Effects of Cadence Control on Upper-Limb Kinematics and Muscle Activation During Manual Wheelchair Propulsion in Individuals with Spinal Cord Injury.

Manual wheelchair propulsion is a frequent activity among people with spinal cord injury (SCI) and is linked to upper limb loading and shoulder pain. We compared propulsion strategies at cadences of 30 and 50 bpm. Kinematics and surface electromyography (EMG) were recorded across the propulsion cycle, push/recovery phases, and events. Ranges of motion for shoulder flexion/extension, adduction/abduction, and elbow flexion/extension did not differ significantly, although ROM tended to be smaller at 50 bpm; push angle was larger at 50 bpm but not significant. Propulsion cycle duration was shorter at 50 bpm (p < 0.001). Push duration was similar, but its proportion of the cycle increased at 50 bpm (p < 0.001). Recovery duration was shorter at 50 bpm (p < 0.001), yet its cycle proportion increased (p < 0.01). EMG showed cadence-specific redistribution: higher activity at 50 bpm at preparation (anterior deltoid, pectoralis major, biceps brachii, upper trapezius; p < 0.01) and at contact (posterior deltoid; p < 0.05); higher biceps brachii at release and higher anterior deltoid at end-range extension at 30 bpm (both p < 0.05). Cadence manipulation reorganized timing and muscle demands without large ROM changes, supporting rhythm-based training and propulsion design to mitigate shoulder loading.