Postexercise muscle glycogen recovery enhanced with a carbohydrate-protein supplement

The Effect of Alginate Encapsulated Plant-Based Carbohydrate and Protein Supplementation on Recovery and Subsequent Performance in Athletes

The main purpose of this study was to investigate the effect of a novel alginate-encapsulated carbohydrate-protein (CHO-PRO ratio 2:1) supplement (ALG) on cycling performance. The ALG, designed to control the release of nutrients, was compared to an isocaloric carbohydrate-only control (CON). Alginate encapsulation of CHOs has the potential to reduce the risk of carious lesions.

METHODS

In a randomised cross-over clinical trial, 14 men completed a preliminary test over 2 experimental days separated by ~6 days. An experimental day consisted of an exercise bout (EX1) of cycling until exhaustion at W~73%, followed by 5 h of recovery and a subsequent time-to-exhaustion (TTE) performance test at W~65%. Subjects ingested either ALG (0.8 g CHO/kg/hr + 0.4 g PRO/kg/hr) or CON (1.2 g CHO/kg/hr) during the first 2 h of recovery.

RESULTS

Participants cycled on average 75.2 ± 5.9 min during EX1. Levels of plasma branched-chain amino acids decreased significantly after EX1, and increased significantly with the intake of ALG during the recovery period. During recovery, a significantly higher plasma insulin and glucose response was observed after intake of CON compared to ALG. Intake of ALG increased plasma glucagon, free fatty acids, and glycerol significantly. No differences were found in the TTE between the supplements (p = 0.13) nor in the pH of the subjects' saliva.

CONCLUSIONS

During the ALG supplement, plasma amino acids remained elevated during the recovery. Despite the 1/3 less CHO intake with ALG compared to CON, the TTE performance was similar after intake of either supplement.

Carbohydrate-Protein drink is effective for restoring endurance capacity in masters class athletes after a two-Hour recovery

BACKGROUND

Carbohydrate (CHO) and carbohydrate-protein co-ingestion (CHO-P) have been shown to be equally effective for enhancing glycogen resynthesis and subsequent same-day performance when CHO intake is suboptimal (≤0.8 g/kg). Few studies have specifically examined the effect of isocaloric CHO vs CHO-P consumption on subsequent high-intensity aerobic performance with limited time to recover (≤2 hours) in masters class endurance athletes.

METHODS

This was a randomized, double-blind between-subject design. Twenty-two male masters class endurance athletes (age 49.1 ± 6.9 years; height 175.8 ± 4.8 cm; body mass 80.7 ± 8.6 kg; body fat (%) 19.1 ± 5.8; VO_2peak 48.6 ± 6.7 ml·kg·min^-1) were assigned to consume one of three beverages during a 2-hour recovery period: Placebo (PLA; electrolytes and water), CHO (1.2 g/kg bm), or CHO-P (0.8 g/kg bm CHO + 0.4 g/kg bm PRO). All beverages were standardized to one liter (~32 oz.) of total fluid volume regardless of the treatment group. During Visit #1, participants completed graded exercise testing on a cycle ergometer to determine VO₂peak and peak power output (PPO, watts). Visit #2 consisted of familiarization with the high-intensity protocol including 5 × 4 min intervals at 70-80% of PPO with 2 min of active recovery at 50 W, followed by a time to exhaustion (TTE) test at 90% PPO. During Visit#3, the same high-intensity interval protocol with TTE was conducted pre-and post-beverage consumption.

RESULTS

A one-way ANCOVA indicated a significant difference among the group means for the posttest TTE (F_2,18 = 6.702, p = .007, ƞ² = .427) values after adjusting for the pretest differences. TTE performance in the second exercise bout improved for the CHO (295.48 ± 24.90) and CHO-P (255.08 ± 25.07 sec) groups. The water and electrolyte solution was not effective in restoring TTE performance in the PLA group (171.13 ± 23.71 sec).

CONCLUSIONS

Both CHO and CHO-P effectively promoted an increase in TTE performance with limited time to recover in this sample of masters class endurance athletes. Water and electrolytes alone were not effective for restoring endurance capacity during the second bout of exhaustive exercise.

The Effects of Sports Drinks During High-Intensity Exercise on the Carbohydrate Oxidation Rate Among Athletes: A Systematic Review and Meta-Analysis

Background: This study examines the effects of sports drinks ingestion during high-intensity exercise for carbohydrate oxidation rate (CHO-O) among athletes.

Methods: PubMed, Embase, and the Cochrane library were searched for available papers published up to November 2019. The primary outcome is the carbohydrate oxidation rate (CHO-O), and the secondary outcome is the fat oxidation rate (Fat-O). Statistical heterogeneity among the included studies was evaluated using Cochran's Q test and the I² index. The random-effects model was used for all analyses, regardless of the I² index.

Results: Five studies are included, with a total of 58 participants (range, 8–14/study). All five studies are randomized crossover trials. Compared to the control beverages, sports drinks have no impact on the CHO-O of athletes [weighted mean difference (WMD) = 0.29; 95% CI, −0.06 to 0.65, P = 0.106; I² = 97.4%, P < 0.001] and on the Fat-O of athletes (WMD = −0.074; 95% CI, −0.19 to 0.06, P = 0.297; I² = 97.5%, P < 0.001). Carbohydrate–electrolyte solutions increase CHO-O (WMD = 0.47; 95% CI, 0.08–0.87, P = 0.020; I² = 97.8%, P < 0.001) but not Fat-O (WMD = −0.14; 95% CI, −0.31 to 0.03, P = 0.103; I² = 98.2%, P < 0.001). Caffeine has a borderline effect on Fat-O (WMD = 0.05; 95% CI, 0.00–0.10, P = 0.050).

Conclusions: Compared with the control beverages, sports drinks show no significant improvement in CHO-O and Fat-O in athletes. Carbohydrate–electrolyte solutions increase CHO-O in athletes but not Fat-O.

Carbohydrate supplementation: a critical review of recent innovations

PURPOSE

To critically examine the research on novel supplements and strategies designed to enhance carbohydrate delivery and/or availability.

METHODS

Narrative review.

RESULTS

Available data would suggest that there are varying levels of effectiveness based on the supplement/supplementation strategy in question and mechanism of action. Novel carbohydrate supplements including multiple transportable carbohydrate (MTC), modified carbohydrate (MC), and hydrogels (HGEL) have been generally effective at modifying gastric emptying and/or intestinal absorption. Moreover, these effects often correlate with altered fuel utilization patterns and/or glycogen storage. Nevertheless, performance effects differ widely based on supplement and study design. MTC consistently enhances performance, but the magnitude of the effect is yet to be fully elucidated. MC and HGEL seem unlikely to be beneficial when compared to supplementation strategies that align with current sport nutrition recommendations. Combining carbohydrate with other ergogenic substances may, in some cases, result in additive or synergistic effects on metabolism and/or performance; however, data are often lacking and results vary based on the quantity, timing, and inter-individual responses to different treatments. Altering dietary carbohydrate intake likely influences absorption, oxidation, and and/or storage of acutely ingested carbohydrate, but how this affects the ergogenicity of carbohydrate is still mostly unknown.

CONCLUSIONS

In conclusion, novel carbohydrate supplements and strategies alter carbohydrate delivery through various mechanisms. However, more research is needed to determine if/when interventions are ergogenic based on different contexts, populations, and applications.

Coingestion of protein and carbohydrate in the early recovery phase, compared with carbohydrate only, improves endurance performance despite similar glycogen degradation and AMPK phosphorylation

Endurance athletes competing consecutive days need optimal dietary intake during the recovery period. We report that coingestion of protein and carbohydrate soon after exhaustive exercise, compared with carbohydrate only, resulted in better performance the following day. The better performance after coingestion of protein and carbohydrate was not associated with a higher rate of glycogen synthesis or activation of anabolic signaling compared with carbohydrate only. Importantly, nitrogen balance was positive after coingestion of protein and carbohydrate, which was not the case after intake of carbohydrate only, suggesting that protein synthesis contributes to the better performance the following day.

Twice-a-day training improves mitochondrial efficiency, but not mitochondrial biogenesis, compared with once-daily training

Exercise training performed with lowered muscle glycogen stores can amplify adaptations related to oxidative metabolism, but it is not known if this is affected by the "train-low" strategy used (i.e., once-daily versus twice-a-day training). Fifteen healthy men performed 3 wk of an endurance exercise (100-min) followed by a high-intensity interval exercise 2 (twice-a-day group, n = 8) or 14 h (once-daily group, n = 7) later; therefore, the second training session always started with low muscle glycogen in both groups. Mitochondrial efficiency (state 4 respiration) was improved only for the twice-a-day group (group × training interaction, P < 0.05). However, muscle citrate synthase activity, mitochondria, and lipid area in intermyofibrillar and subsarcolemmal regions, and PGC1α, PPARα, and electron transport chain relative protein abundance were not altered with training in either group (P > 0.05). Markers of aerobic fitness (e.g., peak oxygen uptake) were increased, and plasma lactate, O₂ cost, and rating of perceived exertion during a 100-min exercise task were reduced in both groups, although the reduction in rating of perceived exertion was larger in the twice-a-day group (group × time × training interaction, P < 0.05). These findings suggest similar training adaptations with both training low approaches; however, improvements in mitochondrial efficiency and perceived effort seem to be more pronounced with twice-a-day training.NEW & NOTEWORTHY We assessed, for the first time, the differences between two "train-low" strategies (once-daily and twice-a-day) in terms of training-induced molecular, functional, and morphological adaptations. We found that both strategies had similar molecular and morphological adaptations; however, only the twice-a-day strategy increased mitochondrial efficiency and had a superior reduction in the rating of perceived exertion during a constant-load exercise compared with once-daily training. Our findings provide novel insights into skeletal muscle adaptations using the "train-low" strategy.

Protein intake in the early recovery period after exhaustive exercise improves performance the following day

The aim of the present study was to investigate the effect of protein and carbohydrate ingestion during early recovery from exhaustive exercise on performance after 18-h recovery. Eight elite cyclists (V̇o2max: 74.0 ± 1.6 ml·kg−1·min−1) completed two exercise and diet interventions in a double-blinded, randomized, crossover design. Participants cycled first at 73% of V̇o2max (W73%) followed by 1-min intervals at 90% of V̇o2max until exhaustion. During the first 2 h of recovery, participants ingested either 1.2 g carbohydrate·kg−1·h−1 (CHO) or 0.8 g carbohydrate + 0.4 g protein·kg−1·h−1 (CHO + PROT). The diet during the remaining recovery period was similar for both interventions and adjusted to body weight. After an 18-h recovery, cycling performance was assessed with a 10-s sprint test, 30 min of cycling at W73%, and a cycling time trial (TT). The TT was 8.5% faster (41:53 ± 1:51 vs. 45:26 ± 1:32 min; P < 0.03) after CHO + PROT compared with CHO. Mean power output during the sprints was 3.7% higher in CHO + PROT compared with CHO (1,063 ± 54 vs. 1,026 ± 53 W; P = 0.01). Nitrogen balance in the recovery period was negative in CHO and neutral in CHO + PROT (−82.4 ± 11.5 vs. 7.0 ± 15.4 mg/kg; P < 0.01). In conclusion, TT and sprint performances were improved 18 h after exhaustive cycling by CHO + PROT supplementation during the first 2 h of recovery compared with isoenergetic CHO supplementation. Our results indicate that intake of carbohydrate plus protein after exhaustive endurance exercise more rapidly converts the body from a catabolic to an anabolic state than carbohydrate alone, thus speeding recovery and improving subsequent cycling performance.

NEW & NOTEWORTHY Prolonged high intensity endurance exercise depends on glycogen utilization and high oxidative capacity. Still, exhaustion develops and effective recovery strategies are required to compete in multiday stage races. We show that coingestion of protein and carbohydrate during the first 2 h of recovery is superior to isoenergetic intake of carbohydrate to stimulate recovery, and improves both endurance time-trial and 10-s sprint performance the following day in elite cyclists.

Role of Functional Beverages on Sport Performance and Recovery

Functional beverages represent a palatable and efficient way to hydrate and reintegrate electrolytes, carbohydrates, and other nutrients employed and/or lost during physical training and/or competitions. Bodily hydration during sporting activity is one of the best indicators of health in athletes and can be a limiting factor for sport performance. Indeed, dehydration strongly decreases athletic performance until it is a risk to health. As for other nutrients, each of them is reported to support athletes' needs both during the physical activity and/or in the post-workout. In this study, we review the current knowledge of macronutrient-enriched functional beverages in sport taking into account the athletes' health, sports performance, and recovery.

Macronutrient Intakes of Male Rugby Union Players: A Review

Rugby is a worldwide intermittent team sport. Players tend to be heavier than the majority of similar team sport athletes on whom the dietary guidelines have been developed. Therefore, the aim of the current review was to describe the intakes of rugby union players. Article databases were searched up to February 2017 and were included if they were published in English and reported dietary intakes of male rugby union players. Of the research articles identified, energy intakes were lower than two of three studies that reported intakes and expenditure, which would suggest the players were losing weight that is somewhat supported by the decreases in skinfolds seen during preseason. However, it should also be noted that there are errors in both the measurement of energy intakes and expenditure. Carbohydrate intakes ranged from 2.6 to 6.5 g·kg^-1·day^-1, which is lower than the current relative to body mass recommendations; however, this would not be classed as a low-carbohydrate diet. The consistently low intakes of carbohydrate suggest that these intake levels maybe sufficient for performance, given the players greater body mass or there are errors in the measurements. However, there is currently no evidence for the carbohydrate needs of rugby union players in terms of performance. The lower intakes than expenditure would suggest the players were losing weight. Previous research shows that rugby union players lose body fat during preseason training.

Chocolate milk for recovery from exercise: a systematic review and meta-analysis of controlled clinical trials

BACKGROUND/OBJECTIVES

Chocolate milk (CM) contains carbohydrates, proteins, and fat, as well as water and electrolytes, which may be ideal for post-exercise recovery. We systematically reviewed the evidence regarding the efficacy of CM compared to either water or other "sport drinks" on post-exercise recovery markers.

SUBJECTS/METHODS

PubMed, Scopus, and Google scholar were explored up to April 2017 for controlled trials investigating the effect of CM on markers of recovery in trained athletes.

RESULTS

Twelve studies were included in the systematic review (2, 9, and 1 with high, fair and low quality, respectively) and 11 had extractable data on at least one performance/recovery marker [7 on ratings of perceived exertion (RPE), 6 on time to exhaustion (TTE) and heart rate (HR), 4 on serum lactate, and serum creatine kinase (CK)]. The meta-analyses revealed that CM consumption had no effect on TTE, RPE, HR, serum lactate, and CK (P > 0.05) compared to placebo or other sport drinks. Subgroup analysis revealed that TTE significantly increases after consumption of CM compared to placebo [mean difference (MD) = 0.78 min, 95% confidence interval (CI): 0.27, 1.29, P = 0.003] and carbohydrate, protein, and fat-containing beverages (MD = 6.13 min, 95% CI: 0.11, 12.15, P = 0.046). Furthermore, a significant attenuation on serum lactate was observed when CM was compared with placebo (MD = -1.2 mmol/L, 95% CI: -2.06,-0.34, P = 0.006).

CONCLUSION

CM provides either similar or superior results when compared to placebo or other recovery drinks. Overall, the evidence is limited and high-quality clinical trials with more well-controlled methodology and larger sample sizes are warranted.

Restoration of Muscle Glycogen and Functional Capacity: Role of Post-Exercise Carbohydrate and Protein Co-Ingestion

The importance of post-exercise recovery nutrition has been well described in recent years, leading to its incorporation as an integral part of training regimes in both athletes and active individuals. Muscle glycogen depletion during an initial prolonged exercise bout is a main factor in the onset of fatigue and so the replenishment of glycogen stores may be important for recovery of functional capacity. Nevertheless, nutritional considerations for optimal short-term (3–6 h) recovery remain incompletely elucidated, particularly surrounding the precise amount of specific types of nutrients required. Current nutritional guidelines to maximise muscle glycogen availability within limited recovery are provided under the assumption that similar fatigue mechanisms (i.e., muscle glycogen depletion) are involved during a repeated exercise bout. Indeed, recent data support the notion that muscle glycogen availability is a determinant of subsequent endurance capacity following limited recovery. Thus, carbohydrate ingestion can be utilised to influence the restoration of endurance capacity following exhaustive exercise. One strategy with the potential to accelerate muscle glycogen resynthesis and/or functional capacity beyond merely ingesting adequate carbohydrate is the co-ingestion of added protein. While numerous studies have been instigated, a consensus that is related to the influence of carbohydrate-protein ingestion in maximising muscle glycogen during short-term recovery and repeated exercise capacity has not been established. When considered collectively, carbohydrate intake during limited recovery appears to primarily determine muscle glycogen resynthesis and repeated exercise capacity. Thus, when the goal is to optimise repeated exercise capacity following short-term recovery, ingesting carbohydrate at an amount of ≥1.2 g kg body mass⁻¹·h⁻¹ can maximise muscle glycogen repletion. The addition of protein to carbohydrate during post-exercise recovery may be beneficial under circumstances when carbohydrate ingestion is sub-optimal (≤0.8 g kg body mass⁻¹·h⁻¹) for effective restoration of muscle glycogen and repeated exercise capacity.

Recent Perspectives Regarding the Role of Dietary Protein for the Promotion of Muscle Hypertrophy with Resistance Exercise Training

Skeletal muscle supports locomotion and serves as the largest site of postprandial glucose disposal; thus it is a critical organ for physical and metabolic health. Skeletal muscle mass is regulated by the processes of muscle protein synthesis (MPS) and muscle protein breakdown (MPB), both of which are sensitive to external loading and aminoacidemia. Hyperaminoacidemia results in a robust but transient increase in rates of MPS and a mild suppression of MPB. Resistance exercise potentiates the aminoacidemia-induced rise in MPS that, when repeated over time, results in gradual radial growth of skeletal muscle (i.e., hypertrophy). Factors that affect MPS include both quantity and composition of the amino acid source. Specifically, MPS is stimulated in a dose-responsive manner and the primary amino acid agonist of this process is leucine. MPB also appears to be regulated in part by protein intake, which can exert a suppressive effect on MPB. At high protein doses the suppression of MPB may interfere with skeletal muscle adaptation following resistance exercise. In this review, we examine recent advancements in our understanding of how protein ingestion impacts skeletal muscle growth following resistance exercise in young adults during energy balance and energy restriction. We also provide practical recommendations for exercisers who wish to maximize the hypertrophic response of skeletal muscle during resistance exercise training.

Hyper-hippocampal glycogen induced by glycogen loading with exhaustive exercise

Glycogen loading (GL), a well-known type of sports conditioning, in combination with exercise and a high carbohydrate diet (HCD) for 1 week enhances individual endurance capacity through muscle glycogen supercompensation. This exercise-diet combination is necessary for successful GL. Glycogen in the brain contributes to hippocampus-related memory functions and endurance capacity. Although the effect of HCD on the brain remains unknown, brain supercompensation occurs following exhaustive exercise (EE), a component of GL. We thus employed a rat model of GL and examined whether GL increases glycogen levels in the brain as well as in muscle, and found that GL increased glycogen levels in the hippocampus and hypothalamus, as well as in muscle. We further explored the essential components of GL (exercise and/or diet conditions) to establish a minimal model of GL focusing on the brain. Exercise, rather than a HCD, was found to be crucial for GL-induced hyper-glycogen in muscle, the hippocampus and the hypothalamus. Moreover, EE was essential for hyper-glycogen only in the hippocampus even without HCD. Here we propose the EE component of GL without HCD as a condition that enhances brain glycogen stores especially in the hippocampus, implicating a physiological strategy to enhance hippocampal functions.

Co-ingestion of protein or a protein hydrolysate with carbohydrate enhances anabolic signaling, but not glycogen resynthesis, following recovery from prolonged aerobic exercise in trained cyclists

PURPOSE

The effect of carbohydrate (CHO), or CHO supplemented with either sodium caseinate protein (CHO-C) or a sodium caseinate protein hydrolysate (CHO-H) on the recovery of skeletal muscle glycogen and anabolic signaling following prolonged aerobic exercise was determined in trained male cyclists [n = 11, mean ± SEM age 28.8 ± 2.3 years; body mass (BM) 75.0 ± 2.3 kg; VO_2peak 61.3 ± 1.6 ml kg^-1 min^-1].

METHODS

On three separate occasions, participants cycled for 2 h at ~ 70% VO_2peak followed by a 4-h recovery period. Isoenergetic drinks were consumed at + 0 and + 2 h of recovery containing either (1) CHO (1.2 g kg ^-1 BM), (2) CHO-C, or (3) CHO-H (1.04 and 0.16 g kg^-1 BM, respectively) in a randomized, double-blind, cross-over design. Muscle biopsies from the vastus lateralis were taken prior to commencement of each trial, and at + 0 and + 4 h of recovery for determination of skeletal muscle glycogen, and intracellular signaling associated with protein synthesis.

RESULTS

Despite an augmented insulin response following CHO-H ingestion, there was no significant difference in skeletal muscle glycogen resynthesis following recovery between trials. CHO-C and CHO-H co-ingestion significantly increased phospho-mTOR Ser²⁴⁴⁸ and 4EBP1 Thr^37/46 versus CHO, with CHO-H displaying the greatest change in phospho-4EBP1 Thr^37/46. Protein co-ingestion, compared to CHO alone, during recovery did not augment glycogen resynthesis.

CONCLUSION

Supplementing CHO with intact sodium caseinate or an insulinotropic hydrolysate derivative augmented intracellular signaling associated with skeletal muscle protein synthesis following prolonged aerobic exercise.

Effects of Alpha-Lactalbumin or Whey Protein Isolate on Muscle Damage, Muscle Pain, and Mood States Following Prolonged Strenuous Endurance Exercise

This study compared the effect of alpha-lactalbumin and whey protein on muscle damage, muscle pain, and mood states during short term recovery following strenuous prolonged exercise. In a two-stage crossover counterbalanced design, 12 endurance male runners were recruited (age: 30.4 ± 2.8 year, height: 172.7 ± 5.6 cm, body mass: 66.7 ± 6.5 kg, VO_2max: 58.0 ± 6.9 ml/kg⁻/min), ran for 90 min at 70% VO_2max, and followed by a 4-h recovery. Two treatments (carbohydrate+alpha-lactalbumin, CA; carbohydrate+whey protein isolate, CW) were applied during the main trials. During the first 2-h of recovery, CHO was served at the rate of 0.66 g/kg/h and PRO at 0.34 g/kg/h every 30 min. Creatine kinase (CK), interleukin-6 (IL-6), salivary cortisol, rating of muscle pain, pressure pain threshold (PPT), and mood states were evaluated before (Pre-ex), immediately (Post-ex0), 2 h (Post-ex2h) and 4 h (Post-ex4h) after exercise. 24 h after exercise (Post-ex24h), CK and IL-6, muscle pain, and PPT were evaluated. Compared with Pre-ex, Post-ex24h CK was higher in both trials of CA (398.16 ± 41.37 vs. 184.77 ± 22.68 IU/L, P = 0.039) and CW (418.17 ± 67.86 vs. 202.41 ± 22.26 IU/L, P = 0.037). IL-6 was also higher than Pre-ex at Post-ex0 and Post-ex2h in trials of CA (Post-ex0 vs. Pre-ex0: 7.87 ± 0.74 vs. 1.69 ± 0.23, P < 0.01; Post-ex2h vs. Pre-ex0: 5.39 ± 0.88 vs. 1.69 ± 0.23, P = 0.02) and CW (Post-ex0 vs. Pre-ex0: 8.63 ± 1.06 vs. 1.59 ± 0.19, P < 0.01; Post-ex2h vs. Pre-ex0: 5.75 ± 1.33 vs. 1.59 ± 0.19, P < 0.01). No difference was found in CK and IL-6 between two trials at all time points (all P > 0.05). Compared with Pre-ex0, salivary cortisol was elevated at Post-ex0 in both trials (CA: 0.96 ± 0.13 vs. 0.41 ± 0.05 ng/ml, P < 0.01; CW: 1.15 ± 0.18 vs. 0.43 ± 0.06 ng/ml, P < 0.01) and was lower at Post-ex24h than Pre-ex in CA trial (0.17 ± 0.02 vs. 0.41 ± 0.05 ng/ml, P < 0.01). Compared with CW, PPT was higher at Post-2h in CA trial (31.55 ± 3.09 vs. 26.99 ± 2.32 N/cm², P < 0.01). Compared with Post-ex0, feeling of fatigue was lower at Post-ex2h (P = 0.014) and Post-ex4h (P < 0.01) in CA, while it was lower at Post-ex4h (P = 0.038) in CW. Compared with CW, feeling of fatigue was marginally lower in the CA trial at Post-ex2h (P = 0.056). In conclusion, compared with the co-ingestion of CHO and whey PRO isolate, co-ingestion of CHO and alpha-lactalbumin reduced sensitivity to the muscle pain, attenuated feeling of fatigue and was more beneficial to reduce the feeling of fatigue and cortisol responses during 4-h recovery following 90-min running at 70% VO_2max.

International society of sports nutrition position stand: nutrient timing

The International Society of Sports Nutrition (ISSN) provides an objective and critical review regarding the timing of macronutrients in reference to healthy, exercising adults and in particular highly trained individuals on exercise performance and body composition. The following points summarize the position of the ISSN:

Nutrient timing incorporates the use of methodical planning and eating of whole foods, fortified foods and dietary supplements. The timing of energy intake and the ratio of certain ingested macronutrients may enhance recovery and tissue repair, augment muscle protein synthesis (MPS), and improve mood states following high-volume or intense exercise.

Endogenous glycogen stores are maximized by following a high-carbohydrate diet (8–12 g of carbohydrate/kg/day [g/kg/day]); moreover, these stores are depleted most by high volume exercise.

If rapid restoration of glycogen is required (< 4 h of recovery time) then the following strategies should be considered:

aggressive carbohydrate refeeding (1.2 g/kg/h) with a preference towards carbohydrate sources that have a high (> 70) glycemic index

the addition of caffeine (3–8 mg/kg)

combining carbohydrates (0.8 g/kg/h) with protein (0.2–0.4 g/kg/h)

Extended (> 60 min) bouts of high intensity (> 70% VO₂max) exercise challenge fuel supply and fluid regulation, thus carbohydrate should be consumed at a rate of ~30–60 g of carbohydrate/h in a 6–8% carbohydrate-electrolyte solution (6–12 fluid ounces) every 10–15 min throughout the entire exercise bout, particularly in those exercise bouts that span beyond 70 min. When carbohydrate delivery is inadequate, adding protein may help increase performance, ameliorate muscle damage, promote euglycemia and facilitate glycogen re-synthesis.

Carbohydrate ingestion throughout resistance exercise (e.g., 3–6 sets of 8–12 repetition maximum [RM] using multiple exercises targeting all major muscle groups) has been shown to promote euglycemia and higher glycogen stores. Consuming carbohydrate solely or in combination with protein during resistance exercise increases muscle glycogen stores, ameliorates muscle damage, and facilitates greater acute and chronic training adaptations.

Meeting the total daily intake of protein, preferably with evenly spaced protein feedings (approximately every 3 h during the day), should be viewed as a primary area of emphasis for exercising individuals.

Ingestion of essential amino acids (EAA; approximately 10 g)either in free form or as part of a protein bolus of approximately 20–40 g has been shown to maximally stimulate muscle protein synthesis (MPS).

Pre- and/or post-exercise nutritional interventions (carbohydrate + protein or protein alone) may operate as an effective strategy to support increases in strength and improvements in body composition. However, the size and timing of a pre-exercise meal may impact the extent to which post-exercise protein feeding is required.

Post-exercise ingestion (immediately to 2-h post) of high-quality protein sources stimulates robust increases in MPS.

In non-exercising scenarios, changing the frequency of meals has shown limited impact on weight loss and body composition, with stronger evidence to indicate meal frequency can favorably improve appetite and satiety. More research is needed to determine the influence of combining an exercise program with altered meal frequencies on weight loss and body composition with preliminary research indicating a potential benefit.

Ingesting a 20–40 g protein dose (0.25–0.40 g/kg body mass/dose) of a high-quality source every three to 4 h appears to most favorably affect MPS rates when compared to other dietary patterns and is associated with improved body composition and performance outcomes.

Consuming casein protein (~ 30–40 g) prior to sleep can acutely increase MPS and metabolic rate throughout the night without influencing lipolysis.

Postexercise muscle glycogen resynthesis in humans

Since the pioneering studies conducted in the 1960s in which glycogen status was investigated using the muscle biopsy technique, sports scientists have developed a sophisticated appreciation of the role of glycogen in cellular adaptation and exercise performance, as well as sites of storage of this important metabolic fuel. While sports nutrition guidelines have evolved during the past decade to incorporate sport-specific and periodized manipulation of carbohydrate (CHO) availability, athletes attempt to maximize muscle glycogen synthesis between important workouts or competitive events so that fuel stores closely match the demands of the prescribed exercise. Therefore, it is important to understand the factors that enhance or impair this biphasic process. In the early postexercise period (0–4 h), glycogen depletion provides a strong drive for its own resynthesis, with the provision of CHO (~1 g/kg body mass) optimizing this process. During the later phase of recovery (4–24 h), CHO intake should meet the anticipated fuel needs of the training/competition, with the type, form, and pattern of intake being less important than total intake. Dietary strategies that can enhance glycogen synthesis from suboptimal amounts of CHO or energy intake are of practical interest to many athletes; in this scenario, the coingestion of protein with CHO can assist glycogen storage. Future research should identify other factors that enhance the rate of synthesis of glycogen storage in a limited time frame, improve glycogen storage from a limited CHO intake, or increase muscle glycogen supercompensation.

Novel Tools in Determining the Physiological Demands and Nutritional Practices of Ontario FireRangers during Fire Deployments

INTRODUCTION

The seasonal profession of wildland fire fighting in Canada requires individuals to work in harsh environmental conditions that are physically demanding. The purpose of this study was to use novel technologies to evaluate the physiological demands and nutritional practices of Canadian FireRangers during fire deployments.

METHODS

Participants (n = 21) from a northern Ontario Fire Base volunteered for this study and data collection occurred during the 2014 fire season and included Initial Attack (IA), Project Fire (P), and Fire Base (B) deployments. Deployment-specific energy demands and physiological responses were measured using heart-rate variability (HRV) monitoring devices (Zephyr BioHarness3 units). Food consumption behaviour and nutrient quantity and quality were captured using audio-video food logs on iPod Touches and analyzed by NutriBase Pro 11 software.

RESULTS

Insufficient kilocalories were consumed relative to expenditure for all deployment types. Average daily kilocalories consumed: IA: 3758 (80% consumption rate); P: 2945±888.8; B: 2433±570.8. Average daily kilocalorie expenditure: IA: 4538±106.3; P: 4012±1164.8; B: 2842±649.9. The Average Macronutrient Distribution Range (AMDR) for protein was acceptable: 22-25% (across deployment types). Whereas the AMDR for fat and carbohydrates were high: 40-50%; and low: 27-37% respectively, across deployment types.

CONCLUSIONS

This study is the first to use the described methodology to simultaneously evaluate energy expenditures and nutritional practices in an occupational setting. The results support the use of HRV monitoring and video-food capture, in occupational field settings, to assess job demands. FireRangers expended the most energy during IA, and the least during B deployments. These results indicate the need to develop strategies centered on maintaining physical fitness and improving food practices.

Long-term Leucine Supplementation Improves Metabolic But Not Molecular Responses in the Skeletal Muscle of Trained Rats Submitted to Exhaustive Exercise

AIM

Although there is some evidence of an ergogenic effect of leucine supplementation on acute response to exercise, there is a paucity of information on whether long-term leucine supplementation influences the adaptive response to chronic endurance training and performance. The main aim of our study was to assess the role of long-term leucine supplementation on molecular and metabolic response in skeletal muscle of trained rats after an exhaustion test.

METHODS

Twenty-four male Wistar rats were randomly allocated into 4 groups. Two of them (control and trained groups) received a balanced control diet (18% protein) and the other 2 (control leucine and trained leucine groups) received a leucine-rich diet (15% protein with 3% leucine) for 6 weeks. The trained groups were submitted to 1 hour of swimming exercise, 5 d/wk for 6 weeks. Three days after the exercise training period, trained groups were submitted to swimming exercise until exhaustion and muscle metabolic and molecular parameters were assessed.

RESULTS

Endurance training increased citrate synthase activity significantly, whereas exercise until exhaustion increased cytokine levels and led to a lack of activation of phosphorylation of the signaling intermediates assessed. Long-term leucine supplementation enhanced muscle glycogen level in trained rats and citrate synthase activity in sedentary ones. However, it failed to enhance endurance performance of trained rats submitted to an exhaustion test and did not prevent exercise-induced reduction in Akt and mTOR activation.

CONCLUSION

Long-term leucine supplementation can enhance citrate synthase activity by itself in sedentary individuals and glycogen content when combined with exercise; however, it does not improve endurance performance or prevent Akt and mTOR exercise-induced inhibition.

Intake of Protein Plus Carbohydrate during the First Two Hours after Exhaustive Cycling Improves Performance the following Day

Intake of protein immediately after exercise stimulates protein synthesis but improved recovery of performance is not consistently observed. The primary aim of the present study was to compare performance 18 h after exhaustive cycling in a randomized diet-controlled study (175 kJ·kg^-1 during 18 h) when subjects were supplemented with protein plus carbohydrate or carbohydrate only in a 2-h window starting immediately after exhaustive cycling. The second aim was to investigate the effect of no nutrition during the first 2 h and low total energy intake (113 kJ·kg^-1 during 18 h) on performance when protein intake was similar. Eight endurance-trained subjects cycled at 237±6 Watt (~72% VO_2max) until exhaustion (TTE) on three occasions, and supplemented with 1.2 g carbohydrate·kg^-1·h^-1 (CHO), 0.8 g carbohydrate + 0.4 g protein·kg^-1·h^-1 (CHO+PRO) or placebo without energy (PLA). Intake of CHO+PROT increased plasma glucose, insulin, and branch chained amino acids, whereas CHO only increased glucose and insulin. Eighteen hours later, subjects performed another TTE at 237±6 Watt. TTE was increased after intake of CHO+PROT compared to CHO (63.5±4.4 vs 49.8±5.4 min; p<0.05). PLA reduced TTE to 42.8±5.1 min (p<0.05 vs CHO). Nitrogen balance was positive in CHO+PROT, and negative in CHO and PLA. In conclusion, performance was higher 18 h after exhaustive cycling with intake of CHO+PROT compared to an isocaloric amount of carbohydrate during the first 2 h post exercise. Intake of a similar amount of protein but less carbohydrate during the 18 h recovery period reduced performance.

Nutrition habits in 24-hour mountain bike racers

We investigated seventy-four ultra-mountain bikers (MTBers) competing in the solo category in the first descriptive field study to detail nutrition habits and the most common food before during and after the 24 hour race using questionnaires. During the race, bananas (86.5%), energy bars (50.0%), apples (43.2%) and cheese (43.2%) were the most commonly consumed food, followed by bread (44.6%), rice (33.8%) and bananas (33.8%) after the race. Average fluid intake was 0.5 ± 0.2 l/h. The main beverage was isotonic sports drink (82.4%) during and pure water (66.2%) after the race. The most preferred four supplements in the four weeks before, the day before, during and after the race were vitamin C (35.1%), magnesium (44.6%), magnesium (43.2%) and branched-chain amino acids (24.3%), respectively. Total frequency of food intake (30.6 ± 10.5 times/24 hrs) was associated with fluid intake (r = 0.43, P = 0.04) and both were highest at the beginning of the race and lower during the night hours and the last race segment in a subgroup of twenty-three ultra-MTBers. Supplement intake frequency (6.8 ± 8.4 times/24 hrs) was highest during the night hours and lower at the beginning and end of the race. Elevated food and fluid intake among participants tracked across all race segments (P < 0.001). In conclusion, the nutrition strategy employed by ultra-MTBers was similar to those demonstrated in previous studies of ultra-cyclists with some exceptions among selected individuals.

Effects of protein in combination with carbohydrate supplements on acute or repeat endurance exercise performance: a systematic review

BACKGROUND

Protein supplements are consumed frequently by athletes and recreationally active adults for various reasons, including improved exercise performance and recovery after exercise. Yet, far too often, the decision to purchase and consume protein supplements is based on marketing claims rather than available evidence-based research.

OBJECTIVE

The purpose of this review was to provide a systematic and comprehensive analysis of the literature that tested the hypothesis that protein supplements, when combined with carbohydrate, directly enhance endurance performance by sparing muscle glycogen during exercise and increasing the rate of glycogen restoration during recovery. The analysis was used to create evidence statements based on an accepted strength of recommendation taxonomy.

DATA SOURCES

English language articles were searched with PubMed and Google Scholar using protein and supplements together with performance, exercise, competition, and muscle, alone or in combination as keywords. Additional articles were retrieved from reference lists found in these papers.

STUDY SELECTION

Inclusion criteria specified recruiting healthy active adults less than 50 years of age and evaluating the effects of protein supplements in combination with carbohydrate on endurance performance metrics such as time-to-exhaustion, time-trial, or total power output during sprint intervals. The literature search identified 28 articles, of which 26 incorporated test metrics that permitted exclusive categorization into one of the following sections: ingestion during an acute bout of exercise (n = 11) and ingestion during and after exercise to affect subsequent endurance performance (n = 15). The remaining two articles contained performance metrics that spanned both categories.

STUDY APPRAISAL AND SYNTHESIS METHODS

All papers were read in detail and searched for experimental design confounders such as energy content of the supplements, dietary control, use of trained or untrained participants, number of subjects recruited, direct measures of muscle glycogen utilization and restoration, and the sensitivity of the test metrics to explain the discrepant findings.

RESULTS

Our evidence statements assert that when carbohydrate supplementation was delivered at optimal rates during or after exercise, protein supplements provided no further ergogenic effect, regardless of the performance metric used. In addition, the limited data available suggested recovery of muscle glycogen stores together with subsequent rate of utilization during exercise is not related to the potential ergogenic effect of protein supplements.

LIMITATIONS

Many studies lacked ability to measure direct effects of protein supplementation on muscle metabolism through determination of muscle glycogen, kinetic assessments of protein turnover, or changes in key signaling proteins, and therefore could not substantiate changes in rates of synthesis or degradation of protein. As a result, the interpretation of their data was often biased and inconclusive since they lacked ability to test the proposed underlying mechanism of action.

CONCLUSIONS

When carbohydrate is delivered at optimal rates during or after endurance exercise, protein supplements appear to have no direct endurance performance enhancing effect.

Post-Exercise Protein Trial: Interactions between Diet and Exercise (PEPTIDE): study protocol for randomized controlled trial

BACKGROUND

Performing regular exercise is known to manifest a number of health benefits that mainly relate to cardiovascular and muscular adaptations to allow for greater oxygen extraction and utilization. There is increasing evidence that nutrient intake can affect the adaptive response to a single exercise bout, and that protein feeding is important to facilitate this process. Thus, the exercise-nutrient interaction may potentially lead to a greater response to training. The role of post-exercise protein ingestion in enhancing the effects of running-based endurance exercise training relative to energy-matched carbohydrate intervention remains to be established. Additionally, the influence of immediate versus overnight protein ingestion in mediating these training effects is currently unknown. The current protocol aims to establish whether post-exercise nutrient intake and timing would influence the magnitude of improvements during a prescribed endurance training program.

METHODS/DESIGN

The project involves two phases with each involving two treatment arms applied in a randomized investigator-participant double-blind parallel group design. For each treatment, participants will be required to undergo six weeks of running-based endurance training. Immediately post-exercise, participants will be prescribed solutions providing 0.4 grams per kilogram of body mass (g · kg(-1)) of whey protein hydrolysate plus 0.4 g · kg(-1) sucrose, relative to an isocaloric sucrose control (0.8 g · kg(-1); Phase I). In Phase II, identical protein supplements will be provided (0.4 + 0.4 g · kg(-1) · h(-1) of whey protein hydrolysate and sucrose, respectively), with the timing of ingestion manipulated to compare immediate versus overnight recovery feedings. Anthropometric, expired gas, venous blood and muscle biopsy samples will be obtained at baseline and following the six-week training period.

DISCUSSION

By investigating the role of nutrition in enhancing the effects of endurance exercise training, we will provide novel insight regarding nutrient-exercise interactions and the potential to help and develop effective methods to maximize health or performance outcomes in response to regular exercise.

TRIAL REGISTRATION

Current Controlled Trials registration number: ISRCTN27312291 (date assigned: 4 December 2013). The first participant was randomized on 11 December 2013.

Lactose-free milk prolonged endurance capacity in lactose intolerant Asian males

Background

Several studies on Caucasian volunteers have proven that milk is an effective recovery drink for athletes. Such benefit, however, cannot be directly applied to the lactose-intolerant Asian population. This study investigated the effects of ingesting water (WT), sports drink (SPD) and lactose-free milk (LFM) on cycling capacity.

Methods

Ten healthy young men completed 3 randomized experimental trials. Each trial consisted of an intermittent glycogen depleting session, a 2 h recovery period during which they ingested the test drink, followed by cycling at 70% of their maximum oxygen consumption (VO₂max) to volitional exhaustion. Each trial was separated by at least one week.

Results

There were no complaints or symptoms of lactose intolerance during any of the trials. The cycling periods were different (p < 0.05) amongst the 3 trials, namely, lactose-free milk (LFM; 69.6 ± 14.0 min), sports drink (SPD; 52.1 ± 11.6 min), and water (WT; 36.0 ± 11.1 min), respectively. The VO₂ and VCO₂ of LFM (30 ± 4 and 29 ± 4 ml/kg/min) were lower (p < 0.05) than that of SPD (34 ± 4 and 34 ± 4 ml/kg/min) and WT (35 ± 4 and 33 ± 5 ml/kg/min). There were no differences (p = 0.45) in VO₂ and VCO₂ between SPD and WT. Mean rating of perceived exertion was lowest in LFM (14 ± 5; p < 0.05), while no difference was found between the other two trials (SPD: 16 ± 4 and WT: 16 ± 4; p = 0.18).

Conclusion

Lactose-free milk is likely to be an effective recovery drink for enhancing subsequent cycling capacity in lactose intolerant Asian males.

Co-ingestion of carbohydrate and pea protein does not enhance muscle recovery after strenuous exercise

OBJECTIVE: To assess the influence of carbohydrate and added pea protein concentrate supplementation on muscle recovery after a military operation called Leader's Reaction Test. METHODS: Twenty-four soldiers from the Brazilian Army were divided into three equal groups (n=8). They received either carbohydrate (0.8.g/kg body weight/h), carbohydrate+carbohydrate (1.0.g/kg body weight/h), or carbohydrate+protein (0.8 g/kg body weight/h of carbohydrate + 0.2 g/kg body weight/h of protein), immediately, 60, and 120 minutes after the Leader’s Reaction Test. Prior, immediately after and 24 hours after the Leader’s Reaction Test, maximal isometric strength and body composition were assessed. Blood samples were also collected for later analysis of concentrations of lactate dehydrogenase and creatine kinase. RESULTS: Twenty-four hours after the Leader's Reaction Test, maximal creatine kinase levels were significantly lower than its levels immediately after (501.00 ± 422.09 versus 275.29 ± 242.08 U/L (carbohydrate); 616.88 ± 291.45 versus 334.57 ± 191.61 U/L (carbohydrate+carbohydrate); and 636.75 ± 340.67 versus 382.88 ± 234.42 U/L (carbohydrate+protein), p=0.004). The maximal isometric strength and lactate dehydrogenase levels were not significantly different during the time trials. CONCLUSION: The present findings suggest that carbohydrate+protein co-ingestion did not improve the recovery of muscle function nor did it attenuate post-exercise muscle damage markers over carbohydrate alone.

Pre-exercise nutrition: the role of macronutrients, modified starches and supplements on metabolism and endurance performance

Endurance athletes rarely compete in the fasted state, as this may compromise fuel stores. Thus, the timing and composition of the pre-exercise meal is a significant consideration for optimizing metabolism and subsequent endurance performance. Carbohydrate feedings prior to endurance exercise are common and have generally been shown to enhance performance, despite increasing insulin levels and reducing fat oxidation. These metabolic effects may be attenuated by consuming low glycemic index carbohydrates and/or modified starches before exercise. High fat meals seem to have beneficial metabolic effects (e.g., increasing fat oxidation and possibly sparing muscle glycogen). However, these effects do not necessarily translate into enhanced performance. Relatively little research has examined the effects of a pre-exercise high protein meal on subsequent performance, but there is some evidence to suggest enhanced pre-exercise glycogen synthesis and benefits to metabolism during exercise. Finally, various supplements (i.e., caffeine and beetroot juice) also warrant possible inclusion into pre-race nutrition for endurance athletes. Ultimately, further research is needed to optimize pre-exercise nutritional strategies for endurance performance.

Exploring mechanisms of fatigue during repeated exercise and the dose dependent effects of carbohydrate and protein ingestion: study protocol for a randomised controlled trial

Background

Muscle glycogen has been well established as the primary metabolic energy substrate during physical exercise of moderate- to high-intensity and has accordingly been implicated as a limiting factor when such activity is sustained for a prolonged duration. However, the role of this substrate during repeated exercise after limited recovery is less clear, with ongoing debate regarding how recovery processes can best be supported via nutritional intervention. The aim of this project is to examine the causes of fatigue during repeated exercise bouts via manipulation of glycogen availability through nutritional intervention, thus simultaneously informing aspects of the optimal feeding strategy for recovery from prolonged exercise.

Methods/Design

The project involves two phases with each involving two treatment arms administered in a repeated measures design. For each treatment, participants will be required to exercise to the point of volitional exhaustion on a motorised treadmill at 70% of previously determined maximal oxygen uptake, before a four hour recovery period in which participants will be prescribed solutions providing 1.2 grams of sucrose per kilogram of body mass per hour of recovery (g.kg^-1.h^-1) relative to either a lower rate of sucrose ingestion (that is, 0.3 g.kg^-1. h^-1; Phase I) or a moderate dose (that is, 0.8 g.kg^-1.h^-1) rendered isocaloric via the addition of 0.4 g.kg^-1.h^-1 whey protein hydrolysate (Phase II); the latter administered in a double blind manner as part of a randomised and counterbalanced design. Muscle biopsies will be sampled at the beginning and end of recovery for determination of muscle glycogen resynthesis rates, with further biopsies taken following a second bout of exhaustive exercise to determine differences in substrate availability relative to the initial sample taken following the first exercise bout.

Discussion

Phase I will inform whether a dose–response relationship exists between carbohydrate ingestion rate and muscle glycogen availability and/or the subsequent capacity for physical exercise. Phase II will determine whether such effects are dependent on glycogen availability per se or energy intake, potentially via protein mediated mechanisms.

Trial registration

ISRCTN87937960.

Protein supplementation for military personnel: a review of the mechanisms and performance outcomes

Protein supplement use is common among athletes, active adults, and military personnel. This review provides a summary of the evidence base that either supports or refutes the ergogenic effects associated with different mechanisms that have been proposed to support protein supplementation. It was clear that if carbohydrate delivery was optimal either during or after an acute bout of exercise that additional protein will not increase exercise capacity. Evidence was also weak to substantiate use of protein supplements to slow the increase in brain serotonin and onset of central fatigue. It was also evident that additional research is warranted to test whether the benefits of protein supplements for enhancing recovery of fluid balance after exercise will affect subsequent work in the heat. In contrast, with repeated exercise, use of protein supplementation was associated with reductions in muscle soreness and often a faster recovery of muscle function due to reductions in protein degradation. There was also good supportive evidence for long-term benefits of protein supplementation for gains in muscle mass and strength through accelerated rates of protein synthesis, as long as the training stimulus was of sufficient intensity, frequency, and duration. However, studies have not examined the impact of protein supplements under the combined stress of a military environment that includes repeated bouts of exercise with little opportunity for feeding and recovery, lack of sleep, and exposure to extreme environments. Both additional laboratory and field research is warranted to help provide evidence-based guidance for the choice of protein supplements to enhance soldier performance.

Nutrient Timing

As the incidence rate of lifestyle-related chronic conditions such as cardiovascular disease, obesity, and type 2 diabetes continues to increase, the importance of regular exercise and a healthy diet for improving or maintaining good health is critical. Exercise training is known to improve fitness and many health risk factors, as well as to improve the performance of competitive athletes. It has become increasingly clear, however, that nutrient intake before, during, and after exercise sessions has a powerful influence on the adaptive response to the exercise stimuli. In this review, the science behind nutrient timing will be discussed as it relates to exercise performance, recovery, and training adaptation. Evidence will be provided that validates intake of appropriate nutrients before, during, and immediately after exercise not only to improve exercise performance but also to maximize the training response. Ultimately, the combined response to exercise and proper nutrient intake leads to not only better performance in athletes but also greater health benefits for all exercisers.

Liver and muscle glycogen repletion using 13C magnetic resonance spectroscopy following ingestion of maltodextrin, galactose, protein and amino acids

The present study evaluated whether the inclusion of protein (PRO) and amino acids (AA) within a maltodextrin (MD) and galactose (GAL) recovery drink enhanced post-exercise liver and muscle glycogen repletion. A total of seven trained male cyclists completed two trials, separated by 7 d. Each trial involved 2 h of standardised intermittent cycling, followed by 4 h recovery. During recovery, one of two isoenergetic formulations, MD–GAL (0·9 g MD/kg body mass (BM) per h and 0·3 g GAL/kg BM per h) or MD–GAL-PRO+AA (0·5 g MD/kg BM per h, 0·3 g GAL/kg BM per h, 0·4 g whey PRO hydrolysate plus l-leucine and l-phenylalanine/kg BM per h) was ingested at every 30 min. Liver and muscle glycogen were measured after depletion exercise and at the end of recovery using 1H-13C-magnetic resonance spectroscopy. Despite higher postprandial insulin concentations for MD–GAL-PRO+AA compared with MD–GAL (61·3 (se 6·2) v. 29·6 (se 3·0) mU/l, (425·8 (se 43·1) v. 205·6 (se 20·8) pmol/l) P= 0·03), there were no significant differences in post-recovery liver (195·3 (se 2·6) v. 213·8 (se 18·0) mmol/l) or muscle glycogen concentrations (49·7 (se 4·0) v. 51·1 (se 7·9) mmol/l). The rate of muscle glycogen repletion was significantly higher for MD–GAL compared with MD–GAL-PRO+AA (5·8 (se 0·7) v. 3·7 (se 0·6) mmol/l per h, P= 0·04), while there were no significant differences in the rate of liver glycogen repletion (15·0 (se 2·5) v. 13·0 (se 2·7) mmol/l per h). PRO and AA within a MD–GAL recovery drink, compared with an isoenergetic mix of MD–GAL, did not enhance but matched liver and muscle glycogen recovery. This suggests that the increased postprandial insulinaemia only compensated for the lower MD content in the MD–GAL-PRO+AA treatment.

Nutrient timing revisited: is there a post-exercise anabolic window?

Nutrient timing is a popular nutritional strategy that involves the consumption of combinations of nutrients--primarily protein and carbohydrate--in and around an exercise session. Some have claimed that this approach can produce dramatic improvements in body composition. It has even been postulated that the timing of nutritional consumption may be more important than the absolute daily intake of nutrients. The post-exercise period is widely considered the most critical part of nutrient timing. Theoretically, consuming the proper ratio of nutrients during this time not only initiates the rebuilding of damaged muscle tissue and restoration of energy reserves, but it does so in a supercompensated fashion that enhances both body composition and exercise performance. Several researchers have made reference to an anabolic “window of opportunity” whereby a limited time exists after training to optimize training-related muscular adaptations. However, the importance - and even the existence - of a post-exercise ‘window’ can vary according to a number of factors. Not only is nutrient timing research open to question in terms of applicability, but recent evidence has directly challenged the classical view of the relevance of post-exercise nutritional intake with respect to anabolism. Therefore, the purpose of this paper will be twofold: 1) to review the existing literature on the effects of nutrient timing with respect to post-exercise muscular adaptations, and; 2) to draw relevant conclusions that allow practical, evidence-based nutritional recommendations to be made for maximizing the anabolic response to exercise.

Whey protein addition to a carbohydrate-electrolyte rehydration solution ingested after exercise in the heat

CONTEXT

Many active people finish exercise hypohydrated, so effective rehydration after exercise is an important consideration.

OBJECTIVE

To determine the effects of a rehydration solution containing whey protein isolate on fluid balance after exercise-induced dehydration.

DESIGN

Randomized controlled clinical trial.

SETTING

University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twelve healthy men (age = 21 ± 1 years, height = 1.82 ± 0.08 m, mass = 82.71 ± 10.31 kg) participated.

INTERVENTION(S)

Participants reduced body mass by 1.86% ± 0.07% after intermittent exercise in the heat and rehydrated with a volume of drink in liters equivalent to 1.5 times their body mass loss in kilograms of a solution of either 65 g/L carbohydrate (trial C) or 50 g/L carbohydrate and 15 g/L whey protein isolate (trial CPl. Solutions were matched for energy density and electrolyte content. Urine samples were collected before and after exercise and for 4 hours after rehydration.

MAIN OUTCOME MEASURE(S)

We measured urine volume, drink retention, net fluid balance, urine osmolality, and subjective responses. Drink retention was calculated as the difference between the volume of drink ingested and urine produced. Net fluid balance was calculated from fluid gained through drink ingestion and fluid lost through sweat and urine production.

RESULTS

Total cumulative urine output after rehydration was not different between trial C (1173 ± 481 mL) and trial CP (1180 ± 330 mL) (F(1) = 0.002, P = .96), and drink retention during the study also was not different between trial C (50% ± 18%) and trial CP (49% ± 13%) (t(11) = -0.159, P =.88). At the end of the study, net fluid balance was negative compared with baseline for trial C (-432 ± 436 mL) (t(11) = 3.433, P = .03) and trial CP (-432 ± 302 mL) (t(11) = 4.958, P = .003).

CONCLUSIONS

When matched for energy density and electrolyte content, a solution of carbohydrate and whey protein isolate neither increased nor decreased rehydration compared with a solution of carbohydrate.

Coingestion of carbohydrate and protein during training reduces training stress and enhances subsequent exercise performance

Researchers have focused primarily on investigating the effects of coingesting carbohydrate (CHO) and protein (PRO) during recovery and, as such, there is limited research investigating the benefits of CHO+PRO coingestion during exercise for enhancing subsequent exercise performance. The aim of this study was to investigate whether coingestion of CHO+PRO during endurance training would enhance recovery and subsequent exercise performance. Ten well-trained male cyclists (aged 29.7 ± 7.5 years; maximal oxygen uptake, 66.2 ± 6 mL·kg(-1)·min(-1)) took part in a randomized, double-blind, cross-over trial. Each trial consisted of a 2.5-h morning training bout during which the cyclists ingested a CHO+PRO or energy-matched CHO beverage followed by a 4-h recovery period and a subsequent performance time trial (total work, 7 kJ·kg(-1)). Blood was collected before and after exercise. Time-trial performance was 1.8% faster in the CHO+PRO trial compared with the CHO trial (p = 0.149; 95% CI, -13 to 87 s; 75.8% likelihood of benefit). The increase in myoglobin level from before the training bout to after the training bout was lower in the CHO+PRO trial (0.74 nmol·L(-1); 95% CI, 0.3-1.17 nmol·L(-1)) compared with the CHO trial (1.16 nmol·L(-1); 95% CI, 0.6-1.71 nmol·L(-1)) (p = 0.018). Additionally, the decrease in neutrophil count over the recovery period was greater in the CHO+PRO trial (p = 0.034), and heart rate (p < 0.022) and rating of perceived exertion (RPE) (p < 0.01) were lower during training in the CHO+PRO trial compared with the CHO trial. Ingesting PRO, in addition to CHO, during strenuous training lowered exercise stress, as indicated by reduced heart rate, RPE, and muscle damage, when compared with CHO alone. CHO+PRO ingestion during training is also likely to enhance recovery, providing a worthwhile improvement in subsequent cycling time-trial performance.

Personal food systems of male collegiate football players: a grounded theory investigation

CONTEXT

Factors that affect food choices include the physical and social environments, quality, quantity, perceived healthfulness, and convenience. The personal food choice process was defined as the procedures used by athletes for making food choices, including the weighing and balancing of activities of daily life, physical well-being, convenience, monetary resources, and social relationships.

OBJECTIVE

To develop a theoretical model explaining the personal food choice processes of collegiate football players.

DESIGN

Qualitative study.

SETTING

National Collegiate Athletic Association Division II football program.

PATIENTS OR OTHER PARTICIPANTS

Fifteen football players were purposefully sampled to represent various positions, years of athletic eligibility, and ethnic backgrounds.

DATA COLLECTION AND ANALYSIS

For text data collection, we used predetermined, open-ended questions. Data were analyzed using the constant comparison method. The athletes' words were used to label and describe their interactions and experiences with the food choice process. Member checks and an external audit were conducted by a qualitative methodologist and a nutrition specialist, and the findings were triangulated with the current literature to ensure trustworthiness of the text data.

RESULTS

Time was the core category and yielded a cyclic graphic of a theoretical model for the food choice system. Planning hydration, macronutrient strategies, snacks, and healthful food choices emerged as themes.

CONCLUSIONS

The athletes planned meals and snacks around their academic and athletic schedules while attempting to consume foods identified as healthful. Healthful foods were generally lower in fat but high in preferred macronutrients. High-protein foods were the players' primary goal; carbohydrate consumption was secondary. The athletes had established plans to maintain hydration. Professionals may use these findings to implement educational programs on food choices for football players.

Metabolism and performance during extended high-intensity intermittent exercise after consumption of low- and high-glycaemic index pre-exercise meals

The metabolic and performance benefits of prior consumption of low-glycaemic index (GI) meals v. high-GI meals were determined in extended high-intensity intermittent exercise. Participants (ten males and four females, aged 25·8 (sd 7·3) years) completed two testing days (each consisting of back-to-back 90-min intermittent high-intensity treadmill running protocols separated by 3 h) spaced by at least 7 d. Using a randomised counterbalanced cross-over design, low-GI, lentil-based meals (GI about 42) or high-GI, potato-based meals (GI about 78) matched for energy value were consumed 2 h before, and within 1 h after, the first exercise session. Performance was measured by the distance covered during five 1-min sprints (separated by 2·5 min walking) at the end of each exercise session. Peak postprandial blood glucose was higher by 30·8 % in the high-GI trial compared with the low-GI trial, as was insulin (P = 0·039 and P = 0·003, respectively). Carbohydrate oxidation was lower by 5·5 % during the low-GI trials compared with the high-GI trials at the start of the first exercise session (P < 0·05). Blood lactate was significantly higher (6·1 v. 2·6 mmol/l; P = 0·019) and blood glucose significantly lower (4·8 v. 5·4 mmol/l; P = 0·039) at the end of the second exercise session during the high-GI trial compared with the low-GI trial. Sprint distance was not significantly different between conditions. A low-GI meal improved the metabolic profile before and during extended high-intensity intermittent exercise, but did not affect performance. Improvements in metabolic responses when consuming low-GI meals before exercise may be beneficial to the long-term health of athletes.

Impact of postprandial glycaemia on health and prevention of disease

Postprandial glucose, together with related hyperinsulinemia and lipidaemia, has been implicated in the development of chronic metabolic diseases like obesity, type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). In this review, available evidence is discussed on postprandial glucose in relation to body weight control, the development of oxidative stress, T2DM, and CVD and in maintaining optimal exercise and cognitive performance. There is mechanistic evidence linking postprandial glycaemia or glycaemic variability to the development of these conditions or in the impairment in cognitive and exercise performance. Nevertheless, postprandial glycaemia is interrelated with many other (risk) factors as well as to fasting glucose. In many studies, meal-related glycaemic response is not sufficiently characterized, or the methodology with respect to the description of food or meal composition, or the duration of the measurement of postprandial glycaemia is limited. It is evident that more randomized controlled dietary intervention trials using effective low vs. high glucose response diets are necessary in order to draw more definite conclusions on the role of postprandial glycaemia in relation to health and disease. Also of importance is the evaluation of the potential role of the time course of postprandial glycaemia.

Recovery from cycling exercise: effects of carbohydrate and protein beverages

The effects of different carbohydrate-protein (CHO + Pro) beverages were compared during recovery from cycling exercise. Twelve male cyclists (VO(2peak): 65 ± 7 mL/kg/min) completed ~1 h of high-intensity intervals (EX1). Immediately and 120 min following EX1, subjects consumed one of three calorically-similar beverages (285-300 kcal) in a cross-over design: carbohydrate-only (CHO; 75 g per beverage), high-carbohydrate/low-protein (HCLP; 45 g CHO, 25 g Pro, 0.5 g fat), or low-carbohydrate/high-protein (LCHP; 8 g CHO, 55 g Pro, 4 g fat). After 4 h of recovery, subjects performed subsequent exercise (EX2; 20 min at 70% VO(2peak) + 20 km time-trial). Beverages were also consumed following EX2. Blood glucose levels (30 min after beverage ingestion) differed across all treatments (CHO > HCLP > LCHP; p < 0.05), and serum insulin was higher following CHO and HCLP ingestion versus LCHP. Peak quadriceps force, serum creatine kinase, muscle soreness, and fatigue/energy ratings measured pre- and post-exercise were not different between treatments. EX2 performance was not significantly different between CHO (48.5 ± 1.5 min), HCLP (48.8 ± 2.1 min) and LCHP (50.3 ± 2.7 min). Beverages containing similar caloric content but different proportions of carbohydrate/protein provided similar effects on muscle recovery and subsequent exercise performance in well-trained cyclists.

Physiological and nutritional aspects of post-exercise recovery: specific recommendations for female athletes

Gender-based differences in the physiological response to exercise have been studied extensively for the last four decades, and yet the study of post-exercise, gender-specific recovery has only been developing in more recent years. This review of the literature aims to present the current state of knowledge in this field, focusing on some of the most pertinent aspects of physiological recovery in female athletes and how metabolic, thermoregulatory, or inflammation and repair processes may differ from those observed in male athletes. Scientific investigations on the effect of gender on substrate utilization during exercise have yielded conflicting results. Factors contributing to the lack of agreement between studies include differences in subject dietary or training status, exercise intensity or duration, as well as the variations in ovarian hormone concentrations between different menstrual cycle phases in female subjects, as all are known to affect substrate metabolism during sub-maximal exercise. If greater fatty acid mobilization occurs in females during prolonged exercise compared with males, the inverse is observed during the recovery phase. This could explain why, despite mobilizing lipids to a greater extent than males during exercise, females lose less fat mass than their male counterparts over the course of a physical training programme. Where nutritional strategies are concerned, no difference appears between males and females in their capacity to replenish glycogen stores; optimal timing for carbohydrate intake does not differ between genders, and athletes must consume carbohydrates as soon as possible after exercise in order to maximize glycogen store repletion. While lipid intake should be limited in the immediate post-exercise period in order to favour carbohydrate and protein intake, in the scope of the athlete's general diet, lipid intake should be maintained at an adequate level (30%). This is particularly important for females specializing in long-duration events. With protein balance, it has been shown that a negative nitrogen balance is more often observed in female athletes than in male athletes. It is therefore especially important to ensure that this remains the case during periods of caloric restriction, especially when working with female athletes showing a tendency to limit their caloric intake on a daily basis. In the post-exercise period, females display lower thermolytic capacities than males. Therefore, the use of cooling recovery methods following exercise, such as cold water immersion or the use of a cooling vest, appear particularly beneficial for female athletes. In addition, a greater decrease in arterial blood pressure is observed after exercise in females than in males. Given that the return to homeostasis after a brief intense exercise appears linked to maintaining good venous return, it is conceivable that female athletes would find a greater advantage to active recovery modes than males. This article reviews some of the major gender differences in the metabolic, inflammatory and thermoregulatory response to exercise and its subsequent recovery. Particular attention is given to the identification of which recovery strategies may be the most pertinent to the design of training programmes for athletic females, in order to optimize the physiological adaptations sought for improving performance and maintaining health.

Carbohydrate-protein ingestion improves subsequent running capacity towards the end of a football-specific intermittent exercise

The majority of football players succumb to fatigue towards the end of the game. This study was designed to examine the influence of protein coingestion with carbohydrate (CHO) vs. an isocaloric CHO supplement on subsequent running capacity towards the end of a simulated football match. Six male amateur football players participated in 3 trials applied in a randomized cross-over experimental design. A laboratory-based, football-specific intermittent exercise was allocated for 75 min interspersed with a 15-min recovery, immediately followed by run time to fatigue (RTF) at 80% peak oxygen consumption. In each trial, prior to exercise and during half-time, participants randomly ingested a placebo (PLC), 6.9% CHO, or 4.8% CHO plus 2.1% protein (CHO-P) supplements matched for color and taste. CHO-P resulted in longer RTF (23.02 ± 5.27 min) than did CHO (16.49 ± 3.25 min) and PLC (11.00 ± 2.80 min) (p < 0.05). Blood glucose was higher in CHO-P at the point of fatigue (4.68 ± 0.64) compared with CHO and PLC (3.92 ± 0.29 and 3.66 ± 0.36, respectively; p < 0.05). Ratings of perceived exertion were lower in the CHO-P subjects at the onset of exercise and towards the end of intermittent exercise when compared with the PLC and CHO subjects (p < 0.05). When protein was added to a CHO supplement, subsequent running capacity following limited recovery from intermittent exercise was enhanced. This improvement suggests that protein coingestion may exert an ergogenic benefit upon endurance capacity during intermittent activity.