Consumption of fat-free fluid milk after resistance exercise promotes greater lean mass accretion than does consumption of soy or carbohydrate in young, novice, male weightlifters

BACKGROUND: Acute consumption of fat-free fluid milk after resistance exercise promotes a greater positive protein balance than does soy protein. OBJECTIVE: We aimed to determine the long-term consequences of milk or soy protein or equivalent energy consumption on training-induced lean mass accretion. DESIGN: We recruited 56 healthy young men who trained 5 d/wk for 12 wk on a rotating split-body resistance exercise program in a parallel 3-group longitudinal design. Subjects were randomly assigned to consume drinks immediately and again 1 h after exercise: fat-free milk (Milk; n = 18); fat-free soy protein (Soy; n = 19) that was isoenergetic, isonitrogenous, and macronutrient ratio matched to Milk; or maltodextrin that was isoenergetic with Milk and Soy (control group; n = 19). RESULTS: Muscle fiber size, maximal strength, and body composition by dual-energy X-ray absorptiometry (DXA) were measured before and after training. No between-group differences were seen in strength. Type II muscle fiber area increased in all groups with training, but with greater increases in the Milk group than in both the Soy and control groups (P < 0.05). Type I muscle fiber area increased after training only in the Milk and Soy groups, with the increase in the Milk group being greater than that in the control group (P < 0.05). DXA-measured fat- and bone-free mass increased in all groups, with a greater increase in the Milk group than in both the Soy and control groups (P < 0.05). CONCLUSION: We conclude that chronic postexercise consumption of milk promotes greater hypertrophy during the early stages of resistance training in novice weightlifters when compared with isoenergetic soy or carbohydrate consumption.     

Glomerular filtration rate after a 12-wk resistance exercise program with post-exercise protein ingestion in community dwelling elderly

ObjectiveIncreased protein intake and resistance exercise can be beneficial for maintenance of lean body mass (LBM) in older adults. However, these factors could also negatively affect renal function. We investigated changes in renal function after a 12-wk resistance exercise program combined with protein supplementation in community dwelling older adults.MethodsPatients (N = 237, 73.7 ± 5.7 y, 58.2% female) participated in a 12-wk resistance exercise program (3 times/wk) designed to increase strength and muscle mass of major muscle groups. Participants were randomly assigned to one of three dietary supplements consumed directly after training: whey protein drink (20 g whey protein, 20 g carbohydrates), milk protein drink (20 g milk protein, 20 g carbohydrates), or carbohydrate drink (40 g carbohydrates). Renal function was estimated as glomerular filtration rate (GFR, Cockcroft-Gault formula), and dietary intake was measured as 3-d-weighed food record at baseline and endpoint.ResultsDuring the intervention, energy intake did not increase. Carbohydrate intake increased in the carbohydrate group and protein intake increased in the milk group, both approximately in accordance with the supplementation. In the whey group, protein intake did not increase, but carbohydrate intake did. GFR increased after the intervention (+4.4 mL/min/1.73 m²; P < 0.001), and the changes were similar in men and women or in the age quartiles. Changes in GFR at endpoint were not associated with LBM, dietary supplements, or total protein intake.ConclusionsA 12-wk resistance exercise program combined with protein supplementation in community dwelling older adults does not negatively affect GFR. The supplementation had only minor effects on total dietary intake.     

Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage

BACKGROUND: Resistance exercise leads to net muscle protein accretion through a synergistic interaction of exercise and feeding. Proteins from different sources may differ in their ability to support muscle protein accretion because of different patterns of postprandial hyperaminoacidemia. OBJECTIVE: We examined the effect of consuming isonitrogenous, isoenergetic, and macronutrient-matched soy or milk beverages (18 g protein, 750 kJ) on protein kinetics and net muscle protein balance after resistance exercise in healthy young men. Our hypothesis was that soy ingestion would result in larger but transient hyperaminoacidemia compared with milk and that milk would promote a greater net balance because of lower but prolonged hyperaminoacidemia. DESIGN: Arterial-venous amino acid balance and muscle fractional synthesis rates were measured in young men who consumed fluid milk or a soy-protein beverage in a crossover design after a bout of resistance exercise. RESULTS: Ingestion of both soy and milk resulted in a positive net protein balance. Analysis of area under the net balance curves indicated an overall greater net balance after milk ingestion (P < 0.05). The fractional synthesis rate in muscle was also greater after milk consumption (0.10 +/- 0.01%/h) than after soy consumption (0.07 +/- 0.01%/h; P = 0.05). CONCLUSIONS: Milk-based proteins promote muscle protein accretion to a greater extent than do soy-based proteins when consumed after resistance exercise. The consumption of either milk or soy protein with resistance training promotes muscle mass maintenance and gains, but chronic consumption of milk proteins after resistance exercise likely supports a more rapid lean mass accrual.     

Potential role for protein in assisting post‐exercise rehydration

The latest International Olympic Committee Consensus Statement on Sports Nutrition 2010 concluded that when athletes must compete in several events in a short time‐period, strategies to enhance recovery of fluid and fuel are important. In fact, all athletes and recreational exercisers might benefit from effective rehydration strategies, as rapid rehydration is not limited only to optimal subsequent performance. Rehydration also regulates cell function in favour of the adaptive processes and improvements in body composition, which take place during recovery. The composition of a fluid consumed soon after exercise has an important impact on body water restoration and should be considered if rapid rehydration is a goal. Typically, guidelines recommend using sports drinks or foods and fluids that contain carbohydrate for replacement of glycogen stores and electrolyte sodium, which promotes greater fluid absorption and retention. However, more effective restoration of body water and plasma volume have been observed in some studies when more nutrients and food compounds are consumed. It suggests a role for other nutrients, such as protein, in the strategy to enhance rehydration. Emerging research looking into milk proteins, whey and casein, points to a role for protein in assisting post‐exercise fluid retention. The most obvious mechanisms are enhanced sodium and water absorption from the gut, and increased plasma protein synthesis resulting in higher osmotic pressure exerted by plasma proteins. This article reviews current strategies to enhance post‐exercise recovery of fluid balance, with a focus on protein.     

The effects of nutritional supplementation throughout an endurance run on leucine kinetics during recovery

This study determined the effect of nutritional supplementation throughout endurance exercise on whole-body leucine kinetics (leucine rate of appearance [Ra], oxidation [Ox], and nonoxidative leucine disposal [NOLD]) during recovery. Five trained men underwent a 2-h run at 65% VO(2max), during which a carbohydrate (CHO), mixed protein-carbohydrate (milk), or placebo (PLA) drink was consumed. Leucine kinetics were assessed during recovery using a primed, continuous infusion of 1-13C leucine. Leucine Ra and NOLD were lower for milk than for PLA. Ox was higher after milk-supplemented exercise than after CHO or PLA. Although consuming milk during the run affected whole-body leucine kinetics, the benefits of such a practice for athletes remain unclear. Additional studies are needed to determine whether protein supplementation during exercise can optimize protein utilization during recovery.     

Fluids and hydration in prolonged endurance performance

Numerous studies have confirmed that performance can be impaired when athletes are dehydrated. Endurance athletes should drink beverages containing carbohydrate and electrolyte during and after training or competition. Carbohydrates (sugars) favor consumption and Na(+) favors retention of water. Drinking during competition is desirable compared with fluid ingestion after or before training or competition only. Athletes seldom replace fluids fully due to sweat loss. Proper hydration during training or competition will enhance performance, avoid ensuing thermal stress, maintain plasma volume, delay fatigue, and prevent injuries associated with dehydration and sweat loss. In contrast, hyperhydration or overdrinking before, during, and after endurance events may cause Na(+) depletion and may lead to hyponatremia. It is imperative that endurance athletes replace sweat loss via fluid intake containing about 4% to 8% of carbohydrate solution and electrolytes during training or competition. It is recommended that athletes drink about 500 mL of fluid solution 1 to 2 h before an event and continue to consume cool or cold drinks in regular intervals to replace fluid loss due to sweat. For intense prolonged exercise lasting longer than 1 h, athletes should consume between 30 and 60 g/h and drink between 600 and 1200 mL/h of a solution containing carbohydrate and Na(+) (0.5 to 0.7 g/L of fluid). Maintaining proper hydration before, during, and after training and competition will help reduce fluid loss, maintain performance, lower submaximal exercise heart rate, maintain plasma volume, and reduce heat stress, heat exhaustion, and possibly heat stroke.     

Coingestion of carbohydrate and protein hydrolysate stimulates muscle protein synthesis during exercise in young men, with no further increase during subsequent overnight recovery

We investigated the effect of carbohydrate and protein hydrolysate ingestion on whole-body and muscle protein synthesis during a combined endurance and resistance exercise session and subsequent overnight recovery. Twenty healthy men were studied in the evening after consuming a standardized diet throughout the day. Subjects participated in a 2-h exercise session during which beverages containing both carbohydrate (0.15 g x kg(-1) x h(-1)) and a protein hydrolysate (0.15 g x kg(-1) x h(-1)) (C+P, n = 10) or water only (W, n = 10) were ingested. Participants consumed 2 additional beverages during early recovery and remained overnight at the hospital. Continuous i.v. infusions with L-[ring-(13)C(6)]-phenylalanine and L-[ring-(2)H(2)]-tyrosine were applied and blood and muscle samples were collected to assess whole-body and muscle protein synthesis rates. During exercise, whole-body and muscle protein synthesis rates increased by 29 and 48% with protein and carbohydrate coingestion (P < 0.05). Fractional synthetic rates during exercise were 0.083 +/- 0.011%/h in the C+P group and 0.056 +/- 0.003%/h in the W group, (P < 0.05). During subsequent overnight recovery, whole-body protein synthesis was 19% greater in the C+P group than in the W group (P < 0.05). However, mean muscle protein synthesis rates during 9 h of overnight recovery did not differ between groups and were 0.056 +/- 0.004%/h in the C+P group and 0.057 +/- 0.004%/h in the W group (P = 0.89). We conclude that, even in a fed state, protein and carbohydrate supplementation stimulates muscle protein synthesis during exercise. Ingestion of protein with carbohydrate during and immediately after exercise improves whole-body protein synthesis but does not further augment muscle protein synthesis rates during 9 h of subsequent overnight recovery.     

Chocolate milk as a post-exercise recovery aid

Nine male, endurance-trained cyclists performed an interval workout followed by 4 h of recovery, and a subsequent endurance trial to exhaustion at 70% VO2max, on three separate days. Immediately following the first exercise bout and 2 h of recovery, subjects drank isovolumic amounts of chocolate milk, fluid replacement drink (FR), or carbohydrate replacement drink (CR), in a single-blind, randomized design. Carbohydrate content was equivalent for chocolate milk and CR. Time to exhaustion (TTE), average heart rate (HR), rating of perceived exertion (RPE), and total work (WT) for the endurance exercise were compared between trials. TTE and WT were significantly greater for chocolate milk and FR trials compared to CR trial. The results of this study suggest that chocolate milk is an effective recovery aid between two exhausting exercise bouts.     

Dietary effects on liver and muscle glycogen repletion in exhaustively exercised rats: energy composition and type of complex carbohydrates

Previous reports have indicated that administration of a glucose-citrate (G-C) drink after a bout of exhaustive exercise results in more effective glycogen repletion in liver and skeletal muscle in rats as compared with administration of glucose alone. The present studies report the effects of the energy pattern and the type of carbohydrates, dextrin or starch from rice, in diet given following the G-C drink after exercise, on further glycogen repletion in the tissues of rats. Rats were adapted to meal-feeding 3 times a day and trained with light swimming for 7 to 10 days. On the final day of experiments, rats received the G-C drink after 2 h of exhaustive swimming and were then fed on diets with different energy patterns or carbohydrate types. Results showed that a high-carbohydrate diet is more effective than a high-fat diet for further glycogen repletion in liver and skeletal muscle. In addition, dextrin was revealed to be superior to starch as a carbohydrate source in tissue glycogen repletion. As compared with the high-fat diet, the high-carbohydrate diet, however, resulted in a lower serum free fatty acid concentration 4 h after ingestion of food possibly by decreasing adipose tissue lipolysis.     

Glycemic Carbohydrates Consumed with Amino Acids or Protein Right after Exercise Enhance Muscle Formation

This review shows the importance of high– glycemic carbohydrates consumed together with protein in enhancing the exercise-induced muscle formation relative to timing of intake. Insulin, which increases in blood after glycemic carbohydrate ingestion, seems to effectively stimulate protein synthesis and inhibit protein degradation right after exercise rather than later. This presents a new aspect in nutrition: the importance of intake timing in addition to the composition and amount of nutrients.     

What Should I Eat before Exercise? Pre-Exercise Nutrition and the Response to Endurance Exercise: Current Prospective and Future Directions

The primary variables influencing the adaptive response to a bout of endurance training are exercise duration and exercise intensity. However, altering the availability of nutrients before and during exercise can also impact the training response by modulating the exercise stimulus and/or the physiological and molecular responses to the exercise-induced perturbations. The purpose of this review is to highlight the current knowledge of the influence of pre-exercise nutrition ingestion on the metabolic, physiological, and performance responses to endurance training and suggest directions for future research. Acutely, carbohydrate ingestion reduces fat oxidation, but there is little evidence showing enhanced fat burning capacity following long-term fasted-state training. Performance is improved following pre-exercise carbohydrate ingestion for longer but not shorter duration exercise, while training-induced performance improvements following nutrition strategies that modulate carbohydrate availability vary based on the type of nutrition protocol used. Contrasting findings related to the influence of acute carbohydrate ingestion on mitochondrial signaling may be related to the amount of carbohydrate consumed and the intensity of exercise. This review can help to guide athletes, coaches, and nutritionists in personalizing pre-exercise nutrition strategies, and for designing research studies to further elucidate the role of nutrition in endurance training adaptations.     

The science of muscle hypertrophy: making dietary protein count

Growing evidence supports the conclusion that consumption of protein in close temporal proximity to the performance of resistance exercise promotes greater muscular hypertrophy. We can also state with good certainty that merely consuming energy, as carbohydrate for example, is also not sufficient to maximise muscle protein synthesis leading to anabolism and net new muscle protein accretion. Recent work also indicates that certain types of proteins, particular those that are rapidly digested and high in leucine content (i.e. whey protein), appear to be more efficient at stimulating muscle protein synthesis. Continued practice of consumption of these types or proteins after exercise should lead to greater hypertrophy. Reviews of numerous training studies indicate that studies in which milk proteins and principally whey protein show an advantage of these proteins over and above isoenergetic carbohydrate and soya protein in promoting hypertrophy. Thus, the combined evidence suggests a strategic advantage of practising early post-exercise consumption of whey protein or dairy-based protein to promote muscle protein synthesis, net muscle protein accretion and ultimately hypertrophy.     

Nutritional regulation of muscle protein synthesis with resistance exercise: strategies to enhance anabolism

ABSTRACT: Provision of dietary amino acids increases skeletal muscle protein synthesis (MPS), an effect that is enhanced by prior resistance exercise. As a fundamentally necessary process in the enhancement of muscle mass, strategies to enhance rates of MPS would be beneficial in the development of interventions aimed at increasing skeletal muscle mass particularly when combined with chronic resistance exercise. The purpose of this review article is to provide an update on current findings regarding the nutritional regulation of MPS and highlight nutrition based strategies that may serve to maximize skeletal muscle protein anabolism with resistance exercise. Such factors include timing of protein intake, dietary protein type, the role of leucine as a key anabolic amino acid, and the impact of other macronutrients (i.e. carbohydrate) on the regulation of MPS after resistance exercise. We contend that nutritional strategies that serve to maximally stimulate MPS may be useful in the development of nutrition and exercise based interventions aimed at enhancing skeletal muscle mass which may be of interest to elderly populations and to athletes.     

Endothelial function after high-sugar-food ingestion improves with endurance exercise performed on the previous day

BACKGROUND: Endothelial function deteriorates after glucose ingestion. This may be attributed to hyperglycemia-induced oxidative stress. Acute endurance exercise might improve postprandial endothelial function by enhancing glucoregulation and reducing postprandial hyperglycemia. OBJECTIVE: The objective was to determine whether endurance exercise performed 17 h before high-sugar-food ingestion attenuates postprandial impairment in endothelial function. DESIGN: Healthy men and women (n = 13; age: 48 +/- 17 y) were studied on 2 occasions: after > or = 48 h with no exercise and 17 h after a 60-min bout of endurance exercise. During each trial, brachial artery flow mediated dilation (FMD) was used to assess endothelial function before and after the ingestion of a candy bar and soft drink. Glucose, insulin, and thiobarbituric acid-reactive substances (TBARS), a marker of oxidative stress, were measured in blood obtained during each FMD measurement. The insulin sensitivity index was calculated from the glucose and insulin data. RESULTS: FMD decreased significantly after food ingestion in both trials. However, prior exercise shifted the entire FMD curve upward (main treatment effect: P = 0.0002), which resulted in a greater area under the curve for FMD (774 +/- 122%.min) than did no exercise (607 +/- 122%.min) (P = 0.01). Prior exercise shifted the glucose and insulin curves downward (main treatment effects: P = 0.05 and P = 0.0007, respectively) and resulted in a significantly greater insulin sensitivity index (10.8 +/- 0.7) than did no exercise (9.2 +/- 0.7) (P = 0.01). TBARS did not differ significantly between trials. CONCLUSION: Postprandial endothelial function was improved by endurance exercise performed approximately 17 h earlier. This effect was accompanied by exercise-induced improvements in insulin action and reductions in glycemia, but did not correspond with reductions in oxidative stress, as assessed by TBARS.     

Carbohydrate and exercise

Total body carbohydrate stores are limited, and are often less than the carbohydrate requirements of athletic training and competition. However, the availability of carbohydrate as a substrate for muscle metabolism is a critical factor in the performance of both high-intensity intermittent work and prolonged aerobic exercise. The rate of carbohydrate oxidation during exercise is tightly regulated, with glucose availability closely matching the needs of the working muscles. Both the absolute and relative work rate play important roles in the regulation of substrate metabolism: carbohydrate-based fuels predominate at moderate to high power outputs, with muscle glycogen and glucose utilization scaling exponentially to the relative work rate. As such, strategies to maintain or enhance carbohydrate availability, such as the ingestion of carbohydrate before, during and after exercise, are critical to the performance of a variety of sports events, and are a key recommendation in current sports nutrition guidelines.     

Effects of a herbal ergogenic drink on cycling performance in young cyclists

It is essential to replace fluids lost so as to remain well hydrated during exercise. The intake of fluids is considered a physiological ergogenic aid to enhance exercise performance. There are currently several products in the market that are believed to have ergogenic properties which act as fluid replacement drinks during exercise. One such drink available in the Malaysian market is 'AgroMas?' herbal drink whose efficacy is yet to be proven. The purpose of this study was, therefore, to evaluate the effects of acute ingestion of this herbal drink (H) or a coloured water placebo (P) on cycling performance. Nine healthy and trained young male cyclists (age: 16.2 ± 0.5 years) exercised on a cycle ergometer at 71.9 ± 0.7% of maximal oxygen consumption (VO2max) until exhaustion on two occasions at 1-week intervals. During each exercise bout, subjects received 3ml kg-1 body weight of H or P every 20 min in a double-blind randomised study design. There was no significant difference between H and P trials in the total work time to exhaustion (83.7 ± 4.6 and 81.5 ± 5.0 min respectively). Changes in oxygen consumption, heart rate and perceived rate of exertion were similar for both types of drinks. These results demonstrate that the herbal drink and the placebo elicited similar physiological responses and exercise performance during endurance cycling. It is therefore concluded that AgroMas? herbal drink and water ingestion resulted in a similar ergogenic response on cycling performance in young cyclists.     

Feeding meals containing soy or whey protein after exercise stimulates protein synthesis and translation initiation in the skeletal muscle of male rats

The purpose of this investigation was to compare the early response of skeletal muscle protein synthesis and translation initiation following the ingestion of different protein sources after endurance exercise. Treadmill-acclimated rats were designated as either nonexercised controls (NEX) or treadmill exercised for 2 h at 26 m/min (approximately 75% VO2max) and then fed either carbohydrate only (EC), carbohydrate plus soy protein (ES), or carbohydrate plus whey protein (EW). One hour after exercise, serum insulin concentrations in EC, ES, and EW were greater than in NEX (P<0.05); the concentration in EW was greater than in EC, with that in ES intermediate. Serum concentrations of branched-chain amino acids in ES and EW were higher than in EC, but serum leucine and isoleucine in EW were higher than in ES (P<0.05). Nevertheless, both ES and EW promoted the fractional rate of skeletal muscle protein synthesis significantly more than EC. Likewise, compared with EC, both ES and EW increased formation of the mRNA cap binding complex eIF4F and stimulated phosphorylation of the translational repressor, 4E-BP1, the 70kD ribosomal protein S6 kinase (S6K1), and the mammalian target of rapamycin (mTOR) kinase at serine 2448. On the other hand, phosphorylation of S6K1 and mTOR was greater in EW than in ES (P<0.05). In conclusion, general protein synthesis and the mRNA cap binding step are promoted comparably by soy protein and whey protein in the skeletal muscle of exercised rats. Furthermore, the data suggest that mTOR signaling in skeletal muscle is acutely responsive to physiological variations in dietary amino acids.     

Strategic Ingestion of High-Protein Dairy Milk during a Resistance Training Program Increases Lean Mass,Strength, and Power in Trained Young Males

Background: We evaluated the effects of high-protein dairy milk ingestion on changes in body composition, strength, power, and skeletal muscle regulatory markers following 6 weeks of resistance training in trained young males. Methods: Thirty resistance-trained young males (age: 27 ± 3 years; training experience: 15 ± 2 months) were randomly assigned to one of two groups: high-protein dairy milk (both whey and casein) + resistance training (MR; n = 15) or isoenergetic carbohydrate (maltodextrin 9%) + resistance training (PR; n = 15). Milk and placebo were ingested immediately post-exercise (250 mL; 30 g protein) and 30 min before sleep (250 mL; 30 g protein). Before and after 6 weeks of linear periodized resistance training (4 times/week), body composition (bioelectrical impedance), strength, power, and serum levels of skeletal muscle regulatory markers (insulin-like growth factor 1 (IGF-1), growth hormone, testosterone, cortisol, follistatin, myostatin, and follistatin–myostatin ratio) were assessed. Results: The MR group experienced a significantly higher (p < 0.05) increase in lean mass, strength, and power (upper- and lower-body) than the PR group. Further, IGF-1, growth hormone, testosterone, follistatin, and follistatin–myostatin ratio were significantly increased, while cortisol and myostatin significantly decreased in the MR group than the PR group (p < 0.05). Conclusions: The strategic ingestion of high-protein dairy milk (post-exercise and pre-sleep) during 6 weeks of resistance training augmented lean mass, strength, power, and altered serum concentrations of skeletal muscle regulatory markers in trained young males compared to placebo.     

Effect of a carbohydrate-protein supplement on endurance performance during exercise of varying intensity

Increasing the plasma glucose and insulin concentrations during prolonged variable intensity exercise by supplementing with carbohydrate has been found to spare muscle glycogen and increase aerobic endurance. Furthermore, the addition of protein to a carbohydrate supplement will enhance the insulin response of a carbohydrate supplement. The purpose of the present study was to compare the effects of a carbohydrate and a carbohydrate-protein supplement on aerobic endurance performance. Nine trained cyclists exercised on 3 separate occasions at intensities that varied between 45% and 75% VO2max for 3 h and then at 85% VO2max until fatigued. Supplements (200 ml) were provided every 20 min and consisted of placebo, a 7.75% carbohydrate solution, and a 7.75% carbohydrate/1.94% protein solution. Treatments were administered using a double-blind randomized design. Carbohydrate supplementation significantly increased time to exhaustion (carbohydrate 19.7 +/- 4.6 min vs. placebo 12.7 +/- 3.1 min), while the addition of protein enhanced the effect of the carbohydrate supplement (carbohydrate-protein 26.9 +/- 4.5 min, p < .05). Blood glucose and plasma insulin levels were elevated above placebo during carbohydrate and carbohydrate-protein supplementation, but no differences were found between the carbohydrate and carbohydrate-protein treatments. In summary, we found that the addition of protein to a carbohydrate supplement enhanced aerobic endurance performance above that which occurred with carbohydrate alone, but the reason for this improvement in performance was not evident.