Quantitative relationship between kinematics and muscle activity during unstable sitting

Recent work suggests that kinematics-based electrical stimulation can restore trunk stability following neuromuscular impairment. However, knowledge of the relation between body motion and muscle activity during unstable sitting may be beneficial. Our objective was to quantify the spatial and temporal relationship between characteristic angular kinematics and trunk and upper leg muscle activity in unstable sitting as elicited via a wobble board. Wobble board motion and electromyograms from 14 trunk and upper leg muscles were recorded in 15 non-disabled participants sitting on a wobble board. The relationship between wobble board tilt and electromyograms was quantified using cross-correlation analysis. During unstable sitting, the trunk was found to be stabilized through direction-specific activation of the trunk and upper leg muscles, preceding wobble board displacement. Future work will use the gained insights in defining the muscle activation patterns of kinematics-based neuroprostheses that can restore trunk stability following impairment.