Dietary protein to support muscle hypertrophy

Intact protein, protein hydrolysates, and free amino acids are popular ingredients in contemporary sports nutrition, and have been suggested to augment post-exercise recovery. Protein and/or amino acid ingestion stimulates skeletal muscle protein synthesis, inhibits protein breakdown and, as such, stimulates muscle protein accretion following resistance and endurance type exercise. This has been suggested to lead to a greater adaptive response to each successive exercise bout, resulting in more effective muscle reconditioning. Despite limited evidence, some basic guidelines can be defined regarding the preferred type, amount, and timing of dietary protein that should be ingested to maximize post-exercise muscle protein accretion. Whey protein seems most effective in stimulating muscle protein synthesis during acute post-exercise recovery. This is likely attributable to its rapid digestion and absorption kinetics and specific amino acid composition. Ingestion of approximately 20 g protein during and/or immediately after exercise is sufficient to maximize post-exercise muscle protein synthesis rates. Coingestion of a large amount of carbohydrate or free leucine is not warranted to further augment post- exercise muscle protein synthesis when ample protein is already ingested. Future research should focus on the relevance of the acute anabolic response following exercise to optimize the skeletal muscle adaptive response to exercise training

Nutritional strategies to promote postexercise recovery

During postexercise recovery, optimal nutritional intake is important to replenish endogenous substrate stores and to facilitate muscle-damage repair and reconditioning. After exhaustive endurance-type exercise, muscle glycogen repletion forms the most important factor determining the time needed to recover. Postexercise carbohydrate (CHO) ingestion has been well established as the most important determinant of muscle glycogen synthesis. Coingestion of protein and/or amino acids does not seem to further increase muscle glycogensynthesis rates when CHO intake exceeds 1.2 g x kg-1 x hr-1. However, from a practical point of view it is not always feasible to ingest such large amounts of CHO. The combined ingestion of a small amount of protein (0.2-0.4 g x kg-1 x hr-1) with less CHO (0.8 g x kg-1 x hr-1) stimulates endogenous insulin release and results in similar muscle glycogen-repletion rates as the ingestion of 1.2 g x kg-1 x hr-1 CHO. Furthermore, postexercise protein and/or amino acid administration is warranted to stimulate muscle protein synthesis, inhibit protein breakdown, and allow net muscle protein accretion. The consumption of ~20 g intact protein, or an equivalent of ~9 g essential amino acids, has been reported to maximize muscle protein-synthesis rates during the first hours of postexercise recovery. Ingestion of such small amounts of dietary protein 5 or 6 times daily might support maximal muscle protein-synthesis rates throughout the day. Consuming CHO and protein during the early phases of recovery has been shown to positively affect subsequent exercise performance and could be of specific benefit for athletes involved in multiple training or competition sessions on the same or consecutive days

No improvement in endurance performance after a single dose of beetroot juice.

INTRODUCTION: Dietary nitrate supplementation has received much attention in the literature due to its proposed ergogenic properties. Recently, the ingestion of a single bolus of nitrate-rich beetroot juice (500 mL; ~6.2 mmol NO3-) was reported to improve subsequent time trial performance. However, this large volume of ingested beetroot juice does not represent a realistic dietary strategy for athletes to follow in a practical, performance-based setting. Therefore, we investigated the impact of ingesting a single bolus of concentrated nitrate-rich beetroot juice (140 mL; ~8.7 mmol NO3-) on subsequent 1 h time trial performance in well-trained cyclists. METHODS: Using a double-blind, repeated-measures crossover design (1 wk washout period), 20 trained male cyclists (26+/-1 y; O2peak=60+/-1 mL.kg-1.min-1; Wmax=398+/-7.7 W) ingested 140 mL of concentrated beetroot juice (8.7 mmol NO3-; BEET) or a placebo (nitrate-depleted beetroot juice; PLAC) with breakfast 2.5 h prior to an ~1 h cycling time trial (1073+/-21 kJ). Resting blood samples were collected every 30 min following BEET or PLAC ingestion and immediately post the time trial. RESULTS: Plasma nitrite concentration was higher in BEET vs PLAC prior to the onset of the time trial (532+/-32 vs 271+/-13 nM; P0.05). CONCLUSION: Ingestion of a single bolus of concentrated (140 mL) beetroot juice (8.7 mmol NO3-) does not improve subsequent 1 h time trial performance in well-trained cyclists

Eccentric exercise increases satellite cell content in type II muscle fibers.

CERMAK, N. M., T. SNIJDERS, B. R. MCKAY, G. PARISE, L. B. VERDIJK, M. A. TARNOPOLSKY, M. J. GIBALA, and L. J. C. VAN LOON. Eccentric Exercise Increases Satellite Cell Content in Type II Muscle Fibers. Med. Sci. Sports Exerc., Vol. 45, No. 2, pp. 230–237, 2013. Introduction: Satellite cells (SCs) are of key importance in skeletal muscle tissue growth, repair, and regeneration. A single bout of high-force eccentric exercise has been demonstrated to increase mixed muscle SC content after 1–7 d of postexercise recovery. However, little is known about fiber type–specific changes in SC content and their activation status within 24 h of postexercise recovery. Methods: Nine recreationally active young men (23 T 1 yr) performed 300 eccentric actions of the knee extensors on an isokinetic dynamometer. Skeletal muscle biopsies from the vastus lateralis were collected preexercise and 24 h postexercise. Muscle fiber type–specific SC content and the number of activated SCs were determined by immunohistochemical analyses. Results: There was no difference between Type I and Type II muscle fiber SC content before exercise. SC content significantly increased 24 h postexercise in Type II muscle fibers (from 0.085 T 0.012 to 0.133 T 0.016 SCs per fiber, respectively; P G 0.05), whereas there was no change in Type I fibers. In accordance, activation status increased from preexercise to 24 h postexercise as demonstrated by the increase in the number of DLK1+ SCs in Type II muscle fibers (from 0.027 T 0.008 to 0.070 T 0.017 SCs per muscle fiber P G 0.05). Although no significant changes were observed in the number of Ki-67+ SCs, we did observe an increase in the number of proliferating cell nuclear antigen-positive SCs after 24 h of postexercise recovery. Conclusion: A single bout of high-force eccentric exercise increases muscle fiber SC content and activation status in Type II but not Type I muscle fibers

Acute Ketone Monoester Supplementation Impairs 20-min Time-Trial Performance in Trained Cyclists: A Randomized, Crossover Trial

Acute ketone monoester (KE) supplementation can alter exercise responses, but the performance effect is unclear. The limited and equivocal data to date are likely related to factors including the KE dose, test conditions, and caliber of athletes studied. We tested the hypothesis that mean power output during a 20-min cycling time trial (TT) would be different after KE ingestion compared to a placebo (PL). A sample size of 22 was estimated to provide 80% power to detect an effect size dz of 0.63 at an alpha level of .05 with a two-tailed paired t test. This determination considered 2.0% as the minimal important difference in performance. Twenty-three trained cyclists (N = 23; peak oxygen uptake: 65 +/- 12 ml center dot kg-1 min-1; M +/- SD), who were regularly cycling >5 hr/week, completed a familiarization trial followed by two experimental trials. Participants self-selected and replicated their diet and exercise for -24 hr before each trial. Participants ingested either 0.35 g/kg body mass of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate KE or a flavor-matched PL 30 min before exercise in a randomized, triple-blind, crossover manner. Exercise involved a 15-min warm-up followed by the 20-min TT on a cycle ergometer. The only feedback provided was time elapsed. Preexercise venous [13-hydroxybutyrate] was higher after KE versus PL (2.0 +/- 0.6 vs. 0.2 +/- 0.1 mM, p < .0001). Mean TT power output was 2.4% (0.6% to 4.1%; mean [95% confidence interval]) lower after KE versus PL (255 +/- 54 vs. 261 +/- 54 W, p < .01; dz = 0.60). The mechanistic basis for the impaired TT performance after KE ingestion under the present study conditions remains to be determined