Cerebellar Excitability Regulates Physical Fatigue Perception

Fatigue is the subjective sensation of weariness, increased sense of effort, or exhaustion and is pervasive in neurologic illnesses. Despite its prevalence, we have a limited understanding of the neurophysiological mechanisms underlying fatigue. The cerebellum, known for its role in motor control and learning, is also involved in perceptual processes. However, the role of the cerebellum in fatigue remains largely unexplored. We performed two experiments to examine whether cerebellar excitability is affected after a fatiguing task and its association with fatigue. Using a crossover design, we assessed cerebellar inhibition (CBI) and perception of fatigue in humans before and after fatigue and control tasks. Thirty-three participants (16 males, 17 females) performed five isometric pinch trials with their thumb and index finger at 80% maximum voluntary capacity (MVC) until failure (force ,40% MVC; fatigue) or at 5% MVC for 30 s (control). We found that reduced CBI after the fatigue task correlated with a milder perception of fatigue. In a follow-up experiment, we investigated the behavioral consequences of reduced CBI after fatigue. We measured CBI, perception of fatigue, and performance during a ballistic goal-directed task before and after the same fatigue and control tasks. We replicated the observation that reduced CBI after the fatigue task correlated with a milder perception of fatigue and found that greater endpoint variability after the fatigue task correlated with reduced CBI. The proportional relation between cerebellar excitability and fatigue indicates a role of the cerebellum in the perception of fatigue, which might come at the expense of motor control.

Automated summary

Fatigue is a common sensation in neurologic illnesses, but the neurophysiological mechanisms underlying it are not well understood. This study conducted two experiments to investigate the changes in cerebellar excitability after a fatiguing task and its association with fatigue. The results showed that reduced cerebellar inhibition after the fatigue task correlated with a milder perception of fatigue. Another experiment found that reduced cerebellar inhibition after fatigue was associated with increased endpoint variability in motor performance. These findings suggest that the cerebellum plays a role in the perception of fatigue, potentially at the expense of motor control.