Impacts of Disability Duration and Physical Activity Level on Wheelchair Propulsion Strategies in People with T12/L1 Spinal Cord Injury

Numerous wheelchair biomechanics studies have investigated movement dynamics to improve propulsion efficiency and minimize the risk of upper extremity pain and overuse injuries in individuals with spinal cord injury (SCI). These studies typically classify the SCI population into sub-categories based on impairment level, assuming that propulsion strategy is significantly determined by this factor. However, other factors such as disability duration and physical activity (PA) level may also influence propulsion strategies, leading to variations within the same impairment level sub-category.

This study explores the impacts of disability duration and PA level on wheelchair propulsion strategies in individuals with complete T12/L1 SCI. Eleven participants were categorized into three levels of PA (Low, Moderate, High) and disability duration (Short, Medium, Long). Participants performed a 15-s maximum speed propulsion (MAX) and a 30-s self-selected speed propulsion (SEL) on a roller ergometer. Propulsion strategies were analyzed through kinematics and electromyography (EMG), focusing on five key body joint angles and muscle activity.

The study found significant effects of disability duration on MAX-SEL observed range of joint angles (ORJA) of the elbow angle and PA level on MAX-SEL Valley of the trunk angle. A Tukey post hoc test revealed significant differences between the elbow’s medium and long disability duration groups in MAX-SEL ORJA and between the low and high PA level groups in MAX-SEL valley displacement of the trunk angle. Disability duration significantly affected biceps activity in both percent dynamic movement cycle (%DMC)_MAX and MAX-SEL %DMC, while PA level impacted %DMC_MAX of the upper trapezius and MAX-SEL %DMC of anterior deltoid muscles.

The findings suggest that disability duration and PA level significantly influence wheelchair propulsion strategies among individuals with complete T12/L1 SCI. Trunk kinematics varied with PA level, consistent with previous studies suggesting the use of trunk flexion as a compensatory movement for fatigue. The study highlights that adaptations in wheelchair propulsion are closely linked to PA level, even among individuals with identical SCI impairment levels. Further research is needed to understand the effects of these movement adaptations on propulsion efficiency and biomechanical stresses imposed on upper extremity joints.

This study contributes to the existing body of knowledge by revealing the variability of propulsion biomechanics among individuals with the same impairment level, emphasizing the importance of considering factors beyond impairment level when investigating wheelchair propulsion strategies. The findings have implications for determining desirable wheelchair propulsion strategies and developing appropriate wheelchair use training programs.