Pain Response after Maximal Aerobic Exercise in Adolescents across Weight Status

Rowing and pain: does rowing lead to exercise-induced hypoalgesia?

Physical activity acutely alters pain processing known as exercise-induced hypoalgesia (EIH). This randomized controlled crossover study investigated the effects of two different rowing exercises on EIH and to explore whether possible EIH effects are related to individual rowing specific performance. Fifty male experienced rowers conducted two rowing sessions (submaximal: 30 min of moderate rowing (70% of maximum heart rate); maximal: 350 m in an all-out fashion) and a control session. Pre and post exercise pain sensitivity was measured bilaterally using pressure pain thresholds (PPT; Newton (N)) at the elbow, knee, ankle, sternum, and forehead. Individual performance was determined as maximum watt/kg and was tested for correlations with changes in PPT. Higher PPT values were observed after maximal exercise at all landmarks with a mean change ranging from 2.5 ± 7.8 N (right elbow; p = 0.027; dz = 0.323) to 10.0 ± 12.2 N (left knee; p ≤ 0.001; dz = 0.818). The submaximal (range from -1.6 ± 8.8 N (Sternum; p = 0.205; dz = 0.182) to 2.0 ± 10.3 N (right ankle; p = 0.176; dz = 0.194)) and control session (range from -0.5 ± 7.6 N (left elbow; p = 0.627; dz = 0.069) to 2.6 ± 9.1 N (right ankle; p = 0.054; dz = 0.279)) did not induce changes. Relative performance levels were not correlated to EIH (range from: r = -0.129 (p = 0.373) at sternum to r = 0.176 (p = 0.221) at left knee). EIH occurred globally after a short maximal rowing exercise while no effects occurred after rowing for 30 min at submaximal intensity. EIH cannot be explained by rowing specific performance levels in experienced rowers. However, the sample may lack sufficient heterogeneity in performance levels to draw final conclusions.

The Rating of Perceived Exertion-Pediatric (RPE-P) Scale: Preliminary Validation

Physical activity is critical to functional rehabilitation for youth with chronic pain, which may be especially true for those with co-occurring obesity. To facilitate the development of physical activity interventions for youth with chronic pain, the newly developed "Rating of Perceived Exertion-Pediatric" scale was modeled after the widely used pain numeric rating scale-11. This study is an initial evaluation of the scale in a sample of adolescents (n = 157, 13-17 years, 51% female) with four subgroups: (1) healthy controls (healthy weight/no pain); (2) chronic pain/healthy weight; (3) obese (no pain); (4) chronic pain/obese. Participants rated perceived exertion using the new scale and the Borg 6-20 Scale of Perceived Exertion while holding a three-minute yoga pose (Warrior II). In the whole sample, the Perceived Exertion-Pediatric scale showed good concurrent (p < 0.001), convergent (all ps < 0.05), discriminant (p = 0.431), and known-groups validity (all ps < 0.05). The chronic pain subgroup also showed good concurrent (p < 0.001), mixed convergent (ps < 0.001 to 0.315), and good discriminant validity (p = 0.607). Limitations include the restricted age range, lack of diversity, and lack of test-retest reliability. The RPE-P shows promise as an assessment tool for perceived exertion in adolescents with and without chronic pain.

Can we improve exercise-induced hypoalgesia with exercise training? An overview and suggestions for future studies

Exercise-induced hypoalgesia refers to a reduction in pain sensitivity following a single bout of exercise, which has been shown to be diminished or impaired with aging and chronic pain. Exercise training (repeated bouts of exercise over time) is often recommended as a non-pharmacological treatment for chronic pain and age-related functional declines. However, whether exercise training can augment the exercise-induced hypoalgesia has not been well studied. The purpose of this paper is to 1) provide an overview of the existing literature investigating the effect of exercise training on the magnitude of exercise-induced hypoalgesia, and 2) discuss potential underlying mechanisms as well as considerations for future research. Given the paucity of randomized controlled trials in this area, the effects of exercise training on exercise-induced hypoalgesia are still unclear. Several potential mechanisms have been proposed to explain the impaired exercise-induced hypoalgesia in chronic pain and older individuals (e.g., endogenous opioid, cardiovascular, and immune system). Exercise training appears to induce physiological changes in those systems, however, further investigations are necessary to test whether this will lead to improved exercise-induced hypoalgesia. Future research should consider including a time- and age-matched non-training group and utilizing the same exercise protocol for testing exercise-induced hypoalgesia across intervention groups.

The effectiveness of different aerobic exercises to improve pain intensity and disability in chronic low back pain patients: a systematic review

Background: Physical activity, including aerobic exercise, is highly recommended for chronic low back pain (CLBP) patients to improve pain intensity and functional disability. Objectives: To assess the effectiveness of different aerobic exercises to reduce pain intensity and functional disability in patients with CLBP. Methods: A computer-aided search was performed to find Randomised Controlled Trials (RCTs) that evaluated the effectiveness of different aerobic exercises in CLBP. Articles published between January 2007 to December 2020 were included in the review. Quality assessment using the PEDro scale, extraction of relevant information, and evaluation of outcomes were done by two reviewers independently. Results: A total of 17 studies were included that involved 1146 participants. Outcomes suggested that aerobic exercise combined with other interventions was more effective than aerobic exercise alone. Aerobic exercise with higher frequency (≥ 5 days/week) and longer duration (≥ 12 weeks) were effective to gain clinically significant (≥ 30%) improvements. Environment and using pedometer did not seem to influence the outcomes. Conclusions: Pain intensity and functional disability in CLBP patients can be minimized by prescribing aerobic exercise. However, to get better improvements, aerobic exercise should be done in combination with other interventions and at optimum frequency and duration. Further studies should emphasize examining the optimal doses and duration of different aerobic exercises.

Lean Mass is Associated with, but Does Not Mediate Sex Differences in Pressure Pain Sensitivity in Healthy Adults

Background

Sex differences exist in pain sensitivity, however, the underlying mechanism(s) that explain these differences are not fully understood. Pain sensitivity has been shown to be influenced by body mass index, but limited data exist on the role of body composition on pain sensitivity. The purpose was to examine the influence of body composition on pain sensitivity in males and females.

Methods

This cross-sectional study design used pressure pain thresholds (PPT) of 87 participants (45 female) who were assessed in the vastus lateralis (leg PPT) and brachioradialis (arm PPT) using a pressure algometer. Fat and lean tissue were assessed via dual-energy X-ray absorptiometry (DXA). A two group by two limb, repeated measured ANOVA was used to assess differences between limbs and sex. Spearman correlations and hierarchical regression analyses were employed to determine the association between body composition and PPT.

Results

Males had higher PPTs then females (P<0.05) and had higher DXA assessed lean and lower levels fat mass (P<0.05). Total body and limb specific lean mass was associated with PPTs (r≥0.34; P<0.05). Hierarchical regression analysis revealed lean mass was a significant predictor of 8% of the variance in arm PPT (P<0.006) and 18% of the variance in leg PPT (P<0.001). However, lean mass was not found to statistically mediate the observed sex differences in PPT.

Conclusion

This finding suggests lean mass may play a previously unknown role in sex differences in pressure pain sensitivity. Future studies are needed to confirm this finding and a larger sample size is likely required to have sufficient power to perform the mediation analysis.

Body Composition does not influence Conditioned Pain Modulation and Exercise Induced Hyperalgesia in Healthy Males and Females

BACKGROUND

Obese individuals report a higher susceptibility to chronic pain. Females are more likely to have chronic pain and excess adipose tissue. Chronic pain is associated with dysfunctional pain modulatory mechanisms. Body composition differences may be associated with pain modulation differences in males and females. The purpose of this study was to investigate body composition (lean vs fat mass) differences and pain modulatory functioning in healthy males and females.

METHODS

Pressure pain thresholds (PPT) of 96 participants (47M; 49F) were assessed in both arms and legs before and after a double footed ice bath (2°C) for 1min and an isometric knee extension, time to failure task. The difference between post and pre measures was defined conditioned pain modulatory (CPM) response (ice bath) and exercise induced hypoalgesia (EIH) response. Whole body and site-specific fat and lean tissue were assessed via DXA scan.

RESULTS

Sex differences were found in whole body lean mass (61.5±6.7kg vs 41.2±5.4kg; P<0.001) but not fat mass amount (17.2±10.5kg vs 21.0±9.7kg; P=0.068). No effect of sex was found between limb CPM (P=0.237) and limb EIH (P=0.512). When controlling for lean mass there was no significant effect of sex on CPM (P=0.732) or EIH (P=0.474) response. Similar findings were found for fat mass.

CONCLUSION

The lack of difference suggests that males and females have similar modulatory functioning. It appears that in healthy adults free from chronic pain, neither fat mass nor lean mass has an influence on endogenous pain modulatory function.

Effect of Neuromuscular Electrical Stimulation During Walking on Pain Sensitivity in Women With Obesity With Knee Pain: A Randomized Controlled Trial

OBJECTIVE

To assess the extent to which pain sensitivity is altered in women with obesity with frequent knee symptoms who walk with either a hybrid training system (HTS) that provides antagonist muscle electrical stimulation vs sensory transcutaneous electrical nerve stimulation (TENS).

DESIGN

Randomized, double-blinded, controlled trial.

SETTING

University-based fitness center.

PARTICIPANTS

Twenty-eight women (N=28) with obesity, aged 40-70 years, with daily knee symptoms.

INTERVENTIONS

Participants were randomized to 12 weeks of biweekly 30-minute walking exercise with either HTS (HTSW group) or sensory TENS (control group).

MAIN OUTCOME MEASURES

Pressure pain thresholds (PPTs) at the more symptomatic knee (local PPT) and PPT at the ipsilateral pain-free wrist (remote PPT).

RESULTS

After adjustment for preintervention values and body mass index (BMI), there was a statistically significant improvement in local PPT in the HTSW group compared with the control group (P=.039). After adjustment for pretraining value, age, and BMI, changes in remote PPT when comparing groups did not reach statistical significance, although the HTS group tended to demonstrate increased remote PPT (P=.052) compared with the control group. Moreover, after adjustment for pretraining value, knee pain, and quality of life, comparing groups did not reach statistical significance, although the HTS group tended to demonstrate decreased knee pain (P=.069) compared with the control group.

CONCLUSIONS

Augmentation of walking exercise with HTS was more effective than application of sensory TENS in improving local pain sensitivity at the knee but not at the wrist in women with obesity with frequent knee symptoms.

Helping Children with Obesity "Move Well" To Move More: An Applied Clinical Review

ABSTRACT

Children with obesity experience musculoskeletal pain and reduced physical function and well-being, which collectively impact their fitness, strength, motor skills, and even their ability to undertake simple tasks, like walking and climbing stairs. Disrupting obesity-related disability may be critical to increasing children's physical activity. Thus, barriers to movement should be considered by health practitioners to improve the efficacy of prescribed physical activity. This applied clinical review highlights key subjective and objective findings from a hypothetical case scenario, linking those findings to the research evidence, before exploring strategies to enhance movement and increase physical activity.

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

BACKGROUND

Exercise is recommended to promote and maintain health and as treatment for more than 25 diseases and pain conditions. Exercise-induced hypoalgesia (EIH), a measure of descending pain inhibitory control, has been found to be impaired in some chronic pain conditions, but it is currently unclear if EIH is modifiable. This study investigated whether a long-term exercise intervention could modulate EIH in healthy subjects.

METHODS

In 38 healthy subjects, EIH was assessed as change in pressure pain threshold (PPT) after a three-minute isometric wall squat within the first week and after approximately seven weeks of military training (MT). Further, temporal summation of pain (TSP) and Knee injury and Osteoarthritis Outcome Score (KOOS) were assessed. Physical performance capacity was assessed using the Endurance 20-m shuttle run fitness test (20MSR). Hypoalgesic (EIH > 0.0 kPa) and hyperalgesic (EIH ≤ 0.0 kPa) subgroups were defined based on baseline EIH. Change in EIH following MT was used as the primary outcome.

RESULTS

Increased EIH (P = 0.008), PPT (P < 0.003), and 20MSR (P < 0.001) were found following MT, with no changes in TSP and KOOS (P > 0.05). Subjects with a hyperalgesic EIH response at baseline (26% of the participants) presented significantly improved EIH following MT (P = 0.010). Finally, an association between 20MRS change and EIH change was found (r = 0.369, P = 0.023).

CONCLUSIONS

MT increased EIH, especially in subjects who demonstrated a hyperalgesic response at baseline. Improvement in physical performance capacity was associated with an improvement in EIH, indicating that improvement in physical performance capacity may improve central pain mechanisms.

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.

Quantitative Sensory Testing in Adolescents with Co-occurring Chronic Pain and Obesity: A Pilot Study

Factors such as gender, ethnicity, and age affect pain processing in children and adolescents with chronic pain. Although obesity has been shown to affect pain processing in adults, almost nothing is known about pediatric populations. The aim of this pilot study was to explore whether obesity alters sensory processing in adolescents with chronic pain. Participants were recruited from a chronic pain clinic (Chronic Pain (CP), n = 12 normal weight; Chronic Pain + Obesity (CPO), n = 19 overweight/obesity) and from an obesity clinic (Obesity alone (O), n = 14). The quantitative sensory testing protocol included assessments of thermal and mechanical pain thresholds and perceptual sensitization at two sites with little adiposity. The heat pain threshold at the hand was significantly higher in the CPO group than in either the CP or O groups. Mechanical pain threshold (foot) was significantly higher in the CPO group than the CP group. No differences were found on tests of perceptual sensitization. Correlations between experimental pain and clinical pain parameters were found for the CPO group, but not for the CP group. This preliminary study provides important lessons learned for subsequent, larger-scale studies of sensory processing for youth with co-occurring chronic pain and obesity.

Beneficial Effects of Regular Physical Activity on Exercise-Induced Analgesia in Adolescent Males

PURPOSE

To evaluate exercise-induced analgesia (EIA) effectiveness in healthy adolescent males and to investigate possible associations between EIA and physiological/psychological variables.

METHODS

Twenty-eight healthy adolescent males (14-17 y) participated in this study. EIA was evaluated by comparing perceptions of heat pain stimulations before and after an increasing maximal load test on a cycle ergometer (VO2max).

RESULTS

Pain intensity for mild and strong heat pain stimulations significantly decreased following physical exercise (mild: EIA = 28.6%; 95% confidence interval, 0.9-1.9; P < .001 and strong: EIA = 11.3%; 95% confidence interval, 0.3-1.4; P = .002). The number of physical activity hours per week was positively correlated with the effectiveness of EIA for mild and strong pain intensity (r = .41, P = .03 and r = .43, P = .02, respectively).

CONCLUSIONS

Intense physical exercise decreases perception of intensity of experimental heat pain in healthy adolescent males. The least physically active adolescents have reduced EIA effectiveness to experimental heat pain stimulations compared with physically active ones. Adolescents adopting an active lifestyle have more endogenous pain inhibition and could, therefore, potentially be less disposed to suffer from chronic pain later in life.

Systemic Exercise-Induced Hypoalgesia Following Isometric Exercise Reduces Conditioned Pain Modulation

Objective

Physically active individuals show greater conditioned pain modulation (CPM) compared with less active individuals. Understanding the effects of acute exercise on CPM may allow for a more targeted use of exercise in the management of pain. This study investigated the effects of acute isometric exercise on CPM. In addition, the between-session and within-session reliability of CPM was investigated.

Design

Experimental, randomized crossover study.

Setting

Laboratory at Marquette University.

Subjects

Thirty healthy adults (19.3±1.5 years, 15 males).

Methods

Subjects underwent CPM testing before and after isometric exercise (knee extension, 30% maximum voluntary contraction for three minutes) and quiet rest in two separate experimental sessions. Pressure pain thresholds (PPTs) at the quadriceps and upper trapezius muscles were assessed before, during, and after ice water immersions.

Results

PPTs increased during ice water immersion (i.e., CPM), and quadriceps PPT increased after exercise (P < 0.05). CPM decreased similarly following exercise and quiet rest (P > 0.05). CPM within-session reliability was fair to good (intraclass correlation coefficient [ICC] = 0.43-0.70), and the between-session reliability was poor (ICC = 0.20-0.35). Due to the variability in the systemic exercise-induced hypoalgesia (EIH) response, participants were divided into systemic EIH responders (N = 9) and nonresponders (N = 21). EIH responders experienced attenuated CPM following exercise (P = 0.03), whereas the nonresponders showed no significant change (P > 0.05).

Conclusions

Isometric exercise decreased CPM in individuals who reported systemic EIH, suggesting activation of shared mechanisms between CPM and systemic EIH responses. These results may improve the understanding of increased pain after exercise in patients with chronic pain and potentially attenuated CPM.

Physical Fitness and the Level of Pain Intensity in Adolescents: A School-based Study

Background: The main aim of the study was to explore the association between objectively measured physical fitness and the level of pain intensity. Methods: In this cross-sectional study, we included 1036 adolescents (m_age ± SD = 16.3 ± 1.1 years; m_height ± SD = 1.74 ± 0.1 m; m_weight ± SD = 64.7 ± 12.4 kg; m_{body-mass index} ± SD = 21.3 ± 3.0 kg/m²) from 11 secondary schools located in the city of Zagreb (Croatia). Physical fitness was determined by using waist circumference, sit-ups in 1 min, standing long jump and sit-and-reach tests. Overall physical fitness index was calculated by summing the z-score values of each physical fitness test. The level of pain intensity was assessed with the Numeric Pain Rating Scale, a one-dimensional measure of pain intensity. Associations were calculated with correlation analyses. Results: In boys, pain intensity was associated with sit-ups in 1 min (r = -0.16, p < 0.001), standing long jump (r = -0.14, p = 0.003) and overall physical fitness index (r = -0.13, p = 0.004), while no significant associations with waist circumference (r = 0.04, p = 0.438) and sit-and-reach test (r = -0.01, p = 0.822) were observed. In girls, pain intensity was associated with standing long jump (r = -0.17, p < 0.001) and overall physical fitness index (r = -0.10, p = 0.018), while no significant associations with waist circumference (r = 0.01, p = 0.735), sit-ups in 1 min (r = -0.06, p = 0.126) and sit-and-reach test (r = -0.05, p = 0.232) were observed. When we adjusted for self-rated health, sleep duration, smoking status, alcohol consumption, screen-time and psychological distress, similar associations remained. Conclusions: Our study shows a weak association between physical fitness and pain intensity in a large sample of adolescents. Although a cross-sectional design, health-professionals should use physical fitness as a screening tool to assess the level of pain intensity.

Does Weight Status Impact Metabolic Health in Adolescents When Controlling for Physical Fitness?

PURPOSE

To determines whether adolescents who are fit with overweight/obesity are similar in their metabolic profile to adolescents who are fit and normal weight.

METHODS

Adolescents participated in 3 sessions: (1) resting vitals and anthropometrics; (2) maximal aerobic treadmill test ((Equation is included in full-text article.)) to determine physical fitness; and (3) dual-energy x-ray absorptiometry and fasting laboratory draw for analysis of insulin, glucose, high-density lipoprotein, triglycerides, and C-reactive protein.

RESULTS

Of the 30 fit adolescents who are normal weight and 16 adolescents who are fit and overweight/obese (OW/OB), metabolic syndrome was apparent in 1 adolescent who are normal weight and 4 adolescents who are OW/OB. Metabolic syndrome severity was positively associated with body mass index, waist circumference, total body fat, insulin resistance, and C-reactive protein but inversely associated with peak relative, but not lean (Equation is included in full-text article.).

CONCLUSIONS

Despite good physical fitness, adolescents who are OW/OB demonstrated greater metabolic syndrome than adolescents who are normal weight. Future intervention research is necessary to explore the relation between physical fitness and metabolic syndrome.

Lean mass mediates the relation between temporal summation of pain and sex in young healthy adults

Background

Previous studies have shown that women experience greater temporal summation (TS) of pain than men using a repetitive thermal stimulus. These studies, however, did not individualize the thermal stimulus to each subject’s thermal pain sensitivity. The aim of this study was to investigate sex differences in TS using an individualized protocol and potential mediators that have been shown to influence TS including physical activity and body composition.

Methods

Fifty young healthy men and women (21 men) participated in the study. Subjects completed TS testing on the right forearm using a repetitive thermal stimulus at a temperature that the subject reported 6/10 pain. Other testing included body composition (lunar iDXA), activity monitoring (Actigraph), and Pain Catastrophizing Scale (PCS).

Results

Women reported greater TS than men (p = 0.019), and TS was correlated with right arm lean mass (r = − 0.36, p = 0.01) and magnification subscale of PCS (r = − 0.32, p = 0.03). Mediation analysis showed a complete mediation for the relation between sex and TS by right arm lean mass (indirect effect = 2.33, 95% BCa CI [0.42, 4.58]) after controlling for the temperature, the magnification subscale of PCS, and the average time spent in moderate to vigorous physical activity.

Conclusion

The results of this study suggest that lean mass is a contributing factor to the sex differences in TS. Future studies should investigate whether interventions that increase lean mass have a positive effect on TS.

The effect of exercise on vaccine-related pain, anxiety and fear during HPV vaccinations in adolescents

INTRODUCTION

With increased school-based vaccinations for improved coverage rates and practicality, the World Health Organization (WHO) recently endorsed research to identify possible interventions to reduce vaccine-related pain in mass clinical and school-based settings. In particular, the lack of research in adolescents indicate a particular need in this population. Acute exercise has analgesic effects and has been used as a behavioural adjuvant to vaccination. Here, we examine the effect of exercise on vaccine-related pain, anxiety and fear in adolescents, during a school-based program for HPV vaccinations.

METHODS

116 students (Female: 61, Male: 55) aged 11-13 years were randomly allocated to either an Exercise (n = 60) or Control (n = 56) group. All participants completed demographic and Trait-anxiety questionnaires prior to receiving the vaccine according to usual care. The Exercise group also performed upper body exercise for 15 min prior to receiving the vaccine. Immediately after the vaccine administration, all participants reported on pain, anxiety and fear at the time of receiving the vaccine.

RESULTS

Female adolescents in the Exercise group reported significantly less pain (3.64; 95% CI, 2.98-4.30) than Controls (4.58; 95% CI, 3.96-5.19; p = 0.04). Further, females reported greater pain and anxiety than males in the Control group but not the Exercise group.

CONCLUSION

This study supports the use of exercise prior to vaccine administration, especially in female adolescents who are particularly vulnerable to negative experiences during vaccination procedures. Furthermore, the ease of application, as well as the benefit of exercise, provides support for the use of simple exercise prior to vaccination in mass vaccination settings. Clinical trial registry: ANZCTR, ACTRN12614001185651.

Exercise-induced hypoalgesia in women with varying levels of menstrual pain

Background and aims:

Exercise-induced hypoalgesia (EIH) is a well-established phenomenon in pain-free individuals that describes a decrease in pain sensitivity after an acute bout of exercise. The EIH response has been demonstrated to be sub-optimal in the presence of persisting pain. Menstrual pain is a common recurrent painful problem with many women experiencing high levels of pain each cycle. However, the EIH response has not been examined in a cohort of women with high levels of menstrual pain. This research aimed to examine whether EIH manifests differently in women with varying levels of menstrual pain. The primary hypothesis was that women with high levels of menstrual pain would demonstrate compromised EIH. Secondary aims were to explore relationships between EIH and emotional state, sleep quality, body mass index (BMI) or physical activity levels.

Methods:

Pressure pain thresholds (PPT) were measured in 64 participants using a digital handheld algometer before and after a submaximal isometric-handgrip exercise. EIH index was compared between low (VAS 0–3), moderate (VAS 4–7) and high (VAS 8–10) pain groups, using a linear mixed model analysis with participant as a random effect, and site, menstrual pain category and the interaction between the two, as fixed effects.

Results:

EIH was consistently induced in all groups. However, there was no statistically significant difference between the pain groups for EIH index (p=0.835) or for any co-variates (p>0.05).

Conclusions:

EIH was not found to differ between women who report regular low, moderate or high levels of menstrual pain, when measured at a point in their menstrual cycle when they are pain free.

Implications:

This study provides insight that EIH does not vary in women with differing levels of menstrual pain when they are not currently experiencing pain. The current findings indicate that, although menstrual pain can involve regular episodes of high pain levels, it may not be associated with the same central nervous system dysfunctions as seen in sustained chronic pain conditions.

Exercise does not produce hypoalgesia when performed immediately after a painful stimulus

Background and aims:

Exercise-induced hypoalgesia (EIH) and conditioned pain modulation (CPM) are assumed to reflect descending pain inhibition. Potential interactions between EIH and CPM may be important in the therapy of chronic pain, as reduced CPM and increased pain after exercise are frequently observed. This study compared the EIH response after CPM was activated using a cold pressor task with the EIH response after a control condition.

Methods:

Thirty-one participants (age: 27.7±9.8; 15 female) completed two sessions: a cold pressor task (CPT) session, i.e. testing EIH with preceding CPM activation induced using a 2 min CPT at approximately 2°C, and a control session, i.e. testing EIH after a control condition (2 min of quiet rest). EIH was induced using a 15 min bicycling exercise at a target heart rate corresponding to 75% VO2 max. Repeated measures ANOVAs on pressure pain thresholds (PPTs) at the hand, back and leg were used to determine the effects of exercise after the cold pressor test and control condition. Furthermore, correlations between CPM and EIH, in the CPT session as well as control session, were calculated at each assessment site.

Results:

A significant time x condition interaction (F(1, 30)=43.61, p<0.001, partial η2=0.59), with Bonferroni-corrected post-hoc t-tests showed that PPTs increased after exercise in the control session (p<0.001), but not in the CPT session (p=0.125). Furthermore, there was a small positive correlation of EIH in the control session and CPM at the hand (r=0.37, p=0.043). There was a moderate negative correlation of EIH in the CPT session and CPM at the hand (r=−0.50, p=0.004), and smaller negative correlations at the back (r=−0.37, p=0.036) and at the leg (r=−0.35, p=0.054).

Conclusions:

Attenuated EIH after the CPM activation in comparison to a control condition suggests that EIH and CPM may share underlying pain inhibitory mechanisms on a systemic level. This assumption is further supported by the finding of small to moderate significant correlations between EIH and CPM at the hand. The attenuated EIH response furthermore suggests that these mechanisms are exhaustible, i.e. that its effects decline after a certain amount of inhibition.

Implications:

In patients with chronic pain, assessing the current capacity of the descending pain inhibitory system – as indicated by the CPM response – may aid to make better predictions about how patients will respond to exercise with respect to acute pain reduction.

Does Exercise Decrease Pain via Conditioned Pain Modulation in Adolescents?

PURPOSE

Pain relief after exercise, exercise-induced hypoalgesia (EIH), is established across the lifespan. Conditioned pain modulation (CPM: pain inhibits pain) may be a mechanism for EIH.

METHODS

In 55 adolescents, pressure pain thresholds were measured before and after exercise (deltoid, quadriceps, and nail bed) and during CPM at the nail bed and deltoid test stimulus sites. The relationship between EIH and CPM was explored.

RESULTS

EIH occurred at deltoid and quadriceps; CPM occurred at nail bed and deltoid. CPM and EIH correlated at deltoid; adolescents with greater CPM experienced greater pain relief after exercise. At this site, CPM predicted 5.4% of EIH. Arm lean mass did not add a significant effect. Peak exercise pain did not influence EIH. Adolescents with none, minimal, moderate, or severe peak exercise pain experienced similar EIH.

CONCLUSIONS

A potential relationship exists between CPM and EIH in adolescents. Pediatric physical therapists should consider the CPM response when prescribing exercise as a pain management tool.