Modulatory effects of locomotor training on extensor spasticity in individuals with motor-incomplete spinal cord injury

Purpose: Sparse data exist about effects of locomotor training on spasticity in individuals with spinal cord injury (SCI). We investigated changes in spastic responses in individuals with motor-incomplete SCI (MISCI) associated with locomotor training and examined properties of a biomechanical measure of clonus severity, plantar flexor reflex threshold angle (PF RTA). Methods: In 18 individuals with chronic MISCI, we assessed biomechanical and electrophysiologic measures of extensor spasticity and their relationship with walking speed before and after 12 weeks of body-weight supported locomotor training. Measures included PF RTA, plantar flexor (ankle clonus) and quadriceps spasm duration, soleus H-reflex, and ankle muscle electromyography. PF RTA validity was assessed by measuring PF RTA and clonus duration in 40 individuals with SCI and 10 non-disabled individuals. Results: Locomotor training was associated with decreased PF RTA (p = 0.06), ankle clonus (p = 0.09) and quadriceps spasm (p = 0.05). PF RTA discriminated between non-disabled individuals and individuals with SCI and was moderately correlated with walking speed, soleus H/M ratio, and quadriceps spasm duration. Conclusions: In persons with spastic paresis due to MISCI, locomotor training was associated with decreased spasticity as measured by decreased plantar flexor excitability, ankle clonus, and quadriceps spasm.