Protein blend ingestion following resistance exercise promotes human muscle protein synthesis

Abstract

High-quality proteins such as soy, whey, and casein are all capable of promoting muscle protein synthesis postexercise by activating the mammalian target of rapamycin (mTORC1) signaling pathway. We hypothesized that a protein blend of soy and dairy proteins would capitalize on the unique properties of each individual protein and allow for optimal delivery of amino acids to prolong the fractional synthetic rate (FSR) following resistance exercise (RE). In this double-blind, randomized, clinical trial, 19 young adults were studied before and after ingestion of ∼19 g of protein blend (PB) or ∼18 g whey protein (WP) consumed 1 h after high-intensity leg RE. We examined mixed-muscle protein FSR by stable isotopic methods and mTORC1 signaling with western blotting. Muscle biopsies from the vastus lateralis were collected at rest (before RE) and at 3 postexercise time points during an early (0-2 h) and late (2-4 h) postingestion period. WP ingestion resulted in higher and earlier amplitude of blood branched-chain amino acid (BCAA) concentrations. PB ingestion created a lower initial rise in blood BCAA but sustained elevated levels of blood amino acids later into recovery (P < 0.05). Postexercise FSR increased equivalently in both groups during the early period (WP, 0.078 ± 0.009%; PB, 0.088 ± 0.007%); however, FSR remained elevated only in the PB group during the late period (WP, 0.074 ± 0.010%; PB, 0.087 ± 0.003%) (P < 0.05). mTORC1 signaling similarly increased between groups, except for no increase in S6K1 phosphorylation in the WP group at 5 h postexercise (P < 0.05). We conclude that a soy-dairy PB ingested following exercise is capable of prolonging blood aminoacidemia, mTORC1 signaling, and protein synthesis in human skeletal muscle and is an effective postexercise nutritional supplement.

Trial registration: ClinicalTrials.gov NCT01358305.

Conflict of interest statement

Author disclosures: P. T. Reidy, D. K. Walker, J. M. Dickinson, D. M. Gundermann, M. J. Drummond, K. L. Timmerman, C. S. Fry, M. S. Borack, M. B. Cope, R. Mukherjea, K. Jennings, E. Volpi, and B. B. Rasmussen, no conflicts of interest.

Figures

FIGURE 1

Schematic of randomized, double-blinded experimental protocol. Participants ingested either the PB or WP 1 h following the completion of 8 sets of knee extension RE. The small arrows represent blood draws whereas the large arrows represent biopsies. FSR, fractional synthesis rate; PB, protein blend; RE, resistance exercise; WP, whey protein.

FIGURE 2

Changes from rest in blood phenylalanine (A), leucine (B), valine (C), isoleucine (D), and total BCAA (E) concentrations in young adults during the postexercise recovery period following ingestion of the PB or WP 1 h after completion of RE. Data are mean ± SEM, n = 9 (WP) or 10 (PB). #Different from PB at that time, P < 0.05; *different from resting values for WP, P < 0.05; ^different from resting values for PB, P < 0.05. PB, protein blend; RE, resistance exercise; WP, whey protein.

FIGURE 3

FSR of the vastus lateralis in young adults during the postexercise recovery period following ingestion of the PB or WP 1 h after completion of RE. Data are presented at rest, early (0–2 h), late (2–4 h), and entire (0–4 h) postingestion periods. Data are mean ± SEM, n = 9 (WP) or 10 (PB). *Different from resting values for that group, P < 0.05. FSR, fractional synthesis rate; PB, protein blend; RE, resistance exercise; WP, whey protein.