Physical Activity May Be Associated with Conditioned Pain Modulation in Women but Not Men among Healthy Individuals

Physical Activity Is Predictive of Conditioned Pain Modulation in Healthy Individuals: A Cross-Sectional Study

Even in healthy populations, conditioned pain modulation (CPM) magnitude varies. This may be accounted for by (non-)modifiable factors, including physical activity (PA). Yet, little research has thoroughly examined PA and its relation with CPM magnitude in a representative sample. Therefore, the present study investigated the predictive effect of PA on CPM magnitude in 105 healthy adults. PA was assessed during 7 consecutive days by self-report using the International Physical Activity Questionnaire and by monitor-based accelerometry. CPM was examined using a heterotopic noxious-conditioning stimulation protocol during which the effect of a hot water-conditioning stimulus on pressure pain thresholds was evaluated. Comparative, correlation, and hierarchical linear regression analyses were performed. Report-based walking predicts 4.8% of variance in pain-modulatory capacity, moderate PA predicts 10.2% of variance in pain-modulatory capacity, and report-based time spent on total PA predicts 7.0% of variance in pain-modulatory capacity. More metabolic equivalent-minutes/week spent on total PA, including walking and moderate PA, is associated with greater pain-modulatory capacity. The findings of this study add to the limited evidence on the predictive effect of PA on CPM. It urges to consider PA a confounding factor when examining CPM. The current study provides evidence that a physically active lifestyle benefits endogenous pain modulation in healthy adults. Given its potential, walking and moderate-intensity PA might be achievable treatment strategies for pain patients known to have impaired CPM. PERSPECTIVE: The results of this article show that a physically active lifestyle, including larger amounts of walking and moderate activity, predicts greater pain-modulatory capacity. TRIAL REGISTRATION: This study has not been preregistered.

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.

Associations of pain sensitivity and conditioned pain modulation with physical activity: findings from the Multicenter Osteoarthritis Study (MOST)

OBJECTIVE

Individuals with chronic pain due to knee osteoarthritis (OA) are insufficiently physically active, and alterations of facilitatory and inhibitory nociceptive signaling are common in this population. Our objective was to examine the association of these alterations in nociceptive signaling with objective accelerometer-based measures of physical activity in a large observational cohort.

DESIGN

We used data from the Multicenter Osteoarthritis Study. Measures of peripheral and central pain sensitivity included pressure pain threshold at the knee and mechanical temporal summation at the wrist, respectively. The presence of descending pain inhibition was assessed by conditioned pain modulation (CPM). Physical activity was quantitatively assessed over 7 days using a lower back-worn activity monitor. Summary metrics included steps/day, activity intensity, and sedentary time. Linear regression analyses were used to evaluate the association of pain sensitivity and the presence of descending pain inhibition with physical activity measures.

RESULTS

Data from 1873 participants was analyzed (55.9% female, age = 62.8 ± 10.0 years). People having greater peripheral and central sensitivity showed lower step counts. CPM was not significantly related to any of the physical activity measures, and none of the exposures were significantly related to sedentary time.

CONCLUSIONS

In this cohort, greater peripheral and central sensitivity were associated with reduced levels of objectively-assessed daily step counts. Further research may investigate ways to modify or treat heightened pain sensitivity as a means to increase physical activity in older adults with knee OA.

The persian version of the fear-avoidance beliefs questionnaire among iranian post-surgery patients: a translation and psychometrics

INTRODUCTION

Fear-avoidance beliefs (FAB) play a crucial role in the treatment outcomes of post-surgery patients. These beliefs can lead to activity avoidance, increased pain, and decreased quality of life. Therefore, accurately measuring these beliefs in Iranian patients is of significant importance. The Fear-Avoidance Belief Questionnaire (FABQ) is a patient-reported questionnaire that evaluates individuals' FAB. Since the validity and reliability of the Persian version of FABQ (FABQ-P) have not been assessed based on the Iranian population and sociocultural contexts, the current study has been implemented to determine the reliability and validity of the FABQ-P among Iranian post-operative patients by translation and psychometric properties.

METHODS

This methodological study conducted in 2023, a sample of 400 patients who had undergone surgery were selected using a convenience sampling method. The scale used in the study was translated and its psychometric properties were evaluated through network analysis and assessments of construct validity (including exploratory and confirmatory factor analysis), convergent validity, and discriminant validity. Additionally, the study assessed the internal consistency of the scale.

RESULTS

The MLEFA results with Promax and Kaiser Normalization rotation yielded two factors explaining 57.91% of the variance, encompassing 13 items. Also, the model was approved by CFA. Convergent and discriminant validity have been confirmed through the following criteria: Average Variance Extracted (AVE) exceeding 0.5, Composite Reliability (CR) surpassing 0.7, and Heterotrait-Monotrait Ratio of Correlations (HTMT) equating to 0.597. As for reliability, Cronbach's alpha, composite reliability (CR), and MaxR for all constructs were greater than 0.7, demonstrating good internal consistency.

CONCLUSION

As demonstrated by the results, the FABQ-P has a satisfactory level of reliability along with authentic validity according to the sociocultural contexts of Iranian post-operative patients.

Physical activity, sitting time, and thermal quantitative sensory testing responses in African Americans

Introduction

Prior research suggests that African Americans (AAs) have more frequent, intense, and debilitating pain and functional disability compared with non-Hispanic Whites (NHWs). Potential contributing factors to this disparity are physical activity and sedentary behavior, given that AAs are less physically active, and physical activity is associated with antinociception (whereas sedentary behavior is linked to pronociception). However, impact of these factors on pain processing has largely been unexplored in AAs, especially before chronic pain onset.

Objective

This study examined relationships between physical activity, sedentary behavior (sitting time), and laboratory measures of pain and pain modulation in adult AAs. These included heat pain threshold and tolerance, temporal summation of pain (TSP, a marker of central sensitization), and conditioned pain modulation (CPM, a marker of descending pain inhibition).

Methods

Multiple regressions were conducted to examine the effects of physical activity and sitting time on heat threshold and tolerance. Multilevel models were conducted to assess the relationship between physical activity, sitting time, and temporal summation of pain. Additional multilevel models were conducted to assess the relationship between physical activity, sitting time, and conditioned pain modulation.

Results

Higher level of physical activity, but not sitting time, was associated with reduced TSP slopes. Neither physical activity nor sitting time was associated with CPM slopes. No significant relationships between physical activity or sitting time and heat pain threshold or tolerance were detected.

Conclusions

These findings suggest that physical activity is associated with reduced TSP, an effect which may be driven by reduced spinal hyperexcitability in more active individuals. Thus, structural and individual interventions designed to increase physical activity in healthy, young AAs may be able to promote antinociceptive processes (ie, reduced TSP/reduced pain facilitation) potentially protective against chronic pain.

Sex-related differences in experimental pain sensitivity in subjects with painful or painless neuropathy after surgical repair of traumatic nerve injuries

Higher pain intensities at all experimental stimuli but a tendency to faster recovery after cold conditioning stimuli were seen in women with neuropathy in comparison with men.

Introduction:

Sex-related influences represent a contributor to greater pain sensitivity and have a higher prevalence of many chronic pain conditions, including neuropathic pain (NP), among women.

Objectives:

The aim was to analyze how differences in ongoing pain, experimental pain intensity, and conditioned pain modulation (CPM) relate to sex in subjects with neuropathy after traumatic nerve injuries.

Methods:

Endogenous pain modulation was compared between male (n = 77) and female (n = 55) subjects and between subjects with NP (female = 31, male = 39) and pain-free subjects with posttraumatic neuropathy (female = 24, male = 38). Conditioned pain modulation was assessed by pain ratings to pressure stimuli before and after a noxious conditioning stimulus (CS) conducted with one arm submerged in cold water (4°C) for 1 minute. Time of recovery (Time off) of pain intensity from peak VAS_maxc after CS was recorded and compared between male and female patients.

Results:

Greater ongoing pain intensity was found among female patients compared with male patients and more experimental pain after pressure and cold induced pain. Summing all groups together, women had 0.8 times higher odds (20%) of recovering sooner than men after CS (95% CI = 0.65–2.9). No differences in CPM, time off, and psychosocial variables were seen between female and male patients (P < 0.05).

Conclusion:

Our hypothesis for sex differences in endogenous pain modulation was only supported by a shorter after-sensation time after cold CS in female patients. No sex differences in the magnitude of CPM effect were identified. Increased pain intensity for experimental pain, in both neuropathic pain and neuropathy without pain, was found in female patients.

Symptomatic but not Asymptomatic COVID-19 Impairs Conditioned Pain Modulation in Young Adults

Pain is a common symptom reported in COVID-19 patients. Impaired endogenous pain-modulatory mechanisms such as conditioned pain modulation (CPM), and exercise-induced hypoalgesia (EIH) have been found in chronic pain conditions but is often overlooked in acute conditions that evoke painful symptoms, such as COVID-19. The purpose was to compare pressure-pain sensitivity, CPM, and EIH function among individuals who previously had COVID-19, both symptomatically and asymptomatically, and a healthy control group. Pressure pain thresholds of 59 participants were assessed in the forearm and leg using a pressure algometer before and after 1) submersion of their dominant foot in cold water (2°C) for 1min; and 2) isometric knee extension performed to task-failure at 25% of their maximal contraction. The CPM response was attenuated in individuals who were infected with symptomatic COVID-19 (N = 26) compared to asymptomatic COVID-19 (N = 13) in arm (-1.0% ± 20.3 vs 33.3% ± 26.2; P < .001) and leg (12.8% ± 22.0 vs 33.8% ± 28.2; P = .014) and compared to controls (N = 20) in arm only (-1.0% ± 26.2 vs 23.4% ± 28.2; P = .004). The EIH response was not different between groups. CPM was impaired in individuals who had symptomatic COVID-19, which may have long-term implications on pain modulation.

Perspective

This study reveals that CPM was impaired in individuals who had symptomatic COVID-19 during the first wave of COVID-19, pre vaccine. These findings present a preliminary motive to study the long-term implications of COVID-19 and its effects on pain modulation.

Personal influencing factors for pressure pain threshold in healthy people: A systematic review and meta-analysis

All studies that investigated personal factors influencing pressure pain threshold (PPT) in healthy people were synthesized. Data was summarized, and risk of bias (RoB) and level of evidence were determined. Results were pooled per influencing factor, grouped by body region and included in meta-analyses. Fifty-four studies were eligible. Five had low, nine moderate, and 40 high RoB. Following meta-analyses, a strong conclusion was found for the influence of scapular position, a moderate for the influence of gender, and a weak for the influence of age (shoulder/arm region) and blood pressure on PPT. In addition, body mass index, gender (leg region), alcohol consumption and pain vigilance may not influence PPT. Based on qualitative summary, depression and menopause may not influence PPT. For other variables there was only preliminary or conflicting evidence. However, caution is advised, since the majority of included studies showed a high RoB and several were not eligible to include in meta-analyses. Heterogeneity was high in the performed meta-analyses, and most conclusions were weak. More standardized research is necessary.

The influence of physical activity on the nociceptive flexion reflex in healthy people

BACKGROUND

The nociceptive flexion reflex (NFR) is a spinal reflex induced by painful stimuli resulting in an appropriate withdrawal response. The NFR is considered to be an objective physiological correlate of spinal nociception. Previous research has already demonstrated that physical activity (PA) can influence pain assessments. To date, no studies have directly examined the relationship between PA and spinal nociception. Hence, this study aimed to investigate whether the NFR threshold can be predicted by report-based and monitor-based measures of PA in healthy adults.

METHODS

PA and the NFR threshold of 58 healthy adults were assessed. PA was evaluated by self-report using the International Physical Activity Questionnaire and by monitor-based accelerometry data. The NFR threshold was elicited through transcutaneous electrical stimulation of the sural nerve and quantified by the biceps femoris muscle electromyogram. Hierarchical linear regression analyses were performed to determine the relationship between PA and the NFR, while controlling for confounders.

RESULTS

Monitor-based measured step count and activities of moderate- to vigorous-intensity predicted the NFR threshold accounting for 23.0% (p = .047) to 37.1% (p = .002) of the variance. Larger amounts of step counts and higher participation in moderate- to vigorous-intensity activities predicted higher NFR thresholds. Monitor-based activities of sedentary intensity predicted the NFR threshold accounting for 35.8% (p = .014) to 35.9% (p = .014) of the variance. Spending more time per day on activities of sedentary intensity predicted lower NFR thresholds.

CONCLUSIONS

The study provides preliminary evidence indicating that a physically active lifestyle may reduce spinal nociception in healthy adults, while a sedentary lifestyle enhances spinal nociception.

SIGNIFICANCE

The present study provides preliminary evidence that the influencing effects of physical activity on pain are the result of a strong descending control and do not purely rely on supraspinal mechanisms. These study results highlight the importance of considering physical activity levels when evaluating nociceptive processing, given the prognostic value of physical activity in spinal nociception. Furthermore, this study encourages future research to examine the effects of moderate- to vigorous-intensity exercise programmes on spinal nociception in chronic pain populations.

Relationships Between Psychological, Sleep, and Physical Activity Measures and Somatosensory Function in People With Peripheral Joint Pain: A Systematic Review and Meta-Analysis

OBJECTIVE

Alteration in somatosensory function has been linked to pain experience in individuals with joint pain. In this systematic review we aimed to establish the level of evidence of associations between psychological, social, physical activity, and sleep measures and somatosensory function that were assessed via quantitative sensory testing (QST) among individuals with joint pain.

METHODS

A comprehensive literature search was conducted in 6 electronic databases from their inception to July 2019. Two reviewers independently assessed the methodological quality using a modified Quality in Prognostic Studies (QUIPS) tool and supplemented with recommendations from the Critical Appraisal and Data Extraction for Systematic Review of Prediction Modelling Studies (CHARMS) checklist and the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. The level of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) system. Data were pooled to evaluate the strength of the relationships of interest.

RESULTS

Seventeen studies related to joint pain were included. Pain catastrophizing, depression, anxiety, and physical activity level have been shown to have a significant (small to fair) association with several QST measures. Pressure pain threshold (PPT) is the only measure that was found to be consistently correlated with all the domains. The overall quality of evidence for all factors ranged from very low to moderate. Subgroup analysis revealed a stronger association for depression and pain catastrophizing and PPT and temporal pain summation in individuals with shoulder pain.

CONCLUSION

Psychological factors and physical activity levels are associated with somatosensory function in people with joint pain. These factors need to be adjusted when establishing predictive relationships between somatosensory function and pain outcomes in individuals with joint pain.

Influence of self-reported physical activity and sleep quality on conditioned pain modulation in the orofacial region

OBJECTIVES

To evaluate the influence of self-reported physical activity and sleep quality on conditioned pain modulation (CPM) in the orofacial region.

MATERIALS AND METHODS

Ninety healthy participants aged 18-50 years old were evenly distributed according to the level of physical activity into low, moderate, and high level. The classification of physical activity was based on modified criteria of the International Physical Activity Questionnaire (IPAQ), considering intensity, duration, and frequency of physical activity. The Pittsburgh Sleep Quality Index (PSQI) assessed sleep quality and the individuals were then classified as good or poor sleepers. CPM was assessed using the pressure pain threshold (PPT) of the anterior temporalis as test stimulus and hand immersion in hot water as conditioning stimulus. ANOVA was applied to the data and Tukey's posttest was applied when the main effects or interactions were significant (p < 0.050).

RESULTS

There was no significant main effect of neither physical activity nor sleep quality on pain modulation. However, individuals who reported high level of physical activity and good quality of sleep had a greater pain modulation (- 0.60 ± 0.34) when compared with those who reported moderate (- 0.10 ± 0.25) and low level of physical activity (- 0.10 ± 0.52) and good sleep quality (p < 0.028).

CONCLUSIONS

Pain modulation seems to be more efficient in individuals who report a good sleep quality and a high level of physical activity.

CLINICAL RELEVANCE

Conditioned pain modulation is highly variable in healthy people. Therefore, a multifactorial approach should be taken into consideration in the evaluation of the efficacy of endogenous analgesia.

Relationships Between Psychological, Social, Physical Activity, and Sleep Measures and Somatosensory Function in Individuals With Spinal Pain: A Systematic Review and Meta-analysis

OBJECTIVE

Somatosensory abnormalities are linked to clinical pain outcomes in individuals with spinal pain. However, a range of factors might confound the relationship between altered somatosensory function and clinical pain outcomes. This systematic review aimed to evaluate the literature to assess the level of evidence of associations between psychological, social, physical activity, and sleep measures and somatosensory function (assessed via sensory psychophysical testing) among individuals with spinal pain.

METHODS

A comprehensive literature search was performed in 6 electronic databases from their inception to June 2018. Two reviewers independently assessed the methodological quality using a modified Quality in Prognostic Studies (QUIPS) tool and supplemented with recommendations from the Critical Appraisal and Data Extraction for the Systematic Review of Prediction Modelling Studies (CHARMS) checklist and the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. The level of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) system. Data were pooled to evaluate the strength of the relationships of interest.

RESULTS

Among the 17 factors identified in the included studies, pain catastrophizing, depression, and pain-related fear have significant negative (small to fair) associations with pain thresholds. A "very low" to "moderate" quality of evidence was found for all the investigated factors. Subgroup analysis showed a smaller effect size for pain catastrophizing/fear of movement and pain thresholds in individuals with low back pain.

CONCLUSIONS

Psychological factors are associated negatively with pain thresholds and they need to be adjusted when establishing predictive relationships between somatosensory function and pain outcomes in individuals with spinal pain.

Comparisons of Conditioned Pain Modulation and Physical Activity Between Hispanic and Non-Hispanic White Adults

It is well-documented that adults of racial/ethnic minorities experience pain more frequently and suffer from more severe pain compared to non-Hispanic White (NHW) adults. These observations are consistent with laboratory findings that adults of racial/ethnic minorities show increased sensitivity to laboratory pain stimuli compared to NHW adults. Research generally shows that central pain inhibitory processing, as quantified using conditioned pain modulation (CPM), serves as a risk factor of clinical pain. Currently, racial/ethnic differences in CPM are poorly understood, and research suggests that physical activity (PA) may help understand potential racial/ethnic differences in CPM. However, very little is known regarding CPM in Hispanic compared to NHW adults. Therefore, the present study compared CPM and PA between Hispanic and NHW adults. Twenty-one young, healthy Hispanic and 21 NHW adults completed validated questionnaires to assess PA, pain catastrophizing, and dispositional optimism. The participants then completed the CPM test to quantify changes in pain ratings to electrical stimuli delivered to the ankle during concurrent application of pressure pain applied to the finger compared to baseline. Results indicated that Hispanic and NHW adults exhibited comparable CPM responses and PA levels, along with similar levels of pain catastrophizing and dispositional optimism (p > 0.05). These results suggest that young, healthy Hispanic and NHW adults may possess a similar risk of clinical pain when they are comparable in PA, pain catastrophizing, and dispositional optimism. More research is needed to explore the role of PA in racial/ethnic disparities in clinical pain and central pain inhibitory processing.