DIFFERENCES IN MUSCLE ENDURANCE AND RECOVERY BETWEEN FALLERS AND NONFALLERS, AND BETWEEN YOUNG AND OLDER WOMEN

Background. Significant morbidity and mortality are associated with fa lls in older adults. We tested the hypothesis that older women with a history of falls demonstrate decreased muscle endurance and longer rec overy times following fatiguing exercise. Methods. We evaluated dynami c endurance and recoverability of the quadriceps femoris of 29 young w omen (YW) (M age = 21.7), 26 older women with a history of falls (FA) (M age = 73.3), and 27 older women with no history of falls (NF) (M ag e = 71.2) using an isokinetic dynamometer. Subjects performed repeated maximal concentric knee extensions until the force output of two cons ecutive repetitions fell below 50% of their maximal voluntary contract ion (MVC). Recovery was defined as the time required for the return of force output greater than or equal to 80% MVC for 2 consecutive repet itions, within a set consisting of 3 maximal contractions. One-minute rest was allowed between sets. We collected electromyographic (EMG) da ta from the quadriceps during all testing to evaluate spectral shifts. Results. ANOVA with a post-hoc Bonferroni-Dunn test revealed time to fatigue was significantly faster in FA than YW (p < .02) and in FA tha n NF (p < .05), but not different between YW and NF. Time to recovery was significantly slower in FA than YW (p = .01), but not different be tween YW and NF, or between FA and NF. EMG median frequency power shif t (from the beginning to the end of the test) was significantly less i n FA (p < .001) than either YW (p < .002) or NF (p < .05). Conclusions . Older women with a history of falls demonstrate decreased muscular e ndurance compared to YW and NF and increased time to recover from fati guing exercise when compared to young women.