Soleus Stretch Reflex Inhibition in the Early Swing Phase of Gait Using Deep Peroneal Nerve Stimulation in Spastic Stroke Participants Marco M. Voormolen, MSc*,† ▪ Michel Ladouceur, PhD* ▪ Peter H. Veltink, PhD† ▪ Thomas Sinkjaer PhD* *Center for Sensory–Motor Interaction, Department of Medical Informatics and Image Analysis, Aalborg University, Denmark and †Department of Biomedical Engineering, Faculty of Electrical Engineering, University of Twente, The Netherlands  ABSTRACT Objectives. To investigate the feasibility of inhibiting the of more than 90% (p < 0.05). For all five participants investigated, there was a significant reduction in the stretch reflex of the soleus muscle by a conditioning stimulus applied to the deep peroneal nerve in spastic sensitivity of the soleus stretch reflex after conditioning (p < 0.02). stroke participants during the early swing phase of gait. Conclusions. It is concluded that the inhibition of the Materials and Methods. This study investigated the effect soleus stretch reflex with an electrical conditioning stimu- of an electrical conditioning stimulus applied to the lus applied to the deep peroneal nerve is feasible in the deep peroneal nerve on the magnitude at the peak of early swing phase of walking. This shows a potential for the soleus stretch reflex in the early swing phase of gait being used in the rehabilitation of walking by spastic in six spastic stroke participants. stroke persons.  Results . Five of the six participants showed a reduced stretch reflex of more than 80%. On average (n  4), it KEY WORDS: electrical stimulation, gait, inhibition, so- was shown that maximal inhibition occurred at a condi- tioning-test interval of 114 ms and had a magnitude leus muscle, spasticity, stretch reflex, stroke. INTRODUCTION spinal cord injury) show a significant reduction of the short latency stretch reflex (and/or H-reflex) Participants with injuries to the central nervous sys- modulation during gait(1–3). In stroke participants tem (like multiple sclerosis, stroke, or incomplete this impaired modulation results from the absence of an increased stretch reflex threshold in the swing Address correspondence and reprint requests to: M. Ladouceur, PhD, phase in comparison to the stance phase of gait(4) Aalborg University, Department of Medical Informatics and Image Anal- ysis, Center for Sensory–Motor Interaction, Fredrik Bayers Vej 7D-3, 9220 as seen in able-bodied participants. This lowered Aalborg, Denmark. E-mail: mla@smi.auc.dk threshold for the stretch reflex in spastic patients The study has been supported by the University Fund Twente Founda- tion, the Royal Dutch Engineers Institute (KIvI), the Danish National Re- could lead to an increased soleus activity(5). Lack search Foundation, Danish National Research Council and the of foot clearance in the transition from stance to European Union (Training and Mobility of Researchers program, NEUROS swing is often observed during walking by spastic project). participants, severely impairing their walking ability (4,6). It is often assumed to be related to the weak-  2000 International Neuromodulation Society, 1094–715900$15.000 Neuromodulation, Volume 3, Number 2, 2000 107–117 ness of the dorsi-flexors, but could equally well be