Medial and lateral gastrocnemius H-reflex intersession reliability during standing and lying postures at varied foot positions in healthy participants.

Available H-reflex procedures do not allow a reliable or valid examination for the L5 radiculopathy. However, recording the gastrocnemius H-reflex may allow a reliable and valid method for examination of the L5 nerve root. Therefore, the purpose of this study was to examine the intersession reliability of the medial gastrocnemius (MG) and lateral gastrocnemius (LG) H-reflexes recordings during standing and lying postures at varied ankle positions in healthy participants. The MG and LG H-reflexes of eight healthy participants were elicited by stimulating the tibial nerve and recording the resultant muscle response using surface electrodes. The stimulation parameters were 1.0 ms, 0.2 PPS, with incremented stimulus intensity. Four traces of the maximum amplitude H-reflex and M-wave were recorded during lying and standing with the ankle in neutral, full dorsiflexion, and full plantarflexion over two consecutive days. The averaged traces were used to calculate the intersession intraclass correlation coefficients (ICC) among conditions. Intersession ICCs (2, 1) of MG and LG during standing and lying with varied ankle positions were moderate to high (ranging from 0.58 to 0.94). The MG was more stable than LG and the ICCs were greater during standing (ranging from 0.76 to 0.94) than during lying (ranging from 0.58 to 0.85), indicating higher sensitivity of the MG H-reflex when the limb is engaged in functional standing However, the LG H-reflex reliability was robust and, thus, could be recorded consistently in the examination of the L5 nerve root.