Article

Timing Protein Intake Increases Energy Expenditure 24 h after Resistance Training

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

To determine whether protein supplementation (PRO) before an acute bout of heavy resistance training (HRT) would influence postexercise resting energy expenditure (REE) and the nonprotein respiratory exchange ratio (RER). REE would be increased and RER would be decreased up to 48 h after timed PRO and HRT compared with CHO supplementation and HRT. Eight resistance-trained subjects (five men and three women) participated in a double-blind two-trial crossover design, where REE and RER were measured (7:00 a.m.) on four consecutive days. On the second day of trial 1, subjects consumed 376 kJ of either PRO (18 g of whey protein, 2 g of carbohydrate, 1.5 g of fat) or CHO (1 g of whey protein, 19 g of carbohydrate, 1 g of fat) 20 min before a single bout of HRT (nine exercises, 4 sets, 70%-75% 1-repetition maximum). REE and RER were measured 24 and 48 h after HRT. During trial 2, the same protocol was followed except subjects consumed the second supplement before HRT. Compared with baseline, REE was elevated significantly in both CHO and PRO at 24 and 48 h after HRT (P < 0.05). At 24 h after HRT, REE in response to PRO was significantly greater compared with CHO (P < 0.05). RER decreased significantly in both CHO and PRO at 24 h after HRT compared with baseline (P < 0.05). No differences were observed in total energy intake, macronutrient intake, or HRT volume (P > 0.05). Timing PRO before HRT may be a simple and effective strategy to increase energy expenditure by elevating REE the day after HRT. Increasing REE could facilitate reductions in body fat mass and improve body composition if nutritional intake is stable.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... In this study, whey or casein protein increased energy expenditure and fat oxidation for up to 60-min post-exercise compared to carbohydrate. Further, Hackney and colleagues (7) have previously reported that preexercise ingestion of whey protein increases energy expenditure rates for up to 24 h after ingestion while Paoli et al. (8) concluded that a protein-centric meal before aerobic exercise significantly increases resting metabolism rates for 24 h after exercise. Different types of protein have divergent digestive rates and muscle protein synthesis rates in response to acute feeding (9-11), but research has not fully explored the impact of protein source on substrate oxidation rates during and after acute exercise. ...
... As such, any potential augmentation of fat oxidation that may occur during longer (>30 min) bouts of aerobic exercise with preexercise protein feeding is largely unknown. In addition, the research completed by Gieske et al. (7) included males while Wingfield et al. (5) included females. Previous research has indicated that gender differences exist in terms of substrate oxidation (18,19). ...
Article
Full-text available
Background The metabolic impact of pre-exercise feeding of protein or carbohydrate on fat oxidation and energy expenditure rates, especially, in females, is poorly understood. Methods Recreationally active females ( n = 15, 32 ± 10 years, 164.8 ± 5.6 cm, 63.5 ± 9.3 kg, 23.4 ± 3.2 kg/m ² ) completed four testing sessions in a randomized, double-blind, crossover fashion after fasting overnight. Participants ingested isovolumetric and isoenergetic solutions containing either 25 g of whey protein, casein protein, carbohydrate (CHO), or a non-caloric placebo (PLA). Participants then completed 60 min of treadmill exercise at 15% below ventilatory threshold 30 min after ingestion. Respiratory exchange ratio (RER) was evaluated throughout exercise and resting energy expenditure (REE) was assessed pre-exercise, and 0-, 60-, and 120-min post-exercise. Results A significant condition x time interaction was observed for RER ( p = 0.008) during exercise, with CHO exhibiting higher RER values (vs. PLA) at four time points. A significant main effect for condition was observed for carbohydrate ( p = 0.001) and fat ( p = 0.02) oxidation rates during exercise, with fat oxidation rates being higher in PLA vs. CHO ( p = 0.01). When total fat oxidized was calculated across the entire exercise bout, a significant main effect for condition was observed ( p = 0.01), with PLA being greater than CHO ( p = 0.04). A significant condition x time interaction ( p = 0.02) was found for both absolute and normalized REE, with casein and whey protein having significantly higher values than CHO ( p < 0.05) immediately post-exercise. Conclusion When compared to a fasted control (PLA), consuming CHO, but not protein, decreased total fat oxidation prior to a 60-min bout of moderate-intensity exercise in females.
... A variety of investigations have demonstrated that the consumption of caffeine-containing energy drinks may acutely increase metabolic rate [11][12][13], which could potentially result in preferential changes in body composition over time with prolonged use [14]. Similar short-term metabolic effects have also been noted following the acute consumption of supplemental protein prior to an exercise session [15][16][17]. For example, Wingfield and colleagues [16] examined the metabolic impact of supplemental protein ingestion prior to aerobic exercise, high-intensity interval training, and resistance training. ...
... Importantly, EE in the energy drink condition was found to be approximately 0.77 kcal·min − 1 higher than placebo during the post-beverage time period, and approximately 0.37 kcal·min − 1 higher than placebo during the post-exercise time period. These results align with the findings of previous studies which reported significant elevations in EE following consumption of caffeine-containing energy drinks [11][12][13] as well as those which administered supplemental protein prior to exercise [15][16][17]. Several physiological mechanisms are responsible for these results. ...
Article
Full-text available
Background: Energy drinks are often consumed by the general population, as well as by active individuals seeking to enhance exercise performance and augment training adaptations. However, limited information is available regarding the efficacy of these products. Thus, the purpose of this study was to determine the effects of a commercially available caffeine- and protein-containing energy drink on metabolism and muscular performance. Methods: Sixteen resistance-trained males (n = 8; mean ± SD; age: 22.4 ± 4.9 years; body mass: 78.8 ± 14.0 kg; body fat: 15.3 ± 6.4%) and females (n = 8; age: 24.5 ± 4.8 years; body mass: 67.5 ± 11.9 kg; body fat: 26.6 ± 7.1%) participated in this randomized, double-blind, placebo-controlled, crossover study. Following a familiarization visit, participants completed two identical visits to the laboratory separated by 5-10 days, each of which consisted of indirect calorimetry energy expenditure (EE) assessments before and after consumption of the beverage (Bang® Keto Coffee; 130 kcal, 300 mg caffeine, 20 g protein) or placebo (30 kcal, 11 mg caffeine, 1 g protein) as well as after exercise testing. In addition, participants' subjective feelings of energy, fatigue, and focus as well as muscular performance (leg press one-repetition maximum and repetitions to fatigue, maximal isometric and isokinetic squat testing) were assessed. Multiple repeated measures ANOVAs with Tukey post-hoc tests were used to analyze data. Estimates of effect size were quantified via partial eta squared (ηP2) and Hedge's g. Results: A significant interaction effect was identified for EE (p < 0.001, ηP2 = 0.52) but not respiratory exchange ratio (p = 0.17, ηP2 = 0.11). Following consumption of the beverage, EE was 0.77 kcal·min- 1 greater than placebo at the post-beverage time point (p < 0.001) and 0.37 kcal·min- 1 greater than placebo at the post-exercise time point (p = 0.011). However, no between-condition differences were detected for any subjective or muscular performance outcomes. Conclusions: The results of this study suggest that consumption of the energy drink had minimal effects on lower-body muscular performance and subjective factors in the context of a laboratory setting. However, the beverage was found to significantly increase energy expenditure compared to placebo immediately following ingestion as well as during the recovery period after an exercise bout, suggesting that active individuals may improve acute metabolic outcomes via consumption of a caffeine- and protein-containing energy drink. Trial registration: This trial was prospectively registered at ClinicalTrials.gov (Identifier: NCT04180787 ; Registered 29 November 2019).
... The decrease in body fat mass is related to the intake of different protein varieties. For example, a study assessing the intake of a commercial WPI + WPC + WPH supplement 20 minutes before a high-intensity strength training session in trained men and women showed an increase in resting energy expenditure, which is an effective strategy to reduce body fat mass without decreasing muscle mass [Hackney et al., 2010]. Weight loss without affecting muscle mass occurred in young men with WPI intake 5 minutes after the strength training session when followed by a full meal 60 minutes after supplementation [Monteyne et al., 2018]. ...
... Supplementation with WPC decreased total body and abdominal fat and increased muscle mass when administered to untrained men after strength training [Hulmi et al., 2015] and promoted weight and body fat loss among women [Gomes et al., 2017]. These results can be attributed to the WP content, which correlates with decreased energy consumption because it increases satiety, thereby decreasing energy consumption [Bendtsen et al., 2013] and/or increasing resting energy expenditure [Hackney et al., 2010]. Furthermore, these proteins participate in beta-oxidation processes [Acheson et al., 2011] and lipolysis [Hector et al., 2015] and can be recommended for body fat loss after strength training [Hulmi et al., 2015]. ...
Article
Full-text available
The inactivation and sublethal injury of two strains of Listeria innocua (one collection strain and one wild strain isolated from beetroot juice) suspended in beetroot juice and in model solutions, after high hydrostatic pressure (HHP) were investigated. Changes within the population assessed by plating count methods of both L. innocua strains suspended in a buffer pH 4.0 were more noticeable than in the natural beetroot juice environment. In beetroot juice the lethal effect was reported after 1 min of pressure treatment at 400 MPa for the collection strain. In the case of the wild type strain, exposure to the maximal parameters of the compression process (400 MPa, 10 min) decreased the population number below 1 log (CFU/mL) but did not cause complete injury. The collection strain of L. innocua was easier to inactivate in beetroot juice than the strain isolated from this environment. The maximum level of sublethal injury was observed when the cells were suspended in a buffer pH 7.0. Structural damage in cell membranes after HHP processing was observed using a transmission electron microscope (TEM). © Copyright by Institute of Animal Reproduction and Food Research of the Polish Academy of Sciences
... The decrease in body fat mass is related to the intake of different protein varieties. For example, a study assessing the intake of a commercial WPI + WPC + WPH supplement 20 minutes before a high-intensity strength training session in trained men and women showed an increase in resting energy expenditure, which is an effective strategy to reduce body fat mass without decreasing muscle mass [Hackney et al., 2010]. Weight loss without affecting muscle mass occurred in young men with WPI intake 5 minutes after the strength training session when followed by a full meal 60 minutes after supplementation [Monteyne et al., 2018]. ...
... [2017]). and promoted weight and body fat loss among women [Gomes et al., 2017]. These results can be attributed to the WP content, which correlates with decreased energy consumption because it increases satiety, thereby decreasing energy consumption [Bendtsen et al., 2013] and/or increasing resting energy expenditure [Hackney et al., 2010]. Furthermore, these proteins participate in beta-oxidation processes [Acheson et al., 2011] and lipolysis [Hector et al., 2015] and can be recommended for body fat loss after strength training [Hulmi et al., 2015]. ...
Article
Full-text available
Whey protein (WP) is a highly nutritious, commercially available alternative food source that is used primarily as a food supplement by athletes and physically active individuals to provide them with essential amino acids and bioactive peptides, and additional benefits have been attributed to WP consumption. In this context, the objective of this review was to explore current evidence regarding the consumption of different WP supplements in sports nutrition to elucidate their efficiency in affecting muscle hypertrophy, physical performance, response to muscle injury, weight loss, and body composition changes. Furthermore, these effects were assessed by comparing whey protein hydrolysate (WPH), whey protein concentrate (WPC), and whey protein isolate (WPI) supplementation. Supplementation with WPI or WPC was related to increased muscle protein synthesis (MPS), and WPH caused muscle hypertrophy and improved physical performance. Compared to WPC and WPI, WPH improved peak torque associated with strength training without reducing the creatine kinase (CK) and tumor necrosis factor alpha (TNF-α) levels in this type of physical activity, and the decreases in CK and lactate dehydrogenase (LDH) associated with aerobic exercise were significant. Supplementation with WPC resulted in weight loss, satiety, and improved body composition, without compromising whole-body lean mass loss. WPH was more effective than WPC and WPI regarding improved peak torque and muscle hypertrophy associated with strength training, and WPH reduced muscle damage associated with aerobic exercise via decreased CK levels. © Copyright by Institute of Animal Reproduction and Food Research of the Polish Academy of Sciences.
... In addition, dietary protein exerts an anti-catabolic stimulus when ingested before or during exercise, providing a practical rationale for exercising individuals who may wish to minimize protein degradation during endurance exercise modalities [18]. Furthermore, preliminary evidence suggests that the acute ingestion of a high-protein meal immediately before exercise may have beneficial effects on post-exercise energy expenditure compared to pre-exercise carbohydrate ingestion [19,20] or fasted conditions [5]. Indeed, research by Wingfield and investigators [20] used a crossover study design to examine the acute impact of protein or carbohydrate feedings prior to moderate aerobic exercise, high-intensity interval training, or resistance exercise sessions. ...
... When a single dose of whey protein was consumed before exercise, significantly greater increases in energy expenditure and fat oxidation were found to occur during the hour after exercise. Hackney and colleagues [19] noted that this effect of pre-exercise whey protein feeding on resting metabolism appears to last for at least 24 h after resistance exercise, though rates of fat oxidation were not different between carbohydrate or protein treatments. Likewise, Paoli et al. [5] reported that consuming a protein-rich meal prior to moderate-intensity cardiovascular exercise resulted in significant increases in resting metabolism for 24 h after exercise. ...
Article
Full-text available
Background Augmenting fat oxidation is a primary goal of fitness enthusiasts and individuals desiring to improve their body composition. Performing aerobic exercise while fasted continues to be a popular strategy to achieve this outcome, yet little research has examined how nutritional manipulations influence energy expenditure and/or fat oxidation during and after exercise. Initial research has indicated that pre-exercise protein feeding may facilitate fat oxidation while minimizing protein degradation during exercise, but more research is needed to determine if the source of protein further influences such outcomes. Methods Eleven healthy, college-aged males (23.5 ± 2.1 years, 86.0 ± 15.6 kg, 184 ± 10.3 cm, 19.7 ± 4.4%fat) completed four testing sessions in a randomized, counter-balanced, crossover fashion after observing an 8–10 h fast. During each visit, baseline substrate oxidation and resting energy expenditure (REE) were assessed via indirect calorimetry. Participants ingested isovolumetric, solutions containing 25 g of whey protein isolate (WPI), 25 g of casein protein (CAS), 25 g of maltodextrin (MAL), or non-caloric control (CON). After 30 min, participants performed 30 min of treadmill exercise at 55–60% heart rate reserve. Substrate oxidation and energy expenditure were re-assessed during exercise and 15 min after exercise. Results Delta scores comparing the change in REE were normalized to body mass and a significant group x time interaction (p = 0.002) was found. Post-hoc comparisons indicated the within-group changes in REE following consumption of WPI (3.41 ± 1.63 kcal/kg) and CAS (3.39 ± 0.82 kcal/kg) were significantly greater (p < 0.05) than following consumption of MAL (1.57 ± 0.99 kcal/kg) and tended to be greater than the non-caloric control group (2.00 ± 1.91 kcal/kg, p = 0.055 vs. WPI and p = 0.061 vs. CAS). Respiratory exchange ratio following consumption of WPI and CAS significantly decreased during the post exercise period while no change was observed for the other groups. Fat oxidation during exercise was calculated and increased in all groups throughout exercise. CAS was found to oxidize significantly more fat (p < 0.05) than WPI during minutes 10–15 (CAS: 2.28 ± 0.38 g; WPI: 1.7 ± 0.60 g) and 25–30 (CAS: 3.03 ± 0.55 g; WPI: 2.24 ± 0.50 g) of the exercise bout. Conclusions Protein consumption before fasted moderate-intensity treadmill exercise significantly increased post-exercise energy expenditure compared to maltodextrin ingestion and tended to be greater than control. Post-exercise fat oxidation was improved following protein ingestion. Throughout exercise, fasting (control) did not yield more fat oxidation versus carbohydrate or protein, while casein protein allowed for more fat oxidation than whey. These results indicate rates of energy expenditure and fat oxidation can be modulated after CAS protein consumption prior to moderate-intensity cardiovascular exercise and that fasting did not lead to more fat oxidation during or after exercise.
... [10][11][12] Furthermore, energy contribution from fat oxidation following aerobic and resistance exercise has also been shown to increase during EPOC. [13][14][15] This suggests that intermittent functional exercise may be an effective method to increase overall EE and decrease body fat. No previous studies have investigated EPOC following functional exercise. ...
... This is congruent with previous studies investigating both aerobic and resistance exercise. [13][14][15] Therefore, although overall EE remained elevated for only 15 minutes, 99 kcal of energy came from fat oxidization over the 45-minute post-exercise period compared to only 50 kcal of fat used during an equivalent period of time at rest, representing nearly a 100% increase in overall fat oxidation. Furthermore, RER has been shown to remain depressed for 120 minutes following resistance exercise resulting in an EPOC of a lesser magnitude but longer duration, 13 suggesting that increased fat oxidation caused by the LMT protocol may have continued past the 45 minutes measured in this study. ...
Article
Full-text available
Background: Few studies have investigated the metabolic demands of functional exercise. We determined the oxygen cost, heart rate (HR) response, and energy expenditure (EE) both during and immediately following a loaded movement training (LMT) workout. Methods: Ten participants (5 male, age = 23.5 ± 3.7 years, VO2peak = 53.3 ± 6.4 ml∙kg-1∙min- 1) completed baseline resting metabolic rate testing, a maximal oxygen uptake (VO2) test, and a familiarization trial. After 48 hours rest, participants completed a 19-minute LMT protocol using functional exercise equipment, consisting of 10 x 60-second work intervals followed by 60 seconds of rest. VO2, HR, respiratory exchange ratio (RER), and EE were measured during the entire LMT protocol and for 45 minutes post-exercise. Results: Participants had a mean VO2 of 65.3 ± 4.1% VO2peak, HR of 91.8 ± 4.0% HRmax, RER of 1.06 ± 0.06, EE of 13.0 ± 3.0 kcal∙min-1 (0.176 ± 0.021 kcal∙kg-1∙min-1), and Rating of Perceived Exertion of 17.3 ± 1.6. The mean overall caloric expenditure was 247 kcal. Post- exercise metabolic recovery data showed a mean overall excess post-exercise oxygen consumption (EPOC) of 7.89 ± 3.78 L. EE remained elevated through 15 minutes, VO2 through 30 minutes, and HR through 45 minutes (p < 0.05). RER remained depressed throughout the 45- minute collection (p < 0.05). Conclusions: LMT meets the American College of Sports Medicine's recommendations for improving cardiovascular fitness and achieving the daily caloric expenditure from exercise. It may be used to improve cardiovascular fitness and body composition in healthy adults.
... Another potential reason that there was no observed increase in FFM or muscle CSA compared to carbohydrates alone was that the subjects only took supplements after workouts, i.e. 2-3 times per week. In addition to energy intake, whey proteins have been reported to increase postexercise resting energy expenditure (REE) when compared to carbohydrates [45] or non-energy placebo [46], up to 24 hours [45]. Whey proteins have been also shown to increase fat oxidation [47] and lipolysis [48] when compared to carbohydrates and also markers of lipolysis directly in visceral fat pad at least in rodents [49]. ...
... Another potential reason that there was no observed increase in FFM or muscle CSA compared to carbohydrates alone was that the subjects only took supplements after workouts, i.e. 2-3 times per week. In addition to energy intake, whey proteins have been reported to increase postexercise resting energy expenditure (REE) when compared to carbohydrates [45] or non-energy placebo [46], up to 24 hours [45]. Whey proteins have been also shown to increase fat oxidation [47] and lipolysis [48] when compared to carbohydrates and also markers of lipolysis directly in visceral fat pad at least in rodents [49]. ...
Article
Full-text available
Background Nutrition intake in the context of a resistance training (RT) bout may affect body composition and muscle strength. However, the individual and combined effects of whey protein and carbohydrates on long-term resistance training adaptations are poorly understood. Methods A four-week preparatory RT period was conducted in previously untrained males to standardize the training background of the subjects. Thereafter, the subjects were randomized into three groups: 30 g of whey proteins (n = 22), isocaloric carbohydrates (maltodextrin, n = 21), or protein + carbohydrates (n = 25). Within these groups, the subjects were further randomized into two whole-body 12-week RT regimens aiming either for muscle hypertrophy and maximal strength or muscle strength, hypertrophy and power. The post-exercise drink was always ingested immediately after the exercise bout, 2–3 times per week depending on the training period. Body composition (by DXA), quadriceps femoris muscle cross-sectional area (by panoramic ultrasound), maximal strength (by dynamic and isometric leg press) and serum lipids as basic markers of cardiovascular health, were analysed before and after the intervention. Results Twelve-week RT led to increased fat-free mass, muscle size and strength independent of post-exercise nutrient intake (P < 0.05). However, the whey protein group reduced more total and abdominal area fat when compared to the carbohydrate group independent of the type of RT (P < 0.05). Thus, a larger relative increase (per kg bodyweight) in fat-free mass was observed in the protein vs. carbohydrate group (P < 0.05) without significant differences to the combined group. No systematic effects of the interventions were found for serum lipids. The RT type did not have an effect on the adaptations in response to different supplementation paradigms. Conclusions Post-exercise supplementation with whey proteins when compared to carbohydrates or combination of proteins and carbohydrates did not have a major effect on muscle size or strength when ingested two to three times a week. However, whey proteins may increase abdominal fat loss and relative fat-free mass adaptations in response to resistance training when compared to fast-acting carbohydrates.
... The combined effect of varying exercise modalities and pre-workout nutrition on energy substrate utilization and EE in women is limited. Pre-exercise ingestion of protein (PRO) has been found to increase post-exercise REE more than that of pre-exercise ingestion of carbohydrate (CHO) [13,14]. While women rely heavily on fat as an energy substrate during exercise, previous data has demonstrated the importance of pre-exercise feedings on augmenting lipolysis [15]. ...
... Combined acute PRO feedings with exercise resulted in a significantly higher REE for PRO than for CHO up to 60 min post exercise (Δ = 59.3 kcal/day). This is similar to previous findings [13,14] that demonstrate greater postexercise REE and fat oxidation following a pre-exercise meal or snack with higher PRO content. The increase in post-exercise REE with PRO ingestion can be contributed to PRO's thermic effect of food, which is higher and more prolonged than that of CHO and fat [28]. ...
Article
Full-text available
The purpose of this study was to examine the effect of exercise modality and pre-exercise carbohydrate (CHO) or protein (PRO) ingestion on post-exercise resting energy expenditure (REE) and respiratory exchange ratio (RER) in women. Twenty recreationally active women (mean ± SD; age 24.6 ± 3.9 years; height 164.4 ± 6.6 cm; weight 62.7 ± 6.6 kg) participated in this randomized, crossover, double-blind study. Each participant completed six exercise sessions, consisting of three exercise modalities: aerobic endurance exercise (AEE), high-intensity interval running (HIIT), and high-intensity resistance training (HIRT); and two acute nutritional interventions: CHO and PRO. Salivary samples were collected before each exercise session to determine estradiol-β-17 and before and after to quantify cortisol. Post-exercise REE and RER were analyzed via indirect calorimetry at the following: baseline, immediately post (IP), 30 minutes (30 min) post, and 60 minutes (60 min) post exercise. A mixed effects linear regression model, controlling for estradiol, was used to compare mean longitudinal changes in REE and RER. On average, HIIT produced a greater REE than AEE and HIRT (p < 0.001) post exercise. Effects of AEE and HIRT were not significantly different for post-exercise REE (p = 0.1331). On average, HIIT produced lower RER compared to either AEE or HIRT after 30 min (p < 0.001 and p = 0.0169, respectively) and compared to AEE after 60 min (p = 0.0020). On average, pre-exercise PRO ingestion increased post-exercise REE (p = 0.0076) and decreased post-exercise RER (p < 0.0001) compared to pre-exercise CHO ingestion. HIIT resulted in the largest increase in REE and largest reduction in RER.
... Milk serum proteins do not coagulate in acidic conditions; they resist the action of quimosine from the stomach, quickly reach the jejunum[19], are rapidly digested, and raise plasma amino acid concentrations of[21,26]. Therefore, milk serum proteins perform several functions, such as mineral absorption, improvement of protein synthesis, sensitivity to hormones, and decreased blood glucose and lipid levels[7,15,16,21,23,[27][28][29]. In summary, the main nutritional and functional components of whey protein are presented inTable 1. ...
... There was a significant decrease in the activity of hepatic enzymes (AST: 92.5%, ALT: 98%, LDH: 65%, hyaluronic acid: 60%) after consumption of whey protein compared to casein. In trained subjects, Hackney et al.[27]observed a significant increase (5%) after 24 hours of resting energy expenditure with the consumption of 18 g of whey protein before of a single session of resistance training (70– 75% of one repetition maximum) when compared to an intake of 19 g of carbohydrates. The authors speculate that this increase occurred by the increased availability of amino acids to skeletal muscle after whey protein intake. ...
Article
Full-text available
Obesity and type 2 diabetes mellitus (DM) have grown in prevalence around the world, and recently, related diseases have been considered epidemic. Given the high cost of treatment of obesity/DM-associated diseases, strategies such as dietary manipulation have been widely studied; among them, the whey protein diet has reached popularity because it has been suggested as a strategy for the prevention and treatment of obesity and DM in both humans and animals. Among its main actions, the following activities stand out: reduction of serum glucose in healthy individuals, impaired glucose tolerance in DM and obese patients; reduction in body weight; maintenance of muscle mass; increases in the release of anorectic hormones such as cholecystokinin, leptin, and glucagon like-peptide 1 (GLP-1); and a decrease in the orexigenic hormone ghrelin. Furthermore, studies have shown that whey protein can also lead to reductions in blood pressure, inflammation, and oxidative stress.
... Evidence suggests that dietary protein consumed before or during exercise provides an anticatabolic stimulus, which provides a sensible rationale for exercising individuals concerned with minimizing protein breakdown during endurance exercise (29). Moreover, preliminary research suggests that consuming a highprotein meal immediately before exercise may have positive effects on postexercise energy expenditure compared to preexercise carbohydrate intake (22,64) or fasted conditions (47). Finally, consuming a high-protein meal in the morning has demonstrated to improve feelings of satiety during the day, decrease continuous snacking, enhance body composition, and improve weight loss in conjunction with a hypocaloric diet (36)(37)(38)63). ...
Article
Full-text available
Physique athletes often incorporate aerobic exercise as part of their exercise program to increase caloric expenditure for the purposes of improving their body composition. One method used by some physique competitors is to perform aerobic exercise in the fasted state under the assumption that low glycogen levels after an overnight fast allow for greater mobilization of stored fat to be used for fuel because carbohydrates are not readily available to produce energy. The purpose of this article is to examine the existing literature on the effect of fasted versus fed cardio on improving body composition for physique athletes.
... The theorized metabolic advantage from higher PRO intakes may be at least in part mediated by an increase in 24-h energy expenditure and sleep energy expenditure [24]. Hackney et al. [25] provided further support for this theory, observing greater increases in resting energy expenditure at 24 h post-exercise when resistance-trained individuals consumed an isocaloric bolus of PRO versus carbohydrate 20 min prior to an intense RT session. Taken together, results suggest that a higher PRO diet can be beneficial for BBs to optimize body composition during the offseason, as the strategy may help to prevent excessive fat gain without compromising muscular development. ...
Article
Full-text available
Bodybuilding is an aesthetic sport whereby competitors aspire to achieve a combination of high levels of muscularity combined with low levels of body fat. Protein is an important macronutrient for promoting muscle growth, and meeting daily needs is necessary to optimize the accretion of lean mass. Current recommendations for muscle hypertrophy suggest a relative protein intake ranging from 1.4 g/kg/d up to 2.0 g/kg/d is required for those involved in resistance training. However, research indicates that the actual ingestion of protein in competitive bodybuilders is usually greater than advocated in guidelines. The purpose of this current opinion article is to critically evaluate the evidence as to whether higher intakes of protein are warranted in competitive bodybuilders. We conclude that competitive bodybuilders may benefit from consuming a higher protein intake than what is generally prescribed for recreationally-trained lifters; however, the paucity of direct research in this population makes it difficult to draw strong conclusions on the topic.
... Whey protein (18 g) intake prior to a bout of heavy resistance training increases post-training resting energy expenditure in humans compared to carbohydrate intake [41]. Interestingly, this effect diminishes if the whey protein meal was ingested after the resistance exercise, even if the protein content in the diet was at 30 g [42]. ...
Article
Full-text available
Obesity develops due to energy (food) intake exceeding energy expenditure. Nutrients that reduce the positive energy balance are thus being considered as therapies to combat obesity. Here, we review the literature related to the physiological, cellular and endocrine effects of intake of whey proteins, namely α-lactalbumin, β-lactoglobulin, glycomacropeptide and lactoferrin. Moreover, we discuss how dietary composition and obesity may influence whey protein effects on the above parameters. Evidence suggests that intake of whey proteins causes a decrease in energy intake, increase in energy expenditure, influence insulin sensitivity and glucose homeostasis and alter lipid metabolism in the adipose, liver and muscle. These physiological changes are accompanied by alterations in the plasma levels of energy balance related hormones (cholecystokinin, ghrelin, insulin and glucagon-like peptide-1) and the expression of catabolic and anabolic genes in the above tissue in the direction to cause a negative energy balance.
Article
Full-text available
The elderly usually suffer from many diseases. Improving the quality of life of the elderly is an urgent social issue. In this present study, D-galactose treated aging mice models were used to reveal the effects of different animal sources and different doses of whey protein (WP) on the immune indexes organs and intestinal flora. A total of 9 groups were set up, including normal control (NC), negative control (NS), positive control (Vc), low-, medium- and high-doses of cow WP intervention groups (CL, CM and CH for short, correspondingly) and low-, medium- and high-doses of goat WP intervention groups (GL, GM and GH for short, correspondingly). The body weight gain, thymus/body weight ratio, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, spleen immunoglobulins G (IgG), spleen interleukin-2 (IL-2) and spleen interleukin-2 (IL-6) were measured. Then, the intestinal contents were collected, and 16s genes of intestinal bacteria were sequenced to reveal the changes in bacterial flora structure. WP intervention significantly increased the weight gain, thymus/body ratio and SOD activity, but decrease the content of MDA. WP intervention increased some immune indicators. All the WP treated aging mice showed similar values of physiological indexes to that of the Vc group, even better. The relative abundance of Lactobacillus and Stenotrophomonas was increased and decreased, respectively, by both cow and goat WP. Lactobacillus may be involved in regulating the functional repair of organisms. In contrast, Stenotrophomonas might play a negative role in the immune and antioxidant capacity of the body. Combining physiological indicators and intestinal flora structure, low-concentration WP for cow and goat might be optimal for aging models.
Article
Full-text available
Background: To analyze the association between a 34-week military training on body composition, physical fitness and compensatory changes in resting energy expenditure (REE) recognized as adaptive thermogenesis (AT). We also explored if regional body composition changes were related to AT. Methods: Twenty-nine male army cadets, aged 17 to 22 years were tested at baseline (T0) and after 34-weeks military training (T1). Physical training was performed 5 days/week during 90 minutes/day. Measurements included body composition by dual-energy x-ray absorptiometry; physical fitness by 3000-m running, pull-up, 50-m freestyle swimming, push-up and sit-up tests; REE measured by indirect calorimetry (REEm) and predicted from fat-free mass (FFM), fat mass (FM) and ethnicity at T0 (REEp). %AT was calculated using values at T1: 100(REEm/REEp-1); and AT (kcal/day) as %AT/100 multiplied by baseline REEm. Results: Physical training was associated with increases of lean soft tissue (LST) (∆1.2±1.3 kg), FM (∆1.4±1.3 kg), FFM (∆1.2±1.3 kg) and physical fitness (P<0.01), but no REE changes (∆59.6±168.9 kcal/day) and AT were observed (P>0.05). Though a large variability was found, AT was partially explained by trunk LST (r2=0.17, P=0.027). Individuals showing a higher AT response demonstrated a higher trunk LST increase (∆0.8±0.7 kg, P<0.05). Conclusions: The military training increased LST, FM, FFM and physical fitness. Though no mean changes in AT occurred, a large individual variability was observed with some participants increasing REE beyond the expected body composition changes, suggesting a spendthrift phenotype. Changes of trunk LST may play an important role in the AT response observed in these individuals.
Chapter
Nutrient timing is a popular strategy used by athletes, coaches, and researchers to maximize performance and the adaptations resulting from exercise training. Ingestion of key nutrients before, during, and after various forms of exercise has been shown to favorably impact a number of factors that go on to effect health, performance, and recovery. Research in this area is rapidly expanding, and findings are changing on an annual basis. This chapter is broken into sections discussing current recommendations and scientific findings concerning the administration of macronutrients, micronutrients, and other non-nutrients before, during, and after both endurance and resistance exercise. Finally, recommendations are put forth regarding when to employ various strategies, as well as whether certain strategies are worthy of consideration. Key points related to protein timing, caffeine timing, meal patterns, and caloric distribution are all covered in this chapter.
Article
Learning Objectives: To realize that following a strength training session muscle protein breakdown exceeds muscle protein synthesis, resulting in several hours of net negative protein balance. To recognize that ingesting supplemental protein before and/or after a resistance workout is essential for attaining a net positive protein balance that enhances the potential for muscle development. To review research-based information and recommendations for effective pretraining/posttraining protein/carbohydrate supplementation.
Conference Paper
Full-text available
Acute studies have revealed that insulin and possibly incretin hormone [e.g., glucagon-like peptide-1 (GLP-1)] response in humans is significantly affected by whey protein (WP) form [e.g., whey protein isolate (WPI) versus hydrolysate (WPH)], whereas extensive hydrolysates of casein protein, versus native casein, were recently shown to promote a potentially greater (p=0.10) acute muscle protein synthesis response. Similarly, fractions and specific peptides from WP have been identified that may potentiate exercise recovery and/or the muscle protein synthesis response from heavy resistance training. However, to date, no study has compared the chronic effects WP form or molecular distribution may have when consumed in combination with heavy resistance training. PURPOSE: Therefore, the primary purpose of this investigation was to compare the effects of three different variations of a WP on the physiological response to weight training in previously resistance trained, healthy males. METHODS: Fifty-six resistance trained men (21.40±0.36 yrs; 79.46±1.04 kg; 178.59±0.66 cm; 1.24±0.03 1RM bench press-to-body mass ratio) were randomly assigned to receive one of four double-blinded treatments: 30 g/serving carbohydrate (PLA) or 30 g/serving protein from either a) 80% whey protein concentrate (WPC80), b) high lactoferrin containing 80% WPC (WPC80+), or c) extensively hydrolyzed WPC80 (WPH). All subjects participated in eight weeks of a split-body, linear periodized resistance training program, and consumed two servings of treatment per day (one immediately pre- and post-exercise on training days; twice between meals on non-training days). Body composition, upper- and lower-body strength [1RM Bench Press (1RM BP) and 1RM Hack Squat (1RM HS), respectively] and anaerobic endurance [80% of 1RM for maximal repetitions (80RM BP and 80RM HS, respectively)], and fasted blood measures were assessed before (PRE) and after (POST) the 8-week intervention. Twenty-four hour muscle damage (CK) and immune (WBC) response to lower-body resistance training was assessed during Week 1 and 8. Also, total repetitions to failure, CK and WBC were assessed during POST, prior to and in response to repeated daily (x3) bouts of 80RM HS. Two-way repeated measures ANCOVAs were used for statistical analyses. Significance was set at α = 0.05. RESULTS: No significant differences (p>0.05) were observed between groups for total training volume (kg/min), or relative energy (kcals/kg/d), protein (g/kg/d), carbohydrate (g/kg/d), or lipid (g/kg/d) during the 8-week intervention. All groups increased (p<0.0125) 1RM BP (kg), 1RM HS (kg), 80RM BP (reps) and 80RM HS (reps) from PRE to POST, however, no significant (p>0.05) between-group effects were observed. For repeated 80RM HS tests, only WPC80+ realized a significant difference for total repetitions completed between any of the three days of testing (+15.56% more repetitions for 80RM24 versus 80RMPOST; p<0.0125). No significant between- or within-group (p>0.05 and p>0.0125, respectively) changes were observed for 12-hour fasted blood lipids, glucose, WBC or CK from PRE to POST; however, all groups reduced (p<0.0125) creatinine, and WPH creatinine at POST was shown to be significantly different from WPC80+ (-14.218%∆; p<0.05). Urea nitrogen (BUN) was also shown to decrease significantly (p<0.0125) from PRE to POST for WPH (-18.064%), which differed significantly (p<0.05) from WPC80 (+16.908%; p<0.0125). CK response to Week 1 versus Week 8 lower-body exercise, however, decreased significantly in all groups except WPH (-60.327%; p=0.073), and no significant differences occurred between- or within-groups for WBC. Likewise, repeated 80RM HS resulted in no significant between group differences (p>0.05) for either CK or WBC. Lean body mass and total body muscle mass increased (p<0.0125) in all groups, as did body mass in all groups except WPH (+0.641 kg; p=0.114). However, WPH realized a significant PRE to POST reduction in fat mass (-5.942%) and percent body fat (-1.601%), which was significantly different (p<0.05) from PLA (+9.100% and +0.640%, respectively). CONCLUSION: In previously trained, college-aged men, 60 g/d of WPC80, WPC80+, WPH or PLA provide similar responses to an 8-week heavy resistance training program on measures of total body muscle mass, strength, anaerobic endurance and blood lipids. However, WPH appears to significantly augment lipolysis and may increase nitrogen retention.
Article
Full-text available
Effect of whey protein quality on physiological response to chronic resistance exercise in trained men: A double-blind, placebo-controlled, randomized trial
Article
Full-text available
The purpose of this study was to investigate the magnitude and time course for changes in muscle protein synthesis (MPS) after a single bout of resistance exercise. Two groups of six male subjects performed heavy resistance exercise with the elbow flexors of one arm while the opposite arm served as a control. MPS from exercised (ex) and control (con) biceps brachii was assessed 4 (group A) and 24 h (group B) postexercise by the increment in L-[1-13C]leucine incorporation into muscle biopsy samples. In addition, RNA capacity and RNA activity were determined to assess whether transcriptional and/or translational processes affected MPS. MPS was significantly elevated in biceps of the ex compared with the con arms of both groups (group A, ex 0.1007 +/- 0.0330 vs. con 0.067 +/- 0.0204%/h; group B ex 0.0944 +/- 0.0363 vs. con 0.0452 +/- 0.0126%/h). RNA capacity was unchanged in the ex biceps of both groups relative to the con biceps, whereas RNA activity was significantly elevated in the ex biceps of both groups (group A, ex 0.19 +/- 0.10 vs. con 0.12 +/- 0.05 micrograms protein.h-1.microgram-1 total RNA; group B, ex 0.18 +/- 0.06 vs. con 0.08 +/- 0.02 micrograms protein.h-1.microgram-1 total RNA). The results indicate that a single bout of heavy resistance exercise can increase biceps MPS for up to 24 h postexercise. In addition, these increases appear to be due to changes in posttranscriptional events.
Article
Full-text available
1. Changes in basal metabolic rates (BMR), following alterations in the preceding day's dietary protein (8.6, 11.5 and 14.0% of energy) were studied in eight, young, healthy adults over 4d. 2. Results showed a significant training effect, with BMR values 4.8 % lower on day 4 of the study period. Analysis of the results by ANOVA revealed a significant interaction between subjects and diets ( P <0.005), a significant difference between subjects but no differences in BMR due to the protein content of the diets. 3. Mean coefficient of variation (CV) for intra- and inter-individual differences in BMR from day-to-day was of the order of 4 and 9% respectively. 4. Changes in protein content of the preceding day's diet do not influence variations in BMR which appear to be random in nature with a true CV of 3.8%.
Article
Full-text available
It has been shown that muscle protein synthetic rate (MPS) is elevated in humans by 50% at 4 hrs following a bout of heavy resistance training, and by 109% at 24 hrs following training. This study further examined the time course for elevated muscle protein synthesis by examining its rate at 36 hrs following a training session. Six healthy young men performed 12 sets of 6- to 12-RM elbow flexion exercises with one arm while the opposite arm served as a control. MPS was calculated from the in vivo rate of incorporation of L-[1,2-13C2] leucine into biceps brachii of both arms using the primed constant infusion technique over 11 hrs. At an average time of 36 hrs postexercise, MPS in the exercised arm had returned to within 14% of the control arm value, the difference being nonsignificant. It is concluded that following a bout of heavy resistance training, MPS increases rapidly, is more than double at 24 hrs, and thereafter declines rapidly so that at 36 hrs it has almost returned to baseline.
Article
Full-text available
Mixed muscle protein fractional synthesis rate (FSR) and fractional breakdown rate (FBR) were examined after an isolated bout of either concentric or eccentric resistance exercise. Subjects were eight untrained volunteers (4 males, 4 females). Mixed muscle protein FSR and FBR were determined using primed constant infusions of [2H5]phenylalanine and 15N-phenylalanine, respectively. Subjects were studied in the fasted state on four occasions: at rest and 3, 24, and 48 h after a resistance exercise bout. Exercise was eight sets of eight concentric or eccentric repetitions at 80% of each subject's concentric 1 repetition maximum. There was no significant difference between contraction types for either FSR, FBR, or net balance (FSR minus FBR). Exercise resulted in significant increases above rest in muscle FSR at all times: 3 h = 112%, 24 h = 65%, 48 h = 34% (P < 0.01). Muscle FBR was also increased by exercise at 3 h (31%; P < 0.05) and 24 h (18%; P < 0.05) postexercise but returned to resting levels by 48 h. Muscle net balance was significantly increased after exercise at all time points [(in %/h) rest = -0.0573 +/- 0.003 (SE), 3 h = -0.0298 +/- 0.003, 24 h = -0.0413 +/- 0.004, and 48 h = -0.0440 +/- 0.005], and was significantly different from zero at all time points (P < 0.05). There was also a significant correlation between FSR and FBR (r = 0.88, P < 0.001). We conclude that exercise resulted in an increase in muscle net protein balance that persisted for up to 48 h after the exercise bout and was unrelated to the type of muscle contraction performed.
Article
Full-text available
The present study was designed to determine whether consumption of an oral essential amino acid-carbohydrate supplement (EAC) before exercise results in a greater anabolic response than supplementation after resistance exercise. Six healthy human subjects participated in two trials in random order, PRE (EAC consumed immediately before exercise), and POST (EAC consumed immediately after exercise). A primed, continuous infusion of L-[ring-(2)H(5)]phenylalanine, femoral arteriovenous catheterization, and muscle biopsies from the vastus lateralis were used to determine phenylalanine concentrations, enrichments, and net uptake across the leg. Blood and muscle phenylalanine concentrations were increased by approximately 130% after drink consumption in both trials. Amino acid delivery to the leg was increased during exercise and remained elevated for the 2 h after exercise in both trials. Delivery of amino acids (amino acid concentration times blood flow) was significantly greater in PRE than in POST during the exercise bout and in the 1st h after exercise (P < 0.05). Total net phenylalanine uptake across the leg was greater (P = 0.0002) during PRE (209 +/- 42 mg) than during POST (81 +/- 19). Phenylalanine disappearance rate, an indicator of muscle protein synthesis from blood amino acids, increased after EAC consumption in both trials. These results indicate that the response of net muscle protein synthesis to consumption of an EAC solution immediately before resistance exercise is greater than that when the solution is consumed after exercise, primarily because of an increase in muscle protein synthesis as a result of increased delivery of amino acids to the leg.
Article
Full-text available
In the recovery period after exercise there is an increase in oxygen uptake termed the ‘excess post-exercise oxygen consumption’ (EPOC), consisting of a rapid and a prolonged component. While some studies have shown that EPOC may last for several hours after exercise, others have concluded that EPOC is transient and minimal. The conflicting results may be resolved if differences in exercise intensity and duration are considered, since this may affect the metabolic processes underlying EPOC. Accordingly, the absence of a sustained EPOC after exercise seems to be a consistent finding in studies with low exercise intensity and/or duration. The magnitude of EPOC after aerobic exercise clearly depends on both the duration and intensity of exercise. A curvilinear relationship between the magnitude of EPOC and the intensity of the exercise bout has been found, whereas the relationship between exercise duration and EPOC magnitude appears to be more linear, especially at higher intensities. Differences in exercise mode may potentially contribute to the discrepant findings of EPOC magnitude and duration. Studies with sufficient exercise challenges are needed to determine whether various aerobic exercise modes affect EPOC differently. The relationships between the intensity and duration of resistance exercise and the magnitude and duration of EPOC have not been determined, but a more prolonged and substantial EPOC has been found after hardversus moderate-resistance exercise. Thus, the intensity of resistance exercise seems to be of importance for EPOC. Lastly, training status and sex may also potentially influence EPOC magnitude, but this may be problematic to determine. Still, it appears that trained individuals have a more rapid return of post-exercise metabolism to resting levels after exercising at either the same relative or absolute work rate; however, studies after more strenuous exercise bouts are needed. It is not determined if there is a sex effect on EPOC. Finally, while some of the mechanisms underlying the more rapid EPOC are well known (replenishment of oxygen stores, adenosine triphosphate/creatine phosphate resynthesis, lactate removal, and increased body temperature, circulation and ventilation), less is known about the mechanisms underlying the prolonged EPOC component. A sustained increased circulation, ventilation and body temperature may contribute, but the cost of this is low. An increased rate of triglyceride/fatty acid cycling and a shift from carbohydrate to fat as substrate source are of importance for the prolonged EPOC component after exhaustive aerobic exercise. Little is known about the mechanisms underlying EPOC after resistance exercise.
Article
Full-text available
The necessity of a 12-h fast before resting metabolic rate (RMR) is measured is often a barrier to measuring RMR. We compared RMR measurements obtained in the morning and afternoon and across repeated days to elucidate the magnitude and sources of variability. Healthy men (n = 12) and women (n = 25) aged 21-67 y, with body mass indexes (in kg/m(2)) ranging from 17 to 34 and body fat ranging from 6% to 54%, completed 4 RMR measurements. RMR measurements were made in the morning (after a 12-h fast and 12 h postexercise) and in the afternoon (after a 4-h fast and 12 h postexercise) on 2 separate days with the ventilated-hood technique. Body composition was assessed by dual-energy X-ray absorptiometry. Mean (+/- SE) afternoon RMR was significantly higher than morning RMR on both visit 1 (1593.5 +/- 35.6 compared with 1508.0 +/- 31.5 kcal/d; P = 0.001) and visit 2 (1602 +/- 29.3 compared with 1511.4 +/- 35.9 kcal/d; P = 0.001). The 2 morning measurements (r = 0.93) and the 2 afternoon measurements (r = 0.93) were highly correlated, and no significant differences between measurements were observed. The mean difference between the morning and afternoon measurements was 99.0 +/- 35.8 kcal/d (6%). Repeated morning and evening measurements of RMR were stable and highly correlated. Day-to-day measurements of RMR were not significantly different. RMR measured in the afternoon after a 4-h fast and exercise was approximately 100 kcal/d higher than RMR measured in the morning.
Article
Full-text available
We investigated the effects of a single bout of aerobic and resistance exercise of similar relative intensity and duration on resting energy expenditure (REE) and substrate utilisation. Ten young healthy males volunteered [age 22 (1.8) years, weight 76 (7.9) kg, height 176 (4.1) cm, percentage body fat 10.5 (4.0)%; mean (SEM)]. They randomly underwent three conditions in which they either lifted weights for 60 min at 70-75% of 1-RM (WL), ran for 60 min at 70-75% of maximal oxygen intake (R) or did not exercise (C). REE and substrate utilisation, determined via respiratory exchange ratio ( R), were measured prior to exercise, and 10, 24, 48 and 72 h post-exercise. It was revealed that REE was significantly elevated ( P<0.05) 10 and 24 h after the end of WL [2,124 (78) and 2,081 (76) kcal, respectively] compared to pre-exercise [1,972 (82) kcal]. REE was also significantly increased ( P<0.05) 10 and 48 h after the completion of R [2,150 (73) and 1,995 (74) kcal, respectively] compared to pre-exercise data [1,862 (70) kcal]. R was lower 10 and 24 h following either WL or R [0.813 (0.043); 0.843 (0.040) and 0.818 (0.021); 0.832 (0.021), respectively] compared to baseline measurements [0.870 (0.025) and 0.876 (0.04), respectively]. Creatine kinase was significantly elevated ( P<0.05) 24 h after both WL and R, whereas delayed onset muscle soreness became significantly elevated ( P<0.05) 24 h after only WL. There were no significant changes for any treatment in thyroid hormones (T(3) and T(4)). These results suggest that a single bout of either WL or R exercise, characterised by the same relative intensity and duration, increase REE and fat oxidation for at least 24 h post-exercise.
Article
Full-text available
Resistance exercise disturbs skeletal muscle homeostasis leading to activation of catabolic and anabolic processes within the muscle cell. A current challenge of exercise biology is to describe the molecular mechanisms of regulation by which contractile activity stimulates net protein breakdown during exercise and net protein synthesis during recovery. Muscle growth is optimized by combining exercise and appropriate nutritional strategies, such as amino acid (AA) and carbohydrate ingestion. The effects are integrated at the level of one central regulatory protein, mTOR (mammalian target of rapamycin). mTOR is a complex protein integrating signals of the energetic status of the cell and environmental stimuli to control protein synthesis, protein breakdown and therefore cell growth. mTOR is known to be activated by insulin, and the mechanisms involved are well documented. The ways by which exercise and AA lead to mTOR activation remain partially unclear. Exercise and AA use different signalling pathways upstream of mTOR. Exercise seems to recruit partially the same pathway as insulin, whereas AA could act more directly on mTOR. During resistance exercise, the activity of mTOR could be acutely blunted by AMP-activated protein kinase (AMPK), thus inhibiting protein synthesis and enhancing AA availability for energy metabolism. During recovery, the inhibition of mTOR by AMPK is suppressed, and its activation is maximized by the presence of AA. There appears to be a requirement for a minimal concentration of plasma insulin to stimulate muscle protein synthesis in response to resistance exercise and AA ingestion.
Article
Full-text available
Resistance exercise has been shown to elicit a significant acute hormonal response. It appears that this acute response is more critical to tissue growth and remodelling than chronic changes in resting hormonal concentrations, as many studies have not shown a significant change during resistance training despite increases in muscle strength and hypertrophy. Anabolic hormones such as testosterone and the superfamily of growth hormones (GH) have been shown to be elevated during 15-30 minutes of post-resistance exercise providing an adequate stimulus is present. Protocols high in volume, moderate to high in intensity, using short rest intervals and stressing a large muscle mass, tend to produce the greatest acute hormonal elevations (e.g. testosterone, GH and the catabolic hormone cortisol) compared with low-volume, high-intensity protocols using long rest intervals. Other anabolic hormones such as insulin and insulin-like growth factor-1 (IGF-1) are critical to skeletal muscle growth. Insulin is regulated by blood glucose and amino acid levels. However, circulating IGF-1 elevations have been reported following resistance exercise presumably in response to GH-stimulated hepatic secretion. Recent evidence indicates that muscle isoforms of IGF-1 may play a substantial role in tissue remodelling via up-regulation by mechanical signalling (i.e. increased gene expression resulting from stretch and tension to the muscle cytoskeleton leading to greater protein synthesis rates). Acute elevations in catecholamines are critical to optimal force production and energy liberation during resistance exercise. More recent research has shown the importance of acute hormonal elevations and mechanical stimuli for subsequent up- and down-regulation of cytoplasmic steroid receptors needed to mediate the hormonal effects. Other factors such as nutrition, overtraining, detraining and circadian patterns of hormone secretion are critical to examining the hormonal responses and adaptations to resistance training.
Article
Full-text available
The effects of protein consumption before strength training session on blood hormones, energy metabolites, RER, and excess postexercise oxygen consumption (EPOC) were examined. Ten resistance-trained young men consumed either a 25 g of whey and caseinate proteins (PROT) or a noncaloric placebo (P) in a liquid form 30 min before a heavy strength training session (STS) in a crossover design separated by at least 7 d. STS lasted 50 min and included 5 x 1 RM squats, 3 x 10 RM squats and 4 x 10 RM leg presses with 2-, 3-, and 2-min recoveries, respectively. A protein-carbohydrate supplement was consumed after STS in both trials. Venous blood samples were collected before, during, and after STS and oxygen consumption before and after STS. Serum growth hormone (GH), testosterone, and free fatty acids (FFA) were significantly (P < or = 0.05) higher in P compared with PROT 5 min after an STS. The calculated area under curve (AUC) of the serum insulin response during an STS was significantly (P < 0.001) higher in PROT compared with P. The EPOC value from 90 to 120 min after an STS was significantly greater in the PROT condition compared with P (P = 0.01), and PROT treatment had a significantly higher RER 2 h postexercise (P = 0.04). The AUC of serum FFA during STS correlated significantly and negatively with RER 10-30 min after STS (r = -0.53, P = 0.02). Consuming 25 g of whey and caseinate proteins 30 min before an STS significantly decreases serum GH, testosterone, and FFA levels, and increases serum insulin during an STS. Furthermore, the pre-STS protein increased EPOC and RER significantly during 2-h recovery after STS.
Article
Full-text available
Training and nutrition are highly interrelated in that optimal adaptation to the demands of repeated training sessions typically requires a diet that can sustain muscle energy reserves. As nutrient stores (i.e. muscle and liver glycogen) play a predominant role in the performance of prolonged, intense, intermittent exercise typical of the patterns of soccer match-play, and in the replenishment of energy reserves for subsequent training sessions, the extent to which acutely altering substrate availability might modify the training impulse has been a key research area among exercise physiologists and sport nutritionists for several decades. Although the major perturbations to cellular homeostasis and muscle substrate stores occur during exercise, the activation of several major signalling pathways important for chronic training adaptations take place during the first few hours of recovery, returning to baseline values within 24 h after exercise. This has led to the paradigm that many chronic training adaptations are generated by the cumulative effects of the transient events that occur during recovery from each (acute) exercise bout. Evidence is accumulating that nutrient supplementation can serve as a potent modulator of many of the acute responses to both endurance and resistance training. In this article, we review the molecular and cellular events that occur in skeletal muscle during exercise and subsequent recovery, and the potential for nutrient supplementation (e.g. carbohydrate, fat, protein) to affect many of the adaptive responses to training.
Article
Full-text available
High-resistance strength training (HRST) is one of the most widely practiced forms of physical activity, which is used to enhance athletic performance, augment musculo-skeletal health and alter body aesthetics. Chronic exposure to this type of activity produces marked increases in muscular strength, which are attributed to a range of neurological and morphological adaptations. This review assesses the evidence for these adaptations, their interplay and contribution to enhanced strength and the methodologies employed. The primary morphological adaptations involve an increase in the cross-sectional area of the whole muscle and individual muscle fibres, which is due to an increase in myofibrillar size and number. Satellite cells are activated in the very early stages of training; their proliferation and later fusion with existing fibres appears to be intimately involved in the hypertrophy response. Other possible morphological adaptations include hyperplasia, changes in fibre type, muscle architecture, myofilament density and the structure of connective tissue and tendons. Indirect evidence for neurological adaptations, which encompasses learning and coordination, comes from the specificity of the training adaptation, transfer of unilateral training to the contralateral limb and imagined contractions. The apparent rise in whole-muscle specific tension has been primarily used as evidence for neurological adaptations; however, morphological factors (e.g. preferential hypertrophy of type 2 fibres, increased angle of fibre pennation, increase in radiological density) are also likely to contribute to this phenomenon. Changes in inter-muscular coordination appear critical. Adaptations in agonist muscle activation, as assessed by electromyography, tetanic stimulation and the twitch interpolation technique, suggest small, but significant increases. Enhanced firing frequency and spinal reflexes most likely explain this improvement, although there is contrary evidence suggesting no change in cortical or corticospinal excitability. The gains in strength with HRST are undoubtedly due to a wide combination of neurological and morphological factors. Whilst the neurological factors may make their greatest contribution during the early stages of a training programme, hypertrophic processes also commence at the onset of training.
Article
Full-text available
Resistance exercise is a powerful stimulus to augment muscle protein anabolism, as it can improve the balance between muscle protein synthesis and breakdown. However, the intake of food during post-exercise recovery is necessary for hypertrophy to occur. Therefore, athletes need to ingest protein following exercise to attain a positive protein balance and maximise their skeletal muscle adaptive response. The interaction between exercise and nutrition is not only important for athletes, but is also of important clinical relevance in the elderly. Exercise interventions combined with specific nutritional modulation provide an effective strategy to counteract or reduce the loss of skeletal muscle mass with aging.
Article
Differences in protein requirements for athletes and nonathletes, and different types of athletes (i.e., endurance vs. strength/power) are well acknowledged. This has led many athletes to use protein supplements as a means of achieving required protein intakes. Recent research has begun to examine the importance of protein timing. Specifically, does it make a difference when the protein is ingested in regards to augmenting the acute physiological response to a training session or in enhancing recovery from exercise. This review focuses on the timing of protein intake and its effects on skeletal muscle remodeling. (C) 2007 National Strength and Conditioning Association
Article
The elongation phase of mRNA translation is the stage at which the polypeptide is assembled and requires a substantial amount of metabolic energy. Translation elongation in mammals requires a set of nonribosomal proteins called eukaryotic elongation actors or eEFs. Several of these proteins are subject to phosphorylation in mammalian cells, including the factors eEF1A and eEF1B that are involved in recruitment of amino acyl-tRNAs to the ribosome. eEF2, which mediates ribosomal translocation, is also phosphorylated and this inhibits its activity. The kinase acting on eEF2 is an unusual and specific one, whose activity is dependent on calcium ions and calmodulin. Recent work has shown that the activity of eEF2 kinase is regulated by MAP kinase signalling and by the nutrient-sensitive mTOR signalling pathway, which serve to activate eEF2 in response to mitogenic or hormonal stimuli. Conversely, eEF2 is inactivated by phosphorylation in response to stimuli that increase energy demand or reduce its supply. This likely serves to slow down protein synthesis and thus conserve energy under such circumstances.
Article
Differences in protein requirements for athletes and nonathletes, and different types of athletes (i.e., endurance vs. strength/power) are well acknowledged. This has led many athletes to use protein supplements as a means of achieving required protein intakes. Recent research has begun to examine the importance of protein timing. Specifically, does it make a difference when the protein is ingested in regards to augmenting the acute physiological response to a training session or in i enhancing recovery from exercise, i This review focuses on the timing of protein intake and its effects on skeletal muscle remodeling.
Article
Purpose: The purpose of this investigation was to determine whether muscle damage caused from acute resistance exercise with an eccentric overload would influence resting metabolic rate (RMR) up to 72 h postexercise in resistance-trained (RT) and untrained (UT) subjects. Methods: Nine RT and 9 UT male subjects (mean +/- SD; age = 20.7 +/- 2.1 yr; body mass = 79.0 +/- 1.4 kg; height = 178.3 +/- 3.1 cm; and body fat = 10.2 +/- 1.6%) were measured for RMR, creatine kinase concentration ([CK]), and rating of perceived muscle soreness (RPMS) on five consecutive mornings. To induce muscle damage, after the measurements on day 2, each subject performed leg presses that emphasized the eccentric movement for 8 sets at his six-repetition maximum (6-RM). Results: Compared with baseline, the RMR (kJ.d(-1) and kJ.kg FFM-1.h(-1)) was significantly elevated for RT and UT at 24 h and 48 h postexercise. From 24 h to 48 h to 72 h postexercise, RMR significantly decreased within both groups. The UT group had a significantly higher RMR at 24 h (9705.4 +/- 204.5 kJ.d(-1)) and 48 h postexercise (8930.9 +/- 101.4 kJ.d(-1)) when compared with the RT group (9209.3 +/- 535.3 and 8601.7 +/- 353.7 kT.d(-1)). Both [CK] and RPMS showed a similar time course. Conclusion: There was a significantly higher [CK] for the UT group at 24 h postexercise (320.4 +/- 20.1 U.L-1) and for both [CK] and RPMS at 48 h (1140.3 +/- 37.1 U.L-1 and 4.4 +/- 0.5, respectively) and 72 h postexercise (675.9 +/- 41.7 U.L-1 and 1.67 +/- 0.5, respectively) when compared with the RT group (24 h, 201.9 +/- 13.4 U.L-1; 48 h, 845.4 +/- 30.7 U.L-1 and 3.7 +/- 0.5; and 72 h postexercise, 470.2 +/- 70.2 U.L-1 and 0.89 +/- 0.3). These data indicate that eccentrically induced muscle damage causes perturbations in RMR up to 48 h postexercise.
Article
High-resistance strength training (HRST) is one of the most widely practiced forms of physical activity, which is used to enhance athletic performance, augment musculo-skeletal health and alter body aesthetics. Chronic exposure to this type of activity produces marked increases in muscular strength, which are attributed to a range of neurological and morphological adaptations. This review assesses the evidence for these adaptations, their interplay and contribution to enhanced strength and the methodologies employed. The primary morphological adaptations involve an increase in the cross-sectional area of the whole muscle and individual muscle fibres, which is due to an increase in myofibrillar size and number. Satellite cells are activated in the very early stages of training; their proliferation and later fusion with existing fibres appears to be intimately involved in the hypertrophy response. Other possible morphological adaptations include hyperplasia, changes in fibre type, muscle architecture, myofilament density and the structure of connective tissue and tendons. Indirect evidence for neurological adaptations, which encompasses learning and coordination, comes from the specificity of the training adaptation, transfer of unilateral training to the contralateral limb and imagined contractions. The apparent rise in whole-muscle specific tension has been primarily used as evidence for neurological adaptations; however, morphological factors (e.g. preferential hypertrophy of type 2 fibres, increased angle of fibre pennation, increase in radiological density) are also likely to contribute to this phenomenon. Changes in inter-muscular coordination appear critical. Adaptations in agonist muscle activation, as assessed by electromyography, tetanic stimulation and the twitch interpolation technique, suggest small, but significant increases. Enhanced firing frequency and spinal reflexes most likely explain this improvement, although there is contrary evidence suggesting no change in cortical or corticospinal excitability. The gains in strength with HRST are undoubtedly due to a wide combination of neurological and morphological factors. Whilst the neurological factors may make their greatest contribution during the early stages of a training programme, hypertrophic processes also commence at the onset of training.
Article
summary: Differences in protein requirements for athletes and nonathletes, and different types of athletes (i.e., endurance vs. strength/power) are well acknowledged. This has led many athletes to use protein supplements as a means of achieving required protein intakes. Recent research has begun to examine the importance of protein timing. Specifically, does it make a difference when the protein is ingested in regards to augmenting the acute physiological response to a training session or in enhancing recovery from exercise. This review focuses on the timing of protein intake and its effects on skeletal muscle remodeling. (C) 2007 National Strength and Conditioning Association
Article
The purpose of this investigation was to determine the effect of an acute bout of high-volume, full-body resistance training with an eccentric concentration on resting energy expenditure (REE) and indicators of delayed-onset muscle soreness (DOMS). Eight resistance trained (RT) and eight untrained (UT) participants (mean: age = 23.5 years; height = 180.76 cm; weight = 87.58 kg; body fat = 19.34%; lean mass = 68.71 kg) were measured on four consecutive mornings for REE and indicators of DOMS: creatine kinase (CK) and rating of perceived muscle soreness (RPMS). Delayed-onset muscle soreness was induced by performing eight exercises, eight sets, and six repetitions using a 1-second concentric and 3-second eccentric muscle action duration. A two-factor repeated-measures analysis of variance revealed that REE was significantly (p < 0.05) elevated at 24, 48, and 72 hours post compared with baseline measures for both UT and RT groups. Ratings of perceived muscle soreness were significantly elevated within groups for UT and RT at 24 and 48 hours post and for UT only at 72 hours post compared with baseline (p < 0.05). Nonparametric analyses revealed that CK was significantly increased at 24 hours post for both UT and RT and at 48 and 72 hours post for UT only compared with baseline (p < 0.05). Resting energy expenditure and indicators of DOMS were higher in UT compared with RT on all measures, but no significant differences were determined. The main finding of this investigation is that full-body resistance training with an eccentric concentration significantly increased REE up to 72 hours postexercise in UT and RT participants.
Article
Resting metabolic rate is modulated by the amount of calories consumed in the diet relative to energy expenditure. Excessive consumption of energy appears to increase resting metabolic rate while fasting and very low calorie dieting causes resting metabolic rate to decrease. Since the metabolic rate at rest is the primary component of daily energy expenditure, its reduction with caloric restriction makes it difficult for obese individuals to lose weight and to maintain weight that is lost. Whether exercise has a carry-over effect on resting metabolic rate remains controversial, even though this question has been studied extensively during the last 90 years. Reasons for contradictory results include variations in control of prior diet and exercise patterns, inadequate exercise frequency, intensity and duration, and the possibility of response to exercise varying between individuals. Several lines of evidence suggest exercise may modulate resting metabolic rate. Bed rest in sedentary individuals leads to a reduction in resting metabolic rate. Similarly, in highly trained runners, cessation of daily exercise training lowers resting metabolic rate by about 7 to 10%. Resting metabolic rate is depressed in previously sedentary obese individuals on a very low calorie diet, but it quickly returns to the predieting level when exercise of sufficient frequency, intensity and duration is undertaken while dieting. These findings suggest caloric intake and daily exercise can modulate resting metabolic rate. Exercise of adequate intensity and duration may also enhance resting metabolic rate.
Article
This study examined whether variability among healthy young adults in resting metabolic rate, normalized for the amount of metabolically active tissue (assessed by total body potassium), is related to protein turnover. Resting metabolic rate was measured by indirect calorimetry for 2 h in 26 men and 21 women, 19-33 yr old, with simultaneous estimation of protein turnover during a 4-h infusion of L-[1-13C]leucine. After adjusting metabolic rate for total body potassium, the standard deviation was only 89 kcal/day, or 5.5% of the average value. There was a high correlation between leucine flux (an index of proteolysis) and metabolic rate (r = 0.84) and between the nonoxidized portion of leucine flux (an index of protein synthesis) and metabolic rate (r = 0.83). This relationship was weaker, but still significant, after adjusting leucine metabolism and metabolic rate for total body potassium (r = 0.36 for leucine flux vs. metabolic rate, r = 0.33 for nonoxidized portion of leucine flux vs. metabolic rate, P less than 0.05). The regression analysis suggested that the contribution of protein turnover to resting metabolic rate was approximately 20% in an average subject. Metabolic rate and protein turnover were highest in the subjects with the greatest amount of body fat, even after accounting for differences in whole body potassium. Neither resting metabolic rate nor protein turnover was related to total or free concentrations of thyroxine or triiodothyronine, within the euthyroid range.(ABSTRACT TRUNCATED AT 250 WORDS)
Article
Variations in BMR, body weight and energy intake were measured for 14 consecutive days in 6 young adults on ad libitum energy intakes, whose physical activity was uncontrolled. Energy intakes showed significant differences between days (P less than 0.025, CV = 6.7 per cent), between weeks (P less than 0.005, CV = 8.9 per cent) and between subjects (P less than 0.005, CV = 7.9 per cent). Energy intakes were 14 per cent higher (P less than 0.01) at weekends. Intra-individual variance contributed up to 86 per cent of the total variance in the energy intake. Replicate BMR measurements showed non-significant differences from day to day (CV less than 1.5 per cent), a training effect from week to week (P less than 0.05, CV = 1.5 per cent), and significant differences between subjects (P less than 0.001, CV = 12.4 per cent). Intra-individual variance contributed only 14 per cent to the total variance in BMR. There were no significant changes in body weight (CV = 0.7 per cent) or fat-free mass during the study. Auto-correlations of BMR, body weight and energy intake were non-significant at the different lag times studied. Cross-correlations between the above parameters were also non-significant for each subject. It is concluded that despite wide fluctuations in energy intake from day to day within an individual, the variations in BMR are small with a true CV of less than 1.5 per cent. Hence these variations are unlikely to be important while assessing energy requirements on the basis of the FAO/WHO/UNU (1985) BMR factorial method.
Article
Basal metabolic rate, resting metabolic rate (RMR), and energy cost of selected activities were measured in six healthy young women who were participating in a study of protein requirements. The women were confined to a metabolic unit for 92 days during which they consumed a defined formula diet. The basal metabolic rate of the women was 20.7 +/- 2.6 kcal/kg body weight/day and the caloric requirement for maintenance of weight was 38.7 kcal/kg body weight/day. Basal metabolic rate varied significantly with the menstrual cycle. Basal metabolic rate decreased at menstruation and fell to its lowest point approximately 1 wk before ovulation subsequently rising until the beginning of the next menstrual period. RMR was 0.99 +/- 0.16 kcal/kg/h. The energy expenditure while sitting was 1.06 times RMR, while walking it was 2.81 times RMR, and while performing treadmill exercise it was 3.47 times RMR.
Article
Postexercise energy metabolism was examined in male subjects age 22-35 years in response to three different treatments: a strenuous bout of resistive exercise (REx), a bout of stationary cycling (AEx) at 50% peak VO2, and a control condition (C) of quiet sitting. Resting metabolic rate (RMR) was measured the morning of and the morning following each condition. Recovery oxygen consumption (RcO2) was measured for 5 hr following each treatment. Total 5-hr RcO2 was higher for the REx treatment relative to both AEx and C, with the largest treatment differences occurring early during recovery. There were no large treatment differences in postexercise respiratory exchange ratio values, except for the first hour of recovery following REx. RMR measured 14.5 hr postexercise for the REx condition was significantly elevated compared to C. These results suggest that strenuous resistive exercise results in a greater excess postexercise oxygen consumption compared to steady-state endurance exercise of similar estimated energy cost.
Article
Two separate experiments were performed to determine the effect of acute resistive exercise on postexercise energy expenditure in male subjects previously trained in resistive exercise. In experiment 1, after measurement of their resting metabolic rate (RMR) at 0700 h and their ingestion of a standardized meal at 0800 h, seven subjects (age range 22-40 yr) beginning at 1400 h completed a 90-min weight-lifting protocol. Postexercise metabolic rate (PEMR) was measured continuously for 2 h after exercise and compared with a preexercise baseline. RMR was measured the following morning 15 h after completion of the workout. In experiment 2, six different men (age range 20-35 yr) completed a similar experimental protocol as well as a control condition on a separate day in which metabolic rate was measured for 2 h after a period of quiet sitting. For both experiments, PEMR remained elevated for the entire 2-h measured recovery period, with the average oxygen consumption for the last 6 min elevated by 11-12%. RMR measured the morning after exercise was 9.4% higher in experiment 1 and 4.7% higher in experiment 2 than on the previous day. In experiment 2, the postabsorptive respiratory exchange ratio was significantly lower the morning after the exercise bout. Strenuous resistive exercise may elevate PEMR for a prolonged period and may enhance postexercise lipid oxidation.
Article
A new device based on the plethysmographic measurement of body volume has been developed for the purpose of estimating human body composition. The device, the BOD POD Body Composition System, uses the relationship between pressure and volume to derive the body volume of a subject seated inside a fiberglass chamber. Derivation of body volume, together with measurement of body mass, permits calculation of body density and subsequent estimation of percent fat and fat-free mass. Critical issues which have hampered prior plethysmographic approaches are discussed. The present system's ability to measure the volume of inanimate objects was evaluated for accuracy, reliability, and linearity. Twenty successive tests of a known volume (50,039 ml) on two separate days produced values of 50,037 +/- 12.7 ml and 50,030 +/- 13.5 ml (mean +/- SD) for each day, respectively. The CV for these series were 0.025% and 0.027%. Further testing across a wide range of volumes approximating human size (25-150 1) produced the following regression equation where y = measured volume (1) and x = actual volume (1): y = 0.9998x - 0.0274, r2 = 1.0, SEE = 0.004 1. The resultant device is likely to enhance opportunities for the quick, simple and noninvasive measurement of body composition for both research and clinical applications.
Article
The relationship between energy expenditure and protein metabolism during amino acid (AA) administration was evaluated in normal humans. A balanced AA solution was infused for 180 min at five different rates: 20 (study I), 40 (study II), 80 (study III), 160 (study IV), and 240 mg.m2(-1).min-1 (study V), on separate days, in seven normal, overnight-fasted subjects (age 25 +/- 2 y; height 172 +/- 5 cm; weight 68 +/- 4 kg). Indirect calorimetry and [1-14C] leucine infusion techniques were employed. Basal total plasma AA concentration averaged 1827 +/- 121 mumol/L and increased to 2192 +/- 142, 2576 +/- 158, 3677 +/- 195, 5638 +/- 237, and 7185 +/- 261 mumol/L in studies I-V, respectively. Basal energy expenditure averaged 0.60 +/- 0.02 kcal.m2(-1).min-1 and increased slightly in studies I and II (to 0.62 +/- 0.03, 0.63 +/- 0.02, respectively), and significantly in studies III-V (to 0.65 +/- 0.03, 0.70 +/- 0.04, and 0.77 +/- 0.05 kcal.m2(-1).min-1, respectively, all P < 0.01 versus basal; P < 0.05-0.01 for each study versus preceding study). Basal nonoxidative leucine disposal (NOLD), an index of protein synthesis, averaged 73 +/- 3 mumol.m2(-1).min-1 and increased, albeit not significantly, in studies I and II (to 75 +/- 5, 76 +/- 4, respectively). In contrast, a significant increase in NOLD was observed in studies III-V (to 87 +/- 7, 103 +/- 7, and 127 +/- 9 mumol.m2(-1).min-1, respectively; all P < 0.01 versus basal; P < 0.05-0.01 for each study versus preceding study). Basal respiratory quotient averaged 0.81 +/- 0.02 and did not change significantly in studies I-V (0.80 +/- 0.02, 0.79 +/- 0.02, 0.80 +/- 0.03, 0.82 +/- 0.02 and 0.82 +/- 0.03, respectively). The thermic effect of AA administration, calculated as percent of the AA energy infused, was constant and averaged 24 +/- 4, 19 +/- 3, 17 +/- 4, 17 +/- 3, and 18 +/- 3% in studies I-V, respectively. When AA-induced increase in protein synthesis was plotted with the increment in energy expenditure, a positive correlation was obtained (r = 0.792, P < 0.001). In summary, during AA administration (1) the absolute rise in energy expenditure is dose-dependent and does not show evidence of achieving a plateau; (2) it is positively correlated with AA-induced protein synthesis; and (3) the thermic effect is not dependent upon the AA dose administered. The data provide a quantitative assessment of AA-induced thermogenesis in normal humans and the energy needs associated with an acute stimulation of protein synthesis.
Article
Six normal untrained men were studied during the intravenous infusion of a balanced amino acid mixture (approximately 0.15 g.kg-1.h-1 for 3 h) at rest and after a leg resistance exercise routine to test the influence of exercise on the regulation of muscle protein kinetics by hyperaminoacidemia. Leg muscle protein kinetics and transport of selected amino acids (alanine, phenylalanine, leucine, and lysine) were isotopically determined using a model based on arteriovenous blood samples and muscle biopsy. The intravenous amino acid infusion resulted in comparable increases in arterial amino acid concentrations at rest and after exercise, whereas leg blood flow was 64 +/- 5% greater after exercise than at rest. During hyperaminoacidemia, the increases in amino acid transport above basal were 30-100% greater after exercise than at rest. Increases in muscle protein synthesis were also greater after exercise than at rest (291 +/- 42% vs. 141 +/- 45%). Muscle protein breakdown was not significantly affected by hyperminoacidemia either at rest or after exercise. We conclude that the stimulatory effect of exogenous amino acids on muscle protein synthesis is enhanced by prior exercise, perhaps in part because of enhanced blood flow. Our results imply that protein intake immediately after exercise may be more anabolic than when ingested at some later time.
Article
This study was designed to determine the response of muscle protein to the bolus ingestion of a drink containing essential amino acids and carbohydrate after resistance exercise. Six subjects (3 men, 3 women) randomly consumed a treatment drink (6 g essential amino acids, 35 g sucrose) or a flavored placebo drink 1 h or 3 h after a bout of resistance exercise on two separate occasions. We used a three-compartment model for determination of leg muscle protein kinetics. The model involves the infusion of ring-(2)H(5)-phenylalanine, femoral arterial and venous blood sampling, and muscle biopsies. Phenylalanine net balance and muscle protein synthesis were significantly increased above the predrink and corresponding placebo value (P < 0.05) when the drink was taken 1 or 3 h after exercise but not when the placebo was ingested at 1 or 3 h. The response to the amino acid-carbohydrate drink produced similar anabolic responses at 1 and 3 h. Muscle protein breakdown did not change in response to the drink. We conclude that essential amino acids with carbohydrates stimulate muscle protein anabolism by increasing muscle protein synthesis when ingested 1 or 3 h after resistance exercise.
Article
The purpose of this investigation was to determine whether muscle damage caused from acute resistance exercise with an eccentric overload would influence resting metabolic rate (RMR) up to 72 h postexercise in resistance-trained (RT) and untrained (UT) subjects. Nine RT and 9 UT male subjects (mean +/- SD; age = 20.7 +/- 2.1 yr; body mass = 79.0 +/- 1.4 kg; height = 178.4 +/- 3.1 cm; and body fat = 10.2 +/- 1.6%) were measured for RMR, creatine kinase concentration ([CK]), and rating of perceived muscle soreness (RPMS) on five consecutive mornings. To induce muscle damage, after the measurements on day 2, each subject performed leg presses that emphasized the eccentric movement for 8 sets at his six-repetition maximum (6-RM). Compared with baseline, the RMR (kJ x d(-1) and kJ x kg FFM(-1) x h(-1) was significantly elevated for RT and UT at 24 h and 48 h postexercise. From 24 h to 48 h to 72 h postexercise, RMR significantly decreased within both groups. The UT group had a significantly higher RMR at 24 h (9,705.4 +/- 204.5 kJ x d(-1)) and 48 h postexercise (8,930.9 +/- 104.4 kJ x d(-1)) when compared with the RT group (9,209.3 +/- 535.3 and 8,601.7 + 353.7 kJ x d(-1)). Both [CK] and RPMS showed a similar time course. There was a significantly higher [CK] for the UT group at 24 h postexercise (320.4 +/- 20.1 U x L(-1)) and for both [CK] and RPMS at 48 h (1,140.3 +/- 37.1 U x L(-1) and 4.4 +/- 0.5, respectively) and 72 h postexercise (675.9 +/- 41.7 U x L(-1) and 1.67 +/- 0.5, respectively) when compared with the RT group (24 h, 201.9 +/- 13.4 U x L(-1); 48 h, 845.4 +/- 30.7 U x L(-1) and 3.7 +/- 0.5: and 72 h postexercise, 420.2 +/- 70.2 U x L(-1) and 0.89 +/- 0.3). These data indicate that eccentrically induced muscle damage causes perturbations in RMR up to 48 h postexercise.
Article
Studies have shown metabolism to remain elevated for hours following resistance exercise, but none have gone beyond 16 h, nor have they followed a whole body, high intensity exercise protocol. To examine the duration of excess post-exercise oxygen consumption (EPOC) following a period of heavy resistance exercise, seven healthy men [mean (SD) age 22 (3) years, height 177 (8) cm, mass 83 (10) kg, percentage body fat 10.4 (4.2)%] engaged in a 31 min period of resistance exercise, consisting of four circuits of bench press, power cleans, and squats. Each set was performed using the subject's own predetermined ten-repetition maximum and continued until failure. Oxygen consumption ( ) measurements were obtained at consistent times (34 h pre-, 29 h pre-, 24 h pre-, 10 h pre-, 5 h pre-, immediately post-, 14 h post-, 19 h post-, 24 h post-, 38 h post-, 43 h post-, and 48 h post-exercise). Post-exercise measurements were compared to the baseline measurements made at the same time of day. The was significantly elevated ( P<0.05) above baseline values at immediately post, 14, 19, and 38 h post-exercise. Mean daily values for both post-exercise days were also significantly elevated above the mean value for the baseline day. These results suggest that EPOC duration following resistance exercise extends well beyond the previously reported duration of 16 h. The duration and magnitude of the EPOC observed in this study indicates the importance of future research to examine a possible role for high intensity resistance training in a weight management program for various populations.
Article
The elongation phase of mRNA translation is the stage at which the polypeptide is assembled and requires a substantial amount of metabolic energy. Translation elongation in mammals requires a set of nonribosomal proteins called eukaryotic elongation actors or eEFs. Several of these proteins are subject to phosphorylation in mammalian cells, including the factors eEF1A and eEF1B that are involved in recruitment of amino acyl-tRNAs to the ribosome. eEF2, which mediates ribosomal translocation, is also phosphorylated and this inhibits its activity. The kinase acting on eEF2 is an unusual and specific one, whose activity is dependent on calcium ions and calmodulin. Recent work has shown that the activity of eEF2 kinase is regulated by MAP kinase signalling and by the nutrient-sensitive mTOR signalling pathway, which serve to activate eEF2 in response to mitogenic or hormonal stimuli. Conversely, eEF2 is inactivated by phosphorylation in response to stimuli that increase energy demand or reduce its supply. This likely serves to slow down protein synthesis and thus conserve energy under such circumstances.
Article
A variety of dietary practices designed to enhance acute responses and chronic adaptations to resistance training have been examined with little consensus on the optimal nutritional approach for maximizing muscle and strength gains. From a scientific and practical perspective, the quantity, quality, and timing of nutrient ingestion around a workout are important factors to consider. Manipulation of exercise and nutritional variables can alter events that impact adaptations to training by a variety of mechanisms related to nutrient availability and uptake into tissues, hormonal secretion and interactions with receptors on target tissues, and gene transcription and translation of proteins that eventually impact protein, carbohydrate, and lipid metabolism. If the nutrition-mediated postresistance exercise change in any of these processes is of sufficient magnitude and duration, then over time an effect of muscle size, strength, and body composition is possible. To date, the majority of research has concentrated on providing carbohydrate alone or combined with protein before or after resistance exercise. Carbohydrate and protein intake significantly alters circulating metabolites and the hormonal milieu (i.e., insulin, testosterone, growth hormone, and cortisol), as well as the response of muscle protein and glycogen balance. The pathway of adaptation is proposed as a model to assist in integrating research findings from the current body of literature and future studies examining various diet and resistance exercise configurations.
Article
Although insulin, amino acids and exercise individually activate multiple signal transduction pathways in skeletal muscle, one pathway, the phosphatidylinositol 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) signalling pathway, is a target of all three. Activation of the PI3K-mTOR signal transduction pathway results in both acute (i.e. occurring in minutes to hours) and long-term (i.e. occurring in hours to days) up-regulation of protein synthesis through modulation of multiple steps involved in mediating the initiation of mRNA translation and ribosome biogenesis respectively. In addition, changes in gene expression through altered patterns of mRNA translation promote cell growth, which in turn promotes muscle hypertrophy. The focus of the present discussion is to review current knowledge concerning the mechanism(s) through which insulin, amino acids and resistance exercise act to activate the PI3K-mTOR signal transduction pathway and thereby enhance the rate of protein synthesis in muscle.
Article
Several factors may alter apparent resting metabolic rate (RMR) during measurement with indirect calorimetry. Likewise, numerous indirect calorimetry measurement protocols have been developed over the years, and the methodology employed could influence test results. As part of a larger project to determine the role of indirect calorimetry in clinical practice, a systematic review of the literature was undertaken to determine the ideal subject condition and test methodology for obtaining reliable measurement of RMR with indirect calorimetry. Food, ethanol, caffeine, and nicotine affect RMR for a variable number of hours after consumption; therefore, intake of these items must be controlled before measurement. Activities of daily living increase metabolic rate, but a short rest (< or =20 minutes) before testing is sufficient for the effect to dissipate. Moderate or vigorous physical activity has a longer carryover effect and therefore must be controlled in the hours before a measurement of RMR is attempted. Limited data were found regarding ideal ambient conditions for RMR testing. Measurement duration of 10 minutes with the first 5 minutes deleted and the remaining 5 minutes having a coefficient of variation <10% gave accurate readings of RMR. Individuals preparing for RMR measurement via indirect calorimetry should refrain from eating, consuming ethanol and nicotine, smoking, and engaging in physical activity for varying times before measurement. The test site should be physically comfortable and the individual should have 10 to 20 minutes to rest before measurement commences. A 10-minute test duration with the first 5 minutes discarded and the remaining 5 minutes having a coefficient of variation of <10% will give an accurate measure of RMR.
Article
Muscle plays a central role in whole-body protein metabolism by serving as the principal reservoir for amino acids to maintain protein synthesis in vital tissues and organs in the absence of amino acid absorption from the gut and by providing hepatic gluconeogenic precursors. Furthermore, altered muscle metabolism plays a key role in the genesis, and therefore the prevention, of many common pathologic conditions and chronic diseases. Nonetheless, the maintenance of adequate muscle mass, strength, and metabolic function has rarely, if ever, been targeted as a relevant endpoint of recommendations for dietary intake. It is therefore imperative that factors directly related to muscle mass, strength, and metabolic function be included in future studies designed to demonstrate optimal lifestyle behaviors throughout the life span, including physical activity and diet.
Article
The mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) are important nutrient- and energy-sensing and signalling proteins in skeletal muscle. AMPK activation decreases muscle protein synthesis by inhibiting mTOR signalling to regulatory proteins associated with translation initiation and elongation. On the other hand, essential amino acids (leucine in particular) and insulin stimulate mTOR signalling and protein synthesis. We hypothesized that anabolic nutrients would be sensed by both AMPK and mTOR, resulting in an acute and potent stimulation of human skeletal muscle protein synthesis via enhanced translation initiation and elongation. We measured muscle protein synthesis and mTOR-associated upstream and downstream signalling proteins in young male subjects (n=14) using stable isotopic and immunoblotting techniques. Following a first muscle biopsy, subjects in the 'Nutrition' group ingested a leucine-enriched essential amino acid-carbohydrate mixture (EAC). Subjects in the Control group did not consume nutrients. A second biopsy was obtained 1 h later. Ingestion of EAC significantly increased muscle protein synthesis, modestly reduced AMPK phosphorylation, and increased Akt/PKB (protein kinase B) and mTOR phosphorylation (P<0.05). mTOR signalling to its downstream effectors (S6 kinase 1 (S6K1) and 4E-binding protein 1 (4E-BP1) phosphorylation status) was also increased (P<0.05). In addition, eukaryotic elongation factor 2 (eEF2) phosphorylation was significantly reduced (P<0.05). Protein synthesis and cell signalling (phosphorylation status) was unchanged in the control group (P>0.05). We conclude that anabolic nutrients alter the phosphorylation status of both AMPK- and mTOR-associated signalling proteins in human muscle, in association with an increase in protein synthesis not only via enhanced translation initiation but also through signalling promoting translation elongation.
Article
The purpose of this study was to determine whether resistance exercise performance and postexercise muscle damage were altered when consuming a carbohydrate and protein beverage (CHO-PRO; 6.2% and 1.5% concentrations). Thirty-four male subjects (age: 21.5 +/- 1.7 years; height: 177.3 +/- 1.1 cm; weight: 77.2 +/- 2.2 kg) completed 3 sets of 8 repetitions at their 8 repetition maximum to volitional fatigue. The exercise order consisted of the high pull, leg curl, standing overhead press, leg extension, lat pull-down, leg press, and bench press. In a double-blind, posttest-only control group design, subjects consumed 355 ml of either CHO-PRO or placebo (electrolyte and artificial sweetener beverage) 30 minutes prior to exercise, 177 ml immediately prior to exercise, 177 ml halfway through the exercise bout, and 355 ml immediately following the exercise bout. There were no significant differences between groups relative to exercise performance. Cortisol was significantly elevated in the placebo group compared to the CHO-PRO group at 24 hours postexercise. Insulin was significantly elevated immediately pre-exercise, after the fourth lift, immediately postexercise, 1 hour, and 6 hours postexercise in CHO-PRO compared to the placebo group. Myoglobin levels in the placebo group approached significance halfway through the exercise bout and at 1 hour postexercise (p = 0.06 and 0.07, respectively) and were significantly elevated at 6 hours postexercise compared to the CHO-PRO group. Creatine kinase levels were significantly elevated in the placebo group at 24 hours postexercise compared to the CHO-PRO group. The CHO-PRO supplement did not improve performance during a resistance exercise bout, but appeared to reduce muscle damage, as evidenced by the responses of both myoglobin and creatine kinase. These results suggest the use of a CHO-PRO supplement during resistance training to reduce muscle damage and soreness.
Nutrition: For Health, Fitness, & Sport
  • M H Williams
Williams MH. Nutrition: For Health, Fitness, & Sport. 5th ed. Boston (MA): The McGraw-Hill Companies, Inc; 1999. p. 74-5.
Body Composition from Fluid Spaces and Density. Washington (DC): National Academy of Sciences
  • We Siri
Siri WE. Body Composition from Fluid Spaces and Density. Washington (DC): National Academy of Sciences; 1961. p. 223–4.