THE EFFECTS OF AGE AND GENDER ON MUSCLE QUALITY RESPONSE TO STRENGTH TRAINING AND DETRAINING.

Abstract

495 The measurement of muscle quality (MQ), representing strength per unit of muscle mass, has been used to describe the relative contribution of non-muscle mass factors to the changes in strength with age and strength training (ST). To examine the effects of age and gender on the MQ response to ST and detraining (DT), 11 young men (20-30yr), 9 young women (20-30yr), 11 older men (65-75 yr), and 11 older women (65-75 yr), were assessed for quadriceps MQ at baseline, after 9 weeks of ST, and after 20 weeks of DT. MQ was calculated by dividing quadriceps 1RM strength by MRI-determined quadriceps muscle volume (MV). All groups demonstrated significant increases in IRM strength and MV after training (all P<0.05). At baseline, there was no significant difference in MQ between age groups in either gender. Baseline MQ was, however, significantly higher in young men compared to older women (P<0.05). While all groups significantly increased their MQ with training (P<0.01), the MQ gain was greater in young women than the other three groups (P<0.05). After 20 weeks of DT, MQ values remained significantly elevated above baseline levels in all groups except the older women. These results indicate that factors unrelated to muscle mass contribute to strength gains with ST in all population groups, but may account for a higher portion of the strength gains in young women. These factors continue to maintain strength levels above baseline for up to 20 weeks after cessation of training in young men and women and in older men. Supported by NIH #1AG42148