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MAXIMAL AND RAPID FORCE PRODUCTION IN YOUNG AND MIDDLE-AGED WOMEN FOR LOWER AND UPPER BODY

Abstract

BACKGROUND: Age-related reductions in rapid force production are more dramatic than maximal force, but this has been primarily shown in lower body muscle groups and older adults. Decrements are likely in middle age, yet studies involving this age group and women are lacking. The purpose of our study was to determine age-related differences in maximal and rapid force parameters for handgrip and plantar flexor testing. METHODS: Healthy, untrained young (n = 16; age = 21 ± 2 yrs) and middle-aged (n = 13; age = 55 ± 2 yrs) women completed a testing visit 3-7 days following a familiarization session. Subjects performed rapid, maximal isometric plantar flexion and handgrip actions using an isokinetic (torque) and hand-held electronic dynamometer (force), respectively. Maximal force (or torque) was considered the highest 500 ms rolling average. Rate of force development (slope of force-time curve) and absolute force were calculated at 30, 50, 100, and 200 ms (RFD0-200 and F200, respectively) after contraction onset. Given the different devices and units, independent samples t-tests and effects sizes (g) were used to compare age groups for each testing modality. RESULTS: RFD0-200 (p = 0.036; g = 0.67) and F200 (p = 0.034; g = 0.70) were significantly lower in middle-aged women for the plantar flexors, whereas only a moderate effect size was shown for maximal force (p = 0.055; g = 0.59). There were no age-related differences for handgrip (p > 0.05; g ≤ 0.23). CONCLUSIONS: Rapid force production, particularly the latter phase, was decreased more than maximal force in middle-aged women for the lower body. No age-related differences were found for maximal or rapid force production of the upper body. These findings indicate a preferential decrease in lower body rapid force production occurs prior to older adulthood. Given the importance of rapid force production for physical function, this highlights the importance of exercise targeting rapid force adaptations prior to later life.

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