Neuromuscular Responses to Dorsiflexors and Plantarflexors Fatigue During Backward Leaning

Neuromuscular Responses to Dorsiflexors and Plantarflexors Fatigue During Backward LeaningMuscle fatigue may compromise postural control, but its effects on neuromuscular coordination during backward leaning remain unclear.This study examined how plantarflexor and dorsiflexor fatigue affect center of pressure (COP) dynamics, ankle muscle activity, intermuscular coherence, and electromyography (EMG)-COP coupling during backward leaning.Twenty healthy young adults completed separate plantarflexor and dorsiflexor fatigue sessions involving sustained isometric contractions.Participants maintained a backward lean at 70% of their stability limit with eyes open or closed, before, during, and five minutes after fatigue.Fatigue increased COP mean velocity and irregularity without significantly affecting sway area.Tibialis anterior (TA) activity increased during fatigue with eyes closed, whereas medial gastrocnemius (MG) activity and ankle co-contraction decreased post-fatigue.TA-MG coherence increased across frequency bands spanning 0-40 Hz during fatigue.EMG-COP cross-correlation revealed stronger TA-anteroposterior and weaker MG-mediolateral associations during fatigue.Few fatigue-related responses differed between plantarflexor and dorsiflexor protocols, while visual input primarily influenced TA activity.Together, these findings suggest that ankle fatigue may elicit compensatory neuromuscular adjustments to sustain backward leaning, resulting in altered postural dynamics without a significant increase in sway.