Fatigue of elbow flexor muscles in younger and older adults.

The aim of this study was to assess differences in the behavior of fatigue-related measures of neuromuscular function between younger (n = 10; 20-35 years) and older (n = 11; >65 years) healthy adults. Measures reflecting changes in voluntary activation, neuromuscular propagation, metabolite build-up, and excitation-contraction coupling processes were taken before, during, and after a sustained maximum elbow-flexion fatigue task. We found a greater role for a failure in voluntary activation (central fatigue) in about half of the older subjects compared with none of the younger subjects to explain the decrease in force-generating capacity with sustained activity. In contrast, similar behaviors in measures reflecting changes in peripheral mechanisms were noted for the two age groups. These results point to a potential shift in fatigue mechanisms with age, with a greater contribution of central fatigue in some older adults. Copyright 2001 John Wiley & Sons, Inc.