Elderly women have blunted response to resistance training despite reduced antagonist coactivation.

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.

Explosive force and fractionated reaction time in elderly low- and high-active women.

PURPOSE: The purpose of this study was to determine whether muscle power, activation time, and neuromuscular stimulation are related to physical activity patterns in older women. METHODS: Forty women (65-84 yr) were assigned to high-active (HA) and low-active (LA) groups on the basis of a historical activity questionnaire, and then they performed a series of maximal, voluntary, isometric knee extensions in a visually cued RT task. Fractionated RT measures were taken using three landmarks in the data: the presentation of the visual stimulus, the beginning of the EMG burst, and the initiation of force development. The rate and magnitude of neural stimulation were taken from surface EMG. RESULTS: Peak torque was 15% greater, rate of torque development was 26% greater, motor time was 17% shorter, rate of EMG rise was 25% faster, and onset EMG magnitude was 15% greater in HA than in LA subjects (P<0.05). CONCLUSION: These results indicate that older women with a history of vigorous activity can generate greater force, power, and motor output in comparison with their less active peers. The lower-body mass index of the HA subjects and 310% greater volume of physical activity are likely to account for the enhanced neuromuscular function seen. It is plausible that in addition to aging, physical inactivity is responsible for a large portion of the loss of neuromuscular function seen in older adults.