Effects of localized and general fatigue on postural adjustments coupling during predictable external perturbations

The central nervous system (CNS) coordinates anticipatory (APA) and compensatory postural adjustments (CPA) to face both self-induced and external perturbations. Neuromuscular fatigue (NMF), whether localized or general, impairs the CNS's ability to maintain postural stability, but the differential effects of these fatigue types on the coupling between APA and CPA remain unclear. This study aimed to investigate how localized and general NMF influence the neuromuscular control of postural adjustments during predictable external perturbations.

Fourteen participants were exposed to two exercise protocols: intermittent isometric exercise to induce localized NMF and prolonged upper body exercise at high cardiometabolic effort to induce general NMF. Exercise intensity was monitored by measuring cardiometabolic parameters during exercise and recovery. Postural adjustments were assessed before and after NMF (recovery period) using electromyography and kinematic analyses while participants were exposed to predictable perturbations.

Localized NMF led to decreased muscle activation and co-activation across both fatigued and non-fatigued muscles during APA, with persistent kinematic changes in lower limb joints. In contrast, general NMF induced short-lived increases in EMG activity and co-activation, reflecting a strategic CNS adaptation to maintain stability.

The results suggest that localized NMF induces a more extensive and enduring impact on postural control mechanisms, likely due to altered proprioceptive feedback, whereas general NMF effects are more transient, aligning with the rapid recovery of cardiometabolic parameters. These findings highlight the CNS's role in differentially adapting postural strategies depending on the type of fatigue, with implications for understanding how fatigue impacts stability in dynamic environments.