Comparison of two techniques to measure the motor nerve refractory period distribution

The techniques introduced by Ingram et al. and by Kimura to assess the motor nerve refractory period distribution were compared in the peroneal nerve of 28 healthy subjects. Twenty of these subjects were examined twice with an interval of 6-20 days. Results obtained with Ingram's technique yielded a narrower refractory period distribution, displayed less inter-individual variability, and were more reproducible than those obtained with Kimura's technique. The mean refractory period for the 5% slowest recovering fibres (MRP95) was 1.51 msec (S.D. 0.14) for Ingram's technique and 2.15 msec (S.D. 0.72) for Kimura's technique. The coefficient of variation of the MRP95 was 8% for Ingram's technique, and 22% for Kimura's technique. The present data do not allow a definite conclusion concerning the association of refractory period with age, gender and height. Ingram's technique would be favoured for practical application over Kimura's technique on the basis of this study.