G-15T Free Communication/Poster Protein Metabolism
An increase in mixed muscle protein fractional synthetic rate (FSR) following a resistance training bout is well documented. However, the impact of endurance exercise on mixed muscle FSR have not been well characterized in trained athletes.
To evaluate FSR responses to a prolonged submaximal intensity run in competitive runners.
A primed, continuous infusion of [2H5]-Phenylalanine was used to measure FSR in the vastus lateralis muscle of male endurance runners (n=3, 23 yrs, 71 kg, 180 cm, 9% body fat, VO2peak 72 ± 4 ml/kg/min) on two separate occasions, at rest and following a 75 minute endurance run at 70% VO2peak. Protein intakes for subjects were determined from 3 day dietary food records (rest) and controlled feeding (postexercise) using Nutritionist Pro software. Mean FSR values at rest and postexercise were analyzed using a paired Student's t-test to evaluate rest vs. postexercise FSR responses.
Dietary protein intakes were similar between FSR assessments for each athlete and ranged from 0.9 to 1.8 g/kg/body weight. While there were no statistically significant differences between subjects for each assessment, there was an 80% increase in FSR from rest to postexercise (0.06 ± 0.01 vs. 0.11 ± 0.02 %/hr, p = 0.009).
The increase in FSR in competitive distance runners following an endurance run, was similar to, and in some cases greater than, increases previously noted after a resistance exercise bout in strength trained individuals. Future studies specifically designed to contrast effects of mode of exercise on skeletal muscle protein metabolism are warranted. Supported in part by the NCBA and the UCRF.