Whey Protein Supplementation Enhances Whole Body Protein Metabolism and Performance Recovery after Resistance Exercise: A Double-Blind Crossover Study

Abstract

No study has concurrently measured changes in free-living whole body protein metabolism and exercise performance during recovery from an acute bout of resistance exercise. We aimed to determine if whey protein ingestion enhances whole body net protein balance and recovery of exercise performance during overnight (10 h) and 24 h recovery after whole body resistance exercise in trained men. In a double-blind crossover design, 12 trained men (76 ± 8 kg, 24 ± 4 years old, 14% ± 5% body fat; means ± standard deviation (SD)) performed resistance exercise in the evening prior to consuming either 25 g of whey protein (PRO; MuscleTech 100% Whey) or an energy-matched placebo (CHO) immediately post-exercise (0 h), and again the following morning (~10 h of recovery). A third randomized trial, completed by the same participants, involving no exercise and no supplement served as a rested control trial (Rest). Participants ingested [¹⁵N]glycine to determine whole body protein kinetics and net protein balance over 10 and 24 h of recovery. Performance was assessed pre-exercise and at 0, 10, and 24 h of recovery using a battery of tests. Net protein balance tended to improve in PRO (P = 0.064; effect size (ES) = 0.61, PRO vs. CHO) during overnight recovery. Over 24 h, net balance was enhanced in PRO (P = 0.036) but not in CHO (P = 0.84; ES = 0.69, PRO vs. CHO), which was mediated primarily by a reduction in protein breakdown (PRO < CHO; P < 0.01. Exercise decreased repetitions to failure (REP), maximal strength (MVC), peak and mean power, and countermovement jump performance (CMJ) at 0 h (all P < 0.05 vs. Pre). At 10 h, there were small-to-moderate effects for enhanced recovery of the MVC (ES = 0.56), mean power (ES = 0.49), and CMJ variables (ES: 0.27-0.49) in PRO. At 24 h, protein supplementation improved MVC (ES = 0.76), REP (ES = 0.44), and peak power (ES = 0.55). In conclusion, whey protein supplementation enhances whole body anabolism, and may improve acute recovery of exercise performance after a strenuous bout of resistance exercise.

Keywords: dietary protein; ergogenic aid; net protein balance; power; strength.

Figure 1

A schematic representation of the trial day. Participants were free-living in recovery and consumed a controlled diet that mimicked their habitual dietary intake. * Exercise: on supplemented trials only; whole body, heavy resistance exercise. † Isometric maximal voluntary contraction, squat jump, Wingate test, knee extension repetitions to failure at 75% of 1-repetition maximum. ‡ Mixed-macronutrient meal. A twenty-five gram (25 g) whey protein supplement (PRO) or isocaloric carbohydrate (control; CTL) supplement. Q, nitrogen turnover; S, whole body protein synthesis; B, whole body protein breakdown; NB, whole body net protein balance. Urine collection was collected over two intervals: 0–10 h, and 10–24 h; after obtaining a sample from the 0–10 collection, both collections were pooled to obtain a 24 h recovery sample.

Figure 2

10 h whole body (WB) protein synthesis (A), protein breakdown (B), and protein balance (C), at rest (Rest) and after whole body resistance exercise supplemented with 25 g whey protein (PRO) and isocaloric carbohydrate (CHO), calculated using urinary [¹⁵N]ammonia end product enrichment. P = 0.064 for one-way (condition) repeated-measures ANOVA of whole body protein balance. Values are individual means; n = 12. WB, whole body.

Figure 3

24 h whole body (WB) protein synthesis (A), protein breakdown (B), and protein balance (C) at rest (Rest) and after whole body resistance exercise supplemented with 25 g whey protein (PRO) and isocaloric carbohydrate (CHO), calculated using the harmonic mean of urinary [¹⁵N]ammonia and urea end product enrichments. Data were analysed by one-way (condition) repeated-measures ANOVA: * CHO > PRO, P = 0.017; P = 0.11 for CHO vs. Rest. Protein breakdown: † PRO < CHO, P = 0.006. Net protein balance: ‡ PRO > Rest, P = 0.036; P = 0.11 for PRO vs. CHO. Values are individual means; n = 12.