Differential Effect of Aging on Acute Hormonal Response to Low-Volume Resistance Exercise

Abstract

Age associated decrease in skeletal muscle mass and function (sarcopenia) leads to an increased risk of fall, fracture, and bedridden. Resistance exercise has been shown to be a useful intervention to increase skeletal muscle mass and strength; however, aging seems to blunt the acute hormonal response to high-intensity, high-volume resistance exercise. PURPOSE: To investigate the acute effect of a traditional resistance exercise protocol (i.e. low-volume and high-intensity) on hormonal responses in healthy young and older men. METHODS: Fourteen old men (68 ± 6.8 yrs, 64 ± 4kg) and eight young men (23 ± 1.3 yrs, 68 ± 8kg) were recruited for the study. Before the study, all subjects were assessed for muscle cross sectional area at mid-thigh, maximal knee extension and flexion strength. After taking a baseline blood sample, each subject performed a bout of resistance exercise consisting of bilateral knee extension and flexion at 70% 1-RM (3 sets of 10 reps, 3 min rest between sets). Blood samples were drawn immediately after and following exercise up to 3 hours. Blood samples were analyzed for metabolites and hormones. RESULTS: Although muscle CSA of knee extensor and flexor muscles as well as maximal isometric knee extension and flexion strength were significantly higher in young men as compared to older men(P<0.05), no significant difference in specific strength was observed between young and older subjects (3.24 ± 0.14 and 3.09 ± 0.15 Nm/cm2, P>0.1). In response to a bout of resistance exercise, GH increased significantly in young men, whereas no significant change was observed for older men (11.4 ± 6.0 and 1.7 ± 0.6 ng/ml for young and old; P<0.05). Although no significant change in testosterone or cortisol concentration was observed in either group in response to resistance exercise (P>0.1), hormonal concentrations were significantly suppressed in older men throughout the experiment (P<0.05). CONCLUSION: Although specific strength was well matched, hormonal responses to conventional low-volume, high-intensity resistance exercise protocol were significantly suppressed in older men as compared to those of young men. Further training study is warranted to investigate the relationship between age associated decline in hormonal response and capacity of muscle hypertrophy in older individuals.