Exercise-Induced Hypoalgesia (EIH) refers to reduced pain sensitivity following exercise, particularly in response to noxious stimuli. Various exercise modalities, including isometric, aerobic, and resistance training, contribute to this effect. Pain experienced during exercise may activate descending inhibitory pathways, leading to subsequent pain relief.
Conditioned Pain Modulation (CPM) is a behavioral measure of diffuse noxious inhibitory control (DNIC), where pain inhibits pain. It is proposed that pain within the exercising limb may serve as a conditioning stimulus, activating CPM. For instance, maximal handgrip exercise has been used to trigger CPM responses. In clinical settings, unpleasant physical therapy interventions like exercise, thermal modalities, and electrical stimulation may function through CPM mechanisms.
CPM predicts EIH in both young and older adults, with painful exercise reducing pressure pain ratings across age groups. Isometric exercise has also been shown to decrease CPM in individuals with systemic EIH, suggesting shared mechanisms.
Athletes exhibit higher pain thresholds and tolerance due to repeated exposure to high-intensity exercise. However, they demonstrate lower CPM activation, possibly as a compensatory response to chronic noxious input. This raises the question: Can repeated high-intensity aerobic exercise, perceived as painful, train the nervous system to enhance descending pain inhibition in non-athletes? While alterations in pain sensitivity related to analgesic-induced pain inhibition have been documented, the effects of continuous stimulation of central pain pathways via painful high intensity exercise, along with the mediating influence of psychosocial factors, remain underexplored. This study aims to investigate the central pain modulatory mechanisms (measured by QST) that have differential changes in participants who receive multiple sessions of high intensity aerobic exercise as an intervention compared to receiving single session. Additionally, the study will evaluate the impact of sociocultural factors, including optimism, pain catastrophizing, and marginalization on alterations in pain sensitivity.