Seated Reach Distance and Trunk Excursion Accurately Reflect Dynamic Postural Control in Individuals with Motor-incomplete Spinal Cord Injury

OBJECTIVE: Dynamic seated postural control is essential for individuals who perform their daily activities from a wheelchair. While seated reach distance is used as a proxy measure for postural control, it is unknown whether this is an accurate and reliable measure of the limits of stability in individuals with motor-incomplete spinal cord injury (MISCI). DESIGN: To determine whether kinematic measures of excursion are valid measures of postural control in individuals with MISCI, seated reach test (SRT; obtained from a wrist marker) and associated trunk excursion values (obtained from a C7 marker) were compared with center of pressure excursion (COPE). Data were obtained from individuals with MISCI and from non-disabled individuals for each of four directions. To assess the reliability of these measures in subjects with MISCI, these values were collected on two separate days. RESULTS: The SRT was correlated with the COPE in three directions of reaching (r≥0.71) with the exception being leftward reaching. Trunk excursion was correlated with COPE in all directions (r≥0.93). In ND individuals, both SRT (r≥0.56) and trunk excursion (r≥0.91) were correlated with COPE for all directions. In individuals with MISCI, there was significant intersession agreement for both reach distance (ICC≥0.78) and trunk excursion (ICC≥0.77) measured in all directions. CONCLUSIONS: While both SRT and trunk excursion are reasonable reflections of COPE, measurement of postural control based on trunk excursion has advantages for individuals who may have difficulty maintaining arm position during reaching. Reach distance is highly reliable in individuals with MISCI in all directions of reaching.