Protein ingestion and the ensuing hyperaminoacidemia stimulates skeletal muscle protein synthesis (MPS) in the post-exercise period. This response facilitates muscle remodeling, which is important during intensified training
. The aim of this study was to determine whether supplementation with α-Lactalbumin
(LA), with high leucine and tryptophan contents, would improve responses to short periods of intensified aerobic training compared to supplementation with an isonitrogenous quantity of collagen peptides
Endurance trained participants (5M, 6F, 24 ± 4 years, V[Combining Dot Above]O2
= 53.2 ± 9.1 ml/kg/min, Peak power output (PPO) = 320 ± 48 W; means ± SD) consumed a controlled diet (1.0 g/kg/day protein) and refrained from habitual training for 11 days while taking part in this double-blind randomized, crossover trial. The two intervention phases, which consisted of brief intensified training
(4×4-min cycling intervals at 70% of PPO on 3 consecutive days) combined with the ingestion of LA or CP supplements post-exercise (20g) and pre-sleep
(40g), were separated by 4d of washout without protein supplementation (i.e., the control phase). In response to each phase, myofibrillar (MyoPS), sarcoplasmic protein synthesis (SarcPS) rates (via 2
O ingestion) and parameters of sleep
quality were measured.
LA ingestion increased plasma leucine (p<0.001) and tryptophan concentrations (p<0.001) relative to CP. Intensified training
increased MyoPS and SarcPS above the washout phase in LA- and CP- supplemented phases (p<0.01), with increases being 13 ± 5% and 5 ± 7% greater with LA than CP for MyoPS (p<0.01) and SarcPS, respectively (p<0.01).
Despite an isonitrogenous diet, MPS was enhanced to a greater extent when trained participants consumed LA compared to CP during intensified aerobic training, suggesting protein quality is an important consideration for endurance-trained athletes aiming to augment adaption to exercise training.