Intersession reliability of H:M ratio is greater than the H-reflex at a percentage of M-max

The purpose of this study was to evaluate the intersession reliability of the soleus Hoffmann reflex using two methods of normalizing motoneuron excitability over time. Ten subjects reported to the laboratory on two separate occasions. Soleus Hoffmann reflexes and muscle responses were evaluated at maximal amplitude ratios and at stimuli producing ∼20% of the maximal muscle response. An intraclass correlation coefficient (ICC 2, 1) found strong intersession reliability for both measurement techniques. Assessing motoneuron activation using maximal amplitude ratios demonstrated a robust ICC of 0.979 compared to an ICC of 0.882 when the Hoffmann reflex was assessed at ∼20% of the maximal muscle response.