area under the curve (tAUC) for glucose by 2% [0.1–4.1%] and EX+BR by 3% [0.6–4.7%] (all p < 0.05). Compared to SIT, EX+SIT reduced insulin and insulin:glucose ratio tAUC by 18% [11–22%] and 21% [8–33%], respectively; and EX+BR reduced values by 25% [19–31%] and 28% [15–38%], respectively (all p < 0.001 vs SIT, all p < 0.05 EX+SIT-vs-EX+BR). Compared to SIT, EX+BR reduced triglyceride tAUC by 6% [1–10%] (p = 0.01 vs SIT), and compared to EX+SIT, EX+BR reduced this value by 5% [0.1–8.8%] (p = 0.047 vs EX+SIT). The magnitude of reduction in insulin tAUC from SIT-to-EX+BR was greater in those with increased basal insulin resistance. No reduction in triglyceride tAUC from SIT-to-EX+BR was apparent in those with high fasting triglycerides.
Conclusions: Additional reductions in postprandial insulin-glucose dynamics and triglycerides may be achieved by combining exercise with breaks in sitting. Relative to uninterrupted sitting, this strategy may reduce postprandial insulin more in those with high basal insulin resistance, but those with high fasting triglycerides may be resistant to such intervention-induced reductions in triglycerides.
... any body movement of daily life) were shown to predict individual variation for improvedV O2max after training (Hautala et al. 2012). By contrast, habitual high volumes of sedentary time (too much sitting) and inactivity (not enough exercise) can diminish positive effects of exercise on metabolic health (Akins et al. 2019). These studies suggest that everyday life activity impacts 'trainability' . ...
... It is interesting to note that, even episodes of exercises of moderate-intensity cannot counteract the ill effects of 4 days of inactivity. [2] In men, moderate physical activity has been positively associated with semen quality. Moderate physical activity has been found to be associated with increased fecundity parameters and live birth rates, regardless of body mass index (BMI)-even during assisted reproductive treatment. ...
... It is envisaged that cycle ergometers can be conveniently placed around the office workstations to allow individuals to perform the current proposed short-bouts of exercise throughout the work-day. The benefits of the present dispersed WAnT exercise protocol may also entice sedentary individuals who are in a state of 'exercise resistance' to start exercising because of the low time commitment required [50]. There are several limitations in the present study. ...
Background:
The aim of this study was to evaluate the efficacy of a six-week dispersed Wingate Anaerobic test (WAnT) cycle exercise training protocol on peak aerobic power (VO2peak), isokinetic leg strength, insulin sensitivity, lipid profile and quality of life, in healthy adults. Methods: We conducted a match-controlled cohort trial and participants were assigned to either the training (intervention, INT, N = 16) or non-training (control, CON, N = 17) group. INT performed 30-s WAnT bouts three times a day in the morning, afternoon and evening with each bout separated by ~4 h of rest, performed for 3 days a week for 6 weeks. Criterion measures of peak oxygen uptake (VO2peak), leg strength, insulin markers such as homeostatic model assessment (HOMA) and quantitative insulin-sensitivity check index (QUICKI), blood lipids profile and health-related quality of life (HRQL) survey were assessed before and after 6 weeks in both groups. Results: Absolute VO2peak increased by 8.3 ± 7.0% (p < 0.001) after INT vs. 0.9 ± 6.1% in CON (p = 0.41) group. Maximal voluntary contraction at 30°·s-1 of the dominant lower-limb flexors in INT increased significantly post-training (p = 0.03). There were no changes in the INT individuals' other cardiorespiratory markers, HOMA, QUICKI, blood lipids, and HRQL measures (all p > 0.05) between pre- and post-training; but importantly, no differences were observed between INT and CON groups (all p > 0.05). Conclusions: The results indicate that 6 weeks of dispersed sprint cycle training increased cardiorespiratory fitness and dynamic leg strength but had minimal impact on insulin sensitivity, blood lipids and quality of life in the exercising individuals.
... Inactivity slows the metabolic benefits of exercise, while exercise improves postprandial lipemia levels, glucose tolerance, and insulin sensitivity, all of which are risk factors for CVD. Another study highlights that physical inactivity (e.g., sitting 13.5 h/day and walking fewer than 4000 steps a day) provokes resistance to metabolic improvements that usually result from an acute episode of aerobic exercise, emphasizing that exercise, a heart-healthy diet, and an active lifestyle should be combined to achieve a healthy cardiometabolic profile [44]. ...
While the detrimental effects of a chronic positive energy balance due to a sedentary lifestyle have been well established, the impacts of a short period of abruptly reduced physical activity and overeating arising from strict confinement due to the COVID-19 pandemic will soon start to emerge. To reasonably anticipate major consequences according to the available evidence, we hereby review the literature for studies that have explored the health impacts of several weeks of a reduction in physical activity and daily step-count combined with modified eating habits. These studies identify as main metabolic consequences increases in insulin resistance, total body fat, abdominal fat and inflammatory cytokines. All these factors have been strongly associated with the development of metabolic syndrome, which in turn increases the risk of multiple chronic diseases. A plausible mechanism involved in these impacts could be a positive energy balance promoted by maintaining usual dietary intake while reducing energy expenditure. This means that just as calorie intake restriction could help mitigate the deleterious impacts of a bout of physical inactivity, overeating under conditions of home confinement is very likely to exacerbate these consequences. Moreover, hypertension, diabetes, and cardiovascular disease have been identified as potential risk factors for more severely ill patients with COVID-19. Thus, adequate control of metabolic disorders could be important to reduce the risk of severe COVID-19.
... surrogate marker of cardio-metabolic health [4]. It has been demonstrated that acute exercise induces a reduction in PPL [5,6], [7], but recent evidence suggests that this effect can be attenuated by prolonged sitting [8,9], [3]. Given that prolonged sitting increases CVD risk even in people who meet the recommended exercise guidelines [3,10], it is practical to investigate the effects of reducing prolonged sitting. ...
Prolonged periods of sedentary behavior are linked to cardiometabolic disease independent of exercise and physical activity. This study examined the effects of posture by comparing one day of sitting (14.4 ± 0.3 h) to one day of standing (12.2 ± 0.1 h) on postprandial metabolism the following day. Eighteen subjects (9 men, 9 women; 24 ± 1 y) completed two trials (sit or stand) in a crossover design. The day after prolonged sitting or standing the subjects completed a postprandial high fat/glucose tolerance test, during which blood and expired gas was collected immediately before and hourly for 6 h after the ingestion of the test meal. Indirect calorimetry was used to measure substrate oxidation while plasma samples were analyzed for triglyceride, glucose, and insulin concentrations. Standing resulted in a lower fasting plasma triglyceride concentration (p = 0.021) which was primarily responsible for an 11.3% reduction in total area under the curve (p = 0.022) compared to sitting. However, no difference between trials in incremental area under the curve for plasma triglycerides was detected (p>0.05). There were no differences in substrate oxidation, plasma glucose concentration, or plasma insulin concentration (all p>0.05). These data demonstrate that 12 h of standing compared to 14 h of sitting has a small effect the next day by lowering fasting plasma triglyceride concentration, and this contributed to a 11.3% reduction in postprandial plasma triglyceride total area under the curve (p = 0.022) compared to sitting.
... 37 to an exercise bout also fails to improve PPL in healthy-young individuals. 53 It is possible that in our older MetS individuals 2 days of inactivity could lead to a similar situation. Therefore, there may be 2 possibilities as to why exercise failed to improve PPL; short time after exercise and/or being inactive (prolonged sitting) in 2 days prior testing. ...
Aims
To determine the effects of statins on postprandial lipaemia (PPL) and to study if exercise could enhance statin actions.
Methods
Ten hypercholesteraemic (blood cholesterol 204 ± 36 mg dL⁻¹; low‐density lipoprotein–cholesterol 129 ± 32 36 mg dL⁻¹) overweight (body mass index 30 ± 4 kg m⁻²), metabolic syndrome individuals chronically medicated with statins (>6 months) underwent 5‐hour PPL tests in 4 occasions in a randomized order: (i) substituting their habitual statin medication by placebo for 96 hours (PLAC trial); (ii) taking their habitual statin medicine (STA trial); (iii) placebo combined with a bout of intense aerobic exercise (EXER+PLAC trial); and (iv) combining exercise and statin medicine (EXER+STA trial).
Results
Before the fat meal, statin withdrawal (i.e. PLAC and EXER+PLAC) increased blood triglycerides (TG; 24%), low‐density lipoprotein–cholesterol (31%) and total cholesterol (19%; all P < .05) evidencing treatment compliance. After the meal, statin withdrawal increased 5‐hour postprandial TG (PPTG) compared to its matched trials (94% higher PLAC vs STA and 45% higher EXER+PLAC vs EXER+STA; P < .05). EXER+PLAC trial did not lower PPTG below PLAC (i.e. incremental AUC of 609 ± 152 vs 826 ± 190 mg dL⁻¹ 5 h; P = .09). Adding exercise to statin did not result in larger reductions in PPTG (i.e. EXER+STA vs STA incremental area under the curve of 421 ± 87 vs 421 ± 84 mg dL⁻¹ 5 h; P = .99).
Conclusion
In hypercholesteraemic metabolic syndrome individuals, chronic statin therapy blunts the elevations in TG after a fat meal (i.e. incremental area under the curve of PPTG) reducing the cardiovascular risk associated to their atherogenic dyslipidaemia. However, a single bout of intense aerobic exercise before the high fat meal, does not reduce PPTG but also does not interfere with the effects of statin treatment.
Background: Older people spend approximately 65-80% of their waking hours sedentary. It is concerning that fewer than 30 % of Chinese older adults participate in regular physical activity, indicating that sedentary lifestyles may be common among this population. The long-term presence of low energy expenditure during waking hours is detrimental to physical health and quality of life. Therefore, interventions targeting changes in sedentary lifestyles are necessary to improve health outcomes in older adults. An experimental study will be conducted to verify whether a sedentary lifestyle modification intervention based on the MTM and the staircase approach is more effective than conventional education in reducing sedentary time and improving physical activity levels, functional capacity, and quality of life among community-dwelling older people.
Methods:This community-based, parallel-arm, assessor-blinded randomized controlled trial aims to estimate the effect of Multi-Theory Model based behavior change intervention with staircase approach on sedentary lifestyle among community-dwelling older adults. A total of 56 participants will be enrolled in this study and randomly assigned to the intervention group (participants will receive multi-theory model-based stepped sedentary lifestyle change intervention) and the control group (participants will receive conventional behavioral change advice). Endpoints will be collected at baseline (T1), immediately after the end of intervention (T2), week 12 (T3) and week 18 (T4). The primary endpoint is the change in self-reported sedentary time (min/day). Secondary endpoints include the changes in different domain sedentary time, sedentary behavior characteristics including the longest continuous sedentary time and theprevalence of prolonged sedentary bouts(≥30min), step count,time spent in light-intensity physical activity and moderate-to-vigorous physical activity, MCPAQ score, SPPB score, anthropometric parameters,blood pressure, SF-36score, and adverse events.
Discussion: Our research aims to facilitate the transition from sedentary behaviors to exercise behaviors of varying intensities and to maintain long-term behavioral change through a staircase approach in behavioral change interventions for older people with predominantly sedentary lifestyles. The goal is to promote healthy aging by reducing sedentary behavior and increasing levels of physical activity among older people in the community, thereby improving health-related quality of life and preventing functional decline and non-communicable diseases.
Trial registration: The trial was registered in the China Clinical Trial Registry on 25 Mar 2024 (ChiCTR2400082225)
Physical inactivity is the fourth leading cause of death in the world. It is associated with myriad diseases and premature death. Two possible contributing factors are postprandial lipidaemia (PPL), which accelerates atherosclerosis, and impaired whole‐body fat oxidation, which contributes to obesity. Acute exercise in physically active people is effective for increasing whole body fat oxidation and lowering PPL the next morning. However, in people who have low physical activity (<8000 steps/day), an acute bout of exercise (1 h at 62% maximal oxygen consumption) has no effect on increasing fat oxidation or reducing PPL (‘exercise resistance’). The acute harms of inactivity are not due to the lack of exercise and are more powerful than the benefits of exercise, at least regarding fat metabolism. The increase in mortality with reduced daily steps is remarkably steep. Low background steps/day also impair the metabolic adaptations to short‐term endurance training, suggesting that the ills of inactivity extend beyond fat metabolism. ‘Exercise resistance’ with inactivity could be a culprit, causing atherosclerosis, or maybe also a harbinger (impaired fat oxidation) of more widespread diseases. Recommendations regarding the amount of moderate to vigorous exercise needed for health should factor in the amount of background activity (i.e. ∼8000 steps/day) necessary to avoid ‘exercise resistance’. image
Background: An infection with SARS-CoV-2 can lead to persistent symptoms more than three months after the acute infection and has also an impact on patients’ physical activity behaviour and sleep quality. There is evidence, that inpatient post-COVID rehabilitation can improve physical capacity and mental health impairments, but less is known about the change in physical behaviour and sleep quality.
Methods: This longitudinal observational study used accelerometery to assess the level of physical activity and sleep quality before and after an inpatient rehabilitation program. The study sample consists of 100 post-COVID patients who acquired COVID-19 in the workplace. Group differences related to sex, age, COVID-19 severity, and pre-existing diseases were also analysed.
Results: Level of physical activity and sleep quality didn’t increase after rehabilitation. Overall, there is a high extent of inactivity time and poor sleep quality at both measurement points. Regarding group differences, male patients showed a significantly higher inactivity time before rehabilitation, and younger patients (<55 years) spend significant more time in vigorous physical activity than older patients. Post-COVID patients with pre-existing cardiovascular, respiratory, and metabolic disease show slightly less physical activity than post-COVID patients without these comorbidities. Female patients and younger patients showed better sleep quality in some sleep parameters at both measurement points. However, no differences could be detected related to COVID-19 severity.
Conclusions: Ongoing strategies should be implemented to address the high amount of inactivity time and the poor sleep quality in post-COVID patients.
Sedentary behaviours—i.e. ‘too much sitting as distinct from too little exercise’—are ubiquitous in modern societies. Accumulating epidemiological evidence indicates that higher volumes of sedentary behaviour are associated with elevated risks for all-cause mortality, cardiovascular disease incidence and mortality, type 2 diabetes incidence and some cancers, particularly among those who are not achieving recommended amounts of moderate-to-vigorous intensity physical activity. Based on these observations, and in part on a growing body of experimental research, it has been proposed that sedentary behaviour influences health risk through some mechanisms that act similarly or independently of physical inactivity. However, the observational evidence is well ahead of evidence on the physiological responses to sedentary behaviour, leaving uncertainties around the potential biological mechanisms that may explain the observed associations. Here, we summarise and discuss experimental evidence to date on the physiological effects of sedentary behaviours, including potential solutions-oriented research aiming to address sedentary behaviour as a health risk. We also highlight future research that is needed to fully ascertain the specific impact of sedentary behaviour on altering human physiology.
Purpose:
To examine the effects of daily step-count on same-day fat oxidation and postprandial metabolic responses to an evening high-fat mixed meal (HFMM).
Methods:
Ten healthy participants (5 females, 30±7 y) completed four different daily step-counts - 2,000 (2K), 5,000 (5K), 10,000 (10K), and 15,000 (15K) steps - on separate days in randomized order. On experimental days, participants ate the same meals and walked all steps on an indoor track at a pace of 100 steps/min in three roughly equal bouts throughout the day. After the final walking-bout, participants' resting energy expenditure (REE), respiratory exchange ratio (RER), and fat oxidation rate (FATOX) were measured. Blood samples were obtained before (BL) and 30-, 60-, 90-, 120-, and 240-minutes following consumption of a HFMM (960 kcal; 48% fat) to measure triglycerides (i.e., postprandial lipemia; PPL), non-esterified fatty acids (NEFAs), insulin, and glucose.
Results:
Two-way ANOVAs indicated condition effects where PPL was significantly higher after 2K versus 10K (+23±8 mg/dL, p=0.027), and NEFAs were significantly higher after 15K versus 2K (+86±23 µmol/L; p=0.006). No differences were found for insulin, glucose, or REE among conditions (all p>0.124). Similarly, RER (p=0.055; ηp2=0.24) and FATOX (p=0.070; ηp2=0.23) were not significantly different among conditions.
Conclusion:
In young adults, 10K steps elicited the greatest decrease in PPL, an established cardiovascular disease risk factor. NEFA levels were highest after the 15K condition, likely due to alterations in adipose tissue lipolysis or lipoprotein lipase activity with increased activity.
Lifestyle modification represents the first-line strategy for the prevention and treatment of type 2 diabetes mellitus (T2DM), which is frequently associated with obesity and characterized by defective pancreatic insulin secretion and/or insulin resistance. Exercise training is an essential component of lifestyle modification and has been shown to ameliorate insulin resistance by reducing body fat mass and by enhancing skeletal muscle mitochondrial biogenesis and insulin-independent glucose uptake. Additionally, exercising stimulates the release of exerkines such as metabolites or cytokines, but also long non-coding RNA, microRNAs, cell-free DNA (cf-DNA), and extracellular vesicles (EVs), which contribute to inter-tissue communication. There is emerging evidence that EV number and content are altered in obesity and T2DM and may be involved in several metabolic processes, specifically either worsening or improving insulin resistance. This review summarizes the current knowledge on the metabolic effects of exercise training and on the potential role of humoral factors and EV as new biomarkers for early diagnosis and tailored treatment of T2DM.
Prolonged sedentary behaviour is detrimental to health due to low contractile activity in large lower extremity muscle groups. This muscle inactivity can be measured with electromyography (EMG), but it is unknown how methodological factors affect responsiveness longitudinally. This study ranks 16 different EMG inactivity thresholds based on their responsiveness (absolute and standardized effect size, responsiveness) using data from a randomized controlled trial targeted at reducing and breaking up sedentary time (InPact, ISRCTN28668090). EMG inactivity duration and usual EMG inactivity bout duration (weighted median of bout lengths) were measured from large lower extremity muscle groups (quadriceps, hamstring) with EMG-sensing shorts. The results showed that the EMG inactivity threshold above signal baseline (3 μV) provided overall the best responsiveness indices. At baseline, EMG inactivity duration of 66.8 ± 9.6% was accumulated through 73.9 ± 36.0 s usual EMG inactivity bout duration, both of which were reduced following the intervention (−4.8 percentage points, −34.3 s). The proposed methodology can reduce variability in longitudinal designs and the detailed results can be used for sample size calculations. Reducing EMG inactivity duration and accumulating EMG inactivity in shorter bouts has a potential influence on muscle physiology and health.
The purpose of this systematic review was to synthesize the results from current literature examining the effects of prior exercise on the postprandial triglyceride (TG) response to evaluate current literature and provide future direction. A quantitative review was performed using meta-analytic methods to quantify individual effect sizes. A moderator analysis was performed to investigate potential variables that could influence the effect of prior exercise on postprandial TG response. Two hundred and seventy-nine effects were retrieved from 165 studies for the total TG response and 142 effects from 87 studies for the incremental area under the curve TG response. There was a moderate effect of exercise on the total TG response (Cohen’s d = −0.47; p < .0001). Moderator analysis revealed exercise energy expenditure significantly moderated the effect of prior exercise on the total TG response ( p < .0001). Exercise modality (e.g., cardiovascular, resistance, combination of both cardiovascular and resistance, or standing), cardiovascular exercise type (e.g., continuous, interval, concurrent, or combined), and timing of exercise prior to meal administration significantly affected the total TG response ( p < .001). Additionally, exercise had a moderate effect on the incremental area under the curve TG response (Cohen’s d = −0.40; p < .0001). The current analysis reveals a more homogeneous data set than previously reported. The attenuation of postprandial TG appears largely dependent on exercise energy expenditure (∼2 MJ) and the timing of exercise. The effect of prior exercise on the postprandial TG response appears to be transient; therefore, exercise should be frequent to elicit an adaptation.
Exercise has multiple health benefits and is a critical component in managing overweight and obesity. High Intensity Interval Training (HIIT) involves brief high-intensity anaerobic exercise followed by rest or very low intensity exercise. 24 men and women (age 18–60 years) volunteered to participate in a 6 weeks of modified HIIT exercises program where whole body functional training exercises was provided. Their body weight, body mass index, waist to hip ratio and skin fold fat were measured at the beginning and at the end of the 6 weeks duration . Statistical significance was found between the variables at p < 0.05. The results showed that a Modified HIIT exercise Program based on Body weight training results in considerable decrease in level of sub-cutaneous adiposity up to 77.8%. Obesity and overweight have become complex pandemic disorders where in physical inactivity and lack of time to exercise plays a major role leading to various complications. Reduction in adiposity through structured exercises protocols will improve body composition and Cardio-metabolic health . Novel interventions such as modified HIIT serve as the perfect pathway to address the time factor and enhancement of physical activity as well.
Exercise has multiple health benefits and is a critical component in managing overweight and obesity. High Intensity
Interval Training (HIIT) involves brief high-intensity anaerobic exercise followed by rest or very low intensity exercise. 24 men
and women (age 18–60 years) volunteered to participate in a 6 weeks of modified HIIT exercises program where whole body
functional training exercises was provided. Their body weight, body mass index, waist to hip ratio and skin fold fat were measured
at the beginning and at the end of the 6 weeks duration . Statistical significance was found between the variables at p < 0.05.
The results showed that a Modified HIIT exercise Program based on Body weight training results in considerable decrease in
level of sub-cutaneous adiposity up to 77.8%. Obesity and overweight have become complex pandemic disorders where in
physical inactivity and lack of time to exercise plays a major role leading to various complications. Reduction in adiposity through
structured exercises protocols will improve body composition and Cardio-metabolic health . Novel interventions such as modified
HIIT serve as the perfect pathway to address the time factor and enhancement of physical activity as well.
Since ancient times, the health benefits of regular physical activity/exercise have been recognised and the classic studies of Morris and Paffenbarger provided the epidemiological evidence in support of such an association. Cardiorespiratory fitness, often measured by maximal oxygen uptake, and habitual physical activity levels are inversely related to mortality. Thus, studies exploring the biological bases of the health benefits of exercise have largely focused on the cardiovascular system and skeletal muscle (mass and metabolism), although there is increasing evidence that multiple tissues and organ systems are influenced by regular exercise. Communication between contracting skeletal muscle and multiple organs has been implicated in exercise benefits, as indeed has other inter-organ "cross-talk". The application of molecular biology techniques and 'omics' approaches to questions in exercise biology has opened new lines of investigation to better understand the beneficial effects of exercise and, in so doing, inform the optimisation of exercise regimens and the identification of novel therapeutic strategies to enhance health and well-being.
Physical activity has multiple health beneits and is a critical component in managing overweight and obesity. However, one of the main barriers to achieving regular physical activity in overweight today is lack of time. High- Intensity Interval Training (HIIT) has bridged both these issues systemati- cally. Twenty-four men and women (age 18-60 years) volunteered to partici- pate in 6 weeks of modiied HIIT exercises program where whole-body func- tional training exercises was provided. Their body weight, body mass index, waist to hip ratio and skinfold fat were measured at the beginning and the end of the six weeks duration. Statistical signiicance was found between the variables at p<0.05 The results showed that after modiied HIIT exercise inter- ventions, there is a considerable decrease in the level of adiposity up to 77.8%. Obesity and overweight have become complex pandemic disorders wherein physical inactivity and lack of time to exercise plays a signiicant role leading to various complications. A decrease in adiposity through structured exer- cises protocols will enhance a better lifestyle and thereby increases the overall metabolism of the body. Newer interventions such as HIIT exercises serve as the perfect pathway to address the time factor and enhancement of physical activity as well.
Dietary lipids are efficiently absorbed by the small intestine, incorporated into triglyceride-rich lipoproteins (chylomicrons), and transported in the circulation to various tissues. Intestinal lipid absorption and mobilization and chylomicron synthesis and secretion are highly regulated processes. Elevated chylomicron production rate contributes to the dyslipidemia seen in common metabolic disorders such as insulin-resistant states and type 2 diabetes and likely increases the risk for atherosclerosis seen in these conditions. An in-depth understanding of the regulation of chylomicron production may provide leads for the development of drugs that could be of therapeutic utility in the prevention of dyslipidemia and atherosclerosis. Chylomicron secretion is subject to regulation by various factors, including diet, body weight, genetic variants, hormones, nutraceuticals, medications, and emerging interventions such as bariatric surgical procedures. In this review we discuss the regulation of chylomicron production, mechanisms that underlie chylomicron dysregulation, and potential avenues for future research. Expected final online publication date for the Annual Review of Nutrition Volume 35 is July 17, 2015. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
Acute endurance exercise has been shown to lower postprandial plasma triglyceride concentrations (PPTG); however whether this is due to the negative energy and/or carbohydrate deficit from the exercise bout is not well understood.
To examine the effects of a post-exercise meal consisting of either high or low carbohydrate content on PPTG and postprandial fat oxidation the morning after an exercise bout.
Healthy, young men (n=6) performed each of four experimental treatments: 1) non-exercise control (CON), 2) 80 min of cycling with either no meal replacement (EX), 3) a high carbohydrate post-exercise meal (EX+HCHO), or a 4) low carbohydrate post-exercise meal (EX+LCHO). A standardized meal for PPTG determination was provided (16.0 kcal/kg BM; 1.02 g fat/kg, 1.36 g CHO/kg, 0.31 g Pro/kg) 12h after the exercise and measures of plasma triglyceride concentration (TG) and whole body resting fat oxidation were made in the fasted condition and during the 4h postprandial period.
The total area under the curve for plasma triglyceride (TG AUC) was significantly lower in EX+LCHO [325 (63) mg/dL/4h] compared to EX+HCHO [449 (118) mg/dL/4h; p=0.03]. Postprandial fat oxidation during this period was significantly greater in EX+LCHO [257 (58) kcal/4h; p=0.003] compared to EX+HCHO [209 (56) kcal/4h]. The change in total postprandial fat oxidation (kcal/4h) relative to CON (ΔFO) was significantly and inversely correlated with the change in the total TG area under the curve relative to CON (mg/dL/4h; ΔTG AUC; R=0.37, p=0.008).
The low carbohydrate composition of the post-exercise meal contributes to lower PPTG and increased fat oxidation, with lower PPTG related to an increase in fat oxidation.
Reducing postprandial triglycerides (TG) can lower the risk for cardiovascular disease. The purpose of this study was to perform a meta-analytic review of the literature to estimate of the effect of prior exercise on postprandial lipemia. A total of 121 effects were found from 76 studies for the total TG response and 70 effects from 44 studies for the incremental area under the curve (iAUC) TG response. The weighted mean effect was moderate for the total TG response, Cohen's d = -0.597 (P < 0.0001), and for the iAUC response, Cohen's d = -0.589 (P < 0.0001). Moderator analysis revealed women exhibited a larger reduction (P < .01) in the total TG response following exercise (d = -0.96) than men (d = -0.57); high-intensity interval training induced a larger reduction (P < .05) in the iAUC response (d = -1.49) than aerobic (d = -0.58) or resistance (d = -0.13) exercise; and, participants maintaining an energy deficit following exercise exhibited a greater reduction in the iAUC response (d = -0.67) compared to participants in energy balance (d = -0.28). We conclude that prior acute exercise reduces postprandial lipemia, with the magnitude of effect influenced by sex, type of exercise and energy deficit following exercise.
This review examines the effect of prior exercise on postprandial triacylglycerol (pTAG) concentrations, an independent risk factor for cardiovascular diseases. Numerous studies have shown that a single bout of exercise reduces pTAG concentrations; however, several modulators such as exercise energy expenditure/deficit, mode of exercise (aerobic/resistance/high intensity/intermittent exercise or combinations), type of meal (moderate or high fat), time frame between exercise and meal and target group may individually or in conjunction influence this effect. On the other hand, at least for aerobic exercise, training reduces pTAG concentrations transiently (~2 days); therefore, exercise sessions should be frequent enough to maintain this clinically significant improvement. For the healthy population, it seems that a subject's preference and ability determine which type of exercise to undertake to attenuate pTAG concentrations; an energy expenditure of ~30 kJ/kg of body mass (or ~2-2.5 MJ) not combined with a corresponding increase in energy intake is required; for resistance or intermittent exercise, for those following a moderate rather than a high-fat diet, and for those with obesity (expressed as kJ/kg of body mass), a smaller energy expenditure is probably sufficient. More studies are needed to investigate dose-response/plateau effects, as well as the threshold of energy expenditure in those with diabetes mellitus and other high-risk populations. Finally, investigation of the underlying mechanisms may be clinically helpful in individualizing the appropriate intervention.
Epidemiological studies suggest that excessive sitting time is associated with increased health risk, independent of the performance of exercise. We hypothesized that a daily bout of exercise cannot compensate the negative effects of inactivity during the rest of the day on insulin sensitivity and plasma lipids.
Eighteen healthy subjects, age 21±2 year, BMI 22.6±2.6 kgm(-2) followed randomly three physical activity regimes for four days. Participants were instructed to sit 14 hr/day (sitting regime); to sit 13 hr/day and to substitute 1 hr of sitting with vigorous exercise 1 hr (exercise regime); to substitute 6 hrs sitting with 4 hr walking and 2 hr standing (minimal intensity physical activity (PA) regime). The sitting and exercise regime had comparable numbers of sitting hours; the exercise and minimal intensity PA regime had the same daily energy expenditure. PA was assessed continuously by an activity monitor (ActivPAL) and a diary. Measurements of insulin sensitivity (oral glucose tolerance test, OGTT) and plasma lipids were performed in the fasting state, the morning after the 4 days of each regime. In the sitting regime, daily energy expenditure was about 500 kcal lower than in both other regimes. Area under the curve for insulin during OGTT was significantly lower after the minimal intensity PA regime compared to both sitting and exercise regimes 6727.3±4329.4 vs 7752.0±3014.4 and 8320.4±5383.7 mU•min/ml, respectively. Triglycerides, non-HDL cholesterol and apolipoprotein B plasma levels improved significantly in the minimal intensity PA regime compared to sitting and showed non-significant trends for improvement compared to exercise.
One hour of daily physical exercise cannot compensate the negative effects of inactivity on insulin level and plasma lipids if the rest of the day is spent sitting. Reducing inactivity by increasing the time spent walking/standing is more effective than one hour of physical exercise, when energy expenditure is kept constant.
The purpose of this Position Stand is to provide guidance to professionals who counsel and prescribe individualized exercise to apparently healthy adults of all ages. These recommendations also may apply to adults with certain chronic diseases or disabilities, when appropriately evaluated and advised by a health professional. This document supersedes the 1998 American College of Sports Medicine (ACSM) Position Stand, "The Recommended Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory and Muscular Fitness, and Flexibility in Healthy Adults." The scientific evidence demonstrating the beneficial effects of exercise is indisputable, and the benefits of exercise far outweigh the risks in most adults. A program of regular exercise that includes cardiorespiratory, resistance, flexibility, and neuromotor exercise training beyond activities of daily living to improve and maintain physical fitness and health is essential for most adults. The ACSM recommends that most adults engage in moderate-intensity cardiorespiratory exercise training for ≥30 min·d on ≥5 d·wk for a total of ≥150 min·wk, vigorous-intensity cardiorespiratory exercise training for ≥20 min·d on ≥3 d·wk (≥75 min·wk), or a combination of moderate- and vigorous-intensity exercise to achieve a total energy expenditure of ≥500-1000 MET·min·wk. On 2-3 d·wk, adults should also perform resistance exercises for each of the major muscle groups, and neuromotor exercise involving balance, agility, and coordination. Crucial to maintaining joint range of movement, completing a series of flexibility exercises for each the major muscle-tendon groups (a total of 60 s per exercise) on ≥2 d·wk is recommended. The exercise program should be modified according to an individual's habitual physical activity, physical function, health status, exercise responses, and stated goals. Adults who are unable or unwilling to meet the exercise targets outlined here still can benefit from engaging in amounts of exercise less than recommended. In addition to exercising regularly, there are health benefits in concurrently reducing total time engaged in sedentary pursuits and also by interspersing frequent, short bouts of standing and physical activity between periods of sedentary activity, even in physically active adults. Behaviorally based exercise interventions, the use of behavior change strategies, supervision by an experienced fitness instructor, and exercise that is pleasant and enjoyable can improve adoption and adherence to prescribed exercise programs. Educating adults about and screening for signs and symptoms of CHD and gradual progression of exercise intensity and volume may reduce the risks of exercise. Consultations with a medical professional and diagnostic exercise testing for CHD are useful when clinically indicated but are not recommended for universal screening to enhance the safety of exercise.
The obesity epidemic is attributed in part to reduced physical activity. Evidence supports that reducing time spent sitting, regardless of activity, may improve the metabolic consequences of obesity. Analyses were conducted in a large prospective study of US adults enrolled by the American Cancer Society to examine leisure time spent sitting and physical activity in relation to mortality. Time spent sitting and physical activity were queried by questionnaire on 53,440 men and 69,776 women who were disease free at enrollment. The authors identified 11,307 deaths in men and 7,923 deaths in women during the 14-year follow-up. After adjustment for smoking, body mass index, and other factors, time spent sitting (> or = 6 vs. <3 hours/day) was associated with mortality in both women (relative risk = 1.34, 95% confidence interval (CI): 1.25, 1.44) and men (relative risk = 1.17, 95% CI: 1.11, 1.24). Relative risks for sitting (> or = 6 hours/day) and physical activity (<24.5 metabolic equivalent (MET)-hours/week) combined were 1.94 (95% CI: 1.70, 2.20) for women and 1.48 (95% CI: 1.33, 1.65) for men, compared with those with the least time sitting and most activity. Associations were strongest for cardiovascular disease mortality. The time spent sitting was independently associated with total mortality, regardless of physical activity level. Public health messages should include both being physically active and reducing time spent sitting.
Acute exercise, undertaken on the day before an oral fat tolerance test (OFTT), typically reduces postprandial triglycerides (TG) and increases high-density lipoprotein-cholesterol (HDL-C). However, the benefits of acute exercise may be overstated when studies do not account for compensatory changes in dietary intake. The objective of this study was to determine the influence of acute exercise, with and without carbohydrate (CHO) replacement, on postprandial lipid metabolism. Eight recreationally active young men underwent an OFTT on the morning after three experimental conditions: no exercise [control (Con)], prolonged exercise without CHO replacement (Ex-Def) and prolonged exercise with CHO replacement to restore CHO and energy balance (Ex-Bal). The exercise session in Ex-Def and Ex-Bal consisted of 90 min cycle ergometry at 70% peak oxygen uptake (Vo(2peak)) followed by 10 maximal 1-min sprints. CHO replacement was achieved using glucose solutions consumed at 0, 2, and 4 h postexercise. Muscle glycogen was 40 +/- 4% (P < 0.05) and 94 +/- 3% (P = 0.24) of Con values on the morning of the Ex-Def and Ex-Bal OFTT, respectively. Postprandial TG were 40 +/- 14% lower and postprandial HDL-C, free fatty acids, and 3-hydroxybutyrate were higher in Ex-Def compared with Con (P < 0.05). Most importantly, these exercise effects were not evident in Ex-Bal. Postprandial insulin and glucose and the homeostatic model assessment of insulin resistance (HOMA(IR)) were not significantly different across trials. There was no relation between the changes in postprandial TG and muscle glycogen across trials. In conclusion, the influence of acute exhaustive exercise on postprandial lipid metabolism is largely dependent on the associated CHO and energy deficit.
The present study examined the influence of training, followed by a short period of detraining, on postprandial lipaemia. Fourteen normolipidaemic, recreationally active young adults aged 18-31 years participated, in two self-selected groups: three men and five women (BMI 21.7-27.6 kg/m2) completed 13 weeks of running training, after which they refrained from exercise for 9 d; three men and three women (BMI 21.5-25.6 kg/m2) maintained their usual lifestyle. Oral fat tolerance tests were conducted at baseline and again 15 h, 60 h and 9 d after the runners' last training session. Blood samples were drawn after an overnight fast and at intervals for 6 h after consumption of a high-fat meal (1.2 g fat, 1.4 g carbohydrate, 70.6 kJ energy/kg body mass). Heparin was then administered (100 IU/kg) and a further blood sample was drawn for measurement of plasma lipoprotein lipase (EC 3.1.1.34; LPL) activity. Endurance fitness improved in runners, relative to controls (maximal O2 uptake +3.2 (SE 1.1) ml/kg per min v. -1.3 (SE 1.2) ml/kg per min; P < 0.05). In the absence of the acute effect of exercise, i.e. 60 h after the last training session, there was no effect of training on either postprandial lipaemia or on post-heparin LPL activity. However, changes during 9 d of detraining in both these variables differed significantly between groups; after 2d without exercise (60 h test), the runners' lipaemic response was 37% higher than it was the morning after their last training session (15 h test; runners v. controls P < 0.05), with a reciprocal decrease in post-heparin LPL activity (P < 0.01). These findings suggest that improved fitness does not necessarily confer an effect on postprandial lipaemia above that attributable to a single session of exercise.
Total GLUT4 content in skeletal muscle from individuals with type 2 diabetes is normal; however, recent studies have demonstrated that translocation of GLUT4 to the plasma membrane is decreased in response to insulin stimulation. It is not known whether physical exercise stimulates GLUT4 translocation in skeletal muscle of individuals with type 2 diabetes. Five subjects (two men, three women) with type 2 diabetes and five normal control subjects (5 men), as determined by a standard 75-g oral glucose tolerance test, were recruited to determine whether an acute bout of cycle exercise activates the translocation of GLUT4 to the plasma membrane in skeletal muscle. Each subject had two open biopsies of vastus lateralis muscle; one at rest and one 3-6 weeks later from the opposite leg after 45-60 min of cycle exercise at 60-70% of VO2max. Skeletal muscle plasma membranes were prepared by subcellular fractionation, and GLUT4 content was determined by Western blotting. Plasma membrane GLUT4 increased in each subject in response to exercise. The mean increase in plasma membrane GLUT4 for the subjects with type 2 diabetes was 74 +/-20% above resting values, and for the normal subjects the increase was 71+/-18% above resting values. Although plasma membrane GLUT4 content was approximately 32% lower at rest and after exercise in the muscle of the subjects with type 2 diabetes, the differences were not statistically significant. We conclude that in contrast to the previously reported defect in insulin-stimulated GLUT4 translocation in skeletal muscle of individuals with type 2 diabetes, a single bout of exercise results in the translocation of GLUT4 to the plasma membrane in skeletal muscle of individuals with type 2 diabetes. These data provide the first direct evidence that GLUT4 translocation is an important cellular mechanism through which exercise enhances skeletal muscle glucose uptake in individuals with type 2 diabetes.
This study compared the postprandial triacylglycerol (TAG) response to a high-fat meal in trained and untrained normolipidemic young adults after 2 days' abstinence from exercise. Fifty-three subjects (11 endurance-trained men, 9 endurance-trained women, 10 sprint/strength-trained men, 11 untrained men, 11 untrained women) consumed a meal (1.2 g fat, 1.1 g carbohydrate, 66 kJ per kg body mass) after a 12-h fast. Venous blood samples were obtained in the fasted state and at intervals until 6 h. Postprandial responses were the areas under the plasma or serum concentration-vs.-time curves. Neither fasting TAG concentrations nor the postprandial TAG response differed between trained and untrained subjects. The insulinemic response was 29% lower in endurance-trained men than in untrained men [mean difference -37.4 (95% confidence interval -62.9 to -22.9) microIU/ml x h, P = 0.01]. Responses of plasma glucose, serum insulin, and plasma nonesterified fatty acids were all lower for endurance-trained men than for untrained men. These findings suggest that, in young adults, no effect of training on postprandial lipemia can be detected after 60 h without exercise. The effect on postprandial insulinemia may persist for longer.
The extent to which exercise-induced changes to postprandial metabolism are dependant on the associated energy deficit is not known.
To determine the effects of exercise, with and without energy replacement, on postprandial metabolism.
Each subject underwent three 2-day trials in random order. On day 1 of each trial subjects rested (control), walked at 50% maximal oxygen uptake to induce a net energy expenditure of 27 kJ kg(-1) body mass (energy-deficit) or completed the same walk with the net energy expended replaced (energy-replacement). On day 2 subjects completed an 8.5-h metabolic assessment. For 3 days prior to day 2, subjects consumed an isocaloric diet, avoided planned exercise (apart from exercise interventions) and alcohol.Subjects:A total of 13 overweight/obese men (age: 40+/-8 years, body mass index: 31.1+/-3.0 kg m(-2)).
Postprandial triglyceride, insulin, glucose, non-esterified fatty acid and 3-hydroxybutyrate concentrations and substrate utilization rates were determined.
Energy-deficit lowered postprandial triglyceride concentrations by 14 and 10% compared with control and energy-replacement (P<0.05 for both). Energy-deficit increased postprandial 3-hydroxybutyrate concentrations by 40 and 19% compared with control and energy-replacement (P<0.05 for both). Postprandial insulin concentrations were 18 and 10% lower for energy-deficit and energy-replacement compared with control and 10% lower for energy-deficit than energy-replacement (P<0.05 for all). Postprandial fat oxidation increased by 30 and 14% for energy-deficit and energy-replacement compared to control and was 12% higher for energy-deficit than energy-replacement (P<0.05 for all).
Exercise with energy replacement lowered postprandial insulinaemia and increased fat oxidation. However an exercise-induced energy deficit augmented these effects and was necessary to lower postprandial lipaemia.
Sedentary behaviors are linked to adverse health outcomes, but the total amount of time spent in these behaviors in the United
States has not been objectively quantified. The authors evaluated participants from the 2003–2004 National Health and Nutrition
Examination Survey aged ≥6 years who wore an activity monitor for up to 7 days. Among 6,329 participants with at least one
10-hour day of monitor wear, the average monitor-wearing time was 13.9 hours/day (standard deviation, 1.9). Overall, participants
spent 54.9% of their monitored time, or 7.7 hours/day, in sedentary behaviors. The most sedentary groups in the United States
were older adolescents and adults aged ≥60 years, and they spent about 60% of their waking time in sedentary pursuits. Females
were more sedentary than males before age 30 years, but this pattern was reversed after age 60 years. Mexican-American adults
were significantly less sedentary than other US adults, and White and Black females were similarly sedentary after age 12
years. These data provide the first objective measure of the amount of time spent in sedentary behavior in the US population
and indicate that Americans spend the majority of their time in behaviors that expend very little energy.
Each year, the American Heart Association (AHA), in conjunction with the Centers for Disease Control and Prevention, the National Institutes of Health, and other government agencies, brings together in a single document the most up-to-date statistics related to heart disease, stroke, and the cardiovascular risk factors listed in the AHA's My Life Check - Life's Simple 7 (Figure¹), which include core health behaviors (smoking, physical activity, diet, and weight) and health factors (cholesterol, blood pressure [BP], and glucose control) that contribute to cardiovascular health. The Statistical Update represents a critical resource for the lay public, policy makers, media professionals, clinicians, healthcare administrators, researchers, health advocates, and others seeking the best available data on these factors and conditions. Cardiovascular disease (CVD) and stroke produce immense health and economic burdens in the United States and globally. The Update also presents the latest data on a range of major clinical heart and circulatory disease conditions (including stroke, congenital heart disease, rhythm disorders, subclinical atherosclerosis, coronary heart disease [CHD], heart failure [HF], valvular disease, venous disease, and peripheral artery disease) and the associated outcomes (including quality of care, procedures, and economic costs). Since 2007, the annual versions of the Statistical Update have been cited >20 000 times in the literature. From January to July 2017 alone, the 2017 Statistical Update was accessed >106 500 times. Each annual version of the Statistical Update undergoes revisions to include the newest nationally representative data, add additional relevant published scientific findings, remove older information, add new sections or chapters, and increase the number of ways to access and use the assembled information. This year-long process, which begins as soon as the previous Statistical Update is published, is performed by the AHA Statistics Committee faculty volunteers and staff and government agency partners. This year's edition includes new data on the monitoring and benefits of cardiovascular health in the population, new metrics to assess and monitor healthy diets, new information on stroke in young adults, an enhanced focus on underserved and minority populations, a substantively expanded focus on the global burden of CVD, and further evidence-based approaches to changing behaviors, implementation strategies, and implications of the AHA's 2020 Impact Goals. Below are a few highlights from this year's Update.
Purpose:
To determine if minimum recommended moderate-to-vigorous physical activity (MVPA; 30-min bout of continuous moderate-intensity walking) is sufficient to counteract the detrimental effects of prolonged sitting on postprandial metabolism and if there are any effects of breaking up sitting with intermittent standing when achieving minimum recommended MVPA.
Methods:
Fourteen (n=14) physically inactive healthy adult males underwent four intra-hospital 27-h interventions: 9-h continuous sitting (SIT); 15-min standing bouts every 30 min during the 9-h sitting (STAND); 30-min moderate-intensity walking bout followed by 8.5 h of sitting (MVPA); 30-min moderate-intensity walking bout followed by 15-min standing bouts every 30 min during 8.5 h of sitting (MVPA+STAND). Three standardized meals on intervention day (Day-1) and breakfast the following day (Day-2) were served.
Results:
Cumulative postprandial glucose response (incremental area under the curve) was lower in STAND vs. SIT (↓27%, p=0.04, effect size [ES]=-0.7) due to decreases in postprandial glucose after breakfast on Day-1 (STAND vs. SIT: ↓40%, p=0.01, ES=-0.7) and Day-2 (STAND vs. SIT: ↓33%, p=0.06, ES=-0.6). STAND did not impact postprandial insulin responses. Cumulative postprandial insulin response was lower in MVPA vs. SIT (↓18%, p=0.03, ES=-0.3) and MVPA+STAND vs. SIT (↓26%, p=0.02, ES=-0.4) due to expected exercise-induced decreases in postprandial insulin after breakfast on Day-1 only (MVPA vs. SIT: ↓36%, p=0.003, ES=-0.7; MVPA+STAND vs. SIT: ↓43%, p=0.0001, ES=-0.8).
Conclusion:
Breaking up prolonged sitting with non-ambulatory standing across 9 h acutely reduced postprandial glycemic response during and the day following the intervention independent of insulin levels whereas a 30-min MVPA bout did not.
The interaction of prolonged sitting with physical exercise for maintaining health is unclear. We tested the hypothesis that prolonged siting would have a deleterious effect on postprandial plasma lipemia (PPL, postprandial plasma triglycerides) and abolish the ability of an acute exercise bout to attenuate PPL. Seven healthy young men performed three interventions over 5 days (D1-5) in a randomized crossover design with > 1 week between interventions: 1) sitting >14h/d with hypercaloric energy balance (SH), 2) sitting >14h/d with net energy balance (SB), and 3) active walking/standing with net energy balance (WB) and sitting 8.4 h/d. The first high fat tolerance test (HFTT1) was performed on D3 following 2 days of respective interventions. On the evening of D4 subjects ran on a treadmill for 1-h at ~ 67% VO2max, followed by the second HFTT (HFTT2) on D5. Two days of prolonged sitting increased TG AUCI (i.e., incremental area under the curve for TG), irrespective of energy balance, compared to WB (27% in SH, p=0.003 and 26% in SB, p=0.046). Surprisingly, after four days of prolonged sitting (i.e.; SH and SB), the acute exercise on D4 failed to attenuate TG AUCI or increase relative fat oxidation in HFTT2, compared to HFTT1, independent of energy balance. In conclusion, prolonged sitting over several days was sufficient to amplify PPL and to abolish the beneficial effect of acute exercise on lowering PPL and raising fat oxidation, regardless of energy balance. This underscores the importance of limiting sitting time even in people who have exercised.
Background:
High amounts of sedentary behaviour have been associated with increased risks of several chronic conditions and mortality. However, it is unclear whether physical activity attenuates or even eliminates the detrimental effects of prolonged sitting. We examined the associations of sedentary behaviour and physical activity with all-cause mortality.
Methods:
We did a systematic review, searching six databases (PubMed, PsycINFO, Embase, Web of Science, Sport Discus, and Scopus) from database inception until October, 2015, for prospective cohort studies that had individual level exposure and outcome data, provided data on both daily sitting or TV-viewing time and physical activity, and reported effect estimates for all-cause mortality, cardiovascular disease mortality, or breast, colon, and colorectal cancer mortality. We included data from 16 studies, of which 14 were identified through a systematic review and two were additional unpublished studies where pertinent data were available. All study data were analysed according to a harmonised protocol, which categorised reported daily sitting time and TV-viewing time into four standardised groups each, and physical activity into quartiles (in metabolic equivalent of task [MET]-hours per week). We then combined data across all studies to analyse the association of daily sitting time and physical activity with all-cause mortality, and estimated summary hazard ratios using Cox regression. We repeated these analyses using TV-viewing time instead of daily sitting time.
Findings:
Of the 16 studies included in the meta-analysis, 13 studies provided data on sitting time and all-cause mortality. These studies included 1 005 791 individuals who were followed up for 2-18·1 years, during which 84 609 (8·4%) died. Compared with the referent group (ie, those sitting <4 h/day and in the most active quartile [>35·5 MET-h per week]), mortality rates during follow-up were 12-59% higher in the two lowest quartiles of physical activity (from HR=1·12, 95% CI 1·08-1·16, for the second lowest quartile of physical activity [<16 MET-h per week] and sitting <4 h/day; to HR=1·59, 1·52-1·66, for the lowest quartile of physical activity [<2·5 MET-h per week] and sitting >8 h/day). Daily sitting time was not associated with increased all-cause mortality in those in the most active quartile of physical activity. Compared with the referent (<4 h of sitting per day and highest quartile of physical activity [>35·5 MET-h per week]), there was no increased risk of mortality during follow-up in those who sat for more than 8 h/day but who also reported >35·5 MET-h per week of activity (HR=1·04; 95% CI 0·99-1·10). By contrast, those who sat the least (<4 h/day) and were in the lowest activity quartile (<2·5 MET-h per week) had a significantly increased risk of dying during follow-up (HR=1·27, 95% CI 1·22-1·31). Six studies had data on TV-viewing time (N=465 450; 43 740 deaths). Watching TV for 3 h or more per day was associated with increased mortality regardless of physical activity, except in the most active quartile, where mortality was significantly increased only in people who watched TV for 5 h/day or more (HR=1·16, 1·05-1·28).
Interpretation:
High levels of moderate intensity physical activity (ie, about 60-75 min per day) seem to eliminate the increased risk of death associated with high sitting time. However, this high activity level attenuates, but does not eliminate the increased risk associated with high TV-viewing time. These results provide further evidence on the benefits of physical activity, particularly in societies where increasing numbers of people have to sit for long hours for work and may also inform future public health recommendations.
Funding:
None.
Introducing the Fifth Edition of the more focused version of the best-selling Exercise Physiology text. Ideal for an introductory course, this title emphasizes nutrition as the foundation of exercise and uses a new student-friendly magazine-style design, hallmark pedagogy, and an engaging, accessible writing style to make exercise physiology interesting and understandable for todays students. Featuring updates in every section that reflect the latest trends and research in the field, Essentials of Exercise Physiology helps students develop a deep understanding of the interrelationships among energy intake, energy transfer during exercise, and the related physiologic systems. As they progress through the book, students also master the how-tos of applying key concepts to enhance exercise training, athletic performance, and health. © 2016 Wolters Kluwer 2011 Lippincott Williams & Wilkins|Wolters Kluwer © 2006 and 2000 Lippincott Williams & Wilkins
Pedometers are simple and inexpensive body-worn motion sensors that are readily being used by researchers and practitioners to assess and motivate physical activity behaviours. Pedometer-determined physical activity indices are needed to guide their efforts. Therefore, the purpose of this article is to review the rationale and evidence for general pedometer-based indices for research and practice purposes. Specifically, we evaluate popular recommendations for steps/day and attempt to translate existing physical activity guidelines into steps/day equivalents. Also, we appraise the fragmented evidence currently available from associations derived from cross-sectional studies and a limited number of interventions that have documented improvements (primarily in body composition and/or blood pressure) with increased steps/day. A value of 10 000 steps/day is gaining popularity with the media and in practice and can be traced to Japanese walking clubs and a business slogan 30+ years ago. 10 000 steps/day appears to be a reasonable estimate of daily activity for apparently healthy adults and studies are emerging documenting the health benefits of attaining similar levels. Preliminary evidence suggests that a goal of 10 000 steps/day may not be sustainable for some groups, including older adults and those living with chronic diseases. Another concern about using 10 000 steps/day as a universal step goal is that it is probably too low for children, an important target population in the war against obesity. Other approaches to pedometer-determined physical activity recommendations that are showing promise of health benefit and individual sustainability have been based on incremental improvements relative to baseline values. Based on currently available evidence, we propose the following preliminary indices be used to classify pedometer-determined physical activity in healthy adults: (i) 12 500 steps/day are likely to be classified as ‘highly active’.
Background:
The magnitude, consistency, and manner of association between sedentary time and outcomes independent of physical activity remain unclear.
Purpose:
To quantify the association between sedentary time and hospitalizations, all-cause mortality, cardiovascular disease, diabetes, and cancer in adults independent of physical activity.
Data sources:
English-language studies in MEDLINE, PubMed, EMBASE, CINAHL, Cochrane Library, Web of Knowledge, and Google Scholar databases were searched through August 2014 with hand-searching of in-text citations and no publication date limitations.
Study selection:
Studies assessing sedentary behavior in adults, adjusted for physical activity and correlated to at least 1 outcome.
Data extraction:
Two independent reviewers performed data abstraction and quality assessment, and a third reviewer resolved inconsistencies.
Data synthesis:
Forty-seven articles met our eligibility criteria. Meta-analyses were performed on outcomes for cardiovascular disease and diabetes (14 studies), cancer (14 studies), and all-cause mortality (13 studies). Prospective cohort designs were used in all but 3 studies; sedentary times were quantified using self-report in all but 1 study. Significant hazard ratio (HR) associations were found with all-cause mortality (HR, 1.240 [95% CI, 1.090 to 1.410]), cardiovascular disease mortality (HR, 1.179 [CI, 1.106 to 1.257]), cardiovascular disease incidence (HR, 1.143 [CI, 1.002 to 1.729]), cancer mortality (HR, 1.173 [CI, 1.108 to 1.242]), cancer incidence (HR, 1.130 [CI, 1.053 to 1.213]), and type 2 diabetes incidence (HR, 1.910 [CI, 1.642 to 2.222]). Hazard ratios associated with sedentary time and outcomes were generally more pronounced at lower levels of physical activity than at higher levels.
Limitation:
There was marked heterogeneity in research designs and the assessment of sedentary time and physical activity.
Conclusion:
Prolonged sedentary time was independently associated with deleterious health outcomes regardless of physical activity.
Primary funding source:
None.
The postprandial elevation of triglycerides in the blood (PPTG) is an independent risk factor for atherosclerosis. Although acute exercise typically attenuates PPTG, the effect of exercise intensity on PPTG is less well-established, particularly in well-controlled conditions for physical activities and diet.
We sought to determine the efficacy of exercise at 65% VO2max with an extended sitting time and isoenergetic intermittent walking exercise at a self-selected walking speed (~ 25% VO2max) on PPTG, compared to a sitting control condition. In a randomized crossover design, nine healthy young men completed 3 trials with > 1 week interval between trials. Following 2 days of activity and diet normalization, participants performed prolonged sitting non-exercise control (CON), prolonged sitting with subsequent 1-h running at 65% VO2max (MOD), or isoenergetic intermittent walking at ~ 25% VO2max (LOW) on day 3. This was followed on Day 4 by a 6-h high fat tolerance test.
MOD and LOW reduced incremental TG area under the curve (TG AUCI), compared to CON by 33.6% (p < 0.005) and 19.8% (p < 0.05), respectively. MOD also reduced TG AUCI, compared to LOW by 17.2% (p < 0.03). The reduced TG AUC I in MOD was accompanied by reduced plasma glucose response and enhanced fat oxidation, compared to LOW and CON (for all, p < 0.05), respectively.
Both MOD and LOW were effective in reducing PPTG, compared to CON. However MOD was more effective in reducing PPTG, compared to LOW.
Acute exercise has been shown to attenuate postprandial plasma triglyceride elevation (PPTG); however the direct contribution of exercise intensity is less well understood. The purpose of this study was to examine the effects of exercise intensity on PPTG and postprandial fat oxidation. Healthy, young men (n=6) performed one of three experimental treatments: non-exercise control (CON), moderate-intensity (MIE; 50% VO(2 peak) for 60 min), or isoenergetic high-intensity exercise (HIE; alternating 2 min at 25% and 2 min at 90% VO(2 peak)). The morning after the exercise, a standardized meal was provided (16 kcal/kg BM; 1.02 g fat/kg, 1.36 g CHO/kg, 0.31 g PRO/kg) and measurements of plasma concentrations of triglyceride (TG), glucose, insulin and β-hydroxybutyrate were made in the fasted condition and hourly for 6 h postprandial. Indirect calorimetry was used to determine fat oxidation in the fasted condition and 2, 4 and 6 h postprandial. Compared to CON, both MIE and HIE significantly attenuated PPTG (Incremental AUC) [75.2 (15.5) %, p = 0.033 and 54.9 (13.5) %, p = 0.001], with HIE also significantly lower than MIE (p = 0.03). Postprandial fat oxidation was significantly higher in MIE [83.3 (10.6) % of total energy expenditure) and HIE (89.1 (9.8) % of total] compared to CON [69.0 (16.1) % of total; p = 0.039 and; p = 0.018, respectively], with HIE significantly greater than MIE (p = 0.012). We conclude that, despite similar energy expenditure, HIE was more effective than MIE for lowering PPTG and increasing postprandial fat oxidation.
Prolonged sitting is considered detrimental to health, but evidence regarding the independent relationship of total sitting time with all-cause mortality is limited. This study aimed to determine the independent relationship of sitting time with all-cause mortality.
We linked prospective questionnaire data from 222 497 individuals 45 years or older from the 45 and Up Study to mortality data from the New South Wales Registry of Births, Deaths, and Marriages (Australia) from February 1, 2006, through December 31, 2010. Cox proportional hazards models examined all-cause mortality in relation to sitting time, adjusting for potential confounders that included sex, age, education, urban/rural residence, physical activity, body mass index, smoking status, self-rated health, and disability.
During 621 695 person-years of follow-up (mean follow-up, 2.8 years), 5405 deaths were registered. All-cause mortality hazard ratios were 1.02 (95% CI, 0.95-1.09), 1.15 (1.06-1.25), and 1.40 (1.27-1.55) for 4 to less than 8, 8 to less than 11, and 11 or more h/d of sitting, respectively, compared with less than 4 h/d, adjusting for physical activity and other confounders. The population-attributable fraction for sitting was 6.9%. The association between sitting and all-cause mortality appeared consistent across the sexes, age groups, body mass index categories, and physical activity levels and across healthy participants compared with participants with preexisting cardiovascular disease or diabetes mellitus.
Prolonged sitting is a risk factor for all-cause mortality, independent of physical activity. Public health programs should focus on reducing sitting time in addition to increasing physical activity levels.
There is a lack of large-scale comparable data on the population levels of physical activity (PA) and sedentary activity. We conducted a cross-sectional population-based multicenter study to describe the levels of PA and sedentary activity and to determine adherence to current national PA recommendations in Norwegian adults and older people.
In 2008 and 2009, PA was assessed objectively for seven consecutive days using the ActiGraph GT1M accelerometer in 3867 participants age 20-85 yr. A total of 3267 participants provided valid PA assessments that met all inclusion criteria.
Women and men did not differ in the overall activity levels (335 and 342 counts per minute, respectively) or in steps per day (8113 and 7951 steps per day, respectively). However, for intensity-specific PA, men accumulated significantly more minutes of sedentary activity and moderate-to-vigorous PA (MVPA) compared with women (557 vs 533 min of sedentary activity, P ≤ 0.001 and 35 vs 33 min of MVPA, P = 0.01). Both overall activity levels and steps per day remained steady with age, until 65 yr, after which activity levels declined.
Overall, the study sample spent 62% of their time being sedentary, 25% in low-intensity PA, 9% in lifestyle activity, and 4% in MVPA. One in five people met current national PA recommendations. These results suggest that adults and older people spend the majority of their time being sedentary and that adherence to PA recommendations is low.
Lipoprotein lipase (LPL) is a multifunctional enzyme produced by many tissues, including adipose tissue, cardiac and skeletal muscle, islets, and macrophages. LPL is the rate-limiting enzyme for the hydrolysis of the triglyceride (TG) core of circulating TG-rich lipoproteins, chylomicrons, and very low-density lipoproteins (VLDL). LPL-catalyzed reaction products, fatty acids, and monoacylglycerol are in part taken up by the tissues locally and processed differentially; e.g., they are stored as neutral lipids in adipose tissue, oxidized, or stored in skeletal and cardiac muscle or as cholesteryl ester and TG in macrophages. LPL is regulated at transcriptional, posttranscriptional, and posttranslational levels in a tissue-specific manner. Nutrient states and hormonal levels all have divergent effects on the regulation of LPL, and a variety of proteins that interact with LPL to regulate its tissue-specific activity have also been identified. To examine this divergent regulation further, transgenic and knockout murine models of tissue-specific LPL expression have been developed. Mice with overexpression of LPL in skeletal muscle accumulate TG in muscle, develop insulin resistance, are protected from excessive weight gain, and increase their metabolic rate in the cold. Mice with LPL deletion in skeletal muscle have reduced TG accumulation and increased insulin action on glucose transport in muscle. Ultimately, this leads to increased lipid partitioning to other tissues, insulin resistance, and obesity. Mice with LPL deletion in the heart develop hypertriglyceridemia and cardiac dysfunction. The fact that the heart depends increasingly on glucose implies that free fatty acids are not a sufficient fuel for optimal cardiac function. Overall, LPL is a fascinating enzyme that contributes in a pronounced way to normal lipoprotein metabolism, tissue-specific substrate delivery and utilization, and the many aspects of obesity and other metabolic disorders that relate to energy balance, insulin action, and body weight regulation.
The treatment of elevated levels of low-density lipoprotein cholesterol is standard medical practice supported by conclusive outcome data. Less definitive information exists for hypertriglyceridemia. Only in the setting of severe hyperchylomicronemia is the benefit of triglyceride lowering clear: it is a means to reduce the risk of pancreatitis. The relationship of triglycerides and cardiovascular disease is still unclear. Moreover, the cardiovascular benefits of reducing triglycerides and of using triglyceride-lowering medications remain unproved. Nonetheless it has become almost standard to reduce the levels of triglyceride-rich lipoproteins that are a major component of plasma non-high-density lipoprotein cholesterol.
The hypothesis that plasma chylomicrons in persons who ingest a cholesterol-rich diet are atherogenic is evaluated. Evidence is presented that in humans, and experimental animals, chylomicron remnants as well as low-density lipoproteins are taken up by arterial cells. In persons who do not have familial hyperlipoproteinemia, atherogenesis may occur during the postprandial period. Research directions that may contribute to the evaluation of chylomicron remnants as a risk factor for atherogenesis are discussed. Lipoprotein studies after administration of a test meal containing fat and cholesterol are urgently needed.
We studied physical fitness and risk of all-cause and cause-specific mortality in 10,224 men and 3120 women who were given a preventive medical examination. Physical fitness was measured by a maximal treadmill exercise test. Average follow-up was slightly more than 8 years, for a total of 110,482 person-years of observation. There were 240 deaths in men and 43 deaths in women. Age-adjusted all-cause mortality rates declined across physical fitness quintiles from 64.0 per 10,000 person-years in the least-fit men to 18.6 per 10,000 person-years in the most-fit men (slope, -4.5). Corresponding values for women were 39.5 per 10,000 person-years to 8.5 per 10,000 person-years (slope, -5.5). These trends remained after statistical adjustment for age, smoking habit, cholesterol level, systolic blood pressure, fasting blood glucose level, parental history of coronary heart disease, and follow-up interval. Lower mortality rates in higher fitness categories also were seen for cardiovascular disease and cancer of combined sites. Attributable risk estimates for all-cause mortality indicated that low physical fitness was an important risk factor in both men and women. Higher levels of physical fitness appear to delay all-cause mortality primarily due to lowered rates of cardiovascular disease and cancer.
We investigated the acute effects of prolonged exercise on lipoprotein metabolism. Serum lipid and lipoprotein concentrations and plasma postheparin lipolytic activity were measured in ten well-trained men (ages 21 to 39) the day before and after a 42 km foot race. LDL cholesterol decreased by 10% (113 +/- 31 to 103 +/- 32 mg/dL, P less than 0.01) and total HDL-cholesterol levels increased by 9% (65 +/- 18 to 71 +/- 19 mg/dL, P less than 0.01) the day after the race. No changes in the concentration of apolipoprotein A-I or A-II occurred. Triglyceride levels decreased by 39% (95 +/- 38 to 58 +/- 23 mg/dL, P less than 0.001). Two days after the race, total HDL cholesterol (74 +/- 21 mg/dL, P less than 0.05) and the HDL2 subfraction (37 +/- 19 mg/dL, P less than 0.05) remained significantly elevated compared to pre-race values. Most dramatically, the level of lipoprotein lipase activity measured in postheparin plasma nearly doubled after the race, demonstrating that vigorous exercise acutely increases this enzyme activity. The increase in lipoprotein lipase activity probably mediated the fall in serum triglycerides after exercise and may also account for the increase in HDL cholesterol.
Previous studies have shown that when exercise is stopped there is a rapid reversal of the training-induced adaptive increase in muscle glucose transport capacity. Endurance exercise training brings about an increase in GLUT-4 in skeletal muscle. The primary purpose of this study was to determine whether the rapid reversal of the increase in maximally insulin-stimulated glucose transport after cessation of training can be explained by a similarly rapid decrease in GLUT-4. A second purpose was to evaluate the possibility, suggested by previous studies, that the magnitude of the adaptive increase in muscle GLUT-4 decreases when exercise training is extended beyond a few days. We found that both GLUT-4 and maximally insulin-stimulated glucose transport were increased approximately twofold in epitrochlearis muscles of rats trained by swimming for 6 h/day for 5 days or 5 wk. GLUT-4 was 90% higher, citrate synthase activity was 23% higher, and hexokinase activity was 28% higher in triceps muscle of the 5-day trained animals compared with the controls. The increases in GLUT-4 protein and in insulin-stimulated glucose transport were completely reversed within 40 h after the last exercise bout, after both 5 days and 5 wk of training. In contrast, the increases in citrate synthase and hexokinase activities were unchanged 40 h after 5 days of exercise. These results support the conclusion that the rapid reversal of the increase in the insulin responsiveness of muscle glucose transport after cessation of training is explained by the short half-life of the GLUT-4 protein.
The purpose of the study was to examine the effect of exercise timing on postprandial lipemia responses. Subjects were 21 recreationally trained men (ages 27 +/- 1.7 yr). Each subject performed four trials: 1) Control (fat meal only), 2) Post (exercise 1 h after a fat meal), 3) 1 h-Pre (exercise 1 h before a fat meal), and 4) 12 h-Pre (exercise 12 h before a fat meal). In each trial, subjects had a standard fat meal to induce postprandial hypertriglyceridemia. Blood samples were taken at 0 h (immediately before the fat meal) and at 2, 4, 6, 8, and 24 h after the meal. In the exercise trials, each subject exercised at 60% of maximal O2 consumption for 1 h. The results indicated that triglyceride area under the curve scores in premeal-exercise trials were lower (P < 0. 05) than those in Post and Control. At 24 h, total high-density lipoprotein (HDL)-cholesterol in the premeal-exercise trials was higher (P < 0.05) than that at 0 h, whereas total HDL-cholesterol was not changed in Control and Post. At 24 h, HDL subtype 2-cholesterol was higher (P < 0.05) in the premeal-exercise trials than in Control, which did not differ from Post. These results suggest that exercising before a fat meal may have a beneficial effect on the triglyceride response and HDL metabolism, which may blunt atherosclerotic process induced by the fat meal.
The intestine synthesizes very low density lipoproteins (VLDL) and chylomicrons (CM) to transport fat and fat-soluble vitamins into the blood. VLDL assembly occurs constitutively whereas CM assembly is a characteristic property of the enterocytes during the postprandial state. The secretion of CM is specifically inhibited by Pluronic L81. CM are very heterogeneously-sized particles that consist of a core of triglycerides (TG) and cholesterol esters and a monolayer of phospholipids (PL), cholesterol and proteins. The fatty acid composition of TG, but not PL, in CM mirrors the fatty acid composition of fat in the diet. CM assembly is deficient in abetalipoproteinemia and CM retention disease. Abetalipoproteinemia results due to mutation in the mttp gene and is characterized by the virtual absence of apoB-containing lipoproteins in the plasma. Patients suffer from neurologic disorders, visual impairment, and exhibit acanthocytosis. CM retention disease, an inherited recessive disorder, is characterized by chronic diarrhea with steatorrhea in infancy, abdominal distention and failure to thrive. It is caused by a specific defect in the secretion of intestinal lipoproteins; secretion of lipoproteins by the liver is not affected. Besides human disorders, mice that do not assemble intestinal lipoproteins have been developed. These mice are normal at birth, but defective in fat and fat-soluble vitamin absorption, and fail to thrive. Thus, fat and fat-soluble vitamin transport by the intestinal lipoproteins is essential for proper growth and development of neonates. Recently, differentiated Caco-2 cells and rabbit primary enterocytes have been described that synthesize and secrete CM. These cells can be valuable in distinguishing between the two different models proposed for the assembly of CM. In the first model, the assembly of VLDL and CM is proposed to occur by two 'independent' pathways. Second, CM assembly is proposed to be a product of 'core expansion' that results in the synthesis of lipoproteins of different sizes. According to this model, intestinal lipoprotein assembly begins with the synthesis of 'primordial' lipoprotein particles and involves release of the nascent apoB with PL derived from the endoplasmic reticulum (ER) membrane. In addition, TG-rich 'lipid droplets' of different sizes are formed independent of apoB synthesis. The fusion of lipid droplets and primordial lipoproteins results in the formation of different size lipoproteins due to the 'core expansion' of the primordial lipoproteins.
Prior exercise decreases postprandial plasma triacylglycerol (TG) concentrations, possibly through changes to skeletal muscle TG extraction. We measured postprandial substrate extraction across the leg in eight normolipidemic men aged 21-46 yr. On the afternoon preceding one trial, subjects ran for 2 h at 64 +/- 1% of maximal oxygen uptake (exercise); before the control trial, subjects had refrained from exercise. Samples of femoral arterial and venous blood were obtained, and leg blood flow was measured in the fasting state and for 6 h after a meal (1.2 g fat, 1.2 g carbohydrate/kg body mass). Prior exercise increased time averaged postprandial TG clearance across the leg (total TG: control, 0.079 +/- 0.014 ml.100 ml tissue(-1).min(-1) ; exercise, 0.158 +/- 0.023 ml.100 ml tissue(-1).min(-1), P <0.01), particularly in the chylomicron fraction, so that absolute TG uptake was maintained despite lower plasma TG concentrations (control, 1.53 +/- 0.13 mmol/l; exercise, 1.01 +/- 0.16 mmol/l, P < 0.001). Prior exercise increased postprandial leg blood flow and glucose uptake (both P < 0.05). Mechanisms other than increased leg TG uptake must account for the effect of prior exercise on postprandial lipemia.
One mechanism by which prior exercise decreases the plasma triacylglycerol (TG) response to dietary fat may involve enhanced clearance of TG-rich lipoproteins. The purpose of the present study was to examine the influence of moderate intensity exercise on postprandial lipemia and muscle lipoprotein lipase (LPL) activity. Eight physically active, normolipidemic men aged 27.0 years (SD 4.2), body mass index 24.5 kg. m(-2) (SD 1.3), participated in 2 oral fat-tolerance tests with different preceding conditions. The afternoon before one test ( approximately 16 hours), subjects cycled for 90 minutes at 62.3% (SD 1.7%) of maximal oxygen uptake. Before the other test, subjects refrained from exercise. Samples of muscle, venous blood, and expired air were obtained in the fasted state. Subjects then consumed a high-fat meal (1.4 g fat, 1.2 g carbohydrate, 0.2 g protein, 73 kJ energy per kg body mass) before further blood and expired air samples were collected until 6 hours. The 6-hour areas under the TG concentration v time curves for plasma and for the chylomicron-rich fraction were lower (P <.05) after exercise (plasma, 7.91 [SE 1.09] v 5.72 [SE 0.47] mmol. L(-1). h; chylomicron-rich fraction, 1.98 [SE 0.51] v 0.92 [SE 0.16] mmol. L(-1). h). Muscle LPL activity was not significantly influenced by prior exercise, but the 4 subjects who had higher muscle LPL activity after exercise also had the most noticeable decreases in postprandial lipemia. The difference in lipemia between trials was inversely related to the difference in LPL activity (rho = -.79, P <.05). In the fasted state and postprandially, carbohydrate oxidation was lower after exercise (P <.05). Thus moderate exercise attenuates postprandial lipemia, possibly by altering muscle LPL activity.
We have examined the regulation of lipoprotein lipase (LPL) activity in skeletal muscle during physical inactivity in comparison to low-intensity contractile activity of ambulatory controls. From studies acutely preventing ambulatory activity of one or both the hindlimbs in rats, it was shown that approximately 90-95 % of the heparin-releasable (HR) LPL activity normally present in rat muscle with ambulatory activity is lost, and thus dependent on local contractile activity. Similarly, approximately 95 % of the differences in LPL activity between muscles of different fibre types was dependent on ambulatory activity. The robustness of the finding that physical inactivity significantly decreases muscle LPL activity was evident from confirmatory studies with different models of inactivity, in many rats and mice, both sexes, three muscle types and during both acute and chronic (11 days) treatment. Inactivity caused a local reduction of plasma [3H]triglyceride uptake into muscle and a decrease in high density lipoprotein cholesterol concentration. LPL mRNA was not differentially expressed between ambulatory controls and either the acutely or chronically inactive groups. Instead, the process involved a rapid loss of the HR-LPL protein mass (the portion of LPL largely associated with the vascular endothelium) by an actinomycin D-sensitive signalling mechanism (i.e. transcriptionally dependent process). Significant decreases of intracellular LPL protein content lagged behind the loss of HR-LPL protein. Treadmill walking raised LPL activity approximately 8-fold (P < 0.01) within 4 h after inactivity. The striking sensitivity of muscle LPL to inactivity and low-intensity contractile activity may provide one piece of the puzzle for why inactivity is a risk factor for metabolic diseases and why even non-vigorous activity provides marked protection against disorders involving poor lipid metabolism.
Increased plasma levels of triglycerides (TG) in very low density lipoproteins (VLDL) are not only common characteristics of the dyslipidemia associated with insulin resistance and type 2 diabetes mellitus (T2DM) but are the central pathophysiologic feature of the abnormal lipid profile. Overproduction of VLDL leads to increased plasma levels of TG which, via an exchange process mediated by cholesterol ester transfer protein (CETP), results in low levels of high density lipoprotein (HDL) cholesterol and apolipoprotein A-I, and the generation of small, dense, cholesterol ester depleted low density lipoproteins (LDL). Increased assembly and secretion of VLDL by the liver results from the complex, post-transcriptional regulation of apolipoprotein B (apoB) metabolism in the liver. In the presence of low levels of hepatic TG and cholesterol, much of the constitutively synthesized apoB is degraded by both proteasomal and non-proteasomal pathways. When excess TG, and to a lesser extent, cholesterol, are present, and in the presence of active microsomal triglycerides transfer protein, apoB is targeted for secretion. The major sources of TG in the liver: uptake of fatty acids (FA) released by lipolysis of adipose tissue TG, uptake of TGFA in VLDL and chylomicrons remnants, and hepatic de novo lipogenesis (the synthesis of FA from glucose) are all abnormally increased in insulin resistance. Treatment of the dyslipidemia in insulin resistant individuals and patients with T2DM has been successful in reducing cardiovascular disease; LDL cholesterol, TG, and HDL cholesterol are all appropriate targets for therapy when diet, exercise, and weight loss do not achieve goals.
Exercise/muscle contraction activates glucose transport. The increase in muscle glucose transport induced by exercise is independent of insulin. As the acute effect of exercise on glucose transport wears off, it is replaced by an increase in insulin sensitivity. An increase in insulin sensitivity results in a shift in the insulin dose-response curve to the left, with a decrease in the concentration of insulin needed to induce 50% of the maximal response. This phenomenon, which plays a major role in rapid muscle glycogen accumulation after exercise, is not mediated by amplification of the insulin signal. Development of the increase in insulin sensitivity after contractions does not require protein synthesis or activation of p38 MAPK. It does require the presence of a serum protein during the period of contractile activity. The effect of exercise on muscle insulin sensitivity is mimicked by hypoxia and by treatment of muscles with 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside to activate AMP-activated protein kinase. The postexercise increase in sensitivity of muscle glucose transport to activation is not specific for insulin but also involves an increased susceptibility to activation by a submaximal contraction/hypoxia stimulus. The increase in insulin sensitivity is mediated by translocation of more GLUT4 glucose transporters to the cell surface in response to a submaximal insulin stimulus. Although the postexercise increase in muscle insulin sensitivity has been characterized in considerable detail, the basic mechanisms underlying this phenomenon remain a mystery.
Physical inactivity is a risk factor for lipoprotein disorders and the metabolic syndrome. Physical inactivity has a powerful effect on suppressing lipoprotein lipase (LPL) activity in skeletal muscle, the rate-limiting enzyme for hydrolysis of triglyceride (TG)-rich lipoproteins. We tested the ability of several compounds to prevent the decrease in LPL. The present study minimized standing and ordinary light nonexercise movements in rats to compare the effects of inactivity and nonexercise activity thermogenesis (NEAT) on LPL activity. The key new insight was that the typically quick decrease in LPL activity of oxidative muscle caused by physical inactivity was prevented by nicotinic acid (NA), whereas inhibitors of TNF-alpha, inducible nitric oxide synthase, and NF-kappaB had no such effect. NA was administered at a dose known to acutely impede the appearance of plasma TG from the liver and free fatty acids from adipose tissue, and it was effective at intentionally lowering plasma lipid concentrations to the same level in active and inactive groups. As measured from heparin-releasable LPL activity, LPL in the microvasculature of the most oxidative muscles was approximately 90% lower in the inactive group compared with controls, and this suppression was completely blocked by NA. In contrast to inactivity, NA did not raise muscle LPL in ambulatory controls, whereas a large exogenous fat delivery did decrease LPL activity. In vitro control studies revealed that NA did not have a direct effect on skeletal muscle LPL activity. In conclusion, physical inactivity amplifies the ability of plasma lipids to suppress muscle LPL activity. The light ambulatory contractions responsible for NEAT are sufficient for mitigating these deleterious effects.
To examine the influence of exercise intensity on the increases in vastus lateralis GLUT4 mRNA and protein after exercise, six untrained men exercised for 60 min at 39 +/- 3% peak oxygen consumption (V(O2 peak)) (Lo) or 27 +/- 2 min at 83 +/- 2% V(O2 peak) (Hi) in counterbalanced order. Preexercise muscle glycogen levels were not different between trials (Lo: 408 +/- 35 mmol/kg dry mass; Hi: 420 +/- 43 mmol/kg dry mass); however, postexercise levels were lower (P < 0.05) in Hi (169 +/- 18 mmol/kg dry mass) compared with Lo (262 +/- 35 mmol/kg dry mass). Thus calculated muscle glycogen utilization was greater (P < 0.05) in Hi (251 +/- 24 mmol/kg) than in Lo (146 +/- 34). Exercise resulted in similar increases in GLUT4 gene expression in both trials. GLUT4 mRNA was increased immediately at the end of exercise (approximately 2-fold; P < 0.05) and remained elevated after 3 h of postexercise recovery. When measured 3 h after exercise, total crude membrane GLUT4 protein levels were 106% higher in Lo (3.3 +/- 0.7 vs. 1.6 +/- 0.3 arbitrary units) and 61% higher in Hi (2.9 +/- 0.5 vs. 1.8 +/- 0.5 arbitrary units) relative to preexercise levels. A main effect for exercise was observed, with no significant differences between trials. In conclusion, exercise at approximately 40 and approximately 80% V(O2 peak), with total work equal, increased GLUT4 mRNA and GLUT4 protein in human skeletal muscle to a similar extent, despite differences in exercise intensity and duration.
Dyslipidemia, manifested by increased plasma triglyceride (TG), increased total and LDL-cholesterol concentrations and decreased HDL-cholesterol concentration, is an important risk factor for cardiovascular disease. Premenopausal women have a less atherogenic plasma lipid profile and a lower risk of cardiovascular disease than men, but this female advantage disappears after menopause. This suggests that female sex steroids affect lipoprotein metabolism. The impact of variations in the availability of ovarian hormones during the menstrual cycle on lipoprotein metabolism is not known. We therefore investigated whether very-low-density lipoprotein (VLDL)-TG and VLDL-apolipoprotein B-100 (apoB-100) kinetics are different during the follicular (FP) and luteal phases (LP) of the menstrual cycle. We studied seven healthy, premenopausal women (age 27 +/- 2 yr, BMI 25 +/- 2 kg/m(2)) once during FP and once during LP. We measured VLDL-TG, VLDL-apoB-100, and plasma free fatty acid (FFA) kinetics by using stable isotope-labeled tracers, VLDL subclass profile by nuclear magnetic resonance spectroscopy, whole body fat oxidation by indirect calorimetry, and the plasma concentrations of lipoprotein lipase (LPL) and hepatic lipase (HL) by ELISA. VLDL-TG and VLDL-apoB-100 concentrations in plasma, VLDL-TG and VLDL-apoB-100 secretion rates and mean residence times, VLDL subclass distribution, FFA concentration and rate of appearance in plasma, whole body substrate oxidation, and LPL and HL concentrations in plasma were not different during the FP and the LP. We conclude that VLDL-TG and VLDL-apoB-100 metabolism is not affected by menstrual cycle phase.
It is not uncommon for people to spend one-half of their waking day sitting, with relatively idle muscles. The other half of the day includes the often large volume of nonexercise physical activity. Given the increasing pace of technological change in domestic, community, and workplace environments, modern humans may still not have reached the historical pinnacle of physical inactivity, even in cohorts where people already do not perform exercise. Our purpose here is to examine the role of sedentary behaviors, especially sitting, on mortality, cardiovascular disease, type 2 diabetes, metabolic syndrome risk factors, and obesity. Recent observational epidemiological studies strongly suggest that daily sitting time or low nonexercise activity levels may have a significant direct relationship with each of these medical concerns. There is now a need for studies to differentiate between the potentially unique molecular, physiologic, and clinical effects of too much sitting (inactivity physiology) separate from the responses caused by structured exercise (exercise physiology). In theory, this may be in part because nonexercise activity thermogenesis is generally a much greater component of total energy expenditure than exercise or because any type of brief, yet frequent, muscular contraction throughout the day may be necessary to short-circuit unhealthy molecular signals causing metabolic diseases. One of the first series of controlled laboratory studies providing translational evidence for a molecular reason to maintain high levels of daily low-intensity and intermittent activity came from examinations of the cellular regulation of skeletal muscle lipoprotein lipase (LPL) (a protein important for controlling plasma triglyceride catabolism, HDL cholesterol, and other metabolic risk factors). Experimentally reducing normal spontaneous standing and ambulatory time had a much greater effect on LPL regulation than adding vigorous exercise training on top of the normal level of nonexercise activity. Those studies also found that inactivity initiated unique cellular processes that were qualitatively different from the exercise responses. In summary, there is an emergence of inactivity physiology studies. These are beginning to raise a new concern with potentially major clinical and public health significance: the average nonexercising person may become even more metabolically unfit in the coming years if they sit too much, thereby limiting the normally high volume of intermittent nonexercise physical activity in everyday life. Thus, if the inactivity physiology paradigm is proven to be true, the dire concern for the future may rest with growing numbers of people unaware of the potential insidious dangers of sitting too much and who are not taking advantage of the benefits of maintaining nonexercise activity throughout much of the day.
The purpose of this study was to examine the effects of previous exercise on metabolic, hormonal, and endothelial responses to an oral fat-tolerance test (OFTT).
Twelve healthy, recreationally trained men (age = 22.3 +/- 2.5 yr, weight = 80.7 +/- 12.4 kg, BMI = 25.1 +/- 3.1 kg.m(-2)) volunteered for this study. In a crossover fashion, subjects completed three OFTT trials that involved no exercise (NoEx) or exercise performed 16 h (EX-16) or 4 h (EX-4) before the ingestion of a meal (13 kcal.kg(-1) and 1.4 g of fat per kilogram of body weight). Blood was collected before and after the meal and hourly for 6 h. Brachial artery reactivity was measured using ultrasound before and at 2, 4, and 6 h after the meal. Dietary intake and exercise were standardized 4 d before the OFTT. The exercise session consisted of six resistance exercises and 30 min of running on a treadmill. The washout period between trials was, on average, 5 d.
Compared with NoEx, there were significant (P < 0.05) decreases in triglyceride area under the curve (AUC) during EX-16 (-26%) and EX-4 (-15%). Compared with NoEx, there were decreases in insulin AUC during EX-16 (-7%, P < 0.05) and EX-4 (-5%, NS). EX-4 resulted in a significantly larger fasting arterial diameter than EX-16 and NoEx, but there were no other significant effects on endothelial function. Lipemic variables did not show correlations with endothelium function for any of the trials.
An acute exercise session, regardless of the time point chosen (i.e., EX-16 or EX-4), reduced to a similar extent the total and incremental lipemic responses compared with the NoEx condition.