Effects of sensorimotor trunk impairments on trunk and upper limb joint kinematics and kinetics during sitting pivot transfers in individuals with a spinal cord injury.

BACKGROUND Depending on the level and severity of the sensorimotor impairment in individuals with a spinal cord injury, the subsequent reduced seated postural stability and strength generating-capacity at the upper limbs could affect performance during sitting pivot transfer. This study aimed to determine the effects of sensorimotor impairments on head, trunk and upper limb movement and efforts during sitting pivot transfers. METHODS Twenty-six individuals with a spinal cord injury participated and were stratified in two subgroups: with (N=15) and without voluntary motor control (N=11) of their lower back and abdominal muscles. Kinematics and kinetics of sitting pivot transfer were collected using a transfer assessment system. Mean joint angles and movement amplitudes and peak and average joint moments were compared between subgroups using independent Student t-tests (P<0.05) for the weight-bearing sitting pivot transfer phases. FINDINGS The subgroup without voluntary control of their lower back and abdominal muscles had significantly greater forward trunk flexion compared to the other subgroup resulting in higher wrist extension and elbow flexion at both upper limbs. No significant joint moment difference was found between the subgroups. INTERPRETATION Individuals with spinal cord injury who have no voluntary motor control of their abdominal and lower back muscles increase forward trunk flexion during sitting pivot transfers 1) to increase stiffness of their spine that may optimize the strength-generating ability of their thoracohumeral muscles and 2) to lower their center of mass that may facilitate lift-off and enhance the overall stability during sitting pivot transfers.