A Biomechanical Analysis of Caregiver Assisted Wheelchair to Car Transfers

Car transfers for patients with mobility impairments are risky for caregivers due to constrained spaces and high biomechanical stresses. This study aimed to measure muscle activations and spine loads comparing the manual transfer method with a modified lifter prototype. Muscle activations at eight key muscles using surface electromyography and lumbar loads at the L5/S1 disk using full-body motion tracking, and force plates were evaluated. A total of 13 participants took part in the study. An Analysis of Covariance (ANCOVA) showed that patient weight significantly influenced lumbar loads while caregiver experience and height did not. After adjusting for patient weight, average peak axial compression forces and anterior-posterior (AP) shear forces were significantly lower when the lifter prototype was used (both p < 0.001). Significant reductions in muscle activations were also found with the lifter prototype for the left and right erector spinae longissimus (p < 0.001 and p = 0.028, respectively), left anterior deltoid (p = 0.007) and left biceps brachii (p = 0.003). This study provides the first biomechanical evaluation of car transfers on caregiver, highlighting the high loads experienced. The significant reductions in both lumbar loads and muscle activations with the prototype lifter prove that better interventions are needed to make this process safer for all parties involved.