Soleus long-latency stretch reflexes during walking in healthy and spastichumans

The present study was carried out to investigate the long-latency soleus st retch reflexes M2 (peak latency of approximately 85 ms) and M3 (peak latenc y of approximately 115 ms) during walking in healthy and spastic multiple s clerosis (MS) patients. An 8 degrees stretch was applied to the ankle exten sors of the left leg in 8 healthy subjects during normal walking speed and 9 spastic MS patients and 10 age-matched healthy subjects during slow walki ng. When present in walking healthy subjects, MZ and M3 were modulated in a similar way and with the same amplitudes as previously described for the s hort latency soleus stretch reflex (M1). The spastic patients' soleus M1 wa s significantly less modulated during walking. The patients' M2 long-latenc y response was modulated in the same way as the age-matched healthy subject s. All patients' M3 responses were absent or much suppressed during walking . The origin and functional importance of the short- and long-latency stret ch reflexes in healthy and spastic persons are discussed in relation to the above findings and the behaviour of the stretch reflexes during matched is ometric contractions. M3 is argued to be part of a transcortical reflex in healthy subjects. (C) 1999 Elsevier Science Ireland Ltd. All rights reserve d.