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

Purpose: 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.

Methods: 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.

Results: 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.

Conclusions: 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.