Vastus lateralis-gastrocnemius co-activation during gait is associated with reactive stability to slip-like...

After stroke, neuromuscular coordination during gait is commonly characterized by increased co-activation between lower-limb muscles. Although such alterations are well described during steady walking, their relevance for reactive balance control following unexpected perturbations remains unclear.

To examine the association between vastus lateralis-gastrocnemius medialis (VL-GM) co-activation during gait and reactive balance performance following unexpected slip-like perturbations in individuals with chronic stroke.

Thirty-seven individuals with chronic stroke completed overground gait assessment with surface electromyography to quantify VL-GM coordination during stance. Peak Activation Interval between VL-GM (PAI__VL-GM) and Co-activation Amplitude Index (CAI__VL-GMmax and CAI__GM-VLmax) were computed. In a separate protocol, participants were exposed to unexpected slip-like perturbations induced by a moveable platform during walking. Reactive balance performance was quantified using a dimensionless center-of-mass (CoM) stability metric at the first recovery step.

Higher PAI__VL-GM was associated with greater CoM stability. Additoinally, participants who fell showed lower PAI__VL-GM and higher CAI__GM-VLmax than those who recovered balance.

Gait-phase VL-GM EMG coordination is closely associated with reactive balance control after slip-like perturbations in chronic stroke.