Contraction-Induced H Reflexes of the Upper and Lower Limbs in Healthy Adults

Contraction-induced H reflexes are a late neurophysiologic response elicited with submaximal nerve stimulation during isometric muscle contraction. Mediated by spinal pathways, like other H reflexes, their use has remained somewhat limited despite a long history of development dating back to the original description by Hoffman. There is a paucity of data on normal reference ranges, which this article aims to add to.

Contraction-induced H reflexes were elicited from the first dorsal interosseous, flexor carpi radialis, and tibialis anterior bilaterally in 100 healthy volunteers. Reference values, including side-to-side variation, were calculated. Pearson test and multiple regression were used to evaluate the relationship of H-reflex latency to height, age, and sex of participants.

The mean onset latencies of 28.00, 17.44, and 31.10 ms were seen for first dorsal interosseous, flexor carpi radialis, and tibialis anterior muscles, respectively. The calculated allowable side-to-side latency difference in individual participants was 3 to 4 ms. A correlation to participant height was seen.

This work provides normal reference values of contraction-induced H reflexes to three muscles, including allowable side-to-side variation. The latter suggests that bilateral testing evaluating for asymmetry within an individual is likely to be optimally sensitive. The relationship to height is also confirmed.