INPUT-OUTPUT PROPERTIES OF THE SOLEUS STRETCH REFLEX IN SPASTIC STROKE PATIENTS AND HEALTHY-SUBJECTS DURING WALKING

The input-output properties of the soleus stretch reflex during walkin g and sitting were examined in 11 spastic stroke patients and 10 healt hy subjects. In the early swing phase, the threshold of the input-outp ut relation was significantly lower in the patient group - on average 108 degrees/s compared to 309 degrees/s in the control group (P = 0.02 ). The slope of the input-output properties was unchanged in patients and in control subjects (P = 0.39). In stroke patients we found a mino r, but significant, difference in threshold with 108 degrees/s in the early swing phase compared to 74 degrees/s in sitting position at matc hed TA EMG activity (P = 0.01), Furthermore, we found an unchanged slo pe of 0.25 mu V s/degrees during walking and 0.28 mu V s/degrees in th e sitting position (P = 0.21). In contrast, control subjects showed a large difference in the threshold in the early swing phase during walk ing (309 degrees/s) compared with findings in the sitting position at a matched TA EMG activity (71 degrees/s, P = 0.004). The slope was unc hanged during walking and when the subject was sitting (P = 0.22). The re was a significant correlation between clinical spasticity score and stretch reflex threshold in the early swing phase (P = -0.61, P = 0.0 4) and between clinical spasticity score and the slope in the early sw ing phase (P = 0.72, P = 0.009). It is concluded that in the early swi ng phase, the markedly reduced soleus stretch reflex threshold was pre venting the stroke patients from making fast dorsiflexion of the foot at the ankle joint and thereby impairing the walking speed. (C) 1998 E lsevier Science Ireland Ltd.