Resistance training reduces susceptibility to eccentric exercise-induced muscle dysfunction in older women

This study evaluated the effect of age on susceptibility to muscular weakne ss and damage caused by eccentric (ECC) exercise and determined whether thi s susceptibility was altered by resistance training. Young and older women performed concentric (CON) and ECC one repetition maximum (1 RM) strength t ests of the quadriceps femoris. Older women also performed knee extension t raining for 12 weeks. Art unaccustomed bout of ECC knee extension exercise was performed before and after training, and CON and ECC 1 RM were reassess ed for 11 days after the ECC bout. Magnetic resonance imaging was used to e valuate changes in muscle water content associated with muscle damage. Befo re training, older subjects showed a larger decline in CON (p = .008) and E CC (p = .03) strength induced by the unaccustomed ECC bout, compared with t he young subjects. One day following the ECC bout, the older women showed a 24% reduction in CON and a 27% reduction in ECC 1 RM, compared with only 6 % (CON) and 10% (ECC) in the younger women. A magnetic resonance imaging ev aluation indicated that edema or damage was significantly greater in the ol der untrained women than it was in young women (p < .05), but the resistanc e-trained older women showed no greater muscle injury than the young women (p > .05). Resistance-trained older women showed no greater decline than se dentary young women in either CON (p > .05) or ECC (p > .05) strength. In c onclusion, sedentary older women are more susceptible to ECC-induced muscle dysfunction, but resistance training reduces this susceptibility.