Journal of Applied Physiology
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J Appl Physiol (August 15, 2003). doi:10.1152/japplphysiol.00724.2002
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Submitted on August 6, 2002
Accepted on August 7, 2003

EFFECTS OF AGE ON HUMAN MUSCLE TORQUE, VELOCITY AND POWER IN TWO MUSCLE GROUPS

Ian R Lanza1, Theodore F Towse1, Graham E Caldwell1, Danielle B Wigmore1, and Jane A Kent-Braun1*

1 Exercise Science, University of Massachusetts, Amherst, Amherst, MA, USA

* To whom correspondence should be addressed. E-mail: janekb{at}excsci.umass.edu.

The purpose of this study was to test the hypotheses that, under isovelocity conditions, older compared to young humans would 1) be slower to reach target velocity, and 2) exhibit a downward shift in the torque-velocity and power-velocity relationships in the ankle dorsiflexor and knee extensor muscles. We studied 12 young (26±5 yrs, 6M/6F) and 12 older (72±6 yrs, 6M/6F) healthy adults during maximal voluntary concentric contractions at pre-set target velocities (dorsiflexion: 0-240°/s; knee extension: 0-400°/s) using an isokinetic dynamometer. Time to target velocity was longer in older subjects in the dorsiflexors and knee extensors (p <= 0.02, both). Averaged across all velocities, older subjects produced ~26% less concentric torque and power in the dorsiflexors (p < 0.01) and ~32% less in the knee extensors (p < 0.01). The downward shift in the torque-velocity relationship persisted even when torque was expressed relative to each subject's maximum. In the knee extensors only, the age-related decrement in power increased with increasing velocities, suggesting that this muscle group may be more susceptible to age-related losses of function than are the dorsiflexor muscles. In support of our hypotheses, these results demonstrate an age-related impairment in the dynamic performance of two functionally distinct muscle groups in healthy older adults. With age, the impairment of dynamic performance appears to exceed the loss of isometric performance, particularly in the knee extensor muscles.




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