Vastus medialis H-reflex reliability during standing

Vastus medialis H-reflex is a valid measure to examine quadriceps muscle voluntary activation and inhibition after knee injury. Its reliability during repeated sessions has not been established. The purpose of this study was to establish the intrasession and intersession reliability of vastus medialis H-reflex amplitude recordings during standing with varied knee flexion angles (0, 30, 45, and 60 degrees). Electromyography unit was used to elicit and record the vastus medialis H-reflex from the right leg of five healthy subjects. The femoral nerve was stimulated using 0.5-millisecond pulses at 0.2 pps of H-maximum. Four recordings of the vastus medialis H-reflex amplitude were recorded in three trials for each knee flexion angle within each session for two consecutive days. Reliability was calculated using intraclass correlation coefficients (ICC). Intrasession reliability during standing with varied knee angles was high (ICC [2, 4] range from 0.76 to 0.98), and intersession reliability during standing with varied knee angles was moderate to high (ICC [2, 1] range from 0.51 to 0.84). Recording four traces of vastus medialis H-reflex amplitude per trial was reliable. Vastus medialis H-reflex amplitude recordings while standing during varied knee flexion are reliable within and between sessions.