It is well demonstrated that a single bout of exercise can cause short-term reductions in pain, a phenomenon referred to as exercise-induced hypoalgesia (EIH) (Naugle et al. 2012). However, the effect of chronic exercise training on pain is less clear, as are the mechanisms that mediate EIH. A greater understanding of the effects of chronic exercise training on pain, as well the mechanisms that mediate EIH, may allow for more effective exercise therapies to be developed for individuals with chronic pain (i.e., osteoarthritis, fibromyalgia, chronic low back pain). Understanding the mechanisms by which exercise relieves pain can help substantiate the efficacy of exercise therapy, may permit the design of optimally effective exercise interventions, and may allow the identification of interactions with common pain medications.
WHAT DID WE FIND?
Our study in healthy individuals showed that 30 min of moderate-vigorous intensity cycling exercise performed 3 times per week for 6 weeks increased pain tolerance, but did not affect pain thresholds or pain ratings. That is, participants in the exercise group rated a noxious ischaemic stimulus to be equally as painful following the exercise intervention, but they were willing to tolerate it for longer. The increase in pain tolerance was observed in the arm, despite exercise being performed by the legs. This ensured that changes in the periphery from exercise did not affect out findings and implied that exercise caused a change in the central response to pain.
SIGNIFICANCE AND IMPLICATIONS:
This was the first study to show that chronic aerobic training increases tolerance to a noxious ischaemic stimulus in healthy individuals. It identifies a new perceptual means of adaptation to exercise. These findings could have important implications for individuals with chronic pain. For example, individuals with chronic pain who take regular exercise may not increase their pain threshold, but they may be able to better tolerate their usual level of pain so that it has less impact on their daily life. This capacity to function despite pain is known as pain self-efficacy, which has been shown to be an important predictor of pain and disability in individuals with chronic pain (Arnstein et al 1999; Arnstein 2000). Another important finding of our study was that pain tolerance increased in a non-exercised limb, suggesting that that individuals with chronic pain may gain a pain relieving benefit of exercise without having to use the painful joint or muscle, which in turn could reduce the likelihood of symptom exacerbations by exercise.
Jones MD, Booth J, Taylor JL, Barry B (2014). Aerobic training increases pain tolerance in healthy individuals. Med Sci Sports Exerc 4: 1640-7.
This article was the topic of a recent article in the online version of The New York Times.
Arnstein P (2000). The mediation of disability by self-efficacy in different samples of chronic pain patients. Disabil Rehabil 22: 794-801.
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Naugle KM, Fillingim RB, Riley JL (2012). A meta-analytic review of the hypoalgesic effects of exercise. J Pain 13: 1139-50.