Low Volume Resistance Exercise Prevents Loss of Muscle Mass and Function During 14 Days of Knee Immobilization

Abstract

<p> We aimed to determine the effectiveness of a low volume of high-intensity resistance exercise, alone (EX) or in combination with a whey protein supplement (WHY +EX), on prevention of muscle mass and strength loss following 14 days of knee immobilization in humans. Seventeen recreationally active (i.e., exercise ≤ 2-3 d·wk^-1) 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=5). All subjects wore a knee-immobilization brace such that one leg was completely non-weight bearing for 14d. The resistance exercise (RE) were performed unilaterally and consisted of one set of ten repetitions of leg press (with plantar flexion at full extension), knee extension, and seated calf raises every other day during the 14d immobilization period, at 80% of one repetition maximum. Subjects in the WHY+EX group consumed two 30g boluses of whey protein daily while EX and CON consumed isocaloric carbohydrate beverages. Immobilization induced a significant reduction (p<0.05) in thigh cross-sectional area (CSA), isometric knee extensor strength, and isometric 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 a tendency for losses to be mitigated in both the EX and WHY+EX groups versus CON (p=0.065). The two constituent muscles of the triceps surae muscle group showed a differential response to the RE training with the gastrocnemius showing reductions in CSA almost uniformly across the three groups whereas soleus CSA was significantly reduced in the CON (p<0.05) but not in the EX and WHY+EX groups. We conclude that a relatively low volume of high-intensity resistance exercise is an effective countermeasure against atrophy of the thigh and the soleus muscle, as well as against knee extension and plantar flexion strength loss during 14d of leg immobilization. As a countermeasure to immobilization, there is no additional benefit of consumption of a daily whey protein supplement in combination with resistance exercise in maintaining muscle mass or strength.</p>