Neurobiology of muscle fatigue.
Muscle fatigue encompasses a class of acute effects that impair motor performance. The mechanisms that can produce fatigue involve all elements of the motor system, from a failure of the formulation of the descending drive provided by suprasegmental centers to a reduction in the activity of the contractile proteins. We propose four themes that provide a basis for the systematic evaluation of the neural and neuromuscular fatigue mechanisms: 1) task dependency to identify the conditions that activate the various mechanisms; 2) force-fatigability relationship to explore the interaction between the mechanisms that results in a hyperbolic relationship between force and endurance time; 3) muscle wisdom to examine the association among a concurrent decline in force, relaxation rate, and motor neuron discharge that results in an optimization of force; and 4) sense of effort to determine the role of effort in the impairment of performance. On the basis of this perspective with an emphasis on neural mechanisms, we suggest a number of experiments to advance our understanding of the neurobiology of muscle fatigue.
Enoka
R M
RM
Department of Physiology, University of Arizona, Tucson 85721.
Stuart
D G
DG
D000818:Animals; D004734:Energy Metabolism; D005221:Fatigue / Q000503:physiopathology*; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D009446:Neurobiology; D005082:Physical Exertion / Q000502:physiology