Abstract
Introduction: Protein supplementation is proposed to promote recovery and adaptation following endurance exercise. While prior literature demonstrates improved performance when supplementing protein during or following endurance exercise, chronic supplementation research is limited.Methods: Runners (VO2peak = 53.6 ± 8.9 ml/kg/min) were counter-balanced into a placebo group (PLA; n = 8) or protein group (PRO; n = 9) based on sex and VO2peak, and underwent 10 weeks of progressive endurance training. Prior to training, body composition, blood cell differentials, non-invasive mitochondrial capacity using near-infrared spectroscopy, and a 5 km treadmill time trial (TT) were evaluated. Progressive training then commenced (5–10% increase in weekly volume with a recovery week following 3 weeks of training) whereby PRO supplemented with 25 g of whey protein following workouts and prior to sleep (additional 50 g daily). PLA supplemented similarly with a < 1 g sugar pill per day. Following training, participants were reanalyzed for the aforementioned tests.Results: VO2peak and initial 5 km TT were not significantly different between groups. PRO consumed significantly more dietary protein throughout the training period (PRO = 132 g/d or 2.1 g/kg/day; PLA = 84 g/d or 1.2 g/kg/day). Running volume increased significantly over time, but was not significantly different between groups throughout training. Blood measures were unaltered with training or supplementation. Mitochondrial capacity trended toward improving over time (time p = 0.063) with no difference between groups. PLA increased lean mass 0.7 kg (p < 0.05) while PRO experienced infinitesimal change (−0.1 kg, interaction p = 0.049). PLA improved 5 km TT performance 6.4% (1 min 31 s), while PRO improved only 2.7% (40 s) (interaction p = 0.080).Conclusion: This is the first evidence to suggest long-term protein supplementation during progressive run training is not beneficial for runners.
Highlights
Protein supplementation is proposed to promote recovery and adaptation following endurance exercise
placebo group (PLA) improved 5 km time trial (TT) performance 6.4% (1 min 31 s), while protein group (PRO) improved only 2.7% (40 s)
Our findings refute the hypothesis that protein supplementation would facilitate better improvements in body composition and 5 km TT performance compared to placebo supplementation/run training alone
Summary
Protein supplementation is proposed to promote recovery and adaptation following endurance exercise. While prior literature demonstrates improved performance when supplementing protein during or following endurance exercise, chronic supplementation research is limited. There is a general consensus that dietary protein is important for refueling, skeletal muscle recovery, and adaptation following endurance exercise [5], especially given amino acids can contribute as high as 20% of total energy yield during exhaustive exercise [6, 7]. Leucine oxidation is increased with endurance exercise [8,9,10] limiting its contribution to normal anabolic and recovery processes in skeletal muscle [11]. Post-exercise protein supplementation seemingly provides an opportunity to mitigate muscle damage and enhance recovery in endurance athletes
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