Intensity-dependent effects of aerobic training on pressure pain threshold in overweight men: A randomized trial.

PURPOSE: To investigate the chronic and acute effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on pressure pain thresholds (PPT) in overweight men. METHODS: Twenty-eight participants performed stationary cycling exercise three times per week for 6 weeks. Participants were randomly allocated to HIIT (10 × 1-min intervals at 90% peak heart rate) or MICT (30 min at 65-75% peak heart rate). PPTs were assessed over the rectus femoris, tibialis anterior and upper trapezius before and after the 6-week training programme (chronic effect) as well as before and after the first, middle and final exercise sessions (acute effect). RESULTS: For chronic exercise, PPTs increased more after MICT compared to HIIT over the rectus femoris (p = 0.009, effect size r = 0.54) and tibialis anterior (p = 0.012, r = 0.54), but not the trapezius (p = 0.399, r = 0.29). The effect of acute exercise on PPT was more varied and ranged from moderate hypoalgesia to moderate hyperalgesia. Overall, however, there was no consistent change in PPT after acute exercise for HIIT or MICT (p ≥ 0.231, r ≥ -0.31 and ≤0.31). CONCLUSION: Six weeks of MICT cycling (chronic exercise) increased PPT for the lower body, but not upper body, in overweight men, whereas HIIT did not provide any hypoalgesic effect for chronic exercise. The acute effect of exercise on PPT was highly variable and negligible overall. SIGNIFICANCE: This study shows that aerobic training increases pressure pain threshold in pain-free adults. This effect was observed only for MICT over-exercised muscles, implying intensity- and site-specific effects of exercise training on pain threshold.