Impaired potentiation of H-reflexes in patients with upper motoneurone lesions.

The potentiation of H-reflexes during effort has been studied in 16 patients with mild hemiparesis. Impaired potentiation was present in all but one patient, and was still evident in some who had recovered fully from weakness. A tentative explanation has been proposed for these findings; it is suggested that there is loss of a background facilitatory pathway to motoneurones.