This study compared the characteristics of the H-reflex and M-wave recruitment curves (RC) evoked with 0.05, 0.2 and 1-ms pulse durations in young and old adults.

Increasing pulse duration from brief (0.05 ms) to longer (1 ms) duration mostly induced a similar leftward shift of the H-reflex and M-wave RC in both groups.

Regardless of pulse duration, the results indicate that H-reflex outcomes were impacted by ageing, suggesting a greater loss of sensory than motor axons or alterations of synapses between Ia afferents and motor neurones.