Reliability of individual differences for H-reflex recordings.

Complementary data from two closely-related experiments were analyzed to investigate the reliability of individual differences of H-reflex amplitude. Some concomitant analysis of M-reflex was also included. The purpose was to do this in a manner that was more direct and more detailed than found hitherto in the literature. Fundamental techniques espoused particularly by F.M. Henry (1969) formed the basis of this approach. The aims included a clearer quantification of reliability with a distinction between inter- and intra-individual sources of variation, an analysis of the effects different numbers of trials had on reliability, and an investigation of the progression of reliability over a 20-trial sequence of observations. The control conditions of both experiments were designed to be essentially identical with respect to subject position, stimulus and recording configurations. Experiment 1 had 20 subjects, four control conditions of 10-trials in each while experiment 2 had 18 subjects, five control conditions and 20 trials. The posterior tibial nerve was percutaneously stimulated every 10 sec. and surface electromyographic recordings were made from the soleus muscle. H-reflex and M-reflex amplitudes were measured on every trial. It was found that the reliability of individual differences of both H-reflex and M-reflex was extremely robust with the majority of coefficients being above .950. In addition, the reliabilities remained high when as few as four trials were examined. The pattern of individual differences over the longer series of trials confirmed the stability of interindividual differences and showed that subjects became more consistent in their responses as trials progressed.(ABSTRACT TRUNCATED AT 250 WORDS)