Assessing Endogenous Pain Inhibition: Test-Retest Reliability of Exercise-Induced Hypoalgesia in Local and Remote Body Parts After Aerobic Cycling

Short all-out isokinetic cycling exercises of 90 and 15 s unlock exercise-induced hypoalgesia

BACKGROUND

Acute physical activity leads to exercise-induced hypoalgesia (EIH). However, to what degree it can be induced by very short but highly intensive exercise is largely unknown. This study aims to investigate the effects of two different short all-out isokinetic exercise sessions on EIH.

METHODS

Twenty young male participants underwent three different interventions (90, 15 s all-out isokinetic cycling, respectively, and control) after an individualized low-intensity warm-up in a randomized-controlled-crossover design. Before (pre), after warm-up (post 1) as well as immediately post-intervention (post 2) pain sensitivity was measured employing pressure pain thresholds (PPT; in N) at the elbow, knee and ankle joints as well as the sternum and forehead. Performance parameters (e.g. lactate, perceived exertion, heart rate) were documented.

RESULTS

A 'time' × 'intervention' × 'body site' interaction effect (p < 0.001, η2 partial = 0.110) was observed for PPT. Both isokinetic interventions resulted in EIH at all body sites, even after ruling out any warm-up effects, while effects were larger for 90 s (maximum increase of 25.7 ± 11.7 N) compared to 15 s (maximum increase of 19.3 ± 18.9 N), and control (maximum increase of 8.0 ± 6.1 N). Compared to control, 15 s also resulted in hypoalgesic effects and differences were not observed at all sites. In this study, 90 s resulted in higher lactate, subjective exhaustion and heart rate levels compared to 15 s and control (p < 0.001), while higher values were also observed for 15 s compared to control.

CONCLUSION

Global EIH assessed immediately after exercise can be induced by short highly intensive exercises. The effects are greater when the subjective and the objective exertion are higher as induced by the 90 s intervention.

SIGNIFICANCE STATEMENT

This study investigates the potential for brief, highly intensive exercise sessions to induce exercise-induced hypoalgesia (EIH). The research demonstrates that EIH can indeed be triggered by such short workouts, with greater effects observed during a 90 s session compared to a 15 s one, most likely due to higher subjective and objective exertion. These findings offer insights into the potential for extremely brief but intense exercises to alleviate pain, impacting exercise recommendations and pain management strategies.

Vagal tone, pain sensitivity and exercise-induced hypoalgesia: The effect of physical activity level

BACKGROUND

Vagal activity has analgesic effects that are attributed to exercise-induced hypoalgesia (EIH). High vagal tone and low pain sensitivity are reported in individuals who routinely exercise yet, their association is unclear. Furthermore, it is unknown if the heightened vagal tone following high physical activity predicts and intensifies EIH.

METHODS

Fifty-one healthy participants (27 low-moderately physically active; 27 females) underwent a resting-state electrocardiogram followed by heart rate variability analysis. Pain measurements, including pressure (PPT) and heat (HPT) pain thresholds, ratings of tonic heat pain (THP) and conditioned pain modulation (CPM) paradigm, were conducted pre- and post-exercise on a cycle ergometer.

RESULTS

The highly active group demonstrated higher vagal tone compared to the low-moderately active (root mean square of successive differences between R-R intervals: 63.96.92 vs. 34.78 ms, p = 0.018; percentage of successive R-R intervals that exceed 50 ms: 24.41 vs. 11.52%, p = 0.012). Based on repeated-measure ANOVA, the highly active group showed higher PPT at pre-exercise, compared to the low-moderately active group (382 kPa vs. 327 kPa; p = 0.007). Post-exercise, both groups demonstrated EIH, increased HPT (p = 0.013) and decreased THP ratings (p < 0.001). Linear regression revealed that only in the low-moderately active group, higher vagal tone was associated with more efficient pre-exercise CPM and a greater reduction in THP ratings post-exercise (p ≤ 0.01).

CONCLUSIONS

Highly active individuals demonstrate greater vagal tone and lower pain sensitivity but no greater EIH. Vagal tone moderates pain inhibition efficiency and EIH only in low-moderately active individuals. These findings suggest that physical activity level moderates the vagal-pain association via the endogenous analgesia system.

SIGNIFICANCE

Highly physically active individuals exhibit greater vagal tone and reduced sensitivity to experimental pain, yet they do not benefit more from exercise-induced hypoalgesia (EIH) compared to low-moderately active individuals. Moreover, low-moderately active individuals with greater vagal tone exhibited more efficient endogenous pain inhibition and greater EIH, suggestive of the moderation effect of physical activity level on vagal-pain associations.

Hypoalgesia after aerobic exercise in healthy subjects: A systematic review and meta-analysis

Exercise-Induced Hypoalgesia (EIH) refers to an acute reduced pain perception after exercise. This systematic review and meta-analysis investigated the effect of a single aerobic exercise session on local and remote EIH in healthy individuals, examining the role of exercise duration, intensity, and modality. Pressure pain thresholds (PPT) are used as the main measure, applying the Cochrane risk of bias tool and GRADE approach for certainty of evidence assessment. Mean differences (MD; Newton/cm²) for EIH effects were analysed. Thirteen studies with 23 exercises and 14 control interventions are included (498 participants). Most studies used bicycling, with only two including running/walking and one including rowing. EIH occurred both locally (MD = 3.1) and remotely (MD = 1.8), with high-intensity exercise having the largest effect (local: MD = 7.5; remote: MD = 3.0) followed by moderate intensity (local: MD = 3.1; remote: MD = 3.0). Low-intensity exercise had minimal impact. Neither long nor short exercise duration induced EIH. Bicycling was found to be effective in eliciting EIH, in contrast to the limited research observed in other modalities. The overall evidence quality was moderate with many studies showing unclear risk biases.

Reliability and measurement error of exercise-induced hypoalgesia in pain-free adults and adults with musculoskeletal pain: A systematic review

OBJECTIVES

We systematically reviewed the reliability and measurement error of exercise-induced hypoalgesia (EIH) in pain-free adults and in adults with musculoskeletal (MSK) pain.

METHODS

We searched EMBASE, PUBMED, SCOPUS, CINAHL, and PSYCINFO from inception to November 2021 (updated in February 2024). In addition, manual searches of the grey literature were conducted in March 2022, September 2023, and February 2024. The inclusion criteria were as follows: adults - pain-free and with MSK pain - a single bout of exercise (any type) combined with experimental pre-post pain tests, and assessment of the reliability and/or measurement error of EIH. Two independent reviewers selected the studies, assessed their Risk of Bias (RoB) with the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) RoB tool, and graded the individual results (COSMIN modified Grading of Recommendations Assessment, Development, and Evaluation).

RESULTS

We included five studies involving pain-free individuals (n = 168), which were deemed to have an overall "doubtful" RoB. No study including adults with MSK pain was found. The following ranges of parameters of reliability and measurement error of EIH were reported: intraclass correlation coefficients: 0-0.61; kappa: 0.01-0.46; standard error of measurement: 30.1-105 kPa and 10.4-21%; smallest detectable changes: 83.54-291.1 kPa and 28.83-58.21%.

CONCLUSIONS

We concluded, with a very low level of certainty, that the reliability and measurement error of EIH is, in pain-free adults, respectively, "insufficient" and "indeterminate." Future studies should focus on people with MSK pain and could consider using tailored exercises, other test modalities than pressure pain threshold, rater/assessor blinding, and strict control of the sources of variations (e.g., participants' expectations).

Modulation of pain perceptions following treadmill running with different intensities in females

We aimed to compare the effects of three intensities of treadmill running on exercise-induced hypoalgesia (EIH) in healthy individuals. We anticipated that the primary and secondary changes in pain perception and modulation may differ between running intensities. Sixty-six women were randomly assigned to one of three treadmill running intensities for 35 min: 40% reserved heart rate (HRR), 55% HRR, or 70% HRR. The effects of EIH were assessed using pressure pain thresholds (PPT) and tolerance thresholds (PPTol). We measured conditional pain modulation (CPM). Compared with baseline, PPT and PPTol significantly increased in all groups during running and at the 5-10-min follow-up. The PPT and PPTol changes in the moderate- and low-intensity groups were significantly higher than those in the high-intensity group during running and 24 h after running, while the CPM responses of the high-intensity group were significantly reduced at the 24-h follow-up. Moderate- and low-intensity running may elicit significant primary and secondary (persisting over 24 h) EIH effects and increase CPM responses in females. However, high-intensity running induced only limited analgesic effects and reduced CPM responses, which may be attributed to the activation of endogenous pain modulation.

The role of spontaneous vs. experimentally induced attentional strategies for the pain response to a single bout of exercise in healthy individuals

OBJECTIVES

Exercise-induced pain and exercise-induced hypoalgesia (EIH) are well described phenomena involving physiological and cognitive mechanisms. Two experiments explored whether spontaneous and instructed mindful monitoring (MM) were associated with reduced exercise-induced pain and unpleasantness, and increased EIH compared with spontaneous and instructed thought suppression (TS) in pain-free individuals.

METHODS

Eighty pain-free individuals participated in one of two randomized crossover experiments. Pressure pain thresholds (PPTs) were assessed at the leg, back and hand before and after 15 min of moderate-to-high intensity bicycling and a non-exercise control condition. Exercise-induced pain and unpleasantness were rated after bicycling. In experiment 1 (n=40), spontaneous attentional strategies were assessed with questionnaires. In experiment 2, participants (n=40) were randomly allocated to use either a TS or MM strategy during bicycling.

RESULTS

In experiment 1, the change in PPTs was significantly larger after exercise compared with quiet rest (p<0.05). Higher spontaneous MM was associated with less exercise-induced unpleasantness (r=-0.41, p<0.001), whereas higher spontaneous TS was associated with higher ratings of exercise-induced unpleasantness (r=0.35, p<0.05), but not with pain intensity or EIH. In experiment 2, EIH at the back was increased in participants using instructed TS compared with participants using instructed MM (p<0.05).

CONCLUSIONS

These findings suggest that spontaneous and presumably habitual (or dispositional) attentional strategies may primarily affect cognitive-evaluative aspects of exercise, such as feelings of exercise-induced unpleasantness. MM was related to less unpleasantness, whereas TS was related to higher unpleasantness. In terms of brief experimentally-induced instructions, TS seems to have an impact on physiological aspects of EIH; however, these preliminary findings need further research.

The Interaction Between Psychosocial Factors and Exercise-Induced Hypoalgesia in Pain-Free Nurses

Purpose

This cross-sectional study aimed to investigate whether psychosocial factors were predictive for exercise-induced hypoalgesia (EIH) in pain-free adults.

Methods

A sample of 38 pain-free nurses with a mean (SD) age of 26 (6) years were included in this study. Participants completed psychosocial questionnaires prior to physical tests. Pressure pain threshold (PPT) was assessed bilaterally at the calves (local), lower back (semi-local) and forearm (remote) before and immediately after a maximal graded cycling exercise test. Separate linear mixed effects models were used to determine change in PPT before and after cycling exercise (EIH). Multiple linear regression for all psychosocial variables and best subset regression was used to identify predictors of EIH at all locations.

Results

The relative mean increase in PPT at the forearm, lumbar, calf, and globally (all sites pooled) was 6.0% (p<0.001), 10.1% (p<0.001), 13.9% (p<0.001), and 10.2% (p=0.013), respectively. Separate best subset multiple linear regression models at the forearm (predictors; Multidimensional Scale of Perceived Social Support (MSPSS) total), lumbar (predictors; MSPSS total, Pain Catastrophizing Scale (PCS) total, Depression Anxiety Stress Scale (DASS) depression), calf (predictors; MSPSS friends, PCS total), and global (predictors; MSPSS friends, PCS total) accounted for 7.5% (p=0.053), 13% (p=0.052), 24% (p=0.003), and 17% (p=0.015) of the variance, respectively.

Conclusion

These findings confirm that cycling exercise produced EIH in young nurses and provided preliminary evidence to support the interaction between perceived social support, pain catastrophizing and EIH. Further investigation is required to better understand psychological and social factors that mediate EIH on a larger sample of adults at high risk of developing chronic musculoskeletal pain.

Does Exercise-Induced Hypoalgesia Depend on Exercise Duration?

Acute physical activity is assumed to lead to exercise-induced hypoalgesia (EIH). Yet, little research has been conducted dealing with the influence of exercise duration on EIH. The aim of this study was to investigate the effects of three different exercise durations using the same intensity compared to a control session on EIH. A total of 36 participants conducted three different exercise sessions on a bicycle ergometer for 30, 45, and 60 min, respectively, in addition to a passive control session. The intensity was set to 75% of the individual's VO₂max. Pre and post exercise, pain sensitivity was measured employing pressure pain thresholds (PPT) at the elbow, knee, and ankle joints, as well as the sternum and forehead. In addition, the conditioned pain modulation (CPM) response was conducted pre and post exercise. The results reveal that the exercises neither led to any changes in PPT measured at any landmark nor induced any CPM response effects. These results do not confirm the hypoalgesic effects usually observed after exercise. The reasons explaining these results remain rather elusive but might be explained by the low intensities chosen leading to a milder release of pain inhibiting substances, the landmarks employed for PPT measurements, or potential non-responsiveness of participants.

Exercise-induced hypoalgesia (EIH) in response to different exercise intensities

Purpose

Acute physical activity leads to exercise-induced hypoalgesia (EIH). The aim of this study was to investigate the effects of four different exercise intensities on EIH.

Methods

25 male (age: 24.7 ± 3.0) subjects underwent four different exercise sessions on a bicycle ergometer for 30 min each at 60, 80, 100, and 110% of the individual anaerobic threshold on separate days in a randomized crossover design. Before, as well as 5- and 45-min post-exercise, pain sensitivity was measured employing pain pressure thresholds (PPT) at the elbow, knee, and ankle joints as well as the sternum and forehead. Besides, conditioned pain modulation (CPM) was conducted using thermal test- and conditioned stimuli before, 5-, and 45-min post-exercise.

Results

A main time effect was observed regarding PPT at all landmarks except for the forehead with higher values observed 5 and 45 min post-exercise compared to the pre-values. Yet, no interaction effects occurred. CPM did not change in response to any of the intensities used.

Conclusion

EIH occurs 5 and 45 min after exercise regardless of the intensity used at the joints and sternum which might be explained by local pain-inhibiting pathways and probably to a limited degree by central mechanisms, as no hypoalgesia was observed at the forehead and no changes in CPM occurred.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00421-022-04997-1.

[Pain modulation through exercise : Exercise-induced hypoalgesia in physiotherapy]

Exercise prescription is a central tenet of physiotherapy. One of the numerous benefits of exercise is its influence on endogenous pain modulation. Exercise-induced hypoalgesia (EIH) refers to a short-term change in pain sensitivity following an acute bout of exercise. Interest in this phenomenon has grown considerably with over 150 articles published, including four systematic reviews in 2020 alone.This narrative review provides an overview of EIH including a definition and summary of the underlying mechanisms and mediating factors. Recent systematic reviews assessing EIH in people with and without musculoskeletal complaints were evaluated using AMSTAR2. Review findings confirm the presence of EIH. For asymptomatic people, confidence in the evidence was low to very low due to high heterogeneity of included studies, risk of bias, and study eligibility. For people with pain, there is very low confidence, at best, that subgroups or isometric exercise show altered EIH. Despite the growing body of evidence, challenges within the available evidence due to its complex nature are highlighted. Recommendations regarding outcome measures and exercise parameters are required, and further understanding of reliability and validity of EIH is needed. There is a demand to further elucidate these parameters and contextual factors to advance our understanding of EIH. Additional clinical research, especially in patient populations, is required to then provide implications for rehabilitation.

Aerobic Exercise Attenuates Pain Sensitivity: An Event-Related Potential Study

In this study, electroencephalography (EEG) was utilized to explore the neurophysiological mechanisms of aerobic exercise-induced hypoalgesia (EIH) and provide a theoretical basis for the application of aerobic exercise in pain assessment and treatment. Forty-five healthy subjects were randomly divided into moderate-intensity aerobic exercise [70% heart rate reserve (HRR)], low-intensity aerobic exercise (50% HRR), or control groups (sitting). Aerobic exercise was performed with cycling. Pressure pain threshold (PPT), heat pain threshold (HPT), event-related potential (ERP) induced by contact heat stimulus and pain scoring were measured before and after the intervention. We found that moderate-intensity aerobic exercise can increase the PPT (rectus femoris: t = -2.71, p = 0.017; tibialis anterior muscle: t = -2.36, p = 0.033) and HPT (tibialis anterior muscle: t = -2.219, p = 0.044) of proximal intervention sites rather than distal sites, and decreased pain scorings of contact heat stimulus. After moderate-intensity aerobic exercise, alpha oscillation power reflecting the central descending inhibitory function was enhanced (t = -2.31, p < 0.05). Low-intensity aerobic exercise mainly reduced the pain unpleasantness rating (Block 1: t = 2.415, p = 0.030; Block 2: t = 3.287, p = 0.005; Block 4: t = 2.646, p = 0.019; Block 5: t = 2.567, p = 0.022). Aerobic exercise had an overall EIH effect. Its hypoalgesic effect was related to exercise intensity and affected by the site and type of pain stimulus. Moderate-intensity aerobic exercise effectively reduced the sensitivity to various painful stimuli, and low-intensity aerobic exercise selectively inhibited the negative emotional pain response. The hypoalgesic mechanism of aerobic exercise involves the enhancement of the central descending inhibitory function.

Endogenous Modulation of Pain: The Role of Exercise, Stress, and Cognitions in Humans

BACKGROUND

Pain is a complex and highly subjective phenomenon that can be modulated by several factors. On the basis of results from experimental and clinical studies, the existence of endogenous pain modulatory mechanisms that can increase or diminish the experience of pain is now accepted.

METHODS

In this narrative review, the pain modulatory effects of exercise, stress, and cognitions in humans are assessed.

RESULTS

Experimental studies on the effect of exercise have revealed that pain-free participants show a hypoalgesic response after exercise. However, in some patients with chronic pain, this response is reduced or even hyperalgesic in nature. These findings will be discussed from a mechanistic point of view. Stress is another modulator of the pain experience. Although acute stress may induce hypoalgesia, ongoing clinical stress has detrimental effects on pain in many patients with chronic pain conditions, which have implications for the understanding, assessment, and treatment of stress in patients with pain. Finally, cognitive strategies play differing roles in pain inhibition. Two intuitive strategies, thought suppression and focused distraction, will be reviewed as regards experimental, acute, and chronic pain.

CONCLUSION

On the basis of current knowledge on the role of exercise, stress, and cognitive pain control strategies on the modulation of pain, implications for treatment will be discussed.

Exploration of the Supraspinal Hypotheses about Spinal Cord Stimulation and Dorsal Root Ganglion Stimulation: A Systematic Review

Despite the established efficacy and effectiveness of Spinal Cord Stimulation (SCS), there is still no consensus on the supraspinal mechanisms of action of this therapy. The purpose of this study was to systematically review previously raised hypotheses concerning supraspinal mechanisms of action of SCS based on human, animal and computational studies. Searches were conducted using four electronic databases (PubMed, EMBASE, SCOPUS and Web of Science), backward reference searching and consultation with experts. The study protocol was registered prior to initiation of the review process (PROSPERO CRD42020161531). A total of 54 publications were included, 21 of which were animal studies, and 33 were human studies. The supraspinal hypotheses (n = 69) identified from the included studies could be categorized into six groups concerning the proposed supraspinal hypothesis, namely descending pathways (n = 24); ascending medial pathway (n = 13); ascending lateral pathway (n = 10); affective/motivational influences (n = 8); spinal–cerebral (thalamic)-loop (n = 3) and miscellaneous (n = 11). Scientific support is provided for the hypotheses identified. Modulation of the descending nociceptive inhibitory pathways, medial and lateral pathways were the most frequently reported hypotheses about the supraspinal mechanisms of action of SCS. These hypotheses were mainly supported by studies with a high or moderate confidence in the body of evidence.

A novel metric of reliability in pressure pain threshold measurement

The inter-session Intraclass Correlation Coefficient (ICC) is a commonly investigated and clinically important metric of reliability for pressure pain threshold (PPT) measurement. However, current investigations do not account for inter-repetition variability when calculating inter-session ICC, even though a PPT measurement taken at different sessions must also imply different repetitions. The primary aim was to evaluate and report a novel metric of reliability in PPT measurement: the inter-session-repetition ICC. One rater recorded ten repetitions of PPT measurement over the lumbar region bilaterally at two sessions in twenty healthy adults using a pressure algometer. Variance components were computed using linear mixed-models and used to construct ICCs; most notably inter-session ICC and inter-session-repetition ICC. At 70.1% of the total variance, the source of greatest variability was between subjects (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\sigma }_{subj}^{2}$$\end{document}σsubj2 = 222.28 N²), whereas the source of least variability (1.5% total variance) was between sessions (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\sigma }_{sess}^{2}$$\end{document}σsess2 = 4.83 N²). Derived inter-session and inter-session-repetition ICCs were 0.88 (95%CI: 0.77 to 0.94) and 0.73 (95%CI: 0.53 to 0.84) respectively. Inter-session-repetition ICC provides a more conservative estimate of reliability than inter-session ICC, with the magnitude of difference being clinically meaningful. Quantifying individual sources of variability enables ICC construction to be reflective of individual testing protocols.

Exercise-induced hypoalgesia after acute and regular exercise: experimental and clinical manifestations and possible mechanisms in individuals with and without pain

This review describes methodology used in the assessment of the manifestations of exercise-induced hypoalgesia in humans and previous findings in individuals with and without pain. Possible mechanisms and future directions are discussed.

Exercise and physical activity is recommended treatment for a wide range of chronic pain conditions. In addition to several well-documented effects on physical and mental health, 8 to 12 weeks of exercise therapy can induce clinically relevant reductions in pain. However, exercise can also induce hypoalgesia after as little as 1 session, which is commonly referred to as exercise-induced hypoalgesia (EIH). In this review, we give a brief introduction to the methodology used in the assessment of EIH in humans followed by an overview of the findings from previous experimental studies investigating the pain response after acute and regular exercise in pain-free individuals and in individuals with different chronic pain conditions. Finally, we discuss potential mechanisms underlying the change in pain after exercise in pain-free individuals and in individuals with different chronic pain conditions, and how this may have implications for clinical exercise prescription as well as for future studies on EIH.

Exercise-induced pain threshold modulation in healthy subjects: a systematic review and meta-analysis

Background

The use of exercise is a potential treatment option to modulate pain (exercise-induced hypoalgesia). The pain threshold (PT) response is a measure of pain sensitivity that may be a useful marker to assess the effect of physical exercise on pain modulation.

Aim

The aim of this systematic review and meta-analysis is to evaluate the PT response to exercise in healthy subjects.

Methods

We searched in MEDLINE, EMBASE, Web of Science, Lilacs, and Scopus using a search strategy with the following search terms: "exercise" OR "physical activity" AND "Pain Threshold" from inception to December 2nd, 2019. As criteria for inclusion of appropriate studies: randomized controlled trials or quasi-experimental studies that enrolled healthy subjects; performed an exercise intervention; assessed PT. Hedge's effect sizes of PT response and their 95% confidence intervals were calculated, and random-effects meta-analyses were performed.

Results

For the final analysis, thirty-six studies were included (n=1326). From this we found a significant and homogenous increase in PT in healthy subjects (ES=0.19, 95% CI= 0.11 to 0.27, I2=7.5%). According to subgroup analysis the effect was higher in studies: with women (ES=0.36); performing strength exercise (ES=0.34), and with moderate intensity (ES=0.27), and no differences by age were found. Confirmed by the meta-regression analysis.

Conclusion

This meta-analysis provides evidence of small to moderate effects of exercise on PT in healthy subjects, being even higher for moderate strength exercise and in women. These results support the idea of modulation of the endogenous pain system due to exercise and highlight the need of clinical translation to chronic pain population.

Cognitive Inhibition Correlates with Exercise-Induced Hypoalgesia After Aerobic Bicycling in Pain-Free Participants

Purpose

Exercise-induced hypoalgesia (EIH) is the short-term reduction of pain sensitivity after a single bout of exercise. Descending pain inhibition has been proposed to at least partly underlie EIH. Cognitive inhibition is the ability to inhibit a pre-potent response and has in turn been associated with descending pain inhibition, as indexed by conditioned pain modulation. Therefore, we hypothesized that cognitive inhibition is associated with higher EIH.

Methods

In this cross-sectional study, 37 pain-free participants (16 male, age 27.75 ± 9.91) completed a stop-signal task assessing cognitive inhibition ability and a control condition in the first session. In the second session, pre–post-test design EIH was assessed by means of aerobic bicycling (15 min., 75% VO₂max) and isometric knee extension (90 sec, 30% MVC). EIH was assessed with pressure pain thresholds (PPT) and temporal summation of pain (TSP), each at the hand and at the leg. Correlational analyses quantified the associations between cognitive inhibition and EIH change scores.

Results

Better cognitive inhibition correlated with EIH change scores in PPTs after aerobic bicycling at the hand (r = −0.35, 95% CI: −0.57; −0.08, p =0.021), but not at the leg (rho = −0.10, 95% CI: −0.36; 0.18, p = 0.277). No correlations between cognitive inhibition and change in PPTs after isometric knee extension at the hand (rho = −0.03, 95% CI: −0.30; 0.25, p = 0.857) nor at the leg (rho = −0.03, 95% CI: −0.25; 0.30, p = 0.857) were observed. There were no EIH effects after isometric exercise and, generally, no effects of exercise on TSP.

Conclusion

This study provides preliminary evidence for the notion that cognitive inhibition might play a supportive role in EIH. Although these results are clearly in need of replication, they accord well with previously reported associations between cognitive inhibition, experimental pain and descending pain inhibition.