Reliability of the soleus H-reflex from supine to standing in young and elderly

Objective Many recent studies have used the soleus H-reflex methodology to examine age-related changes in neuromuscular function. However, reliability of the method has only been tested in young adults. The purpose of this study was to evaluate the inter-trial reliability of the soleus H-reflex in both young and elderly subjects during supine and standing conditions. Methods The experiment was carried out on 10 young and 10 elderly subjects. For each subject, 10 standardized soleus H-reflex trials were collected during each of the postural conditions. Intraclass correlations were calculated for the first 4, 6, 8, and 10 trials for each group at each body position. Results The largest decreases in reliability in this study were observed with a decrease in the number of trials used to estimate the elderly soleus H-reflex during the standing condition. The change from using ten trials to using four trials led to an 8% decrease in reliability. Conclusions Due to the decreased postural control ability in the elderly population, at least ten trials should be used to estimate soleus H-reflex characteristics during standing or other functional weight-bearing conditions. Significance Using fewer than 10 trials could lead to an increase in statistical errors and misinterpretation of results.