Balance training alters extrapolated centre-of-mass and base-of-support dynamics and neuromechanical regulation of reactive stepping in people with incomplete spinal cord injury.

Individuals with incomplete spinal cord injury (iSCI) often exhibit impaired reactive stepping ability, contributing to an increased risk of falls. While balance training can improve reactive stepping ability, its effect on the biomechanics of foot placement remains unclear. This study investigated how an 8-week balance training program affected reactive stepping, quantified by the margin-of-stability (MOS). Twelve individuals with iSCI performed the Lean-and-Release test at three time points: baseline, post-intervention, and 3-months post-intervention. We compared the average and trial-to-trial variability (i.e., standard deviation) of MOS-related measures, and correlated MOS with clinical measures of balance and mobility. Following the balance training, participants demonstrated a near-significant increase in the average MOS (p = 0.065) and reduced MOS variability (p = 0.025), indicating more stable and consistent reactive stepping to recover from simulated forward falls. These improvements were driven by a significant decrease in the average extrapolated center-of-mass (XCOM; p = 0.003) and in the variability of base-of-support (BOS: p = 0.010), which indicates better control of body's momentum with a more consistent steps taken. These effects were retained at the 3-month follow-up (XCOM: p = 0.410; BOS: p = 0.305). Average MOS was significantly correlated with clinical measures of balance and mobility, but not with self-reported balance confidence. Furthermore, the changes in MOS following balance training were not correlated with the changes in these clinical measures. In conclusion, balance training elicits more stable and consistent reactive stepping in individuals with iSCI. Additionally, the MOS is a sensitive and objective biomechanical marker that captures training-induced improvements in reactive stepping that are not detected by clinical assessments.