Effects of visual feedback and force level on bilateral ankle-dorsiflexion force control

•Visual feedback improved bilateral ankle-dorsiflexion force control performances.•Interlimb force coordination was enhanced when visual feedback was available.•Stabilizing synergy correlated with improved bilateral force control performances.•Visuomotor processing may be important for fine motor control between both feet. This study investigated the potential effects of visual feedback and force level on bilateral force control capabilities in the lower limbs. Thirty-nine healthy young adults performed bilateral ankle-dorsiflexion isometric force control tasks for different visual feedback conditions, including continuous visual feedback (CVF) and withdrawal of visual feedback (WVF), indicating the removal of visual feedback on force outputs during the task and force level conditions (i.e., 10 % and 40 % of the maximum voluntary contraction). Bilateral force control capabilities were estimated using force accuracy, variability, regularity, and absolute power in 0–4 Hz and interlimb coordination by cross-correlation with time lag and uncontrolled manifold (UCM) variables. Correlation analyses determined the relationship between changes in bilateral force control capabilities and interlimb coordination from the CVF to WVF conditions. The findings revealed better bilateral force control capabilities in the CVF condition as indicated by less force error, variability, regularity, absolute power in 0–4 Hz, and advanced interlimb force coordination. From CVF to WVF conditions, increased bad variability correlated with greater force control deficits. These findings suggest that visuomotor processing is an important resource for successful fine motor control in the lower limbs.