Background: Physical inactivity is a risk factor for chronic pain. Several mechanisms play a role in pain chronification including impairment of pain inhibition.
Objective: This study compared the efficiency of pain inhibitory systems between physical active and inactive healthy subjects. It was hypothesized that active subjects had more efficient pain inhibition compared with inactive subjects.
Design: A randomized, crossover study with 2 days of data collection.
Methods: Fifty-six (28 females) subjects participated in this study. Subjects were subgrouped into active (n = 30) and inactive (n = 26). Conditioned pain modulation (CPM) was assessed by cold pressor testing. Exercise-induced hypoalgesia (EIH) was assessed after 15 minutes bicycling at a heart rate corresponding to 75% VO2max. A control session of 15 minutes quiet rest was also included. Pressure pain thresholds (PPTs) were recorded at the dominant arm and leg before, immediately after, and 15 minutes after conditioning and exercise as well as before and after rest. PPTs were also recorded during conditioning.
Results: At baseline, PPTs in inactive men were increased compared with inactive women (P < 0.003). During cold pressor test and after exercise, PPTs increased to the same degree in active and inactive subjects, and the CPM and EIH responses were correlated (P < 0.05). The CPM response immediately after cold pressor test was maintained in women but not in men.
Conclusions: Cold pressor stimulation and aerobic exercise caused comparable multisegmental increases in PPT in active and inactive men and women. The CPM and EIH responses were correlated, but they have different temporal manifestation of hypoalgesia.
Keywords: Conditioned Pain Modulation; Exercise-Induced Hypoalgesia; Pain Modulation; Physical Activity; Pressure Pain Thresholds.
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