Light-load resistance exercise increases muscle protein synthesis and hypertrophy signaling in elderly men

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.