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Recovery from muscle fatigue in young and older adults: Implications for physical function
As adults age, skeletal muscles become smaller and weaker, which can ultimately lead to declines in physical function and disability. In general, older adults produce less isometric force and dynamic power than younger adults. The effects of this weakness are amplified following a series of muscle contractions that result in muscle fatigue. Since daily routines consist of repeated series of activity followed by rest, it is important to understand how muscle recovers from fatigue. In particular, muscle power has been shown to be related to physical function and balance. Thus, understanding the process of recovery from muscle fatigue will help in preventing declines in physical function in older adults. This dissertation consisted of two studies designed to understand how muscle recover following fatigue and the implications of that recovery on physical function. Study one examined recovery from muscle fatigue following a constrained task. Young and older adults were fatigued to a similar degree using a dynamometer, and recovery of power at 4 velocities, central activation, pre-motor signaling, neural efficiency and contractile properties were recorded over an hour. To evaluate the functional implications of the recovery, ratings of perceived exertion were collected and the amount of fatigue following a second fatigue bout was also recorded. The second study associated changes in physical function and balance with power following an ecologically-relevant fatiguing exercise. Following a 30 minute treadmill walk, chair rise time and balance were measured during the period of recovery from this task. As a result of fatigue, we saw increased power loss at high-velocities that did not recover over the course of an hour in older adults. . This finding was concurrent with other velocity specific changes in rates of force development, muscle acceleration, and pre-motor neural signaling. Functionally, we saw an increased in perceived effort during contraction in older adults, and an increased fatigue during a second fatigue bout. While chair rise didn't differ as a group with fatigue, there was a significant relationship with loss of high-velocity power and change in chair rise time over the hour recovery period. Balance declined immediate post-fatigue but appeared to recover to a point of greater stability over an hour. This dissertation provides novel insight about alterations in the recovery process following an acute bout of muscle fatigue, and ultimately provides data that may be useful for developing strategies to prevent disability in older adults.
Foulis, Stephen A, "Recovery from muscle fatigue in young and older adults: Implications for physical function" (2013). Doctoral Dissertations Available from Proquest. AAI3603082.