The hypoalgesic effects of acute exercise are well documented. However, the effect of chronic exercise training on pain sensitivity is largely unknown.
Purpose: To examine the effect of aerobic exercise training on pain sensitivity in healthy individuals.
Methods: Pressure pain threshold, ischemic pain tolerance and pain ratings during ischemia were assessed in 24 participants before and after 6 wk of structured aerobic exercise training (n = 12) or after 6 wk of usual physical activity (n = 12). The exercise training regimen consisted of cycling three times per week for 30 min at 75% of maximal oxygen consumption reserve.
Results: Significant increases in aerobic fitness (P = 0.004) and ischemic pain tolerance (P = 0.036) were seen in the exercise group after training, whereas pressure pain threshold and pain ratings during ischemia were unchanged (P > 0.2). No change in aerobic fitness (P > 0.1) or pain sensitivity (P > 0.1) was observed in the control group.
Conclusion: Moderate- to vigorous-intensity aerobic exercise training increases ischemic pain tolerance in healthy individuals.
Alex’s Notes: Exercise makes you tough. Personally, I wrestled for ten years from elementary school through high-school, and now when my calf cramps I accept the challenge and fight back in a weird enjoyable way. Okay, maybe that isn’t the best example, but using critical thinking it makes sense that exercise raises your pain tolerance. Look at contact-sport athletes, they must be durable. Interestingly, only one study has ever actually examined the effects of structured exercise training on pain tolerance. Unfortunately it was in unfit males, but it did show that aerobic training via cycling upped the pain ceiling. It also showed that resistance training had no influence on pain tolerance. Regardless, the effects on pain were to assess the acute effects of exercise, not chronic, and that is where the study at hand comes into play. It aimed to examine the effect of chronic aerobic training on pain sensitivity in healthy adults.
Overall, it included 24 adults of which 21 were women, and they were all in their twenties. Pain was assessed by applying pressure to the trapezius (mid-back), biceps brachii, rectus femoris (front thigh), and tibialis anterior (shin). The exercise included three sessions per week for six weeks of cycling at 75% the participant’s heart-rate reserve, which would be considered borderline moderate-to-vigorous.
After the six weeks of cycling, pain tolerance increased! Okay, the title did give the results away, but more interesting is the “why” portion of the discussion. According to the authors,
“The afferents activated during the ischemic task are similar to those activated during exercise. Therefore, it is possible that prolonged performance of the ischemic task was facilitated by repeated exposure to the noxious ischemic stimulus during exercise training. Notably, the subjective rating of the ischemic pain was preserved, implying that a similar degree of discomfort was tolerated for a longer duration.”
Thus, this study suggests that acute and chronic exercise influence pain sensitivity through difference mechanisms, and it can be inferred that at least part of the enhanced endurance performance from training is due to greater tolerance of pain caused by metabolic disturbances within the muscle. Now if only a study on long-term resistance training would be done.