Trunk and shoulder kinematic and kinetic and electromyographic adaptations to slope increase during motorized treadmill propulsion among manual wheelchair users with a spinal cord injury.

The main objective was to quantify the effects of five different slopes on trunk and shoulder kinematics as well as shoulder kinetic and muscular demands during manual wheelchair (MWC) propulsion on a motorized treadmill. Eighteen participants with spinal cord injury propelled their MWC at a self-selected constant speed on a motorized treadmill set at different slopes (0°, 2.7°, 3.6°, 4.8°, and 7.1°). Trunk and upper limb movements were recorded with a motion analysis system. Net shoulder joint moments were computed with the forces applied to the handrims measured with an instrumented wheel. To quantify muscular demand, the electromyographic activity (EMG) of the pectoralis major (clavicular and sternal portions) and deltoid (anterior and posterior fibers) was recorded during the experimental tasks and normalized against maximum EMG values obtained during static contractions. Overall, forward trunk flexion and shoulder flexion increased as the slope became steeper, whereas shoulder flexion, adduction, and internal rotation moments along with the muscular demand also increased as the slope became steeper. The results confirm that forward trunk flexion and shoulder flexion movement amplitudes, along with shoulder mechanical and muscular demands, generally increase when the slope of the treadmill increases despite some similarities between the 2.7° to 3.6° and 3.6° to 4.8° slope increments.

Pushrim biomechanical changes with progressive increases in slope during motorized treadmill manual wheelchair propulsion in individuals with spinal cord injury.

The purpose of this study was to quantify the effects of five distinct slopes on spatiotemporal and pushrim kinetic measures at the nondominant upper limb during manual wheelchair (MWC) propulsion on a motorized treadmill in individuals with spinal cord injury (SCI). Eighteen participants with SCI propelled their MWC at a self-selected natural speed on a treadmill at different slopes (0, 2.7, 3.6, 4.8, and 7.1 degrees). Spatiotemporal parameters along with total force and tangential components of the force applied to the pushrim, including mechanical effective force, were calculated using an instrumented wheel. The duration of the recovery phase was 54% to 70% faster as the slope increased, whereas the duration of the push phase remained similar. The initial contact angles migrated forward on the pushrim, while the final and total contact angles remained similar as the slope increased. As the slope increased, the mean total force was 93% to 201% higher and the mean tangential component of the force was 96% to 176% higher than propulsion with no slope. Measures were similar for the 2.7 and 3.6 degrees slopes. Overall, the recovery phase became shorter and the forces applied at the pushrim became greater as the slope of the treadmill increased during motorized treadmill MWC propulsion.