[Short-latency and long-latency muscle reflex responses in man]

In a group of 70 healthy subjects the author examined repeatedly the reflex response from the m.interosseus dorsalis I during middle voluntary contraction of the muscle induced by electrical stimulation of the dermal branches of the nn. digitalis of the index finger. The aim of the reflexological investigation was analysis of some electrophysiological properties of short-latency (SL) and long-latency (LL) reflex responses which could be identified as excitation and inhibition modulations of the recorded muscular activity after rectification and averaging of the electromyogram. The results of the analysis revealed a constant intraindividual shape and latencies of the SL and LL components of the reflex responses (30 ms, 50 ms resp.), regardless whether one or several different frequencies of stimulation were used. The SL reflex response in the distal muscles of the upper extremity is compatible with the spinal loop; the latency of the LL response is shorter than the voluntary reaction time for the small muscles of the hand, therefore its reflex origin is assumed.