Applied Physiology Nutrition and Metabolism

Published by Canadian Science Publishing

Online ISSN: 1715-5320


Print ISSN: 1715-5312


Standardized use of the terms “sedentary” and “sedentary behaviours”Sedentary Behaviour Research Network (SBRN)Appl Physiol Nutr Metab20123754054210.1139/h2012-02422540258
  • Article

April 2012


504 Reads

Mark Tremblay

Fig. 1. DXA whole-body and CT regional image analysis at 3rd lumbar vertebra (L3).  
Fig. 3. Regional DXA analysis of (A) fat mass (FM) and (B) fatfree mass (FFM) at the L3 region correlates with DXA analysis of whole-body FM and FFM (n = 50).  
Fig. 6. CT-based muscle analysis at L3 was strongly related to appendicular skeletal muscle mass measured with DXA (n = 31). DXAbased low muscle levels [males <7.26 kg/m 2 ; females <5.45 kg/m 2 (10)] generated corresponding CT values [males <55.4 cm 2 /m 2 and females <38.9 cm 2 /m 2 ].  
Mourtzakis M, Prado CM, Lieffers JR, Reiman T, McCargar LJ, Baracos VEA practical and precise approach to quantification of body composition in cancer patients using computed tomography images acquired during routine care. Appl Physiol Nutr Metab 33(5): 997-1006
  • Article
  • Full-text available

October 2008


3,854 Reads

Marina Mourtzakis


Carla M M Prado





Human body composition is important in numerous cancer research domains. Our objective was to evaluate clinically accessible methods to achieve practical and precise measures of body composition in cancer patients. Dual-energy X-ray absorptiometry (DXA)-based analysis of fat and fat-free mass was performed in 50 cancer patients and compared with bioelectrical impedance analysis (BIA) and with regional computed tomography (CT) images available in the patients' medical records. BIA overestimated or underestimated fat-free mass substantially compared with DXA as the method of reference (up to 9.3 kg difference). Significant changes in fat-free mass over time detected with DXA in a subset of 21 patients (+2.2 +/- 3.2%/100 days, p = 0.003), was beyond the limits of detection of BIA. Regional analysis of fat and fat-free tissue at the 3rd lumbar vertebra with either DXA or CT strongly predicted whole-body fat and fat-free mass (r = 0.86-0.94; p < 0.001). CT images provided detail on specific muscles, adipose tissues and organs, not provided by DXA or BIA. CT presents great practical significance due to the prevalence of these images in patient diagnosis and follow-up, thus marrying clinical accessibility with high precision to quantify specific tissues and to predict whole-body composition.

Physical activity, energy intake, and obesity prevalence among urban and rural schoolchildren aged 11-12 years in Japan

December 2012


97 Reads

The prevalence of childhood overweight and obesity has been shown to differ among regions, including rural-urban regional differences within nations. This study obtained simultaneous accelerometry-derived physical activity, 24 h activity, and food records to clarify the potential contributing factors to rural-urban differences in childhood overweight and obesity in Japan. Sixth-grade children (n = 227, 11-12 years old) from two urban elementary schools in Kyoto and four rural elementary schools in Tohoku participated in the study. The children were instructed to wear a pedometer that included a uniaxial accelerometer and, assisted by their parents, keep minute-by-minute 24 h activity and food records. For 12 children, the total energy expenditure was measured by the doubly labeled water method that was used to correct the Lifecorder-predicted activity energy expenditure and physical activity level. The overweight and obesity prevalence was significantly higher in rural than in urban children. The number of steps per day, activity energy expenditure, physical activity level, and duration of walking to school were significantly lower in rural than in urban children. In contrast, the reported energy intake did not differ significantly between the regions. The physical activity and duration of the walk to school were significantly correlated with body mass index. Rural children had a higher prevalence of overweight and obesity, and this may be at least partly caused by lower physical activity, especially less time spent walking to school, than urban children.

Fig. 1. Overview of study design. The order of interventions in weeks 2 and 3 was randomized and counterbalanced. 
Table 1 . Participant characteristics.
Fig. 2. Comparison of the highest and lowest quartile of mean off-task verbal behaviour on change in d2 test performance from no activity days to FUNterval days. A greater negative change is desirable for total errors (E), errors of commission (E Comm ), and % errors (E%), while a greater positive change is desirable for 
Table 2 . Regression R values of average off-task behaviour as a predictor of d2 test performance.
Fig. 3. Effects of FUNtervals on d2 test of attention outcomes. Comparison of FUNterval with no activity days in males and females on total number of items processed (A), errors of omission (B), errors of commission (C), and % errors (D). *, Significant ( p < 0.05) main effect of intervention. 
Four minutes of in-class high-intensity interval activity improves selective attention in 9- to 11-year olds

November 2014


5,460 Reads

The amount of time allocated to physical activity in schools is declining. Time-efficient physical activity solutions that demonstrate their impact on academic achievement-related outcomes are needed to prioritize physical activity within the school curricula. "FUNtervals" are 4-min, high-intensity interval activities that use whole-body actions to complement a storyline. The purpose of this study was to (i) explore whether FUNtervals can improve selective attention, an executive function posited to be essential for learning and academic success; and (ii) examine whether this relationship is predicted by students' classroom off-task behaviour. Seven grade 3-5 classes (n = 88) were exposed to a single-group, repeated cross-over design where each student's selective attention was compared between no-activity and FUNtervals days. In week 1, students were familiarized with the d2 test of attention and FUNterval activities, and baseline off-task behaviour was observed. In both weeks 2 and 3 students completed the d2 test of attention following either a FUNterval break or a no-activity break. The order of these breaks was randomized and counterbalanced between weeks. Neither motor nor passive off-task behaviour predicted changes in selective attention following FUNtervals; however, a weak relationship was observed for verbal off-task behaviour and improvements in d2 test performance. More importantly, students made fewer errors during the d2 test following FUNtervals. In supporting the priority of physical activity inclusion within schools, FUNtervals, a time efficient and easily implemented physical activity break, can improve selective attention in 9- to 11-year olds.

Fig. 1. Glucose infusion rate during a hyperinsulinemic-euglycemic (2 mUÁkg –1 Ámin –1 ) in rats fed water (placebo), caffeinated coffee, or decaffeinated coffee for 4 weeks in combination with a high-fat diet (60% kcal from fat). *, Significant differences (p < 0.05) between treatment groups at individual timepoints. Data represent means ± SE; n = 8 or 9 animals per treatment. Previously published data adapted from Shearer et al. (2007). Results show that decaffeinated coffee, but not caffeinated coffee, mitigates the effects of high-fat food on insulin sensitivity.  
Fig. 2. Blood glucose concentrations of rats after a meal tolerance test with or without chlorogenic acid (CGA) (120 mgÁkg –1 ; n = 8 for each treatment). *, Significant difference (p < 0.05) between treatment groups at individual timepoints. Data represent means ± SE. Significant difference (p < 0.05) also exists for area under the curve for CGA and placebo. Adapted from Tunnicliffe et al. (2008a). These results confirm that CGA may limit T2D by inhibiting intestinal glucose absorption or reducing liver glucose production following a meal.  
Table 2 . Antioxidant intake.
Fig. 3. Schematic of CGA actions on the liver and gut. CGA is a potent antioxidant and inhibitor of hepatic glucose-6-phosphate translocase (G-6-Pase), the enzyme that catalyzes the terminal reaction of glycogenolysis and gluconeogenesis. Specifically, CGA and its derived compounds inhibit the transporting component (T1), resulting in concentration-dependent declines in net hepatic glucose output in vitro. In addition, CGA is known to alter incretin secretion and glucose absorption in the gut. GIP, glucose-dependent insulinotropic polypeptide; GLP-1, glucagon-like peptide-1; T2D, type 2 diabetes.  
Tunnicliffe JM, Shearer JCoffee, glucose homeostasis, and insulin resistance: physiological mechanisms and mediators. Appl Physiol Nutr Metab 33(6): 1290-1300

January 2009


1,296 Reads

Epidemiological studies show coffee consumption to be correlated to large risk reductions in the prevalence of type 2 diabetes (T2D). Such correlations are seen with decaffeinated and caffeinated coffee, and occur regardless of gender, method of brewing, or geography. They also exist despite clear evidence showing that caffeine causes acute postprandial hyperglycemia and lower whole-body insulin sensitivity. As the beneficial effects of coffee consumption exist for both decaffeinated and caffeinated coffee, a component of coffee other than caffeine must be responsible. This review examines the specific coffee compounds responsible for coffee's effects on T2D, and their potential physiological mechanisms of action. Being plant-derived, coffee contains many beneficial compounds found in fruits and vegetables, including antioxidants. In fact, coffee is the largest source of dietary antioxidants in industrialized nations. When green coffee is roasted at high temperatures, Maillard reactions create a number of unique compounds. Roasting causes a portion of the antioxidant, chlorogenic acid, to be transformed into quinides, compounds known to alter blood glucose levels. Coffee consumption may also mediate levels of gut peptides (glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1), hormones intimately involved in the regulation of satiety and insulin secretion. Finally, coffee may have prebiotic-like properties, altering gut flora and ultimately digestion. In summary, it is evident that a better understanding of the role of coffee in the development and prevention of T2D has the potential to uncover novel therapeutic targets and nutraceutical formulations for the disease.

Effect of leucine supplementation on fat free mass with prolonged hypoxic exposure during a 13-day trek to Everest Base Camp: A double-blind randomized study

March 2014


110 Reads

Loss of body weight and fat-free mass (FFM) are commonly noted with prolonged exposure to hypobaric hypoxia. Recent evidence suggests protein supplementation, specifically leucine, may potentially attenuate loss of FFM in subcaloric conditions during normoxia. The purpose of this study was to determine if leucine supplementation would prevent the loss of FFM in subcaloric conditions during prolonged hypoxia. Eighteen physically active male (n = 10) and female (n = 8) trekkers completed a 13-day trek in Nepal to Everest Base Camp with a mean altitude of 4140 m (range 2810-5364 m). In this double-blind study, participants were randomized to ingest either leucine (LEU) (7 g leucine, 93 kcal, 14.5 g whey-based protein) or an isocaloric isonitrogenous control (CON) (0.3 g LEU, 93 kcal, 11.3 g collagen protein) twice daily prior to meals. Body weight, body composition, and circumferences of bicep, thigh, and calf were measured pre- and post-trek. There was a significant time effect for body weight (-2.2% ± 1.7%), FFM (-1.7% ± 1.5%), fat mass (-4.0% ± 6.9%), and circumferences (p < 0.05). However, there was no treatment effect on body weight (CON -2.3 ± 2.0%; LEU -2.2 ± 1.5%), FFM (CON -2.1 ± 1.5%; LEU -1.2 ± 1.6%), fat mass (CON -2.9% ± 5.9%; LEU -5.4% ± 8.1%), or circumferences. Although a significant loss of body weight, FFM, and fat mass was noted in 13 days of high altitude exposure, FFM loss was not attenuated by leucine. Future studies are needed to determine if leucine attenuates loss of FFM with longer duration high altitude exposure.

Anthropometric and dietary predictors of insulin sensitivity in 10- to 14-year-old boys and girl

March 2013


63 Reads

The high prevalence of pediatric obesity has made preventing chronic diseases through healthy lifestyle behaviours a priority within pediatrics. Examining the association between diet and insulin sensitivity (IS) in youth may provide important insights for tailoring preventative dietary interventions. The objective of this study was to explore the associations among anthropometry, diet, and IS in 10- to 14-year-olds. In this cross-sectional study, the primary outcome measure was IS, measured noninvasively using a (13)C glucose breath test. Exposure variables included body mass index (BMI) z score and several dietary variables, including glycemic index (GI), glycemic load, and fiber, magnesium, vegetable and fruit, and fat intakes, all of which were derived from a validated, Web-based 24-h recall tool. Multiple regression analyses were performed for boys and girls separately. In total, 378 students (227 girls) aged 12.1 ± 1.2 years were studied. In this sample ∼24% of youth were considered overweight or obese (BMI z score = 0.41 ± 0.93). Multiple regression analyses showed that BMI z score was negatively and independently associated with (13)C insulin sensitivity score ((13)CISS) in both boys and girls (boys: β = -0.501; girls: β = -0.446; both p < 0.001). GI was negatively and independently related to (13)CISS in boys (β = -0.195, p < 0.05) but not in girls. Other dietary variables were not associated with IS. In addition to BMI z score, a low GI diet predicted (13)CISS in boys but not in girls. This finding suggests that interventions that reduce BMI (in both sexes) and include a low GI diet among boys may improve IS.

Fig. 1. Illustration of the vibratory device strapped to the Achilles tendon 
Table 1 . Mean amplitudes of the Sol, GM and GL M max . 
Hoffmann reflex is increased after 14 days of daily repeated Achilles tendon vibration for the soleus but not for the gastrocnemii muscles

December 2011


470 Reads

In a previous study, Achilles tendon vibrations were enough to improve the triceps surae (TS) activation capacities and also to slightly increase TS Hoffmann reflex (H-reflex) obtained by summing up soleus (Sol) and gastrocnemii (GM and GL) EMGs. The purpose of the present study was to analyze separately Sol and GM or GL reflexes to account for different effects of the vibrations on the reflex excitability of the slow soleus and of the gastrocnemii muscles. A control group (n = 13) and a vibration group (n = 16) were tested in pre-test and post-test conditions. The Achilles tendon vibration program consisted of 1 h of daily vibration (frequency: 50 Hz) applied during 14 days. Maximal Sol, GM and GL H-reflexes, and M-waves were recorded, and their H(max)/M(max) ratios gave the index of reflex excitability. After the vibration protocol, only Sol H(max)/M(max) was enhanced (p < 0.001). The enhanced Sol reflex excitability after vibration is in favor of a decrease in the pre-synaptic inhibition due to the repeated vibrations and the high solicitation of the reflex pathway. Those results of a short period of vibration applied at rest may be limited to the soleus because of its high density in muscle spindles and slow motor units, both structures being very sensitive to vibrations.

A comparison of the relationship of 14 performance-based measures with frailty in older women

November 2011


47 Reads

The purpose of this study was to determine which performance measures of physical function are most closely related to frailty and whether physical function is different across levels of frailty. Fifty-three community-dwelling Greek women (63-100 years) participated in this study. Participants were divided into 3 tertiles based on level of frailty as calculated from a frailty index (FI): lowest FI group (<0.19 FI), intermediate FI group (0.19-0.36 FI), and highest FI group (>0.36 FI). Performance measures tested were handgrip and knee extension muscle strength and fatigue, upper and lower body muscular endurance, walking performance, agility, and dynamic balance. The greatest proportion of variance in the FI was explained by combining all performance-based measures of physical function. The performance measures that were most closely related to frailty yet different across levels of frailty were ambulatory mobility, lower body muscular endurance, and nondominant handgrip strength. Walking at a preferred pace had the strongest relationship to frailty rather than walking at maximal pace. Grip strength of the nondominant hand had a stronger correlation with frailty compared with the dominant hand. The FI was a better predictor of physical function than chronological age. The decline in physical function accelerated after the intermediate FI tertile. Definitions of frailty need to combine performance-based measures that can identify impairments in various domains of physical function. The assessment protocols of these measures are important.

The many ways to regulate glucose transporter 4This paper is one of a selection of papers published in this Special Issue, entitled 14th International Biochemistry of Exercise Conference – Muscles as Molecular and Metabolic Machines, and has undergone the Journal’s usual peer review process.

July 2009


66 Reads

Glucose uptake into skeletal muscle is primarily mediated by glucose transporter 4 (GLUT4). The number of GLUT4 polypeptides at the surface of muscle cells rises rapidly in response to insulin, contraction, depolarization, or energy deprivation. However, distinct mechanisms underlie the gain in surface GLUT4 in each case. Insulin promotes its exocytosis to the membrane, regulating vesicle movement, tethering, docking, and fusion. In contrast, muscle contraction, depolarization, and energy demand reduce GLUT4 endocytosis. The signals involved in each case also differ. Insulin utilizes Akt, Rabs, and selective actin remodelling, whereas depolarization and energy deprivation engage AMP-activated protein kinase and Ca2+-dependent signals. GLUT4 internalizes via 2 major routes that involve dynamin, but only one requires clathrin. The clathrin-independent route is slowed down by energy deprivation, and is regulated by AMP-activated protein kinase. In addition to regulation of the exocytic and endocytic movement of GLUT4, glucose uptake is also modulated through changes in the transporter's intrinsic activity. The glycolytic enzymes glyceraldehyde-3-dehydrogenase and hexokinase II contribute to such regulation, through differential binding to GLUT4.

Fig. 1. Toll-like receptor (TLR) 2 and TLR4 signalling pathways activated by extracellular non-esterified fatty acids. AP1, activator protein 1; CD14, cluster of differentiation 14; IKK, I k B kinase; IRAK; interleukin-1 receptor-associated kinase; MAPK, mitogen-activated kinase; MD-2, myeloid differentiation-2; MYD88, myeloid differentiation primary response gene 88; NF k B, nuclear factor kappa B; TAK1, transforming growth factor beta-activated kinase 1; TIRAP, Toll–interleukin-1 receptor domain-containing adapter protein; TLR1, 6, Toll- like receptors 1 and 6; TRAF6, tumour necrosis factor receptor-associated factor 6. 
Toll-like receptor signalling induced by endurance exerciseThis paper is one of a selection of papers published in this Special Issue, entitled 14th International Biochemistry of Exercise Conference – Muscles as Molecular and Metabolic Machines, and has undergone the Journal’s usual peer review process.
Toll-like receptors (TLRs) are transmembrane proteins that detect a variety of molecular components mostly derived from microorganisms. TLR2 and TLR4 are amongst others present in liver, adipose tissue, and skeletal muscle. Extracellular long-chain fatty acids bind TLR2 and 4 and induce downstream signalling cascades implicated in cellular stress and inflammatory processes. Evidence indicates that TLR activation by non-esterified fatty acids (NEFAs) may participate in the development of insulin resistance. Exercise seems to induce a downregulation of TLR expression in various tissues, a mechanism that may take part in the protective effect of exercise against insulin resistance. Moreover, TLRs seem to mediate the activation of mitogen-activated protein kinase p38 and Jun-amino-terminal kinase by extracellular NEFAs during endurance exercise. During this type of exercise, circulating NEFAs are known to regulate the expression of various genes including pyruvate dehydrogenase kinase 4, uncoupling protein 3, carnitine palmitoyltransferase 1, and peroxisome proliferator-activated receptor-gamma coactivator 1 alpha. Whether these events are initiated by a TLR-dependent signal transduction remains to be investigated.

Role of Akt substrate of 160 kDa in insulin-stimulated and contraction-stimulated glucose transport

July 2007


74 Reads

Insulin and exercise, the most important physiological stimuli to increase glucose transport in skeletal muscle, trigger a redistribution of GLUT4 glucose transporter proteins from the cell interior to the cell surface, thereby increasing glucose transport capacity. The most distal insulin signaling protein that has been linked to GLUT4 translocation, Akt substrate of 160 kDa (AS160), becomes phosphorylated in insulin-stimulated 3T3-L1 adipocytes; this is important for insulin-stimulated GLUT4 translocation and glucose transport. Insulin also induces a rapid and dose-dependent increase in AS160 phosphorylation in skeletal muscle. Available data from skeletal muscle support the concepts developed in adipocytes with regard to the role AS160 plays in the regulation of insulin-stimulated glucose transport. In vivo exercise, in vitro contractions, or in situ contractions can also stimulate AS160 phosphorylation. AMP-activated protein kinase (AMPK) is likely important for phosphorylating AS160 in response to exercise/contractile activity, whereas Akt2 appears to be important for insulin-stimulated AS160 phosphorylation in muscle. Evidence of a role for AS160 in exercise/contraction-stimulated glucose uptake is currently inconclusive. The distinct signaling pathways that are stimulated by insulin and exercise/contraction converge at AS160. Although AS160 phosphorylation is apparently important for insulin-stimulated GLUT4 translocation and glucose transport, it is uncertain whether elevated AS160 phosphorylation plays a similar role with exercise/contraction.

Fig. 1. Relationship ( r ) of the log-transformed peak oxygen uptake ( V  ̇ O 2peak ) with ( a ) chronological and ( b ) skeletal age and with ( c ) log-transformed stature and ( d ) thigh volume. The 95% CIs of the correlation coefficients are also presented. 
Allometric modeling (eq. 2) and proportional multiplicative allometric modeling (eq. 3) of the peak oxygen uptake for body size variables and for body size variables and age, respectively.
Allometric scaling of peak oxygen uptake in male roller hockey players under 17 years old

April 2013


376 Reads

Peak oxygen uptake (V̇O2peak) is routinely expressed in litres per minute and by unit of body mass (mL·kg(-1)·min(-1)) despite the theoretical and statistical limitations of using ratios. Allometric modeling is an effective approach for partitioning body-size effects in a performance variable. The current study examined the relationships among chronological age (CA), skeletal age (SA), total body and appendicular size descriptors, and V̇O2peak in male adolescent roller hockey players. Seventy-three Portuguese, highly trained male athletes (CA, 15.4 ± 0.6 years; SA, 16.4 ± 1.5 years; stature, 169.9 ± 6.9 cm; body mass, 63.7 ± 10.7 kg; thigh volume, 4.8 ± 1.0 L) performed an incremental maximal test on a motorized treadmill. Exponents for body size descriptors were 2.15 for stature (R(2) = 0.30, p < 0.01) and 0.55 for thigh volume (R(2) = 0.46, p < 0.01). The combination of stature or thigh volume and CA or SA, and CA(2) or SA(2), increased the explained variance in V̇O2peak (R(2) ranged from 0.30 to 0.55). The findings of the allometric model combining more than 1 body size descriptor (i.e., stature and thigh volume) in addition to SA and CA(2) were not significant. Results suggest that thigh volume and SA are the main contributors to interindividual variability in aerobic fitness.

Fig. 1. Change in esophageal temperature ( T es , plotted every 30 s) 
Fig. 2. (A) Laser Doppler perfusion measurements of fingertip skin blood flow during 10 min of baseline, 60 min of immersion, and 10 min of recovery. (At start of immersion, time = 0 min.) Data are averaged every 5 min and plotted as percent of baseline. (B) Change in fingertip skin temperature. Data are plotted every 30 s. *, Conditions have different rates of decrease from minute 0 to 30 ( p < 0.04). Not significant (NS) rates of cooling are similar for minutes 30 to 60. Error bars represent SD. Dotted lines indicate start and finish of immersion. Dashed line separates first and second 30-min periods of analysis. 
Fig. 3. Head heat loss during the first and second 30-min periods of immersion. Error bars represent SD. *, Different from all other conditions ( p < 0.001) during both time periods. 
Core cooling and thermal responses during whole-head, facial, and dorsal immersion in 17 °C water

October 2010


282 Reads

This study isolated the effects of dorsal, facial, and whole-head immersion in 17 degrees C water on peripheral vasoconstriction and the rate of body core cooling. Seven male subjects were studied in thermoneutral air (approximately 28 degrees C). On 3 separate days, they lay prone or supine on a bed with their heads inserted through the side of an adjustable immersion tank. Following 10 min of baseline measurements, the water level was raised such that the water immersed the dorsum, face, or whole head, with the immersion period lasting 60 min. During the first 30 min, the core (esophageal) cooling rate increased from dorsum (0.29 ± 0.2 degrees C h-1) to face (0.47 ± 0.1 degrees C h-1) to whole head (0.69 ± 0.2 degrees C h(-1)) (p < 0.001); cooling rates were similar during the final 30 min (mean, 0.16 ± 0.1 degrees C h(-1)). During the first 30 min, fingertip blood flow (laser Doppler flux as percent of baseline) decreased faster in whole-head immersion (114 ± 52% h(-1)) than in either facial (51 ± 47% h-1) or dorsal (41 ± 55% h(-1)) immersion (p < 0.03); rates of flow decrease were similar during minutes 30 to 60 (mean, 22.5 ± 19% h(-1)). Total head heat loss over 60 min was significantly different between whole-head (120.5 ± 13 kJ), facial (86.8 ± 17 kJ), and dorsal (46.0 ± 11 kJ) immersion (p < 0.001). The rate of core cooling, relative to head heat loss, was similar in all conditions (mean, 0.0037 ± 0.001 degree C kJ(-1)). Although the whole head elicited a higher rate of vasoconstriction, the face did not elicit more vasoconstriction than the dorsum. Rather, the progressive increase in core cooling from dorsal to facial to whole-head immersion simply correlates with increased heat loss.

Growth hormone responses to 3 different exercise bouts in 18-to 25-and 40-to 50-year-old men

August 2008


92 Reads

Exercise is a potent stimulus for growth hormone (GH) release, although aging appears to attenuate this response. The aim of this study was to investigate GH responses to different exercise stimuli in young and early middle-aged men. Eight men aged 18-25 y and 8 men aged 40-50 y completed 3 trials, at least 7 days apart, in a random order: 30 s cycle-ergometer sprint (sprint), 30 min resistance exercise bout (resistance), 30 min cycle at 70% maximal oxygen consumption (endurance). Blood samples were taken pre-, during, and post-exercise, and area under the GH vs. time curve was calculated for a total of 120 min. Mean blood lactate concentrations and percentage heart rate maximum at which the participants were working were not different between groups in any of the trials. In both groups, blood lactate concentrations were significantly lower in the endurance trial than in the sprint and resistance trials. There were no significant differences in resting GH concentration between groups or trials. GH AUC was significantly greater in the young group than the early middle-aged group, in both sprint (531 (+/-347) vs. 81 (+/-54) microg.L-1 per 120 min, p = 0.003) and endurance trials (842 (+/-616) vs. 177 (+/-137) microg.L-1 per 120 min, p = 0.010). Endurance exercise elicits a greater GH response than sprint and resistance exercise; however, aging per se, factors associated with aging, or an inability to achieve a sufficient absolute exercise intensity results in a smaller GH response to an exercise stimulus in early middle-aged men.

Women reduced the sex difference in open-water ultra-distance swimming La Traversée Internationale du Lac St-Jean, 1955–2012

February 2014


74 Reads

In La Traversée Internationale du Lac St-Jean, held between 1955 and 2012 in Canada, the fastest women (r(2) = 0.61, p < 0.0001) and men (r(2) = 0.66, p < 0.0001) improved swimming speed over the years but the sex difference remained unchanged at 8.8% ± 5.6% (r(2) = 0.069, p = 0.065). Annually, for the 3 fastest swimmers, both women (r(2) = 0.53, p < 0.0001) and men (r(2) = 0.71, p < 0.0001) improved swimming speed between 1973 and 2012 and the sex difference decreased (r(2) = 0.29, p = 0.0016) from 14.4% ± 11.0% (1973) to 3.7% ± 1.4% (2012).

Dietary intakes of Canadians in the 1990s using population-weighted data derived from the provincial nutrition surveys

January 2007


15 Reads

Provincial nutrition surveys of adults were conducted between 1990 and 1999 in Canada. Eight reports have been issued, and one is forthcoming. The purpose of this study was to estimate the national dietary intake of adult Canadians, using the publicly available data. Group mean-nutrient-intake data from 16 915 adults, aged 18 to 84 years, from published provincial reports were collated by age and sex for each of 9 provinces (Manitoba data were unavailable). Using Canadian census data appropriate to the year of collection, intake data were weighted to provide 1 national intake value for each nutrient, by 8 age and sex categories. In general, the energy and nutrient intake of adults decreased with age. For every age group, with the exception of vitamin C, intake of nutrients by men was greater than that by women. On the basis of a comparison of recently recommended intakes (Dietary Reference Intakes), the nutrients that are of concern because of inadequate intake include dietary fibre, calcium, magnesium, and folate. The data demonstrate the impact of folate fortification on folate intake; the mean intake became twice that of prefortification levels. This study used group mean-intake data; therefore, we cannot make definitive conclusions about the prevalence of inadequacy for the nutrients. Because of limitations with some provincial response rates, our data should not be construed as representative of the Canadian population. However, because these surveys were completed between the 19701972 Nutrition Canada Survey and the 2004 Canadian Community Health Survey, these population-weighted data might be a useful point of comparison for monitoring trends in nutrient intake from food.

. Additional analyses revealed that the odds of having MetS in men decreased in a linear dose-response manner when moving from the low to high 
Cardiorespiratory fitness and metabolic syndrome: US National Health and Nutrition Examination Survey 1999–2002

March 2007


101 Reads

Increasing physical activity is recommended as a therapeutic lifestyle change in the treatment of metabolic syndrome (MetS); however, little evidence exists for a relationship between cardiorespiratory fitness (CRF) and MetS in representative samples. Using data from the US National Health and Nutrition Examination Survey, 1999-2002, the relationship between CRF and MetS was examined in 692 men and 608 women between the ages of 18 and 49 y who were free of major disease and disability. In men, the odds of MetS were significantly lower in moderate and high CRF categories versus the low CRF category, whereas in women there were no significant relationships between CRF and MetS.

Associations of the SREBP-1c gene polymorphism with gender-specific changes in serum lipids induced by a high-carbohydrate diet in healthy Chinese youth

April 2011


31 Reads

We investigated the possible association between the sterol regulatory element-binding protein-1c gene (SREBP-1c) rs2297508 polymorphism and the changes in lipid profiles in a high-carbohydrate and low-fat (high-CHO/LF) diet in a Chinese population well characterized by a lower incidence of coronary heart disease and a diet featuring higher carbohydrate and lower fat. Fifty-six healthy youth (aged 22.89 ± 1.80 years) were given wash-out diets of 31% fat and 54% carbohydrate for 7 days, followed by the high-CHO/LF diet of 15% fat and 70% carbohydrate for 6 days, without total energy restriction. Fasting blood samples were collected. Serum variables of lipid and glucose metabolism after the wash-out and high-CHO/LF diets, as well as the rs2297508 polymorphism, were analyzed. Compared with the male subjects on the wash-out diet, significantly elevated levels of high-density lipoprotein cholesterol (HDL-C) and decreased levels of apolipoprotein B-100 were observed in the male carriers of the C allele after the high-CHO/LF diet. In the female subjects, significantly increased triacylglycerol levels, insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) were found in the GG genotype after the high-CHO/LF diet. These results suggest that the C allele of the rs2297508 polymorphism is associated with a retardation of the increases in serum triacylglycerol, serum insulin, and HOMA-IR in females and with the elevated serum HDL-C in males after the high-CHO/LF diet.

Effects of an acute bout of resistance exercise on fiber-type specific to GLUT4 and IGF-1R expression

May 2013


118 Reads

The effects of resistance exercise on fiber-type-specific expression of insulin-like growth factor I receptor (IGF-1R) and glucose transporter 4 (GLUT4) was determined in 6 healthy males. The expression of both genes increased in Type I fibers (p < 0.05), but only GLUT4 increased (p < 0.05) in Type II fibers. These data demonstrates that an acute bout of resistance exercise can up-regulate mechanisms of glucose uptake in slow and fast-twitch fibers, but the IGF signaling axis may not be as effective in fast-twitch fibers.

Exercise, PGC-1α, and metabolic adaptation in skeletal muscle

July 2009


152 Reads

Endurance exercise promotes skeletal muscle adaptation, and exercise-induced peroxisome proliferator-activated receptor gamma coactivator-1alpha (Pgc-1alpha) gene expression may play a pivotal role in the adaptive processes. Recent applications of mouse genetic models and in vivo imaging in exercise studies have started to delineate the signaling-transcription pathways that are involved in the regulation of the Pgc-1alpha gene. These studies revealed the importance of p38 mitogen-activated protein kinase/activating transcription factor 2 and protein kinase D/histone deacetylase 5 signaling transcription axes in exercise-induced Pgc-1alpha transcription and metabolic adaptation in skeletal muscle. The signaling-transcription network that is responsible for exercise-induced skeletal muscle adaption remains to be fully elucidated.

PGC-1α-induced improvements in skeletal muscle metabolism and insulin sensitivity

July 2009


145 Reads

The peroxisome proliferator-activated receptor gamma (PPARgamma) coactivator 1alpha (PGC-1alpha), a nuclear encoded transcriptional coactivator, increases the expression of many genes in skeletal muscle, including those involved with fatty acid oxidation and oxidative phosphorylation. Exercise increases the expression of PGC-1alpha, and the exercise-induced upregulation of many genes is attributable, in part, to the preceding activation and upregulation of PGC-1alpha. Indeed, PGC-1alpha overexpression, like exercise training, increases exercise performance. PGC-1alpha reductions in humans have been observed in type 2 diabetes, while, in cell lines, PGC-1alpha mimics the exercise-induced improvement in insulin sensitivity. However, unexpectedly, in mammalian muscle, PGC-1alpha overexpression contributed to the development of diet-induced insulin resistance. This may have been related to the massive overexpression of PGC-1alpha, which induced the upregulation of the fatty acid transporter FAT/CD36 and led to an increase in intramuscular lipids, which interfere with insulin signalling. In contrast, when PGC-1alpha was overexpressed modestly, within physiological limits, mitochondrial fatty acid oxidation was increased, GLUT4 expression was upregulated, and insulin-stimulated glucose transport was increased. More recently, similar PGC-1alpha-induced improvements in the insulin-resistant skeletal muscle of obese Zucker rats have been observed. These studies suggest that massive PGC-1alpha overexpression, but not physiologic PGC-1alpha overexpression, induces deleterious metabolic effects, and that exercise-induced improvements in insulin sensitivity are induced, in part, by the exercise-induced upregulation of PGC-1alpha.

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