Post-Tetanic Potentiation of H Reflex in Normal Man

Hoffmann1originally suggested that the electrically induced stretch reflex in man is a monosynaptic one. Later Lloyd2proved in cats that the simple reflex twitch which resulted from muscle nerve stimulation is in fact monosynaptic, and, in 1951, Magladery and others3confirmed this observation for the H reflex in man. It soon became evident that even among normal human volunteers there is considerable variation of H reflex amplitude.4,5Moreover, the reflex in individual subjects varies spontaneously, as well as with changes in muscle length, tonic contraction, the Jendrassik maneuver, and post-tetanic potentiation (PTP). Attempts to correlate H reflexes with specific pathological conditions have met with limited success.6-9The H reflex is absent, or markedly reduced, when the myotatic reflex is itself absent due to a disorder of the reflex arc. An exception to this rule is spinal shock.10Significant augmentation of the H