Effect of continuous vibration on nociceptive flexor reflexes.

The effects of continuous segmental vibration on the biceps femoris (BF) nociceptive flexor reflexes elicited by painful electrical stimulation of the sural nerve at the ankle were investigated in 25 normal subjects. During vibration of 100 Hz frequency, applied either on ipsilateral or contralateral foot skin, the nociceptive BF flexor reflexes increased in amplitude. Marked facilitation was prolonged even 20 minutes after vibration ceased. Pain sensation described by subjects did not change significantly except that radiation of pain was reduced in some cases. The results could not be explained by current views of reflex sensitisation, dishabituation, or the gate control theory.