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laroche - Biodynamics Elderly Women Have Blunted Response...

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Biodynamics Elderly Women Have Blunted Response to Resistance Training Despite Reduced Antagonist Coactivation DAIN P. LAROCHE 1 , STEVEN J. ROY', CHRISTOPHER A. KNIGHT 3 , and JENNIFER L. DICKIE 2 'Department of Kinesiology, University of New Hampshire, Durham, NH; 2Department of Environmental and Health Sciences, Johnson State College, Johnson, VT; and 3 Department of Health, Nutrition Delaware, Newark, DE ABSTRACT LAROCHE, D. P., S. J. ROY, C. A. KNIGHT, and J. L. DICKIE. Elderly Women Have Blunted Response to Resistance Training Despite Reduced Antagonist Coactivation. Med. Sci. Sports Exerc., Vol. 40, No. 9, pp. 1660-1668, 2008. Purpose: To test the ability of a combination high-velocity/high-resistance training program to enhance knee extensor muscle strength, power, nervous activation of muscle, and muscle activation time in inactive women and compare the response to training between young and old women. Methods: The study involved 49 inactive women, with young (18-33 yr, n = 25) and old (65-84 yr, n = 24) distributed to training and control groups using blocked randomization. Electrically evoked muscle twitches were measured for the knee extensors; then maximal, voluntary, isometric knee extensions were performed in a visually cued reaction time (RT) task, followed by 8 wk of explosive resistance training. Results: Training increased peak torque (+12%, P = 0.03) and reduced antagonist coactivation (- 13%, P = 0.02) similarly for both age groups. Young training group increased the rate of torque development by 34% compared to young controls (-7%), old training (+9%), and old controls (+8%) (P = 0.002). Young training group increased impulse by 53%, which was greater than young controls (- 11%), old training (+12%), and old controls (+9%) (P = 0.001). Resistance training did not change electrically evoked twitch, RT (premotor time, motor time, or reaction time), or nervous activation measures (onset EMG amplitude or rate of EMG rise). Conclusions: Explosive force training was ineffective at enhancing muscle twitch characteristics, neural drive, or RT in young or old women. It did enhance peak muscle force in both young and old, modulated through a reduction in antagonist coactivation. Older participants showed less of an improvement in the rate of torque development and contractile impulse than young, indicating either that this sample of older women had a reduced capacity to develop muscle power or that the 8-wk isokinetic resistance training program used in this study was not a sufficient stimulus for adaptation. Key Words: ELECTROMYOGRAPHY, AGING, COCONTRACTION, STRENGTH, NERVOUS ACTIVATION, REACTION TIME A decline in muscle function with aging has been well documented and has been associated with gait abnormalities, balance, and fall risk (3,23,27,30). The increase in fall risk is strongly correlated with muscle
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laroche - Biodynamics Elderly Women Have Blunted Response...

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