Treadmill training induced improvement of spinal reflex modulation in children with cerebral palsy

Objectives: In healthy children short latency leg muscle reflexes are profoundly modulated throughout the step cycle in a functionally meaningful way and contribute to the EMG pattern observed during gait. With the maturation of the corticospinal tract the reflex amplitudes are depressed by supraspinal inhibitory mechanisms. For the soleus muscle the modulation pattern shows a relative maximum in the mid-stance phase and a complete depression during the swing phase. In a recent study we could show, that the rhythmic part of the modulation pattern is present in children with early bilateral supraspinal lesion but compared to healthy children the reflexes were less depressed with increasing age and during the swing phase still reflexes were present. Treadmill training improves clinically the walking pattern in children with cerebral palsy (CP). Presuming that short latency reflexes contribute significantly to the walking pattern a change in the modulation may occur after training. The aim of the present study was to assess whether treadmill training improves the soleus reflex modulation during gait in CP. Methods: Seven children (aged 6–16 years) with diplegic CP underwent a brief treadmill training of 10 minutes daily for 14 consecutive days. All of them were functional walkers. Before the first and one day after the last training session soleus Hoffmann (H-) reflexes were investigated during walking on a treadmill. Reflex amplitudes were normalized with respect to the maximum motor response (Mmax). Reflexes were obtained during 8 different phases of the step cycle. Results: Clinically treadmill training improved gait velocity and step length. Soleus H-reflexes before treadmill training were modulated rhythmically with a relative maximum during mid-stance and smaller amplitudes during the swing phase. After treadmill training reflexes were almost completely depressed during the swing phase. Conclusion: The present data show that treadmill training can induce changes in the modulation of short latency reflexes during gait. The complete supression of the soleus H-reflex during the swing phase similar to healthy subjects could reflect an improvement towards a functionally more useful pattern.