Last Updated: 2007-12-07 11:32:59 -0400 (Reuters Health)
NEW YORK (Reuters Health) – Short-duration, nonexhaustive isometric exercise raises pain threshold and pain tolerance in healthy young women, according to kinesiologists at the University of Wisconsin-Madison.
Hypoalgesia following high-intensity aerobic exercise has been well documented, Dr. Kelli F. Koltyn and Masataka Umeda note in the November issue of the Journal of Pain. More limited evidence suggests similar effects for moderate to high intensity resistance exercise, while findings are contradictory for lower intensity isometric exercise performed to exhaustion.
To examine the effects of short-duration, submaximal isometric exercise, the authors studied 14 healthy women 18 to 22 years old who completed two sets of exercise, squeezing a dynamometer with the dominant hand at 40% to 50% of maximum for 2 minutes.
To measure the effect on pain sensitivity, a pressure stimulator applying 3000 grams of force was applied to the forefinger on the dominant and nondominant hands, in random order, for 2 minutes before and after the isometric exercises.
Pain thresholds increased significantly after isometric exercise, from 21.3 to 37.5 seconds in the dominant hand and from 21.4 to 41.3 seconds in the nondominant hand.
Pain ratings rose significantly during exposure to the pressure stimulations but were attenuated after the isometric exercise.
"The results appear to indicate that a localized muscular contraction resulted in ipsilateral and contralateral pain inhibitory effects indicative of a central response," Dr. Koltyn and Umeda conclude.
They suggest that further research will be required to tease out which of several possible mechanism underlie the induced hypoalgesia, including central antinociceptive effects, activation of neurotransmitters or of the endogenous opioid system, or stimulation of "diffuse noxious inhibitory control."
J Pain 2007;8:887-892.