Skeletal Muscle Protein Turnover in Healthy Men and Women Following an Endurance Exercise Bout

Abstract

2208 While endurance exercise has been shown to significantly impact whole body protein metabolism, there is currently a paucity of data examining its effect on skeletal muscle protein utilization. PURPOSE: To determine the impact of an endurance exercise session on skeletal muscle protein fractional synthetic rate (FSR), fractional breakdown rate (FBR), and NET balance (FSR-FBR) in healthy, endurance trained men and women (6 weeks, 30–45 min, 3–5 d/week, ≥ 65% HR max). METHODS: Primed continuous infusions of [2H5]phenylalanine (FSR) and [15N]phenylalanine (FBR) were used to assess skeletal muscle protein turnover via the precursor-product method at rest and following a 45 min run at 65% VO2 max in eight endurance trained men and women (21.1 yrs, 163.8 cm, 74.9 kg, 33.7% body fat, VO2 max 42.3 ml/kg/min) fed eucaloric diets containing the RDA for protein (0.8 g/kg/d). RESULTS: There was a trend for an increase in both FSR (0.089 ± 0.006 vs. 0.124 ± 0.026 %h, p = 0.14) and FBR (0.143 ± 0.018 vs. 0.209 ± 0.044 %h, p = 0.11) from rest to post exercise. NET balance was negative and did not differ from rest to post exercise (−0.072 ± 0.012 vs. −0.072 ± 0.035 %h). CONCLUSION: Skeletal muscle protein turnover appears to be upregulated in response to an acute endurance exercise bout as evidenced by the trend for an increase in both FSR and FBR. However, NET balance did not change. Additional research is needed to further characterize the impact of an endurance exercise bout on skeletal muscle protein metabolism. Supported in part by the American Egg Board