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. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 98–106, 2001