Alpha Progression
Central fatigue
Redirected from "CNS fatigue"
Central fatigue is an exercise-related reduction in the nervous system's ability to voluntarily activate the working muscles. The relevant processes occur upstream of the neuromuscular junction in the brain and spinal cord, which together form the central nervous system (CNS).
During a demanding task, force can decline because the neural drive reaching the muscle is reduced, because the muscle responds less effectively to that drive, or because both occur. The second category is called peripheral fatigue. Researchers can estimate central contributions by comparing voluntary force with responses produced by electrical or magnetic stimulation, but these laboratory methods are task-specific and have limitations. A review of neuromuscular fatigue during whole-body exercise describes how central and peripheral contributions can change with the exercise protocol and over the course of recovery.
In gym language, "CNS fatigue" is often used much more broadly for low motivation, sleepiness, poor coordination, or a weak day after heavy compound lifts. Those observations do not demonstrate central fatigue. They may reflect systemic fatigue, sleep loss, local muscular fatigue, psychological stress, illness, unfamiliar technique, or normal performance variation. Heavy weight also does not automatically mean that the CNS requires a fixed number of days to recover.
Central fatigue is not evidence that the brain or spinal cord has been damaged or "burned out." It is one possible contributor to an acute performance limitation, not a diagnosis based on how exhausting a workout felt. For training decisions, repeated performance under comparable conditions, effort ratings, technique, and broader recovery context are usually more actionable than trying to assign every poor session to the CNS.
