Changes in soleus H-reflex modulation after treadmill training in children with cerebral palsy

In healthy children, short latency leg muscle reflexes are profoundly modulated throughout the step cycle in a functionally meaningful way and contribute to the electromyographic (EMG) pattern observed during gait. With maturation of the corticospinal tract, the reflex amplitudes are depressed via supraspinal inhibitory mechanisms. In the soleus muscle the rhythmic part of the modulation pattern is present in children with cerebral palsy (CP), but the development of tonic depression with increasing age, as seen in healthy children, is disturbed. Treadmill training clinically improves the walking pattern in children with CP. Presuming that short latency reflexes contribute significantly to the walking pattern, a change in the modulation may occur after training. The aim of this study was to assess whether treadmill training also improves the soleus reflex modulation during gait in children with CP. Seven children with CP underwent brief treadmill training for 10 min a day over 10 consecutive days; all of them were functional walkers. Soleus Hoffmann (H-) reflexes were investigated during walking on a treadmill before the first, and one day after the last, training session. Treadmill training led to a considerable clinical improvement in gait velocity. After 10 days of training, soleus H-reflexes during gait were almost completely depressed during the swing phase. The complete suppression of the soleus H-reflex during the swing phase, which is also exhibited by healthy subjects, could reflect an improvement towards a functionally more useful pattern. In conclusion, treadmill training can induce changes in the modulation of short latency reflexes during gait.