Light-load resistance exercise increases muscle protein synthesis and hypertrophy signaling in elderly men
AJP Endocrinology and Metabolism
Published online on November 15, 2016
Abstract
Introduction. The present study investigated whether well-tolerated light-load resistance exercise (LL-RE) affects skeletal muscle fractional synthetic rate (FSR) and anabolic intracellular signaling as a way to counteract age-related loss of muscle mass. Methods. Untrained healthy men (age: +65 yrs) were subjected to 13 hours supine rest. After 21/2 hours of rest, unilateral LL-RE was conducted consisting of leg extensions (10 sets, 36 repetitions) at 16% 1RM. Subsequently, the subjects were randomized to oral intake of PULSE (4g whey protein/hour; N=10), BOLUS (28g whey protein at 0 hours and 12g whey protein at 7 hours post-exercise; N=10) or placebo (4g maltodextrin/hour; N=10). Quadriceps muscle biopsies were taken at 0, 3, 7 and 10 hours post-exercise from both the resting and exercised leg. Myofibrillar-FSR and activity of select targets from the mTORC1-signalling cascade were analyzed from the biopsies. Results. LL-RE increased myofibrillar-FSR compared to the resting leg throughout the 10h post-exercise period. The p-AKT (T308) expression increased in the exercise leg immediately after exercise. This increase persisted in the placebo group only. Levels of p-4E-BP1 (T37/46) increased throughout the post-exercise period in the exercised leg in the placebo and BOLUS group and peaked at 7h. In all three groups, p-eEF2 (T56) decreased in response to LL-RE. Conclusion. We conclude that resistance exercise at only 16% 1RM increased myofibrillar-FSR, irrespective of nutrient type and feeding pattern, which indicates an anabolic effect of LL-RE in elderly individuals. This finding was supported by increased signaling for translation initiation and translation elongation in response to LL-RE.