Changes in muscle cross‐sectional area and strength during leg immobilization: amelioration through resistance exercise with or without whey protein supplementation

We aimed to determine the effectiveness of low volume resistance exercise, alone or in combination with a whey protein supplement, on muscle mass and strength after unilateral leg immobilization in humans. Sixteen recreationally active participants (23.9±5.0 yr; BMI = 25.4±3.6 kg·m−2) were divided into three groups: exercise (EX; n=6), whey protein supplementation with exercise (WHY+EX; n=6), and control (CON; n=4). All subjects wore a knee‐immobilization brace and were non‐weight bearing for 14 days. Exercise was one set of ten repetitions of leg press, knee extension, and seated calf raises every other day, at 80% of one repetition maximum. WHY+EX consumed 60g of whey protein daily while EX and CON consumed an isocaloric carbohydrate beverage. Immobilization induced a significant reduction (p<0.05) in thigh cross‐sectional area (CSA), knee extensor strength, and plantar flexion strength in CON but not in EX and WHY+EX. There were significant losses in lower leg CSA for all three groups, with losses tending to be lower in both the EX and WHY+EX groups versus CON (p=0.065). We conclude that a low volume of resistance exercise is an effective countermeasure against atrophy and strength loss during immobilization. There was no additional benefit of a daily whey protein supplement in maintaining muscle mass or strength. Supported by NSERC and CIHR.