Effects of Locomotor Exercise Intensity on Gait Performance in Individuals With Incomplete Spinal Cord Injury

Background High-intensity stepping practice may be a critical component to improve gait following motor incomplete spinal cord injury (iSCI). However, such practice is discouraged by traditional theories of rehabilitation that suggest high-intensity locomotor exercise degrades gait performance. Accordingly, such training is thought to reinforce abnormal movement patterns, although evidence to support this notion is limited. Objective The purpose of this study was two-fold. First, we evaluated the effects of short-term manipulations in locomotor intensity on gait performance in subjects with iSCI. Second, we attempted to evaluate potential detrimental effects of high-intensity locomotor training on walking performance. Design Single-day repeated-measures and pre-/post-training study design. Methods Nineteen individuals with chronic iSCI performed a graded-intensity locomotor exercise task with simultaneous collection of lower extremity kinematics and EMG. Measures of interest were compared across intensity levels of 33%, 67%, and 100% of peak gait speed. A subset of 9 individuals participated in 12-weeks of high-intensity locomotor training. Similar measures were collected and compared pre- to post-training. Results Our results indicate short-term increases in intensity led to significant improvements in muscle activity, spatiotemporal metrics, and joint excursions, with selected improvements in measures of locomotor coordination. High-intensity locomotor training led to significant increases in peak gait speed (0.64 to 0.80 m/s; p<0.01), and spatiotemporal and kinematic metrics indicate a trend for improved coordination. Limitations Measures of gait performance were assessed during treadmill ambulation and not compared to a control group. Generalizability of these results to overground ambulation is unknown. Conclusions High-intensity locomotor exercise and training does not degrade, but rather improves locomotor function and quality in individuals with iSCI, which contrasts with traditional theories of motor dysfunction following neurologic injury.