Article

Fat Oxidation in Men and Women Endurance Athletes in Running and Cycling

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Abstract

Recent studies showed that the maximal fat oxidation seems to be different in men and women and that it can be influenced by type and intensity of exercise. Nineteen endurance trained male (V.O (2)peak 61.3 +/- 4.4 ml x kg (-1) x min (-1)) and 17 female (V.O (2)peak 52.8 +/- 4.5 ml x kg (-1) x min (-1)) athletes were studied over 30 min at 55, 65 and 75 % V.O (2)peak on a treadmill and a cycling ergometer in order to find the intensity and kind of exercise with the highest absolute fat oxidation. For women, normalised (per body weight) fat oxidation was higher at 75 % V.O (2)peak than at 55 % V.O (2)peak for both running (p = 0.02) and cycling (p = 0.01). Women also oxidised a significantly higher percentage of fat with regard to total energy expenditure than men in running (p = 0.02) and cycling (p = 0.004). Normalised carbohydrate oxidation was significantly higher for men at each tested intensity (p < 0.05) and compared to kind of exercise in men (p = 0.006) and women (p = 0.002) in cycling than in running. Men and women showed a significantly higher normalised fat oxidation for running compared to cycling (p = 0.01). Cycling produced in men (p = 0.06) and women (p = 0.001) significantly more lactate than running. In summary, we found at 75 % V.O (2)peak a higher fat oxidation rate than at 65 % V.O (2)peak and 55 % V.O (2)peak for men and women in cycling and running. This is coincident with lactate threshold in men and women in cycling but not in running, where lactate threshold is higher than 75 % V.O (2)peak.

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... with women generally relying more on fat than carbohydrate as a fuel source compared with men 4 4 (11, 12). This has been attributed to women having a higher percentage of body fat (12), a greater 25 lipid content in muscles fibers (11) and better mobilization of fatty acids from subcutaneous 26 adipose tissue linked to cyclic changes in estrogen and progesterone (13). ...
... with women generally relying more on fat than carbohydrate as a fuel source compared with men 4 4 (11, 12). This has been attributed to women having a higher percentage of body fat (12), a greater 25 lipid content in muscles fibers (11) and better mobilization of fatty acids from subcutaneous 26 adipose tissue linked to cyclic changes in estrogen and progesterone (13). However, following the 27 provision of an exogenous source of glucose during exercise at sea level, most studies show no 28 statistical sex-differences in exogenous carbohydrate oxidation during exercise (14, 15) with one 29 exception (16). ...
... The fact that fat oxidation was not 351 significantly affected by acute exposure to HA in these women, may be due to their higher fat 352 oxidation at sea level (baseline effect) compared with men. This has been ascribed to women 353 having a greater proportion of body fat (12), a greater lipid content in muscles fibers (11), a higher 354 percentage of type 1 muscle fibers (40) and better mobilization of fatty acids from subcutaneous 355 adipose tissue linked to cyclic changes in estrogen and progesterone (13). However, it is interesting 356 to note that the magnitude of fat oxidation in women at HA, was very similar compared with our 357 previous study in men (50% vs. 51%), as was the use of pre-existing muscle glycogen (17% vs. 358 16%), exogenous carbohydrate oxidation (32% vs. 30%) and glucose release from the liver (3%). ...
Article
Purpose: This study compared the co-ingestion of glucose and fructose on exogenous and endogenous substrate oxidation during prolonged exercise at terrestrial high altitude (HA) versus sea level, in women. Method: Five women completed two bouts of cycling at the same relative workload (55% Wmax) for 120 minutes on acute exposure to HA (3375m) and at sea level (~113m). In each trial, participants ingested 1.2 g.min of glucose (enriched with C glucose) and 0.6 g.min of fructose (enriched with C fructose) before and every 15 minutes during exercise. Indirect calorimetry and isotope ratio mass spectrometry were used to calculate fat oxidation, total and exogenous carbohydrate oxidation, plasma glucose oxidation and endogenous glucose oxidation derived from liver and muscle glycogen. Results: The rates and absolute contribution of exogenous carbohydrate oxidation was significantly lower at HA compared with sea level (ES>0.99, P<0.024), with the relative exogenous carbohydrate contribution approaching significance (32.6±6.1 vs. 36.0±6.1%, ES=0.56, P=0.059) during the second hour of exercise. In comparison, no significant differences were observed between HA and sea level for the relative and absolute contributions of liver glucose (3.2±1.2 vs. 3.1±0.8%, ES=0.09, P=0.635 and 5.1±1.8 vs. 5.4±1.7 grams, ES=0.19, P=0.217), and muscle glycogen (14.4±12.2% vs. 15.8±9.3%, ES=0.11, P=0.934 and 23.1±19.0 vs. 28.7±17.8 grams, ES=0.30, P=0.367). Furthermore, there was no significant difference in total fat oxidation between HA and sea level (66.3±21.4 vs. 59.6±7.7 grams, ES=0.32, P=0.557). Conclusion: In women, acute exposure to HA reduces the reliance on exogenous carbohydrate oxidation during cycling at the same relative exercise intensity.Keys WordsAcute Hypoxia, Carbon Isotope, Exogenous Carbohydrate Oxidation, Liver Glycogen, Muscle Glycogen, Plasma Glucose Oxidation.
... Concerning that with increasing intensity fat oxidation decreases relatively and as a counter reaction carbohydrate oxidation increases [9][10][11]. In relatively high intensities of 65-75% VO2max rate of maximum fat oxidation peaks, however these high intensities cannot be kept for a longer exercise time (several hours) [12][13][14][15]. With such high intensity's body´s own intramuscular substrates should be emptied within hours and intensity has to be reduced [16]. ...
... The accumulation of lactate in Plasma correlates with a decrease in fat oxidation with increasing intensity of exercise [9]. In the range of a lactate concentration of 2 mmol/l [10,12,13] to 2.5 mmol/l [5,10] intensity with maximum fat oxidation seems to be whereby this is probably independent from kind of movement (e.g. running versus cycling), other hints exist [5,18]. ...
... To mention is, that the relative share of fat for energy production is within an intensity of 55-75% VO2max constant at around 50% [13]. With 65% VO2max with 0.5 to 0.6 g fat per min the highest fat oxidation is achieved [9]. ...
... Sex differences in physiological characteristics are likely to be the main factor for the ~10-15% sex difference in endurance performance. Men have a larger skeletal muscle mass compared to women (9), correlating with a greater muscular strength (1), a larger aerobic capacity (11) and lower relative body fatness (12). ...
... A first important finding was that men were faster in cycling, but not in swimming, running and overall race time. The faster cycling speed might be explained by anthropometric and physiological differences be-tween women and men (11,12,14). Sex differences in anthropometric (9, 12) and physiological characteristics (11) are the most likely main reasons for this difference in cycling speed. ...
... The relative skeletal muscle mass is ~8% higher in male Ironman triathletes with ~41.0 kg muscle mass in male versus ~28.0 kg in female Ironman triathletes (12). Furthermore, the aerobic capacity is ~14% higher in men with a VO 2 peak 61.3 ml/kg/min versus 52.8 ml/kg/min in men and women, respectively (11). However, not only body mass per se is a decisive factor to explain sex differences in cycling and running performance. ...
Article
The performance and sex differences of long-distance triathletes competing in 'Ironman Hawaii' are well investigated. However, less information is available with regards to triathlon races of the Ironman distance held under extreme environmental conditions (e.g. extreme cold) such as the 'Isklar Norseman Xtreme Triathlon' which started in 2003. In 'Isklar Norseman Xtreme Triathlon', athletes swim at a water temperature of ~13-15°C, cycle at temperatures of ~5-20°C and run at temperatures of ~12-28°C in the valley and of ~2-12°C at Mt. Gaustatoppen. This study analysed the performance trends and sex differences in 'Isklar Norseman Xtreme Triathlon' held from 2003 to 2015 using mixed-effects regression analyses. During this period, a total of 175 women (10.6%) and 1,852 men (89.4%) successfully finished the race. The number of female (r^2 = 0.53, P = 0.0049) and male (r^2 = 0.37, P = 0.0271) finishers increased and the men-to-women ratio decreased (r^2 = 0.86, P < 0.0001). Men were faster than women in cycling (25.41 ± 2.84 km/h versus 24.25 ± 2.17 km/h) (P < 0.001), but not in swimming (3.06 ± 0.62 km/h vs. 2.94 ± 0.57 km/h), running (7.43 ± 1.13 km/h vs. 7.31 ± 0.93 km/h) and overall race time (874.57 ± 100.62 min vs. 899.95 ± 90.90 min) (P > 0.05). Across years, women improved in swimming and both women and men improved in cycling and in overall race time (P < 0.001). In running, however, neither women nor men improved (P > 0.05). In summary, in 'Isklar Norseman Xtreme Triathlon' from 2003 to 2015, the number of successful women increased across years, women achieved a similar performance to men in swimming, cycling and overall race time, and women improved across years in swimming, cycling and overall race time.
... A myriad of intrinsic biochemical factors influence the relative contributions of fat and carbohydrate to energy expenditure during exercise (Spriet & Watt, 2003;Brooks, 2012), but extrinsic factors such as the intensity and mode of exercise are important regulators of substrate utilization (Romijn et al., 1993;van Loon et al., 2001;Achten et al., 2003;Knechtle et al., 2004). The contribution of fat to energy expenditure is greatest during low-and moderate-intensity exercise but declines thereafter (Romijn et al., 1993;van Loon et al., 2001). ...
... When comparing exercise modes, running elicits a greater rate of fat oxidation (FAT ox ) compared with cycling across a wide range of exercise intensities, a finding that has been attributed to the weight-bearing nature and greater quantity of muscle mass recruited while running (Achten et al., 2003;Knechtle et al., 2004;Capostagno & Bosch, 2010). For individuals with obesity and type 2 diabetes, it is important to identify a mode of exercise that can safely and effectively maximize energy expenditure, but because of complications such as peripheral neuropathy or degenerative arthritis, these individuals require alternative modes of exercise that are non-weightbearing (Colberg et al., 2010). ...
... We report that FAT ox is higher during rowing compared with cycling exercise at the same rate of energy expenditure across a range of exercise intensities up to ∼85%VO 2peak . Similar patterns and higher FAT ox occur during running when compared with cycling (Achten et al., 2003;Knechtle et al., 2004;Capostagno & Bosch, 2010). The highest ...
... Moreover, performance adaptation was more favorable to control diets compared to KD during cycling than running/race walking exercise and for females than males. In this regard, at the same relative exercise intensity, fat oxidation is greater, and CHO is lesser during running than cycling, regardless of sex (Knechtle et al. 2004). Based on differences in the muscle contraction regime, whereas cycling is purely concentric, running exercise requires a greater eccentric component. ...
... Based on differences in the muscle contraction regime, whereas cycling is purely concentric, running exercise requires a greater eccentric component. Thus, cycling involves a higher muscle tension and, consequently, more type II motor unit recruitment, leading to higher CHO oxidation (Knechtle et al. 2004). Also, it has been shown that women oxidize more fat than men at the same relative exercise intensity, and women have more muscle type I fibers and lower maximal capacity of glycolytic enzymes (Hargreaves and Spriet 2020). ...
Article
This systematic review with meta-analysis aimed to determine the effects of the ketogenic diet (KD) against carbohydrate (CHO)-rich diets on physical performance and body composition in trained individuals. The MEDLINE, EMBASE, CINAHL, SPORTDiscus, and The Cochrane Library were searched. Randomized and non-randomized controlled trials in athletes/trained adults were included. Meta-analytic models were carried out using Bayesian multilevel models. Eighteen studies were included providing estimates on cyclic exercise modes and strength one-maximum repetition (1-RM) performances and for total, fat, and free-fat masses. There were more favorable effects for CHO-rich than KD on time-trial performance (mode [95% credible interval]; −3.3% [−8.5%, 1.7%]), 1-RM (−5.7% [−14.9%, 2.6%]), and free-fat mass (−0.8 [−3.4, 1.9] kg); effects were more favorable to KD on total (−2.4 [−6.2, 1.8] kg) and fat mass losses (−2.4 [−5.4, 0.2] kg). Likely modifying effects on cyclic performance were the subject’s sex and VO2max, intervention and performance durations, and mode of exercise. The intervention duration and subjects’ sex were likely to modify effects on total body mass. KD can be a useful strategy for total and fat body losses, but a small negative effect on free-fat mass was observed. KD was not suitable for enhancing strength 1-RM or high-intensity cyclic performances.
... They controlled the exercise intensity of obese men and postmenopausal obese women under 50%. According to observations by Knechtle et al. [22], for people under a steady exercise intensity when compared with men, women had a larger fat energy supply ratio. However, few studies have investigated the effects of fat oxidation from exercise between men and women in a trial. ...
... As observed by Knechtle et al. [22], relative body fat oxidation (i.e., as a percentage of the total energy expenditure) was more significant in women than in men at a steady exercise intensity. During low-intensity exercise, the oxidation rate of carbohydrates and fat in males gradually increased. ...
Article
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(1) Background: Evidence suggests that aerobic exercise and high-intensity interval training (HIIT) might increase fat oxidation and reduce fat. However, limited research has examined the effects of combining progressive aerobic exercise and HIIT interventions in sedentary adults with overweight and obesity, and differences in its effects between men and women remain unclear. The purpose of this study was to investigate the effects of combined progressive aerobic exercise and HIIT (CAEH) on fat oxidation and fat reduction in sedentary Chinese adults and compare sex differences in sedentary adults after seven weeks. (2) Methods: Eighty-four sedentary obese adults were enrolled and allocated to two groups in baseline (experimental (EXP) group:42; control (CON) group:42), and fifty-six subjects (EXP:31; CON:25) completed the experiments and were included in the final analysis. Subjects in the EXP group performed CAEH three times per week for seven weeks. Subjects in the CON group were advised to continue with their normal daily activities. Anthropometric, lipid profile, cardiorespiratory fitness, and fat oxidation outcomes were assessed before and after the intervention. (3) Results: After seven weeks of the CAEH intervention, compared with the CON group, the EXP group showed significant increases in fat oxidation at rest (FO_rest) (+0.03 g/min, p < 0.01), maximal fat oxidation (MFO) (+0.05 g/min, p < 0.01), and maximal oxygen intake (VO2max) (+3.2 mL/kg/min, p < 0.01). The changes in the percentages of the FO_rest (+57%) and the VO2max (+16%) were significantly greater (+20%, +6%) in males than in females (p < 0.05, p < 0.05). The body mass index (BMI) (−1.2 kg/m2, p < 0.01), body fat percentage (−3.2%, p < 0.001), visceral fat area (−12.8 cm2, p < 0.001), and total cholesterol (TC) levels (−0.4 mmol/L, p < 0.05) were significantly decreased in the EXP group. (4) Conclusions: Seven weeks of the CAEH intervention effectively improved FO_rest, MFO, and VO2max in sedentary obese adults, and the improvements in FO_rest and VO2max were more pronounced in males than in females. CAEH also improved body composition and TC levels in sedentary obese adults.
... Such evidence indicates that not only women oxidize significantly more lipids than men (Horton et al. 1998;McKenzie et al. 2000;Lamont et al. 2001a;Henderson et al. 2007;Tarnopolsky et al. 2007;Cheneviere et al. 2011;Dasilva et al. 2011;Isacco et al. 2012;Isacco et al. 2020), but they also use less carbohydrate and protein substrates to sustain moderate exercise (McKenzie et al. 2000;Tarnopolsky 2000;Lamont et al. 2001aLamont et al. , 2003Devries 2016). Comparable findings have been obtained also in athletic, endurance-trained populations (Phillips et al. 1993;Knechtle et al. 2004;Riddell et al. 2003;Wallis et al. 2006). ...
... Of the 17 studies conducted in athletic populations and deemed eligible for the qualitative analysis, 14 contributed data to at least one of the planned meta-analyses (Abramowicz and Galloway 2005; Goedecke et al. 2000;Horton et al. 2006;Knechtle et al. 2004;Phillips et al. 1993;Powers et al. 1980;Riddell et al. 2003;Roepstorff et al. 2002;Romijn et al. 2000;Steffensen et al. 2002;Tarnopolsky et al. 1990;1997;Wallis et al. 2006;Zehnder et al. 2005). ...
Article
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Purpose To explore sex-based differences in energy substrate utilization during moderate-intensity aerobic exercise; to identify the underpinning candidate physiological mechanisms. Methods Three databases were searched from inception to August 2020. Pertinent studies quantifying the utilization of substrates during moderate aerobic exercise in healthy men and reproductive-age women were considered. Studies conducted on sedentary/recreationally active and athletic populations were included and analyzed separately. Results Thirty-five studies entered the meta-analysis (21 in sedentary/recreationally active, 14 in athletic populations). Compared to women, the respiratory exchange ratio was significantly higher both in sedentary (mean difference, MD: + 0.03; p < 0.00001) and athletic men (MD: + 0.02; p < 0.0001). Greater carbohydrate oxidation was observed both in sedentary (standardized MD, SMD: 0.53; p = 0.006) and athletic men (SMD: 1.24; p < 0.00001). Regarding lipid substrates, sedentary men oxidized less fat than women (SMD: − 0.77; p = 0.0002), while no sex-based differences in fat oxidation were observed in athletes (SMD: 0.06; p = 0.77). Paucity of data prevented robust meta-analyses for protein sources. Sex hormones and different adrenergic activation were the most cited mechanisms to discuss sex-based differences. Conclusions Meta-analyses confirmed that men display greater reliance on carbohydrates while women rely more on lipids to sustain moderate aerobic exercise. The latter finding was not confirmed in athletes, a novel aspect of the present study. Mechanistically driven research is needed to further dissect the physiological underpinnings of sex differences in substrate utilization during aerobic exercise, especially for proteins, which are still less investigated than other substrates.
... Cycling recruits a smaller active muscle mass for a given metabolic demand (or oxygen consumption) than running (7). For this reason, when cycling and running are matched for whole-body relative exercise intensity, cycling places a higher demand on carbohydrate utilization than running (6,24). Similarly, in women, the ovarian hormones alter substrate partitioning in favor of greater fat utilization at any given relative exercise intensity (8,24) and may suppress hepatic glucose production (10) compared with men. ...
... For this reason, when cycling and running are matched for whole-body relative exercise intensity, cycling places a higher demand on carbohydrate utilization than running (6,24). Similarly, in women, the ovarian hormones alter substrate partitioning in favor of greater fat utilization at any given relative exercise intensity (8,24) and may suppress hepatic glucose production (10) compared with men. Thus, prescribed training or supplement strategies based on findings in male cyclists can possibly not be extrapolated to running or female athletes. ...
Article
Oosthuyse, T, Florence, GE, Correia, A, Smyth, C, and Bosch, AN. Carbohydrate-restricted exercise with protein increases self-selected training intensity in female cyclists but not male runners and cyclists. J Strength Cond Res XX(X): 000-000, 2021-Carbohydrate-restricted training challenges preservation of euglycemia and exercise intensity that precludes ergogenic gains, necessitating countering strategies. We investigated the efficacy of ingesting casein protein hydrolysate in overnight-fasted male runners, male cyclists, and female cyclists. Twenty-four overnight-fasted athletes ingested 15.8 g·h-1 casein hydrolysate or placebo-water during exercise (60-80 minutes) comprising an incremental test to exhaustion, steady-state exercise (70% Vmax or 60% peak power output, 87 ± 4% HRmax), and 20-minute time trial (TT) in a double-blind randomized crossover design, with p < 0.05 accepted as significant. Ingesting protein vs. placebo increased metabolic demand {oxygen consumption, +4.7% (95% confidence interval [CI] ± 4%), p = 0.0297; +3.2% (95% CI ± 3.4%), p = 0.061}, heart rate (p = 0.0083; p = 0.007) and rating of perceived exertion (RPE) (p = 0.0266; p = 0.0163) in male cyclists and runners, respectively, but not female cyclists. Protein vs. placebo increased carbohydrate oxidation (+0.26 [95% CI ± 0.13] g·min-1, p = 0.0007) in female cyclists alone. Cyclists reported +2 ± 1 higher RPE than runners (p = 0.0062). Glycemia was maintained only in runners and increased with protein vs. placebo after 20 minutes of steady-state exercise (+0.63 [95% CI ± 0.56] mmol·L-1, p = 0.0285). TT performance with protein vs. placebo ingestion was modestly compromised in runners (-2.8% [95% CI ± 2.2%], p = 0.0018), unchanged in male cyclists (+1.9% [95% CI ± 5.6%], p = 0.5794), and modestly improved in female cyclists (+2.5% [95% CI ± 1.8%], p = 0.0164). Casein hydrolysate ingestion during moderate to hard carbohydrate-restricted exercise increases glycemia in runners, but not cyclists. Casein hydrolysate increases metabolic demand in male athletes and carbohydrate oxidation in female cyclists and is suitable for improving carbohydrate-restricted training intensity in female but not male endurance athletes.
... The oxidation of substrates is also known to be further altered extrinsically, via exercise duration (Phillips et al., 1996), and exercise modality (Achten et al., 2003;Capostagno and Bosch, 2010;Egan et al., 2016). Substrate metabolism shifts towards greater fat oxidation and reaches higher rates of maximal fat oxidation (MFO) during walking and running compared to cycling (Achten et al., 2003;Capostagno and Bosch, 2010;Chenevière et al., 2010;Knechtle et al., 2004). These results are believed to stem from differences in muscle recruitment patterns and Type II muscle fiber recruitment in cycling from lower muscle mass contribution to total energy production (Achten et al., 2003;Chenevière et al., 2010). ...
... The present study demonstrated higher blood lactate concentrations postexercise in both the elliptical and rowing conditions. Type II muscle fibres are less efficient than Type I muscle fibers since they rely primarily on carbohydrates as their energy source and produce lactate as a by-product (Knechtle et al., 2004). Treadmill exercise primarily uses muscles of the lower extremities, such as the gastrocnemius (Sozen, 2010), composed of a high percentage of Type I fibres (Costill et al., 1976). ...
Article
Fat oxidation during exercise is associated with cardio-metabolic benefits, but the extent of which whole-body exercise modality elicits the greatest fat oxidation remains unclear. We investigated the effects of treadmill, elliptical and rowing exercise on fat oxidation in healthy individuals. Nine healthy males participated in three, peak oxygen consumption tests, on a treadmill, elliptical and rowing ergometer. Indirect calorimetry was used to assess maximal oxygen consumption (V̇ O2peak), maximal fat oxidation (MFO) rates, and the exercise intensity MFO occurred (Fatmax). Mixed venous blood was collected to assess lactate and blood gases concentrations. While V̇ O2peak was similar between exercise modalities, MFO rates were higher on the treadmill (mean ± SD; 0.61 ± 0.06 gꞏmin-1) compared to both the elliptical (0.41 ± 0.08 gꞏmin-1, p = 0.022) and the rower (0.40 ± 0.08 gꞏmin-1, p = 0.017). Fatmax values were also significantly higher on the treadmill (56.0 ± 6.2 %V̇ O2peak) compared to both the elliptical (36.8 ± 5.4 %V̇ O2peak, p = 0.049) and rower (31.6 ± 5.0 %V̇ O2peak, p = 0.021). Post-exercise blood lactate concentrations were also significantly lower following treadmill exercise (p = 0.021). Exercising on a treadmill maximizes fat oxidation to a greater extent than elliptical and rowing exercises, and remains an important exercise modality to improve fat oxidation, and consequently, cardio-metabolic health.
... It is also known that intermittent aerobic physical training (IAT) consists of alternating periods of greater and lower intensity within an exercise session, which may increase the total metabolic capacity (aerobic and anaerobic). 15,16 Emerging researches have shown that not only moderate-intensity CAT, but also high-intensity interval training (HIIT) treats metabolic diseases including T2DM 17,18 and obesity. 19,20 This is an important consideration for PCOS women given that IR and obesity are prevalent and aggravate the disease process. ...
... Hormonal and metabolic parameters of women with PCOS before and after the observation period without training (CG) and before and after the 16 .748 ...
Article
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Objective To evaluate the effects of continuous (CA) and intermittent (IA) aerobic training on hormonal and metabolic parameters and body composition of women with polycystic ovary syndrome (PCOS). Design Prospective, interventional, randomized study. Methods RCT (Randomized Controlled Training) with sample allocation and stratification into three groups: CAT (n = 28) and IAT (n = 29) training and no training [control (CG), n = 30]. Before and after 16 weeks of intervention (CAT or IAT) or observation (CG), hormonal and metabolic parameters, body composition and anthropometric indices were evaluated. Aerobic physical training on a treadmill consisted of 30‐ to 50‐minute sessions with intensities ranging from 60 to 90% of the maximum heart rate. Results In the CA group, there was reduction in waist circumference (WC) (p = 0.045), hip circumference (p = 0.032), cholesterol (p ≤ 0.001), low‐density lipoprotein (p = 0.030), and testosterone (p ≤ 0.001). In the IAT group, there was a reduction in WC (p = 0.014), waist‐to‐hip ratio (p = 0.012), testosterone (p = 0.019), and the free androgen index (FAI) (p = 0.037). The CG showed increases in WC (p = 0.049), total body mass (p = 0.015), body fat percentage (p = 0.034), total mass of the arms (p ≤ 0.001), trunk fat percentage (p = 0.033), leg fat percentage (p = 0.021), and total gynoid mass (p = 0.011). Conclusion CAT and IAT training reduced anthropometric indices and hyperandrogenism in PCOS, whereas only IAT training reduced the FAI. Furthermore, only CAT training improved the lipid profile.
... Several studies with different subject characteristics and exercise protocols have reported that walking/running on treadmill results in higher fat oxidation than pedalling on a stationary cycle at submaximal intensity. [4][5][6][7][8][9][10] Further, lower systolic blood pressure (SBP) and heart rate (HR) response to treadmill walking than the cycling exercise had been reported. [11][12][13][14] The mode of exercise that causes higher fat oxidation with lower cardiovascular demand might be preferred for physically inactive individuals, as decreasing visceral fat could prevent the development of physical inactivityrelated health disorders. ...
... 7 Similarly, Achten et al, Capostagno and Bosch, Knechtle et al, and King et al reported a higher fat oxidation in response to treadmill than the cycle exercise. 6,[8][9][10] The exact mechanism of the higher fat oxidation and cardiovascular response to treadmill than the cycle endurance exercise has not been elucidated to date. Koyal et al had reported that the arterial lactate was higher while pH and bicarbonate were lower for cycle than the treadmill exercise at similar VO 2 . ...
Article
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Background: Long duration moderate-intensity aerobic exercise is better called an endurance exercise. The commonest machines used for indoor endurance exercise are treadmill and cycle ergometer. The preferred modality of endurance exercise should be the one that induces higher fat oxidation and lesser cardiovascular response. The aim of the present study is to compare treadmill walking with cycling on the stationary upright ergometer for cardiovascular responses and fat oxidation rate at similar energy expenditure.Methods: The present experimental cross-sectional study involved physically inactive but otherwise healthy males, aged 20.1±1.8 years having a normal body mass index. Twenty-one participants completed thirty-minutes of treadmill walking and stationary upright cycling on separate occasions to expend approximately 180 Kcal. Systolic blood pressure (SBP), diastolic blood pressure, and heart rate (HR) were recorded just before and immediately after the exercise. Rate pressure product (RPP), a linear correlate of myocardial oxygen uptake, was calculated as the product of SBP and HR divided by 100. Fat oxidation rate was calculated by an indirect calorimetric equation based on the respiratory gas exchange analysis. The paired t-test was applied for comparative analyses. P<0.05 was considered significant.Results: Treadmill walking caused a significantly lower RPP and HR while a significantly higher fat oxidation rate than cycling on the stationary upright ergometer.Conclusions: Treadmill endurance exercise could be preferred over cycling for young healthy males. However, further studies are required for the external validity of our results which are approximate rather than precise due to limited resources.
... Interestingly, it appears this effect is abolished in overweight/obese individuals (Bogdanis et al., 2008;Haufe et al., 2010). In accordance with these findings, it has been observed that females have greater relative whole-body fat oxidation (i.e., as a percentage of overall energy expenditure) at given steady-state exercise intensities compared to males (Knechtle et al., 2004), indicative of greater reliance on fat metabolism during exercise in females. The ovarian hormone estrogen may explain this sex difference (Oosthuyse and Bosch, 2010;Devries, 2016), as estrogen appears to stimulate lipolysis and NEFA availability (D'Eon et al., 2002), plausibly via activation of 5 ′ adenosine monophosphate-activated protein kinase (AMPK) (D'Eon et al., 2005). ...
... A further consideration is exercise modality. In general, studies comparing running and cycling at given exercise intensities have reported greater fat and reduced carbohydrate oxidation rates during running (Snyder et al., 1993;Achten et al., 2003;Knechtle et al., 2004;Chenevière et al., 2010). However, comparisons of MFO and Fat max between-modalities have not been as conclusive. ...
Article
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Using a short-duration step protocol and continuous indirect calorimetry, whole-body rates of fat and carbohydrate oxidation can be estimated across a range of exercise workloads, along with the individual maximal rate of fat oxidation (MFO) and the exercise intensity at which MFO occurs (Fatmax). These variables appear to have implications both in sport and health contexts. After discussion of the key determinants of MFO and Fatmax that must be considered during laboratory measurement, the present review sought to synthesize existing data in order to contextualize individually measured fat oxidation values. Data collected in homogenous cohorts on cycle ergometers after an overnight fast was synthesized to produce normative values in given subject populations. These normative values might be used to contextualize individual measurements and define research cohorts according their capacity for fat oxidation during exercise. Pertinent directions for future research were identified.
... We hypothesize that intensity could influence our results significantly. The intensity chosen to perform the experimental protocol in our work is the same as Knechtle et al. (2004) used in their experiment. Although they did not consider menstrual cycle phases, they got a RER of 0.86 ± 0.05, which means that fats were oxidized at the same rate as carbohydrates at 75% VO2 peak (Knechtle et al., 2004). ...
... The intensity chosen to perform the experimental protocol in our work is the same as Knechtle et al. (2004) used in their experiment. Although they did not consider menstrual cycle phases, they got a RER of 0.86 ± 0.05, which means that fats were oxidized at the same rate as carbohydrates at 75% VO2 peak (Knechtle et al., 2004). Our research found a higher RER in each of the menstrual cycle phase 0.89 ± 0.01, 0.87±0.01 and 0.88± 0.01, early-follicular phase, mid-follicular phase and luteal phase respectively and 0.91 ± 0.01 non-hormonal phase and 0.89± 0.01 hormonal phase, which VOLUME 13 | ISSUE 3 | 2018 | 11 means that in all the phases, CHO where the preferential energetic substrate in both regular menstrual cycle and OC groups. ...
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The main aim of the study was to investigate the effect of menstrual cycle phases on substrate oxidation during steady state intensity exercise in adult females with regular menstrual cycle and on oral contraceptive (OC). Twenty-four healthy endurance and strength trained females, with regular menstrual cycle phases (n= 15; Age 35.6±4.2; height 163.9±5.9 cm; body mass 58.1±5.2 kg; VO2peak 50.3±3.6 ml·min⁻¹·kg⁻¹) or on oral contraceptives (n=9; Age 30.4±4.5; height 163.9±9.0 cm; body mass 58.1±6.7 kg; VO2peak 52.4±4.2 ml·min⁻¹·kg⁻¹) participated in the study. All participants performed a graded maximal exercise test to determine their peak oxygen consumption (VO2peak). Participants then exercised at the speed corresponding to 75% of VO2peak for 40 minutes on a treadmill in each menstrual cycle phase: regular menstrual cycle group (early follicular phase, mid-follicular phase and luteal phase) and OC group (hormonal phase and non-hormonal phase). There were no differences in the respiratory exchange ratio of each phase, in regular menstrual cycle phase group (mean±SEM): early-follicular phase 0.89±0.01, mid-follicular phase 0.87±0.01 and luteal phase 0.88±0.01 (p > 0.05). There were also no differences in respiratory exchange ratio for the participants using oral contraceptive: hormonal phase 0.89±0.01 and non-hormonal phase 0.91±0.01 (p > 0.05). However, we found that OC may influence fat oxidation (p=0.018) during the hormonal phase. Our preliminary results suggest that menstrual cycle and oral contraceptive do not influence substrate oxidation in females with regular menstrual cycle phases. Regarding the few disparities, more research is needed to understand how sexual hormones influence substrate oxidation in female.
... Physiological, metabolic and ergogenic responses differ between running and cycling. Running promotes larger muscle mass than cycling and the type of muscle contraction during running (concentric and eccentric) contributes to greater fat oxidation at the same relative intensity [32,33]. In addition, excess post-exercise oxygen consumption (EPOC) is greater (? 37%) after a running session than after a cycling session, as shown in the study by Cunha et al. comparing HIIT and MICT treadmill protocol in overweight men (exercises performed at 75% of oxygen uptake reserve, running session corresponding to 400 kcal, and interval training including two series of 200 kcal) [34]. ...
... In addition, excess post-exercise oxygen consumption (EPOC) is greater (? 37%) after a running session than after a cycling session, as shown in the study by Cunha et al. comparing HIIT and MICT treadmill protocol in overweight men (exercises performed at 75% of oxygen uptake reserve, running session corresponding to 400 kcal, and interval training including two series of 200 kcal) [34]. In addition, plasma lactate concentrations are higher in cycling [34], which reflects greater carbohydrate utilization [33]. Together, these results could explain the greater effect of running on decreasing total fat mass. ...
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Background High-intensity interval training (HIIT) is promoted as a time-efficient strategy to improve body composition. Objective The aim of this meta-analysis was to assess the efficacy of HIIT in reducing total, abdominal, and visceral fat mass in normal-weight and overweight/obese adults. Methods Electronic databases were searched to identify all related articles on HIIT and fat mass. Stratified analysis was performed using the nature of HIIT (cycling versus running, target intensity), sex and/or body weight, and the methods of measuring body composition. Heterogeneity was also determined ResultsA total of 39 studies involving 617 subjects were included (mean age 38.8 years ± 14.4, 52% females). HIIT significantly reduced total (p = 0.003), abdominal (p = 0.007), and visceral (p = 0.018) fat mass, with no differences between the sexes. A comparison showed that running was more effective than cycling in reducing total and visceral fat mass. High-intensity (above 90% peak heart rate) training was more successful in reducing whole body adiposity, while lower intensities had a greater effect on changes in abdominal and visceral fat mass. Our analysis also indicated that only computed tomography scan or magnetic resonance imaging showed significant abdominal and/or visceral fat-mass loss after HIIT interventions. ConclusionHIIT is a time-efficient strategy to decrease fat-mass deposits, including those of abdominal and visceral fat mass. There was some evidence of the greater effectiveness of HIIT running versus cycling, but owing to the wide variety of protocols used and the lack of full details about cycling training, further comparisons need to be made. Large, multicenter, prospective studies are required to establish the best HIIT protocols for reducing fat mass according to subject characteristics.
... Knechtle et al. reported a connection between faT max (75% Vo 2max ) and the lT (77.70% Vo 2max ) in male cyclists, but nothing similar was observed in runners when 30 min stages were used. 12 They did not offer explanation for observed occurrences. Studies by Bircher et al. found moderate correlations between faT max and the lT in both male and female cyclists (r=0.75, p<0.01 and r=0.67, p<0.01) with 3 min stages, respectively. ...
... 13 Knechtle et al. reported faT max at 55% of Vo 2max in male athletes using a 30 min constant speed treadmill test. 12 achten et al. determined faT max to occur at 62.50% and 65% of Vo 2max in male cyclists using a GXT protocol with 5-and 3-min exercise stages, respectively. 1, 6 recently, Schwindling et al. reported faT max at 61% of Vo 2max in male cyclists using 6 min stages protocol. ...
Article
Background: The aim of this study was to identify the exercise intensity that elicited the highest rate of fat oxidation (FATmax) and to assess its relationship with the aerobic threshold (AeT) in male athletes. We hypothesized existence of high correlation of these two parameters when a short-staged graded treadmill test with AeT identified through breath-by-breath gas exchange analysis was used. Methods: Fifty-six trained male athletes (age 25.6 ± 3.4 y, height 197.8 ± 5.6 cm, body mass 98.5 ± 6.6 kg) participated in the study. Pearson correlation coefficient (r) and effect size (R2) were used to evaluate the existence of connection between VO2 at AeT and at FATmax. Maximal oxygen consumption (VO2max) and substrates utilization were determined using breath-by-breath indirect calorimetry during a short-staged graded treadmill test to exhaustion. Results: Mean VO2max was 52.12 ± 9.02 ml·kg-1·min-1. FATmax and AeT occurred at 47.47 ± 10.59 % of VO2max and 45.95 ± 10.21 % of VO2max, respectively. Fat utilization at FATmax was 0.59 ± 0.24 g·min-1. A high correlation was found between VO2 at FATmax and at AeT (r = 0.88, p <0.01, 95 % CI 0.80 to 0.93). The effect size was 77.44%. Conclusions: Our results confirm the hypothesis of an existence of a high correlation between AeT and FATmax allowing implementation of more accurate training approach.
... Sex differences in physiological characteristics are likely to be the main factor for the ~10-15% sex difference in endurance performance. Men have a larger skeletal muscle mass compared to women (9), correlating with a greater muscular strength (1), a larger aerobic capacity (11) and lower relative body fatness (12). ...
... A first important finding was that men were faster in cycling, but not in swimming, running and overall race time. The faster cycling speed might be explained by anthropometric and physiological differences be-tween women and men (11,12,14). Sex differences in anthropometric (9, 12) and physiological characteristics (11) are the most likely main reasons for this difference in cycling speed. ...
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The performance and sex differences of long-distance triathletes competing in 'Ironman Hawaii' are well investigated. However, less information is available with regards to triathlon races of the Ironman distance held under extreme environmental conditions (e.g. extreme cold) such as the 'Isklar Norseman Xtreme Triathlon' which started in 2003. In 'Isklar Norseman Xtreme Triathlon', athletes swim at a water temperature of ~13-15°C, cycle at temperatures of ~5-20°C and run at temperatures of ~12-28°C in the valley and of ~2-12°C at Mt. Gaustatoppen. This study analysed the performance trends and sex differences in 'Isklar Norseman Xtreme Triathlon' held from 2003 to 2015 using mixed-effects regression analyses. During this period, a total of 175 women (10.6%) and 1,852 men (89.4%) successfully finished the race. The number of female (r² = 0.53, P = 0.0049) and male (r² = 0.37, P = 0.0271) finishers increased and the men-to-women ratio decreased (r² = 0.86, P < 0.0001). Men were faster than women in cycling (25.41 ± 2.84 km/h versus 24.25 ± 2.17 km/h) (P < 0.001), but not in swimming (3.06 ± 0.62 km/h vs. 2.94 ± 0.57 km/h), running (7.43 ± 1.13 km/h vs. 7.31 ± 0.93 km/h) and overall race time (874.57 ± 100.62 min vs. 899.95 ± 90.90 min) (P > 0.05). Across years, women improved in swimming and both women and men improved in cycling and in overall race time (P < 0.001). In running, however, neither women nor men improved (P > 0.05). In summary, in 'Isklar Norseman Xtreme Triathlon' from 2003 to 2015, the number of successful women increased across years, women achieved a similar performance to men in swimming, cycling and overall race time, and women improved across, years in swimming, cycling and overall race time.
... Neste sentindo, já está descrito na literatura que os exercícios em cicloergômetro apresentam um aumento mais significativo das concentrações de lactato do que a corrida em uma mesma velocidade relativa ao consumo má-ximo de oxigênio 20 . Além disso, a modalidade em cicloergômetro apresenta uma maior ativação da rota glicolítica do que a corrida, provavelmente devido a menor massa muscular envolvida para produzir um dado consumo de oxigênio 20 . ...
... Neste sentindo, já está descrito na literatura que os exercícios em cicloergômetro apresentam um aumento mais significativo das concentrações de lactato do que a corrida em uma mesma velocidade relativa ao consumo má-ximo de oxigênio 20 . Além disso, a modalidade em cicloergômetro apresenta uma maior ativação da rota glicolítica do que a corrida, provavelmente devido a menor massa muscular envolvida para produzir um dado consumo de oxigênio 20 . Os exercícios em bicicleta também apresentam uma maior exigência dos músculos flexores e extensores de joelho e de quadril comparado a corrida. ...
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O objetivo do estudo foi revisar os efeitos de diferentes estratégias metodológicas de treinamento combinado na força e na potência aeróbia de indivíduos idosos saudáveis. A busca incluiu as bases de dados da MEDLINE (via Pubmed) e COCHRANE. A partir dessa busca, 3035 artigos tiveram seus títulos/resumos avaliados, destes 3026 foram excluídos e nove foram selecionados para análise. Foram incluídos dois estudos a partir das referências de outros estudos, totalizando 11 estudos para a leitura na íntegra. Após a leitura dos estudos, foram excluídos quatro por não estarem de acordo com os critérios de elegibilidade, restando sete para análise. Foram observadas melhoras significativas na força com o treinamento combinado. Entretanto, a realização simultânea de um treinamento aeróbio em cicloergômetro e em intensidades próximas ao segundo limiar ventilatório (FCLV2) e de força (nesta ordem de execução) pode apresentar um efeito de interferência nas respostas de força de membros inferiores. O desempenho da potência aeróbia não foi afetado quando o treino de força foi realizado antes. Além disso, uma frequência semanal de duas vezes apresenta iguais benefícios em comparação a uma frequência maior. Desta forma, parece que o treinamento aeróbio em cicloergômetro em intensidades baseadas no FCLV2 realizado antes do treinamento de força, provoca interferência nos ganhos de força muscular de membros inferiores e o treinamento de força antes do aeróbio não afeta o desempenho da potência aeróbia. Ainda, uma frequência semanal de treinamento combinado menor apresenta benefícios em amplitudes semelhantes a uma frequência maior.
... Studies of healthy adult (> 18 years of age) humans were included for analysis. Only studies using two-legged cycling exercise were included, due to differences in substrate utilization between cycling and running [43,44]. Cycling had to be continuous, for at least 5 min in duration and performed at a single exercise intensity. ...
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Background: Multiple factors influence substrate oxidation during exercise including exercise duration and intensity, sex, and dietary intake before and during exercise. However, the relative influence and interaction between these factors is unclear. Objectives: Our aim was to investigate factors influencing the respiratory exchange ratio (RER) during continuous exercise and formulate multivariable regression models to determine which factors best explain RER during exercise, as well as their relative influence. Methods: Data were extracted from 434 studies reporting RER during continuous cycling exercise. General linear mixed-effect models were used to determine relationships between RER and factors purported to influence RER (e.g., exercise duration and intensity, muscle glycogen, dietary intake, age, and sex), and to examine which factors influenced RER, with standardized coefficients used to assess their relative influence. Results: The RER decreases with exercise duration, dietary fat intake, age, VO2max, and percentage of type I muscle fibers, and increases with dietary carbohydrate intake, exercise intensity, male sex, and carbohydrate intake before and during exercise. The modelling could explain up to 59% of the variation in RER, and a model using exclusively easily modified factors (exercise duration and intensity, and dietary intake before and during exercise) could only explain 36% of the variation in RER. Variables with the largest effect on RER were sex, dietary intake, and exercise duration. Among the diet-related factors, daily fat and carbohydrate intake have a larger influence than carbohydrate ingestion during exercise. Conclusion: Variability in RER during exercise cannot be fully accounted for by models incorporating a range of participant, diet, exercise, and physiological characteristics. To better understand what influences substrate oxidation during exercise further research is required on older subjects and females, and on other factors that could explain additional variability in RER.
... With increasing exercise intensity, the absolute CHO oxidation (g·min −1 ) increases gradually up to the maximal oxygen uptake (VO 2max ), whereas the maximal fat oxidation rate (MFO) is reached at low-moderate exercise intensities and undergoes a marked reduction at higher exercise intensities (6). The exercise intensity at MFO is defined as Fat Max (7) and is elicited from~30% ofVO 2max in untrained individuals to~70% ofVO 2max in endurance-trained athletes (1,7,8). Fuel shifts are controlled by a complex interplay between the intracellular and the extracellular metabolic environments (9), are influenced by hormonal control (3), and may occur solely by changing the availability of substrates without any change in metabolic rate. ...
Article
Introduction: Skeletal muscle perfusion and oxygen (O2) delivery are restricted during whole-body exercise because of a limited cardiac output (Q˙). This study investigated the role of reducing central limitations to exercise on the maximal fat oxidation rate (MFO) by comparing mass-specific MFO (per kilogram of active lean mass) during one-legged (1L) and two-legged (2L) cycling. We hypothesized that the mass-specific MFO would be higher during 1L than 2L cycling. Methods: Twelve male subjects (V̇O2peak, 59.3 ± 8.4 mL·kg-1·min-1; mean ± SD) performed step-incremental 2L- (30%-80% of V̇O2peak) and 1L (50% of 2L power output, i.e., equal power output per leg) cycling (counterbalanced) while steady-state pulmonary gas exchanges, Q˙ (pulse-contour analysis), and skeletal muscle (vastus lateralis) oxygenation (near-infrared spectroscopy) were determined. MFO and the associated power output (FatMax) were calculated from pulmonary gas exchanges and stoichiometric equations. A counterweight (10.9 kg) was added to the contralateral pedal arm during 1L cycling. Leg lean mass was determined by DEXA. Results: The absolute MFO was 24% lower (0.31 ± 0.12 vs 0.44 ± 0.20 g·min-1, P = 0.018), whereas mass-specific MFO was 52% higher (28 ± 11 vs 20 ± 10 mg·min-1·kg-1, P = 0.009) during 1L than 2L cycling. FatMax was similar expressed as power output per leg (60 ± 28 vs 58 ± 22 W, P = 0.649). Q˙ increased more from rest to exercise during 1L than 2L cycling when expressed per active leg (ANOVA main effect: P = 0.003). Tissue oxygenation index and Δ[deoxy(Hb + Mb)] were not different between exercise modes (ANOVA main effects: P ≥ 0.587), indicating similar skeletal muscle fractional O2 extraction. Conclusions: Mass-specific MFO is increased by exercising a small muscle mass, potentially explained by increased perfusion and more favorable conditions for O2 delivery than during whole-body exercise.
... (2) the study reported at least one of the markers of interest (AMPK-α2 activity, p-AMPK Thr−172 , or p-ACC Ser−79/80 or Ser−212/221 ) along with at least one of the following markers: VO 2 max , pre-and post-exercise muscle glycogen concentration, exercise intensity (as a percent of VO 2 max ), exercise intensity (as a percent of maximal power determined from an incremental exercise test), or exercise duration (min); (3) skeletal muscle biopsies were performed at rest and immediately post-exercise, as differences in p-AMPK have been reported between 0 and 30 min following exercise [37][38][39]; (4) two-legged cycling exercise was used, due to differences in substrate utilization between cycling and running and the variation in muscle sampling for biopsies in running studies (i.e., gastrocnemius vs. vastus lateralis) [40,41]; (5) subjects had a VO 2 max > 30 mL kg −1 min −1 , which includes ~ 90% of men under the age of 60 years [42]; and (6) analysis was performed on whole muscle and was not fiber-type specific. ...
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Background The 5ʹ adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a cellular energy sensor that is activated by increases in the cellular AMP/adenosine diphosphate:adenosine triphosphate (ADP:ATP) ratios and plays a key role in metabolic adaptations to endurance training. The degree of AMPK activation during exercise can be influenced by many factors that impact on cellular energetics, including exercise intensity, exercise duration, muscle glycogen, fitness level, and nutrient availability. However, the relative importance of these factors for inducing AMPK activation remains unclear, and robust relationships between exercise-related variables and indices of AMPK activation have not been established. Objectives The purpose of this analysis was to (1) investigate correlations between factors influencing AMPK activation and the magnitude of change in AMPK activity during cycling exercise, (2) investigate correlations between commonly reported measures of AMPK activation (AMPK-α2 activity, phosphorylated (p)-AMPK, and p-acetyl coenzyme A carboxylase (p-ACC), and (3) formulate linear regression models to determine the most important factors for AMPK activation during exercise. Methods Data were pooled from 89 studies, including 982 participants (93.8% male, maximal oxygen consumption [𝑉O2max] 51.9 ± 7.8 mL kg−1 min−1). Pearson’s correlation analysis was performed to determine relationships between effect sizes for each of the primary outcome markers (AMPK-α2 activity, p-AMPK, p-ACC) and factors purported to influence AMPK signaling (muscle glycogen, carbohydrate ingestion, exercise duration and intensity, fitness level, and muscle metabolites). General linear mixed-effect models were used to examine which factors influenced AMPK activation. Results Significant correlations (r = 0.19–0.55, p < .05) with AMPK activity were found between end-exercise muscle glycogen, exercise intensity, and muscle metabolites phosphocreatine, creatine, and free ADP. All markers of AMPK activation were significantly correlated, with the strongest relationship between AMPK-α2 activity and p-AMPK (r = 0.56, p < 0.001). The most important predictors of AMPK activation were the muscle metabolites and exercise intensity. Conclusion Muscle glycogen, fitness level, exercise intensity, and exercise duration each influence AMPK activity during exercise when all other factors are held constant. However, disrupting cellular energy charge is the most influential factor for AMPK activation during endurance exercise.
... Die Anpassungen im Bereich der Fettoxidation, die durch eine mittel-bis langfristige Nahrungsumstellung zu erreichen sind, gehen indes mit einer verminderten Aktivität glykolytischer Enzyme einher und reduzieren auf diese Weise die Leistungsfähigkeit in intensiven Belastungsbereichen über 70 %V´O2max (Yeo et al., 2011). Dieser Effekt lässt sich jedoch durch die kurzfristige Zufuhr von Kohlenhydraten nach einer mehrtägigen fettdominanten Diät reduzieren, ohne dabei die enzymatischen Anpassungen im Fettstoffwechsel zu beeinträchtigen (Stellingwerff et al., 2006 (Chenevière, Malatesta, Gojanovic & Borrani, 2010;Knechtle et al., 2004). Als mögliche Ursache kann die erhöhte muskuläre Aktivität beim Laufen gelten (Arkinstall, Bruce, Nikolopoulos, Garnham & Hawley, 2001), aber auch eine verbesserte Bewegungsökonomie durch den Einfluss des Dehnungs-Verkürzungs-Zyklus, welcher beim Radfahren ausbleibt (Bijker, Groot & Hollander, 2002). ...
Thesis
Die Arbeit beleuchtet den Einsatz algorithmischer Datenbearbeitungen bei sportwissenschaftlichen Spiroergometrien aus praktischen und theoretischen Gesichtspunkten. Die aktuelle Verbreitung von algorithmischen Datenbearbeitungen aus Breath-by-Breath Untersuchungen wird über die Ergebnisse eines Fragebogens und einer systematischen Literaturübersicht dargestellt. Zudem erfolgt die Analyse der durch Algorithmen verursachten Messwertvarianzen der Sauerstoffaufnahme in diskontinuierlichen Belastungsuntersuchungen, bei Jugendlichen und im submaximalen Belastungsbereich.
... The above studies validate that FA flux cannot support the OXPHOS in exercise on its own, and despite being substrate-efficient, it tells only a part of the story of the oxidative phenotype. Interestingly, women have been considered better fat "metabolisers" as they have a higher relative whole-body fat oxidation at given steady-state exercise intensities compared with men [48]. Moreover, Fat Max in females occurs usually at higher fractions of VO 2 max relative to males [49]. ...
Article
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Mitochondria are popularly called the “powerhouses” of the cell. They promote energy metabolism through the tricarboxylic acid (TCA) cycle and oxidative phosphorylation, which in contrast to cytosolic glycolysis are oxygen-dependent and significantly more substrate efficient. That is, mitochondrial metabolism provides substantially more cellular energy currency (ATP) per macronutrient metabolised. Enhancement of mitochondrial density and metabolism are associated with endurance training, which allows for the attainment of high relative VO2 max values. However, the sedentary lifestyle and diet currently predominant in the Western world lead to mitochondrial dysfunction. Underdeveloped mitochondrial metabolism leads to nutrient-induced reducing pressure caused by energy surplus, as reduced nicotinamide adenine dinucleotide (NADH)-mediated high electron flow at rest leads to “electron leak” and a chronic generation of superoxide radicals (O2−). Chronic overload of these reactive oxygen species (ROS) damages cell components such as DNA, cell membranes, and proteins. Counterintuitively, transiently generated ROS during exercise contributes to adaptive reduction-oxidation (REDOX) signalling through the process of cellular hormesis or “oxidative eustress” defined by Helmut Sies. However, the unaccustomed, chronic oxidative stress is central to the leading causes of mortality in the 21st century—metabolic syndrome and the associated cardiovascular comorbidities. The endurance exercise training that improves mitochondrial capacity and the protective antioxidant cellular system emerges as a universal intervention for mitochondrial dysfunction and resultant comorbidities. Furthermore, exercise might also be a solution to prevent ageing-related degenerative diseases, which are caused by impaired mitochondrial recycling. This review aims to break down the metabolic components of exercise and how they translate to athletic versus metabolically diseased phenotypes. We outline a reciprocal relationship between oxidative metabolism and inflammation, as well as hypoxia. We highlight the importance of oxidative stress for metabolic and antioxidant adaptation. We discuss the relevance of lactate as an indicator of critical exercise intensity, and inferring from its relationship with hypoxia, we suggest the most appropriate mode of exercise for the case of a lost oxidative identity in metabolically inflexible patients. Finally, we propose a reciprocal signalling model that establishes a healthy balance between the glycolytic/proliferative and oxidative/prolonged-ageing phenotypes. This model is malleable to adaptation with oxidative stress in exercise but is also susceptible to maladaptation associated with chronic oxidative stress in disease. Furthermore, mutations of components involved in the transcriptional regulatory mechanisms of mitochondrial metabolism may lead to the development of a cancerous phenotype, which progressively presents as one of the main causes of death, alongside the metabolic syndrome.
... Especially in premenopausal women, these effects seem to occur through direct adaptions in the lipid metabolic pathway or indirectly through a reduction in fat mass. Investigating the underlying mechanisms of these metabolic adaptations, it is generally accepted that the use of bigger muscle groups during the eccentric muscle loading phase in running causes larger increases in the fat oxidation, whereas in cycling concentric muscle loading phase are in the foreground (12,13). In addition, this divergence in contraction types in running compared to cycling may also provide a sufficient mechanical stimulus for collagen synthesis in the connective tissue (14). ...
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The purpose was to examine the effects of concurrent training (CT) combined with specific collagen peptides (SCP) intake on cardiometabolic parameters and performance indices in women. In a double-blind, placebo-controlled, randomized trial recreationally active women (n = 59) completed a 12-week CT training (3 day/week) and ingested 15 g of SCP (treatment group [TG]) or placebo (control group [CG]) on a daily basis. Running distance as a marker of endurance performance (time trial), velocity and heart rate at the lactate and anaerobic threshold (incremental running test) and body composition (bioelectrical impedance analysis [BIA]) were measured. BIA measurements included determination of fat mass (FM) and fat free mass (FFM). Additionally, muscular strength (one-repetition-maximum [1RM]) and muscular endurance (60% of 1RM) were assessed. After 12-weeks, TG had a higher increase in running distance (1,034 ± 643 m) compared to the CG (703 ± 356 m) indicated by a significant interaction effect (p < 0.05). Velocity at lactate and anaerobic threshold improved in both groups over time (p < 0.001), with no significant differences between groups. Similarly, heart rate at lactate threshold decreased over time (p < 0.001), with no time × group interaction. TG declined more in heart rate at anaerobic threshold (−8 ± 14 bpm) than the CG (−1 ± 7 bpm), which resulted in a significant interaction effect (p < 0.01). FM decreased over time in TG and CG (p < 0.001), with no group differences. On contrary, TG had a higher increase in FFM (0.8 ± 0.9 kg) compared to the CG (0.3 ± 1.0 kg) (time × group interaction: p < 0.05). Both, 1RM and muscular endurance improved over time (p < 0.001), with no significant group differences. In conclusion, supplementation of SCP in combination with CT resulted in a significant increase in endurance performance compared to the control group. This might potentially be a consequence of improved structural and cardiometabolic adaptations.
... Schwindling et al. (2014) assessed a group of male cyclists using a 6 min stages protocol and found that Fat max was reached at 61% of VO 2max . In another study conducted by Knechtle et al. (2004) who used a 30 min constant speed treadmill test, Fat max was observed at 55% of VO 2max in male athletes. More recently, Peric et al. (2018) reported Fat max at 47.47% of VO 2max in 56 trained male athletes. ...
Article
The present study aimed to investigate the potential effect of different aerobic fitness levels on substrate oxidation in trained taekwondo athletes. 57 male athletes (age 21.10±7.79 years; VO 2max 50.67±6.67 ml/kg/min) with regular weekly taekwondo training and training experience of at least three years completed a graded exercise test to exhaustion on a treadmill. Maximal fat oxidation (MFO), the exercise intensity related to MFO (Fat max ), and carbohydrate (CHO) oxidation rate were measured using indirect calorimetry methods. The athletes then were divided into a low (<50 ml/kg/min, n=18) and high (>50 ml/kg/min, n=39) VO 2max group. The average MFO was higher in the high VO 2max group than in the low VO 2max group (0.46±0.19 vs 0.28±0.11 g/min; P<0.001). Although Fat max tended toward higher values in the high VO 2max group, no difference was observed between the groups (49.15±15.22 vs 42.42±12.37% of VO 2max ; P=0.18). It was also shown that the high VO 2max group had a lower CHO oxidation rate and a higher fat oxidation rate at given exercise intensities. In conclusion, it seems that MFO and substrate oxidation rates in taekwondo athletes can be influenced by aerobic fitness level such that the athletes with higher VO 2max appeared to use more fat as a fuel source for energy supply during a given exercise.
... It is well known from laboratory studies with triathletes that heart rate and energy expenditure is higher in running compared to cycling [43]. While the measurement of heart rate with a wrist-worn device might be reliable [44], the reported energy expenditure from these devices should be interpreted with caution [45], given their potential bias and error [46], the current wrist-worn activity trackers are most likely not accurate enough [26]. ...
Article
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This case study analyzed performance, pacing and potential predictors in a self-paced world record attempt of a professional triathlete to finish 40 Ironman triathlons within 40 days. Split times (swimming, cycling, running) and overall times, body weight, daily highest temperature, wind speed, energy expenditure, mean heart rate, and sleeping time were recorded. Non-linear regressions were applied to investigate changes in split and overall times. Multivariate regression analyses were performed to test which variables showed the greatest influence on the dependent variables cycling, running and overall time. The athlete completed the 40xIronman distances in a total time of 444:22 h:min. He invested 50:26 h:min in swimming, 245:37 h:min in cycling, 137:17 h:min in running and 11:02 h:min in transition times. Performance in swimming and cycling became reduced over the days, whereas running performance improved until the 20th day and became reduced to the 40th day. Overall time decreased until the 15th day, improved up to 31st, and started then to decrease until the end. Wind speed, overall time on the previous day and average heart race during cycling were significant independent variables to influence cycling performance. Body weight and average heart rate during running were the significant independent variables to influence running performance. Cycling performance, running performance and body weight were the significant independent variables to influence overall time. In summary, running performance was influenced by body weight, cycling was influenced by wind speed and overall time was influenced by both running and cycling performances. Keywords: swimming; cycling; running; ultra-endurance; recovery
... Energy expenditure was calculated using the following equation, assuming a negligible contribution of protein oxidation. Energy expenditure was calculated assuming that 1 g carbohydrate = 4 kcal, and 1 g fat = 9 kcal 33 . Fat and carbohydrate oxidation were calculated from respiratory measurements (VO 2 , VCO 2 ) according to the table of nonprotein respiratory quotient 34 . ...
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The purpose of this study was to compare differences of energy expenditure and substrate metabolism between motorized-treadmill and overground running in three different velocities in Chinese middle-aged women. In total, 74 healthy middle-aged women (age, 48 ± 4 years; height, 159.4 ± 4.9 cm; weight, 58.6 ± 6.7 kg; and body-mass index (BMI), 23.1 ± 2.7 kg/m²) volunteered to participate in this study. Bioelectrical-impedance analysis was used to measure body composition. Energy expenditure, carbohydrates (CHO), and fat oxidation were calculated with indirect calorimetry during motorized-treadmill and overground running. Running speed from slow to fast was 7.0, 8.0, and 9.0 km/h. The duration of each velocity was 6 min, separated by 5–15 min rest. There was no significant difference in energy expenditure between overground and treadmill running at the speed of 7 km/h (8.10 ± 1.25 vs. 7.75 ± 1.13 kcal/min, p > 0.05). Energy expenditure of overground running at 8 and 9 km/h was higher than that of treadmill running (9.36 ± 1.40 vs. 8.54 ± 1.21 kcal/min; 10.33 ± 1.55 vs. 9.54 ± 1.36 kcal/min; both p < 0.01). Fat contribution to energy consumption was significantly higher during treadmill running than during overground running (both p < 0.01) at speeds of 8 and 9 km/h. Overground running at high intensity incurred greater energy consumption than treadmill running did. However, results showed greater fat utilization during treadmill running than during overground running at high intensity. It is critical that these differences are taken into account when we prescribe training modes and intensities for middle-aged women.
... In addition, aerobic capacity estimated by maximal workload during a graded exercise test was the best predictor of duathlon performance (3). Although no data on sex difference in duathletes' V _ O 2 max exist, it has been observed that men triathletes exhibit higher V _ O 2 max than their women counterparts (7,12). ...
Article
Nikolaidis, PT, Villiger, E, and Knechtle, B. Participation and performance trends in the ITU Duathlon World Championship from 2003 to 2017. J Strength Cond Res XX(X): 000-000, 2018-Participation and performance across years have been studied extensively in various endurance and ultra-endurance sports; however, less information exists with regards to duathlon (i.e., Run 1, Bike, and Run 2). The aim of this study was to examine performance and participation trends of duathletes competing either to short (10-km Run 1, 50-km Bike, and 5-km Run 2) or to long distance (10-km Run 1, 150-km Bike, and 30-km Run 2) in the Powerman World Championship "Powerman Zofingen." We analyzed 7,951 finishers (women, n = 1,236, age 36.7 ± 9.1 years; men, n = 6,715, 40.1 ± 10.1 years) competing in "Powerman Zofingen" from 2003 to 2017. Men were faster than women by 8.2% (171 ± 21 minutes vs. 186 ± 21 minutes, p < 0.001, η = 0.068) and 7.5% (502 ± 57 minutes vs. 543 ± 64 minutes, p < 0.001, η = 0.068) in the short and long distances, respectively. Women were younger than men by 4.6 years (35.0 ± 9.0 years vs. 39.6 ± 10.5 years, p < 0.001, η = 0.026) and 1.8 years (38.8 ± 8.7 years vs. 40.6 ± 9.5 years, p < 0.001, η = 0.005) in the short and long distances, respectively. An increase of women finishers across years in the long distance was observed (e.g., n = 19 in 2003 and n = 58 in 2017; p < 0.001), whereas no change was shown in short distance and men finishers. The men-to-women ratio (MWR) decreased across years in the long, but not in the short distance. No change of race time across years was observed. The sex difference in race time increased in long distance (p = 0.014), whereas it did not change in the short. Age increased across years in both sexes and distances (p < 0.001). The sex difference in age decreased in the long (p = 0.007), but not in the short distance. In summary, the number of women finishers increased and the MWR decreased in the long distance. The age of the finishers increased across years, and their performance remained unchanged. The increase of the sex difference in race time in the long distance might be attributed to the increased number of women finishers.
... marathon running and long-distance triathlons, is the ability to oxidize fat at high rates. 1,2 Accordingly, maximal whole-body fat oxidation (MFO) has been reported as high as 0.6-0.7 g/min in groups of endurance-trained individuals, [3][4][5] whereas values of 0.2-0.4 g/min are commonly observed in untrained humans. ...
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Elite endurance athletes possess a high capacity for whole body maximal fat oxidation (MFO). The aim was to investigate the determinants of a high MFO in endurance athletes. The hypotheses were that augmented MFO in endurance athletes is related to concomitantly increments of skeletal muscle mitochondrial volume density (MitoVD) and mitochondrial fatty acid oxidation (FAOp), i.e. quantitative mitochondrial adaptations as well as intrinsic FAOp per mitochondria, i.e. qualitative adaptations. Eight competitive male cross‐country skiers and eight untrained controls were compared in the study. A graded exercise test was performed to determine MFO, the intensity where MFO occurs (FatMax), and V̇O2Max. Skeletal muscle biopsies were obtained to determine MitoVD (electron microscopy), FAOp and OXPHOSp (high resolution respirometry). The following were higher (p<0.05) in endurance athletes compared to controls: MFO (mean [95% confidence intervals]) (0.60 g/min [0.50‐0.70] vs 0.32 [0.24‐0.39]), FatMax (46% V̇O2Max [44‐47] vs 35 [34‐37]), V̇O2Max (71 ml/min/kg [69‐72] vs 48 [47‐49]), MitoVD (7.8% [7.2‐8.5] vs 6.0 [5.3‐6.8]), FAOp (34 pmol/sec/mg muscle w.w. [27‐40] vs 21 [17‐25]) and OXPHOSp (108 pmol/sec/mg muscle w.w. [104‐112] vs 69 [68‐71]). Intrinsic FAOp (4.0 pmol/sec/mg muscle w.w/MitoVD [2.7‐5.3] vs 3.3 [2.7‐3.9]) and OXPHOSp (14 pmol/sec/mg muscle w.w./MitoVD [13‐15] vs 11 [10‐13]) were, however, similar in the endurance athletes and untrained controls. MFO and MitoVD correlated (r²=0.504, p<0.05) in the endurance athletes. A strong correlation between MitoVD and MFO suggests that expansion of MitoVD might be rate‐limiting for MFO in the endurance athletes. In contrast, intrinsic mitochondrial changes were not associated with augmented MFO. This article is protected by copyright. All rights reserved.
... While our results show opposite effects in protein metabolism among males and females, particularly in regulation of branched-chain amino acids (BCAAs) and protein biosynthesis, the present results also suggest gender differences in lipid and ketone body metabolism, nucleotide sugar metabolism, and energy metabolism. These findings are further supported by exercise physiology studies showing that females oxidize proportionately more fat and less carbohydrate than males 24,25 . ...
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Prenatal stress is known to epigenetically program offspring physiology and behaviour, and may become a risk factor for adult complex diseases. To gain insight into the underlying environment-gene interactions, we used proton nuclear magnetic resonance spectroscopy to analyze urinary metabolomes of male and female adolescents who were in utero during the 1998 Quebec Ice Storm. Metabolomic profiles in adolescent groups were found to be significantly different. Higher prenatal stress exposure generated alterations in metabolic pathways involved in energy metabolism and protein biosynthesis, such as branched-chain amino acid synthesis, alanine metabolism, and ketone body metabolism. Dysregulation of energy and protein metabolism suggests an increased risk of metabolic diseases like insulin resistance, diabetes, and obesity. These findings are consistent with prior observations of physiological phenotypes from this cohort. Understanding the impact of natural disasters on health risks will provide new and improved therapeutic strategies to mitigate stress-associated adverse health outcomes. Using metabolomic biomarkers may also assist in the prediction and prevention of these adverse outcomes.
... In addition, aerobic capacity estimated by maximal workload during a graded exercise test was the best predictor of duathlon performance (3). Although no data on sex difference in duathletes' V _ O 2 max exist, it has been observed that men triathletes exhibit higher V _ O 2 max than their women counterparts (7,12). ...
Article
Background: Participation and performance across years have been studied extensively in various endurance and ultra-endurance sports; however, less information exists with regards to duathlon (i.e. Run1, Bike and Run2). The aim of the present study was to examine performance and participation trends of duathletes competing either to short (10-km Run1, 50-km Bike and 5-km Run2) or long distance (10-km Run1, 150-km Bike and 30-km Run2) in the Powerman World Championship ‘Powerman Zofingen’. Methods: We analyzed 7,951 finishers (women, n=1,236, age 36.7±9.1 years; men, n=6,715, 40.1±10.1 years) competing in ‘Powerman Zofingen’ from 2003 to 2017. Results: Men were faster than women by 8.2% (171±21min versus 186±21min, p<0.001, η2=0.068) and 7.5% (502±57min versus 543±64min, p<0.001, η2=0.068) in the short and long distance, respectively. Women were younger than men by 4.6 years (35.0±9.0 years versus 39.6±10.5years, p<0.001, η2=0.026) and 1.8 years (38.8±8.7years versus 40.6±9.5years, p<0.001, η2=0.005) in the short and long distance, respectively. An increase of women finishers across years in the long distance was observed (e.g. n = 19 in 2003 and n = 58 in 2017; p<0.001), whereas no change was shown in short distance and men finishers. The men-to-women ratio (MWR) decreased across years in the long, but not in the short distance. No change of race time across years was observed. The sex difference in race time increased in long distance (p=0.014), whereas it did not change in the short. Age increased across years in both sexes and distances (p<0.001). The sex difference in age decreased in the long (p=0.007), but not in the short distance. Conclusions: In summary, the number of women finishers increased and the MWR decreased in the long distance. The age of the finishers increased across years and their performance remained unchanged. The increase of the sex difference in race time in the long distance might be attributed to the increased number of women finishers. Keywords: aging, cycling, master athletes, running, sex difference, ultra-endurance
... This is despite the fact that many women exercise to reduce body fat mass or may use the GI to select appropriate carbohydrates to consume before training and competition. Several studies have reported that sex differences exist in the relative contribution from carbohydrate and fat to oxidative metabolism during exercise (15)(16)(17)(18)(19)(20). In contrast, others have reported that no differences exist in the total amount of fat and carbohydrate oxidized by men and women but that different sources of lipid are used (21,22). ...
Article
Background: Few data exist on the metabolic responses to mixed meals with different glycemic indexes and their effects on substrate metabolism during exercise in women. Objective: We examined the effects of preexercise mixed meals providing carbohydrates with high (HGI) or low glycemic index (LGI) on substrate utilization during rest and exercise in women. Design: Eight healthy, active, eumenorrheic women [aged 18.6 ± 0.9 y; body mass: 59.9 ± 7.1 kg; maximal oxygen uptake (V̇O2max): 48.7 ± 1.1 mL · kg⁻¹ · min⁻¹] completed 2 trials. On each occasion, subjects were provided with a test breakfast 3 h before performing a 60-min run at 65% V̇O2max on a motorized treadmill. Both breakfasts provided 2 g carbohydrate/kg body mass and were isoenergetic. The calculated GIs of the meals were 78 (HGI) and 44 (LGI). Results: Peak plasma glucose and serum insulin concentrations were greater after the HGI breakfast than after the LGI breakfast (P < 0.05). No significant differences in substrate oxidation were reported throughout the postprandial period. During exercise, the estimated rate of fat oxidation was greater in the LGI trial than in the HGI trial (P < 0.05). Similarly, plasma free fatty acid and glycerol concentrations were higher throughout exercise in the LGI trial (P < 0.05). No significant differences in plasma glucose or serum insulin were observed during exercise. Conclusion: Altering the GI of the carbohydrate within a meal significantly changes the postprandial hyperglycemic and hyperinsulinemic responses in women. A LGI preexercise meal resulted in a higher rate of fat oxidation during exercise than did an HGI meal.
... [1] Pederson proposed the "diseasome of physical inactivity" hypothesis which states that the visceral fat accumulation due to physical inactivity on comparing running with cycling done by moderately trained males [8,9] and females, [9] male triatheletes, [10] and endurance atheletes. [11] Although both TM and CE have advantages and disadvantages, [12] but for fat oxidation, TM might be more beneficial than CE at equivalent AE intensity. The exercise intensity in these studies was estimated by the variables such as percentage of maximum oxygen uptake (% VO 2max ) and work done or heart rate (HR) (% HR max ) that requires expensive laboratory equipment and is not a practical approach for developing countries as these instruments are not available to the mass population. ...
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Background: Treadmill (TM) and cycle ergometer (CE) are the most commonly used indoor machines for aerobic exercise (AE). Previous studies have indicated that TM causes higher fat oxidation than CE AE; however, data from the Indian subcontinent are lacking regarding the same. Accumulation of visceral fat leads to various cardiovascular and metabolic disorders, and hence, AE modality that causes higher fat oxidation could prove more beneficial in improving healthrelated quality of life. Aims and Objectives: The aim of this study is to compare cardiovascular response and respiratory exchange ratio (RER) in TM and CE AE by moderately active males at similar ratings of perceived exertion (RPE). Materials and Methods: In the present experimental study, sixteen males with normal body mass index were involved to perform 30 min of continuous moderate intensity AE on TM and CE at RPE of 13. Systolic blood pressure (SBP) and diastolic blood pressure (DBP), heart rate (HR), and pulse pressure (PP) were analyzed just before and after the exercise trial. RER was estimated during the last 2 min of exercise. Paired t-test was applied to compare the means, and P < 0.05 was considered statistically significant. Results: HR after TM (136 ± 10) tended (P = 0.063) to be higher than CE (132 ± 9), while changes in SBP, DBP, and PP were non-significant. RER was non-significantly (P = 0.148) higher in CE (0.89 ± 0.05) than TM (0.91 ± 0.06). Oxygen consumption was significantly (P = 0.049) higher in TM (1.11 ± 0.17 L/min) than CE (1.03 ± 0.16 L/min). Conclusion: TM caused significantly higher energy consumption with non-significantly higher HR and fat oxidation than CE AE at RPE of 13.
... No obstante, es necesario conocer cuáles son las intensidades que permiten optimizar la oxidación de grasas para proporcionar un efecto en la composición corporal del cliente. Knechtle et al. 17 determinaron que el ejercicio de carrera o de bicicleta realizado al 75 % del consumo de oxígeno máximo (VO 2 máx) producía una mayor oxidación de grasas que al realizarlo al 65 % o al 55 % de VO 2 máx tanto en atletas hombres y mujeres bien entrenados en resistencia. Estos autores estimaron que el 75 % de VO 2 máx correspondía con el umbral anaeróbico en la bicicleta, pero no en la carrera, donde el umbral anaeróbico era más alto del 75 %. ...
... The sex difference in endurance performance is primarily caused by physiological differences in V _ O 2 max (19) and anthropometric characteristics such as the difference in skeletal muscle mass and body fat (25). It has been shown that female ultrarunners have a lower skeletal muscle mass and a higher percentage of body fat than male ultrarunners, which leads to a disadvantage for women in ultrarunning performance (22,48). ...
Article
In Ironman triathlon, the number of overall male and female finishers increased in the last 30 years, while an improvement in performance has been reported. Studies concluding these numbers only analysed the top ten athletes per age group instead of all finishers, therefore a selection bias might have occurred. The aim of the present study was to investigate participation, performance and the age-related performance decline of all pro and age group triathletes ranked in all Ironman triathlons held worldwide between 2002 and 2015. Split and overall race times of 329,066 (80%) male and 81,815 (20%) female athletes competing in 253 different Ironman triathlon races were analysed. The number of finishers increased in all age groups with exception of women in age group 75-79 years. In pro athletes, performance improved in all disciplines. In age group athletes, performance improved in younger age groups for running (18-24 to 40-44 years) and older age groups for swimming (50-54 to 65-69 years) and cycling (35-39 to 55-59 years), while it impaired in younger age groups for swimming (18-24 to 45-49 years) and cycling (18-24 to 30-34), and older age groups in running (45-49 to 70-74 years). The age-related performance decline started in women in age group 25-29 years in swimming and in age group 30-34 years in cycling, running and overall race time, whereas it started in men in age group 25-29 years in swimming and in age group 35-39 years in cycling, running and overall race time. For athletes and coaches, performance improved in younger age groups for running and older age groups for swimming and cycling and the age-related decline in performance started earlier in swimming than in cycling and running.In summary, women should start competing in Ironman triathlon before the age of 30 years and men before the age of 35 years to achieve their personal best Ironman race time.
... Maximal fat oxidation rates are shown to be significantly higher during running compared to the same intensity of cycling. 78,79 Women oxidize more fat than men at around 40% of VO 2 max, 80,81 although gender difference does not seem to occur at higher intensities. 80 Fat oxidation was also shown to be augmented in exercise that combines aerobic and resistance training. ...
Article
The energy used in post-prandial state during rest and physical activity is derived predominantly from the oxidation of carbohydrate (CHO) and fat. Although protein can also serve as a source of energy, amino acids oxidation is usually tightly adjusted to amino acids intake and their contribution to total energy expenditure is rather insignificant in healthy subjects. Blood glucose, glycogen, plasma fatty acids and intramuscular triglycerides, on the other hand, present major sources for energy production. The amount of energy stored in the form of fat is large, representing 92–98% of all endogenously stored energy with CHO contributing only about 2–8%. Fat is at the bottom of an oxidative hierarchy that determines fuel selection, and its oxidation is governed by the presence or absence of the other macronutrients. In addition, the rate at which it can be oxidized depends on intensity of energy expenditure. In contrast, CHO elicit strong auto-regulatory adjustments in their oxidation. This review aims at summarizing the current state of knowledge on CHO and fat body storage, hierarchy of fuel utilization during resting state, anaerobic and aerobic pathways for energy production during exercise, and the effects of exercise mode, intensity, duration, and training on CHO and fat utilization.
... None of these reviews, however, has comprehensively examined exogenous carbohydrate specific to endurance running, and the majority of studies included in several of these reviews used cycling (59,61). This lack of focus on running is concerning given that the exercise modality modifies substrate use (1,33) and gastrointestinal (GI) tolerance to feedings (17). Rates of substrate (carbohydrate and fat) utilization differ between running and cycling, at least when comparing across the same relative intensity (e.g., %V _ O 2 peak: 1 vs. 33), and these differences persist even when carbohydrate is ingested (19). ...
Article
Previous review articles assessing the effects of carbohydrate ingestion during prolonged exercise have not focused on running. Given the popularity of distance running and the widespread use of carbohydrate supplements, this article reviewed evidence for carbohydrate ingestion during endurance running. Criteria for inclusion were: 1) English-language experimental studies including a performance task; 2) moderate-to-high intensity exercise >60 min (intermittent excluded); and 3) carbohydrate ingestion (mouth rinsing excluded). Thirty studies were identified with 76 women and 505 men. Thirteen of 17 studies comparing a carbohydrate beverage(s) to water or placebo found a between-condition performance benefit with carbohydrate, although heterogeneity in protocols precludes clear generalizations about expected effect sizes. Additional evidence suggests: 1) performance benefits are most likely to occur during events >2 h, although several studies showed benefits for tasks lasting 90-120 min; 2) consuming carbohydrate beverages above ad libitum levels increases GI discomfort without improving performance; 3) carbohydrate gels do not influence performance for events lasting 16 to 21 km; and 4) multiple saccharides may benefit events >2 h if intake is ≥1.3 g[BULLET OPERATOR]min. Given most participants were fasted young men, inferences to women, adolescents, older runners, and those competing in fed conditions are hampered. Future studies should address these limitations to further elucidate the role of carbohydrate ingestion during endurance running.
... In our study, FFA level was markedly lower at the end of the exercise test (—50%) and after 30 min of recovery (—25%) in trained subjects . Nevertheless, the findings of the current study are in contrast with most studies on endurance in trained subjects, which reported highest fat oxidation rate at 65% VO 2 max [13,27,28]. This may be partly explained by the relative ...
... Both exposures are potentially feasible or relevant for public health intervention, because other beverage intake accounts for over 40% of total water intake in free-living adults and children [59,60], and healthy individuals can experience limited access to water [61], involuntary dehydration [62] and/or thirst deficit [63] under daily life conditions. Age, sex, weight, health status, diet and exercise conditions were considered in this review, because these variables determine the water requirements and water intake of free-living individuals [20,64], modify fat oxidation [65,66] and determine body weight. Although smoking also determines water requirements and water intake, smoking was not systematically extracted in this review, because RCTs typically recruit non-smokers and/or prohibit smoking during the study period. ...
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Drinking water has heterogeneous effects on energy intake (EI), energy expenditure (EE), fat oxidation (FO) and weight change in randomized controlled trials (RCTs) involving adults and/or children. The aim of this qualitative review of RCTs was to identify conditions associated with negative, null and beneficial effects of drinking water on EI, EE, FO and weight, to generate hypotheses about ways to optimize drinking water interventions for weight management. RCT conditions that are associated with negative or null effects of drinking water on EI, EE and/or FO in the short term are associated with negative or null effects on weight over the longer term. RCT conditions that are associated with lower EI, increased EE and/or increased FO in the short term are associated with less weight gain or greater weight loss over time. Drinking water instead of caloric beverages decreases EI when food intake is ad libitum. Drinking water increases EE in metabolically-inflexible, obese individuals. Drinking water increases FO when blood carbohydrate and/or insulin concentrations are not elevated and when it is consumed instead of caloric beverages or in volumes that alter hydration status. Further research is needed to confirm the observed associations and to determine if/what specific conditions optimize drinking water interventions for weight management.
... Daussin et al. (2007) observed that V O 2 max improvement in untrained subjects after continuous training at a lower intensity occurred due to peripheral adaptations in skeletal muscles, whereas after intermittent training at a higher intensity the increase in V O 2 max resulted from both peripheral and central adaptations. Accordingly, the greater improvement observed in LT could suggest a higher level of peripheral adaptation after UP training in comparison with LO training, since this threshold has been closely linked to enhanced O 2 extraction by exercising muscle (Midgley et al. 2007b) and higher fat oxidation during exercise (Achten and Jeukendrup 2004;Knechtle et al. 2004). However, as dietary intake was not controlled in the present study, inferences about the changes in substrate utilisation (e.g. ...
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Purpose: Although time spent at [Formula: see text]O2max (t@[Formula: see text]O2max) has been suggested as an optimal stimulus for the promotion of greater [Formula: see text]O2max improvements, scientific findings supporting this notion are surprisingly still lacking. To investigate this, the present study described t@[Formula: see text]O2max in two different severe-intensity interval training regimens and compared its effects on aerobic indexes after a 4-week intervention. Methods: Twenty-one recreational cyclists performed an incremental exercise test and six time-to-exhaustion tests on four different days to determine [Formula: see text]O2max, lactate threshold (LT), critical power (CP) and the highest intensity (I HIGH) and lowest exercise duration (T LOW) at which [Formula: see text]O2max was attained. Subjects were assigned to the lower (LO, n = 11, 4 × 5 min at 105 % CP, 1 min recovery) or the upper severe-intensity training groups (UP, n = 10, 8 × 60 % T LOW at 100 % I HIGH, 1:2 work:recovery ratio). t@[Formula: see text]O2max was measured during the first and last training sessions. Results: A significantly higher t@[Formula: see text]O2max was elicited in the UP during training sessions in comparison with the LO group (P < 0.05), and superior improvements were observed in [Formula: see text]O2max (change in measure ±95 % confidence interval) (6.3 ± 1.9 vs. 3.3 ± 1.8 %, P = 0.034 for interaction terms) and LT (54.8 ± 11.8 vs. 27.9 ± 11.3 %, P = 0.023 for interaction terms). The other aerobic indexes were similarly improved between the groups. Conclusion: The present results demonstrated that UP training produced superior gains in [Formula: see text]O2max and LT in comparison with LO training, which may be associated with the higher t@[Formula: see text]O2max.
... In our study, FFA level was markedly lower at the end of the exercise test (-50%) and after 30 min of recovery (-25%) in trained subjects. Nevertheless, the findings of the current study are in contrast with most studies on endurance in trained subjects, which reported highest fat oxidation rate at 65% VO 2 max [13,27,28]. This may be partly explained by the relative Please cite this article in press as: Djelic high basal FFA level in TG. ...
Article
Objective: Was to investigate glucose and free fatty acid (FFA) responses to a graded maximal exercise test and recovery period in athletes and sedentary subjects. Subjects and methods: Twelve trained man (TG) and twelve untrained men (UTG) performed an incremental maximal treadmill test. Blood samples were taken from all subjects in the morning before, at the end of the test and after 30 minutes of recovery. Insulin, glucose and FFA levels were determined at these points in time. Results: Glucose concentration did not differ between TG and UTG at rest. Glucose levels increased steadily during exercise in both groups, but this increase was significant only in UTG at the end of the exercise test (+18.71%; P < 0.05) and after 30 min of recovery (+12.05%; P < 0.05) compared to basal levels. FFA concentrations at rest were significantly higher in TG than UTG (P < 0.05). FFA concentration initially significantly decreased during exercise in TG (-50.00%; P < 0.05), and increased during recovery period, but stayed significantly lower than rest values (-25.00%; P < 0.05). In UTG, FFA levels insignificantly decreased (P > 0.05) during exercise and recovery period. Insulin concentration significantly increased during exercise in both groups (+23.89% in TG and +47.64% in UTG, P < 0.05), and stayed significantly higher in recovery period in UTG (+60.82%; P < 0.05). Conclusion: The data presented indicate that chronic physical training markedly influences serum FFA profile in trained group. Our findings also indicate that metabolic response to one bout of maximal-intensity exercise test depends on training status of the subjects and that trained subjects (athletes) could have higher substrate flexibility under high energy demand.
... During long-lasting endurance exercise, energy derives mainly from subcutaneous adipose tissue (Reynolds et al., 1999), although existing evidence is equivocal. Another study has shown that more fat is oxidized during running than during an equivalent amount of cycling (Knechtle et al., 2004). Results relating to body mass are similarly inconclusive with evidence of both increases (Dressendorfer & Wade, 1991) and decreases (Knechtle et al., 2005). ...
Article
Appropriate nutrition through adequate dietary intake of total calories, macronutrients, and micronutrients is an essential component of optimizing the performance of all elite athletes. The aim of this study was to describe the food intake, body composition, and biochemical profile of professional cyclists during the Tour of Andalusia, a four-stage race covering a total distance of 647.6 km. Nutritional data were collected by trained investigators who weighed all of the food and fluid ingested by the cyclists. The nutritional intake of the cyclists was as follows: CHO, 12.8 ± 1.7 g/kg of body weight (BW; 62.3%); fat, 2.1 ± 0.2 g/kg BW (23.2%); proteins, 3.0 ± 0.3 g/kg BW (14.5%); total kcal was 5644.3 ± 593.1. Intake of all micronutrients, except for folate and potassium [which were 93.7% and 91.3% of Recommended Dietary Allowances (RDA)] exceeded the RDA/I. Percentage of body fat and fat weight significantly decreased (P < 0.05) while weight of muscle mass remained unchanged after the Tour. Concentrations of urea, aspartate aminotransferase, alanine aminotransferase, creatine kinase, myoglobin, and high-density lipoproteins significantly increased (P < 0.05) after the Tour. To our knowledge, this is the first study to describe both nutritional intake and the body and biochemical composition of a sample of professional road cyclists during a top-class cycling race. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Article
The crossover point occurs during exercise when one transitions energy substrates from fat to carbohydrate predominance. The crossover point varies in an intensity-dependent manner; however, less is known about its specificity in sports with varying metabolic demands. The purpose of our study was to determine if various sports yield differences in the time to crossover and heart rate and percentage of maximal oxygen consumption (V˙O2max) at crossover during a standardized exercise protocol. A total of 77 athletes (39 women, 38 men; 39.1 ± 10.4 yr of age) were measured for respiratory exchange ratio during a modified Taylor V˙O2max treadmill test. Sports included running (n = 20), triathlon (n = 20), rowing (n = 20), and CrossFit (n = 17). A one-way ANOVA determined differences in time to crossover. A Kruskal–Wallis test was applied to determine differences between sport types for percent V˙O2max and heart rate at crossover. Bonferroni correction procedures were used to control the family-wise error rate and maintain alpha levels at P < 0.05. Average time to crossover for all athletes was 3:43 ± 1:12 min. Times to crossover for runners, triathletes, rowers, and CrossFit athletes were 4:16 ± 0:58, 3:28 ± 1:08, 4:00 ± 1:23, and 3:01 ± 0:58 min, respectively. Significant differences were observed between groups for time to crossover (P = 0.007) and percent V˙O2max at crossover (P = 0.01). Pairwise analyses revealed that runners had a significantly longer time to crossover compared with CrossFit athletes (P = 0.009). Triathletes’ percent V˙O2max at crossover was significantly lower than rowers (P = 0.04) and runners (P = 0.04). We found significant differences in time to crossover between runners and CrossFit athletes, which suggests that substrate use may be dependent on sport type.
Chapter
Cycling and running are aerobic activities that represent two different means of exercising, rarely combined. Both cycling and running are essential for overall health, proper function of the cardiovascular system, and weight balance, with few differences between them. Although not widely known, running can contribute to a cyclist’s training and performance. Running and cycling seem to result in different physiological and metabolic responses having different physiological effects. There are certain benefits of running for cyclists, though. These include an increase in bone density, an increased cardiovascular and muscular strength, better exercise tolerance, and psychological benefits as well. Nevertheless, drawbacks also exist. Running in cyclists has been correlated to an increased risk for injury. More specifically, a combination of running and cycling without a proper periodization of the training can lead to overload and injury. The perfect merge of these two activities, running and cycling, is cyclo-cross.
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During graded exercise, absolute whole body fat oxidation rates increase from low to moderate exercise intensities, and then decline at high intensities. Recently, a sinusoidal (SIN) model has been developed to accurately describe the shape of fat oxidation kinetics and to determine the exercise intensity at which the fat oxidation rate is maximal during graded exercise. The SIN model incorporates three independent variables (dilatation, symmetry, and translation) that correspond to the main expected modulations of the basic fat oxidation curve due to factors such as the mode of exercise or training status, providing additional information on characteristics of kinetics. The purpose of this review is to present the effect of various factors such as exercise intensity and duration, form and type of exercise, or gender on whole body fat oxidation kinetics using this model. These data provide interesting insights that could be applied to gain perspective for exercise prescription, for instance, the design of training programs that aim to induce a negative fat balance and to deal with weight management.
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During graded exercise, absolute whole body fat oxidation rates increase from low to moderate exercise intensities, and then decline at high intensities. Recently, a sinusoidal (SIN) model has been developed to accurately describe the shape of fat oxidation kinetics and to determine the exercise intensity at which the fat oxidation rate is maximal during graded exercise. The SIN model incorporates three independent variables (dilatation, symmetry, and translation) that correspond to the main expected modulations of the basic fat oxidation curve due to factors such as the mode of exercise or training status, providing additional information on characteristics of kinetics. The purpose of this review is to present the effect of various factors such as exercise intensity and duration, form and type of exercise, or gender on whole body fat oxidation kinetics using this model. These data provide interesting insights that could be applied to gain perspective for exercise prescription, for instance, the design of training programs that aim to induce a negative fat balance and to deal with weight management.
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The purpose of this study was to determine whether there were differences in blood lactate (La), pulmonary ventilation (VE), rating of perceived exertion (RPE), volume of carbon dioxide expired (VCO2), oxygen consumption (VO2) and heart rate (HR) among four phases of the menstrual cycle during short constant‐load exercise. The subjects of this investigation were 21 female physical education students at Springfield College. After determination of maximal oxygen consumption (VO2 max) on the bicycle ergometer, subjects exercised at intensities designed to elicit 70 and 90% VO2 max in each of four phases of the menstrual cycle : menses, follicular (F), luteal (L) and premenses (PM). Phases were identified by menstrual history and variation in basal morning oral temperatures. For purposes of description the variation in body weight was analysed by a one‐factor ANOVA across the four phases of the menstrual cycle. Post hoc comparisons revealed that body weight was higher (P
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• Contemporary stable isotope methodology was applied in combination with muscle biopsy sampling to accurately quantify substrate utilisation and study the regulation of muscle fuel selection during exercise. • Eight cyclists were studied at rest and during three consecutive 30 min stages of exercise at intensities of 40, 55 and 75 % maximal workload (Wmax). A continuous infusion of [U-13C]palmitate and [6,6-2H2]glucose was administered to determine plasma free fatty acid (FFA) oxidation and estimate plasma glucose oxidation, respectively. Biopsy samples were collected before and after each exercise stage. • Muscle glycogen and plasma glucose oxidation rates increased with every increment in exercise intensity. Whole-body fat oxidation increased to 32 ± 2 kJ min−1 at 55 % Wmax, but declined at 75 % Wmax (19 ± 2 kJ min−1). This decline involved a decrease in the oxidation rate of both plasma FFA and triacylglycerol fat sources (sum of intramuscular plus lipoprotein-derived triacylglycerol), and was accompanied by increases in muscle pyruvate dehydrogenase complex activation and acetylation of the carnitine pool, resulting in a decline in muscle free carnitine concentration. • We conclude that the most likely mechanism for the reduction in fat oxidation during high-intensity exercise is a downregulation of carnitine palmitoyltransferase I, either by this marked decline in free carnitine availability or by a decrease in intracellular pH.
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In 1229 subjects, 521 males and 708 females, with a wide range in body mass index (BMI; 13.9-40.9 kg/m2), and an age range of 7-83 years, body composition was determined by densitometry and anthropometry. The relationship between densitometrically-determined body fat percentage (BF%) and BMI, taking age and sex (males = 1, females = 0) into account, was analysed. For children aged 15 years and younger, the relationship differed from that in adults, due to the height-related increase in BMI in children. In children the BF% could be predicted by the formula BF% = 1.51 x BMI-0.70 x age - 3.6 x sex + 1.4 (R2 0.38, SE of estimate (SEE) 4.4% BF%). In adults the prediction formula was: BF% = 1.20 x BMI + 0.23 x age - 10.8 x sex - 5.4 (R2 0.79, SEE = 4.1% BF%). Internal and external cross-validation of the prediction formulas showed that they gave valid estimates of body fat in males and females at all ages. In obese subjects however, the prediction formulas slightly overestimated the BF%. The prediction error is comparable to the prediction error obtained with other methods of estimating BF%, such as skinfold thickness measurements or bioelectrical impedance.
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To investigate the influence of the midluteal and midfollicular phases of the menstrual cycle on exercise performance and ventilatory drives, we studied six outstanding female athletes, six controls with normal menstrual cycles, and six outstanding athletes who were amenorrheic. In all menstruating subjects resting minute ventilation (Ve) and mouth occlusion pressures (P0.1) were higher in the luteal phase (p less than k0.0001 and p less than 0.02, respectively),. Hypoxic (expressed as the hyperbolic shape parameter A) and hypercapnic (expressed as S, deltaVE/delta PAco2) ventilatory responses were increase in the luteal phase (p less than 0.01). The athletes had lower A values during the luteal phase than the nonathletes (p less than 0.001). Maximal exercise response, expressed either as total exercise time or maximum O2 consumption or CO2 production (VO2 max or Vco2 max) was decreased during the luteal phase but was significantly different at a p less than 0.05 level only among the nonathletes. Ventilatory equivalent (VE/VO2) during progressive exercise on a bicycle ergometer was significantly increased during the luteal phase. The amenorrheic athletes showed no changes between the two test periods. The luteal phase of the menstrual cycle induced increases in ventilatory drives and exercise ventilation in both athletes and controls, but the athletes, in contrast to controls, demonstrated no significant decrease in exercise performance in the luteal phase.
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We have recently demonstrated that people with a high percentage of Type I muscle fibers display a relatively high muscular efficiency when cycling. These individuals generate a relatively high muscular power output at a given steady-state level of oxygen consumption and caloric expenditure. The purpose of this study was to directly determine the extent to which differences in muscle fiber composition and efficiency influence endurance performance in competitive cyclists. The percentage of Type I and II muscle fibers was determined from several biopsies from the vastus lateralis which were histochemically stained for ATPase activity. During a laboratory performance test, 14 endurance trained cyclists (mean +/- SE; VO2max, 5.2 +/- 0.11/min; body weight, 74 +/- 1 kg) cycled an ergometer for 1 h at the highest work rate they could tolerate. VO2 and RER were simultaneously measured using open circuit spirometry for calculating caloric expenditure. Subjects were divided into two groups of seven according to their muscle fiber type composition: High % Type I Group (> 56% Type I fibers); Normal % Type I Group (38-55% Type I fibers). Each subject from High % Type I Group was paired with a subject from the Normal % Type I Group according to their similarity in VO2max, blood lactate threshold and average VO2 maintained during the 1 h performance test. Both groups averaged 4.5 +/- 0.11/min during the 1 h performance test (i.e., 86-88% VO2max).(ABSTRACT TRUNCATED AT 250 WORDS)
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Stable isotope tracers and indirect calorimetry were used to evaluate the regulation of endogenous fat and glucose metabolism in relation to exercise intensity and duration. Five trained subjects were studied during exercise intensities of 25, 65, and 85% of maximal oxygen consumption (VO2max). Plasma glucose tissue uptake and muscle glycogen oxidation increased in relation to exercise intensity. In contrast, peripheral lipolysis was stimulated maximally at the lowest exercise intensity, and fatty acid release into plasma decreased with increasing exercise intensity. Muscle triglyceride lipolysis was stimulated only at higher intensities. During 2 h of exercise at 65% VO2max plasma-derived substrate oxidation progressively increased over time, whereas muscle glycogen and triglyceride oxidation decreased. In recovery from high-intensity exercise, although the rate of lipolysis immediately decreased, the rate of release of fatty acids into plasma increased, indicating release of fatty acids from previously hydrolyzed triglycerides. We conclude that, whereas carbohydrate availability is regulated directly in relation to exercise intensity, the regulation of lipid metabolism seems to be more complex.
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In the present study we examined the hypothesis that fatty acid oxidation is less during high-intensity exercise than during moderate-intensity exercise because of inhibition of long-chain fatty acid entry into the mitochondria. Six volunteers exercised at 40% peak oxygen consumption (VO2peak) for 60 min and at 80% VO2peak for 30 min on two different occasions. [1-13C]oleate, a long-chain fatty acid, and [1-14C]octanoate, a medium-chain fatty acid, were infused for the duration of the studies. Lipids and heparin were infused during exercise at 80% VO2peak to prevent the expected decrease in plasma free fatty acid (FFA) concentration. Plasma oleate and total FFA availability were similar in the two experiments. Oleate oxidation decreased from 2.8 +/- 0.6 (40% VO2peak) to 1.8 +/- 0.2 mumol.kg-1.min-1 (80% VO2peak, P < 0.05), whereas octanoate oxidation increased from 1.0e-05 +/- 1.0e-06 (40% VO2peak) to 1.3e-05 +/- 5.1e-06 mumol.kg-1.min-1 (80% VO2peak, P < 0.05). Furthermore, the percentage of oleate uptake oxidized decreased from 67.7 +/- 2.8% (40% VO2peak) to 51.8 +/- 4.6% (80% VO2peak, P < 0.05), whereas the percentage of octanoate oxidized was similar during exercise at 40 and 80% VO2peak (84.8 +/- 2.7 vs. 89.3 +/- 2.7%, respectively). Our data suggest that, in addition to suboptimal FFA availability, fatty acid oxidation is likely limited during high-intensity exercise because of direct inhibition of long-chain fatty acid entry into mitochondria.
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The estrogen hormones have been shown to be highly glycogenic as well as lipolytic in nature. It is unknown whether the metabolic actions of estrogens impact upon energy metabolism during exercise. The composition of prior diet, however, does affect exercise energy metabolism. This study examined the influence of menstrual cycle phase (mid-follicular [FP; low estrogen] vs. mid-luteal [LP; high estrogen]) and diet composition on the rate of substrate oxidation for carbohydrate (CHO) and lipid at rest and during various intensities of physical exercise. Nine subjects completed an experimental session under four different menstrual cycle-diet conditions: 1) FP following a 3-day high CHO diet [75% total caloric intake], 2) FP following a 3-day low CHO diet [35% total caloric intake], 3) LP following a 3-day high CHO diet, and 4) LP following a 3-day low CHO diet. In each of the experimental sessions substrate oxidation was determined at rest and during cycle ergometer exercise at intensities of 30, 50, and 70% VO2max, respectively. Statistically significant (p < 0.05) interaction effects on substrate oxidation due to the menstrual cycle phase and diet conditions were found at rest and during 30%-50% exercise. In general, CHO oxidation was lowest and lipid oxidation highest in the LP under a low CHO diet condition.
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We examined the hypothesis that glucose flux was directly related to relative exercise intensity both before and after a 12-wk cycle ergometer training program [5 days/wk, 1-h duration, 75% peak O2 consumption (VO2 peak)] in healthy female subjects (n = 17; age 23.8 +/- 2.0 yr). Two pretraining trials (45 and 65% of VO2 peak) and two posttraining trials [same absolute workload (65% of old VO2 peak) and same relative workload (65% of new VO2 peak)] were performed on nine subjects by using a primed-continuous infusion of [1-13C]- and [6,6-2H]glucose. Eight additional subjects were studied by using [6, 6-2H]glucose. Subjects were studied postabsorption for 90 min of rest and 1 h of cycling exercise. After training, subjects increased VO2 peak by 25.2 +/- 2.4%. Pretraining, the intensity effect on glucose kinetics was evident between 45 and 65% of VO2 peak with rates of appearance (Ra: 4.52 +/- 0.25 vs. 5.53 +/- 0.33 mg . kg-1 . min-1), disappearance (Rd: 4.46 +/- 0.25 vs. 5.54 +/- 0.33 mg . kg-1 . min-1), and oxidation (Rox: 2.45 +/- 0.16 vs. 4.35 +/- 0.26 mg . kg-1 . min-1) of glucose being significantly greater (P </= 0.05) in the 65% than in the 45% trial. Training reduced Ra (4.7 +/- 0.30 mg . kg-1 . min-1), Rd (4.69 +/- 0.20 mg . kg-1 . min-1), and Rox (3.54 +/- 0.50 mg . kg-1 . min-1) at the same absolute workload (P </= 0. 05). When subjects were tested at the same relative workload, Ra, Rd, and Rox were not significantly different after training. However, at both workloads after training, there was a significant decrease in total carbohydrate oxidation as determined by the respiratory exchange ratio. These results show the following in young women: 1) glucose use is directly related to exercise intensity; 2) training decreases glucose flux for a given power output; 3) when expressed as relative exercise intensity, training does not affect the magnitude of blood glucose flux during exercise; but 4) training does reduce total carbohydrate oxidation.
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This study presents data collected over the past 10 years on the muscle fiber type composition of the vastus lateralis muscle of young men and women. Biopsies were taken from the vastus lateralis muscle of 55 women (21.2+/-2.2 yr) and 95 men (21.5+/-2.4 yr) who had volunteered to participate in various research projects. Six fiber types (I, IC, IIC, IIA, IIAB, and IIB) were classified using mATPase histochemistry, and cross-sectional area was measured for the major fiber types (I, IIA, and IIB). Myosin heavy chain (MHC) content was determined electrophoretically on all of the samples from the men and on 26 samples from the women. With the exception of fiber Type IC, no significant differences were found between men and women for muscle fiber type distribution. The vastus lateralis muscle of both the men and women contained approximately 41% I, 1% IC, 1% IIC, 31% IIA, 6% IIAB, and 20% IIB. However, the cross-sectional area of all three major fiber types was larger for the men compared to the women. In addition, the Type IIA fibers were the largest for the men, whereas the Type I fibers tended to be the largest for the women. Therefore, gender differences were found with regard to the area occupied by each specific fiber type: IIA>I>IIB for the men and I>IIA>IIB for the women. These data establish normative values for the mATPase-based fiber type distribution and sizes in untrained young men and women.
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We have studied eight endurance-trained women at rest and during exercise at 25, 65, and 85% of maximal oxygen uptake. The rate of appearance (R(a)) of free fatty acids (FFA) was determined by infusion of [(2)H(2)]palmitate, and fat oxidation rates were determined by indirect calorimetry. Glucose kinetics were assessed with [6,6-(2)H(2)]glucose. Glucose R(a) increased in relation to exercise intensity. In contrast, whereas FFA R(a) was significantly increased to the same extent in low- and moderate-intensity exercise, during high-intensity exercise, FFA R(a) was reduced compared with the other exercise values. Carbohydrate oxidation increased progressively with exercise intensity, whereas the highest rate of fat oxidation was during exercise at 65% of maximal oxygen uptake. After correction for differences in lean body mass, there were no differences between these results and previously reported data in endurance-trained men studied under the same conditions, except for slight differences in glucose metabolism during low-intensity exercise (Romijn JA, Coyle EF, Sidossis LS, Gastaldelli A, Horowitz JF, Endert E, and Wolfe RR. Am J Physiol Endocrinol Metab 265: E380-E391, 1993). We conclude that the patterns of changes in substrate kinetics during moderate- and high-intensity exercise are similar in trained men and women.
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The purpose of the present study was to comprehensively examine oxygen consumption (VO(2)) kinetics during running and cycling through mathematical modeling of the breath-by-breath gas exchange responses to moderate and heavy exercise. After determination of the lactate threshold (LT) and maximal oxygen consumption (VO(2 max)) in both cycling and running exercise, seven subjects (age 26.6 +/- 5.1 yr) completed a series of "square-wave" rest-to-exercise transitions at running speeds and cycling power outputs that corresponded to 80% LT and 25, 50, and 75%Delta (Delta being the difference between LT and VO(2 max)). VO(2) responses were fit with either a two- (<LT) or three-phase ( >LT) exponential model. The parameters of the VO(2) kinetic response were similar between exercise modes, except for the VO(2) slow component, which was significantly (P < 0.05) greater for cycling than for running at 50 and 75%Delta (334 +/- 183 and 430 +/- 159 ml/min vs. 205 +/- 84 and 302 +/- 154 ml/min, respectively). We speculate that the differences between the modes are related to the higher intramuscular tension development in heavy cycle exercise and the higher eccentric exercise component in running. This may cause a relatively greater recruitment of the less efficient type II muscle fibers in cycling.
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The purpose of this study was to detect the fraction of peak oxygen consumption (VO2peak) that elicits maximal rates of fat oxidation during submaximal treadmill exercise. It was hypothesized that this point would appear at a work rate just below the ventilatory threshold. Experimental design: subjects completed a protocol requiring them to exercise for 15 min on a treadmill at six different workloads, 25, 40, 55, 65, 75, and 85% VO2peak, over two separate visits. Participants: nine healthy, moderately-trained eumenorrheic females (age = 28.8+/-5.99 yrs, VO2peak = 47.20 +/-2.57 ml x kg(-1) x min(-1)) volunteered for the study. Measures: a one-way ANOVA with repeated measures was used to test for differences across exercise intensities in the metabolic variables (i.e. substrate oxidation, blood lactate concentration ([La-]), RER, and the contribution of fat to total energy expenditure). Following significant F ratios, post-hoc tests were used to detect differences between the means for various exercise intensities. Exercise at 75% VO2peak elicited the greatest rate of fat oxidation (4.75+/-0.49 kcal x min(-1)), and this intensity was coincident with the ventilatory threshold (76+/-7.41% VO2peak). Moreover, a significant difference (t(8) = -3.98, p<0.01) was noted between the mean ventilatory threshold and lactate threshold. The finding that a relatively heavy work rate elicits the highest rate of fat oxidation in an active, female population has application in exercise prescription and refutes the belief that low-intensity exercise is preferred for fat metabolism.
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We investigated the effect of endurance training on whole body substrate, glucose, and glycerol utilization during 90 min of exercise at 60% peak O2 consumption (VO2(peak)) in males and females. Substrate oxidation was determined before and after 7 wk of endurance training on a cycle ergometer, with posttesting performed at the same absolute (ABS, W) and relative (REL, VO2(peak)) intensities. [6,6-2H]glucose and [1,1,2,3,3-2H]glycerol tracers were used to calculate the respective substrate tracee flux. Endurance training resulted in an increase in VO2(peak) for both males and females of 17 and 22%, respectively (P < 0.001). Females demonstrated a lower respiratory exchange ratio (RER) both pretraining and posttraining compared with males during exercise (P < 0.001). Glucose rate of appearance (R(a)) and rate of disappearance (R(d)) were not different between males and females. Glucose metabolic clearance rate (MCR) was lower at 75 and 90 min of exercise for females compared with males (P < 0.05). Glucose R(a) and R(d) were lower during exercise at both ABS and REL posttraining exercise intensities compared with pretraining (P < 0.001). Females had a higher exercise glycerol R(a) and R(d) compared with males both pre- and posttraining (P < 0.001). Glycerol R(a) was not different at either the ABS or REL posttraining exercise intensities compared with pretraining. We concluded that females oxidize proportionately more lipid and less carbohydrate during exercise compared with males both pre- and posttraining, which was cotemporal with a higher glycerol R(a) in females. Furthermore, endurance training resulted in a decrease in glucose flux at both ABS and REL exercise intensities after endurance exercise training.
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The purpose of this study was to determine the extent to which growth hormone (GH) and energy substrate utilization are influenced by basal sex steroid levels during prolonged submaximal exercise across menstrual phase and status. Also the 17 beta-estradiol (E2) and progesterone responses during prolonged exercise were compared according to menstrual phase and menstrual status. Six amenorrheic (AMc) athletes and seven eumenorrheic (EUc) athletes ran at 60% VO2max for 90 min and serial blood samples were taken at rest, every 10 min throughout exercise, and 5 and 15 min post-exercise. The EUc athletes were tested in the early follicular phase (EF) (days 3-5), the late follicular phase (LF) (days 14-16) and the mid-luteal phase (ML) (days 22-25). The incremental GH response to exercise, measured by area under the curve, was consistent with previous reposts and was not altered according to menstrual phase or status (EF-37.5 +/- 11.5, LF-61.9 +/- 11.5, ML-48.1 +/- 12.8 micrograms.1-1.90 min-1). Furthermore, carbohydrate and fat utilization during exercise were not influenced by basal sex steroid levels associated with menstrual phase or status. The incremental E2 response to exercise in AMc athletes was significantly smaller than seen in EUc athletes (AMc-208.1 +/- 44.0, EF-383.0 +/- 116.4, LF-204.7 +/- 84.1, ML-45.1 +/- 18.4 pmol.1(-1).90 min-1), although the pattern of release is similar between groups. In conclusion, GH levels and substrate utilization are independent of both menstrual phase and status; hence, menstrual phase has no negative ramifications on metabolism during exercise. Amenorrhea does not result in metabolic consequences during prolonged exercise by influencing substrate utilization.
Article
To determine whether the hormonal changes associated with the normal menstrual cycle influence FFA metabolism, FFA turnover was measured in 12 women during both the follicular (days 4-10) and luteal (days 18-24) phases of their menstrual cycles. The luteal phase was confirmed by increased serum progesterone concentrations. Overnight postabsorptive FFA flux was similar in the follicular and luteal phases of the menstrual cycle (6.9 +/- 0.8 vs. 5.8 +/- 0.5 mumol kg-1 min-1, respectively, P = NS). In addition, the FFA response to 3 h of somatostatin-induced hypoinsulinemia was virtually identical on both study days. Finally, we compared the intraindividual variability of basal FFA flux from studies performed in different vs. the same phase of the menstrual cycle; no difference was present. We conclude that the cyclic changes in estrogen and progesterone production which occur during the normal menstrual cycle appear to have minor, if any, effects on FFA mobilization.