Endogenous Pain Inhibitory Function: Endurance-Trained Athletes vs Active Controls

Abstract

Objective Athletes are at risk for developing chronic pain conditions, but the role of exercise in the modulation of pain in athletes has not been well established. The aim of this study was to investigate conditioned pain modulation (CPM) and exercise-induced hypoalgesia (EIH) responses between 13 endurance-trained athletes and 13 normally active controls. Methods In a cross-sectional, nonrandomized study with two independent groups of college-aged males and females, pressure pain thresholds (PPTs) were assessed in the vastus lateralis (VL) and brachioradialis (BR) using a pressure algometer before and after a conditioning stimulus, an isometric hand grip exercise to failure, and a 30-minute run. Results PPTs increased following the conditioning stimulus, indicating a CPM response, to a similar degree in the BR (19.3% ± 26.5% vs 18.6% ± 16.2%, P = 0.93) and VL (18.9% ± 25.9% vs 28.7% ± 27.4%, P = 0.73) in the athletes and controls. PPTs increased following isometric exercise to a similar extent in athletes and controls in the BR (23.9% ± 22.8% vs 28.2% ± 24.0%, P = 0.75) and VL (15.8% ± 14.8% vs 15.5% ± 11.6%, P = 0.94). Following 30 minutes of running, EIH was similar between athletes and controls in the VL (21.2% ± 17.2% vs 13.8% ± 13.3%, P = 0.23) but was attenuated in the BR of the athletes (6.1% ± 16.9% vs 20.9% ± 20%, P = 0.047). Conclusions Athletes and controls exhibited similar endogenous pain inhibitory function both locally and systemically following CPM and isometric, upper body exercise. After the 30-minute run, BR EIH was reduced in the athletes compared with controls, suggesting a reduced systemic response following familiar exercise—perhaps due to the exercise being perceived as less painful and/or effortful.

Modulation of Exercise-Induced Hypoalgesia Following an Exercise Intervention in Healthy Subjects

“…[CPM]), and functional performance capacity (VO2-max) in endurance-trained athletes and normally active controls [26]. This is in contrast to the current study which found an association between improvement in physical performance capacity and improvement in EIH.…”

“…Furthermore, EIH has been utilized as a predictive factor for pain progression following total knee replacement [18] and exercise therapy [20] in knee osteoarthritis patients, and lower EIH has been reported in physically inactive individuals compared with physically active people [21,22]. This indicates EIH subgroup differences in relation to physical performance capacity and that exercise or an active lifestyle (enhanced physical performance capacity) may improve EIH although cross-sectional studies have found conflicting evidence in healthy subjects [14,[23][24][25][26].…”

Exercise-induced Hypoalgesia Is Impaired in Chronic Whiplash-associated Disorders (WAD) With Both Aerobic and Isometric Exercise

“…Higher levels of moderate and vigorous physical activity have been found to be associated with a greater magnitude of EIH in older healthy adults [46], but no relationship with EIH in younger adults [47]. It has been suggested that a U-shaped relationship exists between activity and pain where too little and too much physical activity may lead to chronic pain [48]. Our results support a U-shaped relationship but only for isometric exercise: high levels of activity predicted impaired EIH, moderate levels predicted EIH, and low levels showed a trend for impaired EIH (although this was non-significant).…”

<p>Cognitive Inhibition Correlates with Exercise-Induced Hypoalgesia After Aerobic Bicycling in Pain-Free Participants</p>

“…7 Furthermore, a few studies have addressed self-reported psychological variables, such as pain catastrophizing and kinesiophobia. 6,8 However, these have yielded either null-findings or inconclusive evidence. 6,[9][10][11] Concurrently, recent research indicates that cognitive function might affect pain, and in particular, pain inhibition.…”