Comparison of Peak Shoulder and Elbow Mechanical Loads During Weight-relief Lifts and Sitting Pivot Transfers Among Manual Wheelchair Users with Spinal Cord Injury

This study compared shoulder and elbow joint forces and moments between weight-relief lifts (WRLs) and sitting pivot transfers (SPTs) among manual wheelchair users with spinal cord injury (SCI) (N = 13) during biomechanical laboratory assessment. Minimum and maximum values were reported for each triaxial component of the joint force at the dominant shoulder and elbow during SPTs (leading and trailing roles) and WRLs. Peak shoulder flexor and adductor moments, along with elbow flexor and extensor moments, observed during the same period were also analyzed. The SPTs predominantly exposed (p < 0.001) the shoulder joints to substantial posteriorly directed forces (leading = -2.6 N/kg; trailing = -3.1 N/kg) compared with WRLs (-2.2 N/kg), whereas superiorly directed forces (2.9 N/kg) were principally sustained ( p < 0.001) during WRLs compared with SPTs (leading = 1.5 N/kg; trailing = 1.5 N/kg). High superiorly directed forces (3.6 to 3.9 N/kg) were observed at the elbow, which were comparable (p = 0.33) between the two tasks. The peak shoulder flexor (leading = 1.36 N m/kg; trailing = 1.45 N m/kg) and adductor moments (leading only = -0.46 N m/kg), along with the peak elbow flexor moments (leading = 0.24 N m/kg; trailing = 0.15 N m/kg), were significantly more elevated (p < 0.021) during SPTs than during WRLs. Peak shoulder adductor (-0.46 vs -0.24 N m/kg) and elbow flexor moments were also more elevated ( p = 0.03) at the leading upper limb compared with the trailing one. The peak elbow extensor moments did not differ ( p = 0.167) between the two tasks (-0.17 to -0.25 N m/kg). SPTs exposed the shoulder and elbow joints to greater mechanical loads than WRLs among individuals with SCI.