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

Blood flow restriction augments exercise-induced pressure pain thresholds over repetition and effort matched conditions

We sought to determine the effects of blood flow restriction (BFR) on exercise-induced hypoalgesia, specifically using low-load (LL) resistance exercise (30% 1RM) protocols that accounted for each individual's local muscular endurance capabilities. Forty-four participants completed four conditions: (1) 70% of maximal BFR repetitions with blood flow restriction (LL+BFR exercise); (2) 70% maximal BFR repetitions without LL+BFR (LL exercise); (3) 70% maximal free flow repetitions (LL+EFFORT exercise); (4) time-matched, non-exercise control (CON). Pressure pain threshold (PPT) was measured before and after exercise. Ischaemic pain threshold and tolerance was assessed only at post. The change in upper body PPT was greater for LL+BFR exercise compared to LL exercise [difference of 0.15 (0.35) kg/cm2], LL+EFFORT exercise [difference of 0.23 (0.45) kg/cm2], and the CON condition. The change in lower body PPT was greater for LL+BFR exercise compared to LL exercise [difference of 0.40 (0.55) kg/cm2], LL+EFFORT exercise [difference of 0.36 (0.62) kg/cm2], and the CON condition. Ischaemic pain thresholds and tolerances did not change. Submaximal exercise with BFR resulted in systemic increases in PPT but had no influence on ischaemic pain sensitivity. This effect is likely unique to BFR as we did not see changes in the effort matched free flow condition.

Effects of an eight-week physical exercise program on low back pain and function in fruit workers: A randomized controlled trial

BACKGROUND

Low back pain is prevalent in workers' health and functional performance.

OBJECTIVE

To evaluate the effects of a physical exercise program on low back pain and disability in fruit workers.

METHODS

This randomized controlled trial assigned 44 workers (37 ± 9 years) to two groups. The experimental group consisted of 10 men and 12 women with an average age of 38 (± 9) years, and the control group consisted of 8 men and 14 women with an average age of 36 (± 10) years. The experimental group (EG) performed a program of strength and flexibility exercises for eight weeks, twice a week. The control group (CG) received minimal care, with a booklet with guidelines for performing exercises. The primary outcomes included changes in perceived disability and the intensity of pain evaluated by the Rolland-Morris questionnaire and the Numerical Pain Scale, respectively. All outcomes were measured at baseline and after eight weeks of intervention.

RESULTS

A significant difference was observed in the within-group analysis, with a mean reduction in pain intensity in the EG and CG of -4.55 (95%CI -7.01 to -2.09) and -3.81 (95%CI 1.72-5.90), respectively. For disability, a reduction of -4.45 (95% CI -8.89 to -0.02) was observed in the EG and of -4.43 (-7.38 to -1.48) in the CG. There were no significant differences in the between-groups analysis.

CONCLUSIONS

The exercise program was not superior to using the educational booklet. However, both interventions showed substantial decreases in pain and disability levels.

Exercise-induced hypoalgesia with end-stage knee osteoarthritis during different blood flow restriction levels: Sham-controlled crossover study

BACKGROUND

Blood flow restriction (BFR) training could be a valuable treatment to induce exercise-induced hypoalgesia (EIH) in patients with end-stage knee osteoarthritis. However, the use of BFR in these patients is poorly explored and there is no evidence about the training dosage needed.

OBJECTIVE

To evaluate the effect of resistance training protocols with different occlusion levels of blood flow restriction (BFR) on EIH in patients with end-stage knee osteoarthritis.

DESIGN

Crossover study.

SETTING

University physical exercise laboratory.

PARTICIPANTS

26 adults with end-stage knee osteoarthritis.

INTERVENTIONS

Patients performed four sets (30, 15, 15, and 15 repetitions) separated by 1-minute rests of three protocols/sessions of low-load (30% one-repetition-maximum) seated knee extensions with elastic bands and BFR: placebo (sham BFR), BFR at 40% arterial occlusion pressure (AOP) and BFR at 80% AOP.

MAIN OUTCOME MEASURES

Pressure Pain Thresholds (PPT) and Visual Analog Scale (VAS) collected before, immediately after session, and after 10 minutes.

RESULTS

No differences in EIH were found between the different levels of BFR. However, 80% AOP protocol worsened VAS scores immediately (mean difference [MD]: -21.2 (95% confidence interval [CI] -33.9 to -8.5) while improving PPT immediately (MD affected limb: -.6 [95% CI -1.1 to -.2]); contralateral: -.6 (95% CI -1.0 to -.2]) and at 10 minutes (MD affected limb: -.6 [95% CI) -1.2 to -.1]; contralateral: -.7 [95% CI -1.1 to -.2]; and forearm: -.5 [95% CI -.9 to -.05]) post-exercise compared to baseline.

CONCLUSIONS

There is no EIH difference after using different occlusion levels. EIH is modulated by pain-related psychological constructs and self-perceived health status.

The Hypoalgesic Effect of Low-Load Exercise to Failure Is Not Augmented by Blood Flow Restriction

Purpose: To 1) examine whether blood flow restriction would provide an additional exercise-induced hypoalgesic response at an upper and lower limb when it is incorporated with low-load resistance exercise until failure, and 2) examine if increases in blood pressure and discomfort, with blood flow restricted exercise, would mediate the exercise-induced hypoalgesia over exercise without blood flow restriction. Methods: Forty healthy young participants completed two trials: four sets of unilateral knee extension exercise to failure at 30% of one-repetition maximum, with and without blood flow restriction. Pressure pain thresholds were assessed before (twice) and 5-min post exercise at an upper and lower limb. Blood pressure and discomfort ratings were recorded to examine mediating effects on exercise-induced hypoalgesia with blood flow restricted exercise. Results: Pressure pain threshold increased following both exercise conditions compared to a control, without any differences between exercise conditions at the upper (exercise conditions vs. control: ~0.37 kg/cm2) and lower (exercise conditions vs. control: ~0.60 kg/cm2) limb. The total number of repetitions was lower for exercise with blood flow restriction compared to exercise alone [median difference (95% credible interval) of -27.0 (-29.8, -24.4) repetitions]. There were no mediating effects of changes in blood pressure, nor changes in discomfort, for the changes in pressure pain threshold at either the upper or lower limb. Conclusion: The addition of blood flow restriction to low-load exercise induces a similar hypoalgesic response to that of non-blood flow restricted exercise, with a fewer number of repetitions.

Exercise Therapy for Chronic Neck Pain: Tailoring Person-Centred Approaches within Contemporary Management

Exercise therapy is considered the best evidence-based approach for managing chronic neck pain. However, the implementation of exercise therapy presents several challenges. Systematic reviews indicate that it has modest effectiveness, while clinical practice guidelines offer limited guidance on the exercise parameters required to optimise clinical outcomes. Moreover, recommendations often fail to differentiate between different types of neck pain. This article addresses the challenges associated with the prescription of exercise for chronic neck pain and provides recommendations for exercise therapy specific to chronic nociceptive, neuropathic, and nociplastic neck pain. The goal of this article is to facilitate the implementation of high-value evidence-based exercise therapy for these distinct types of chronic neck pain with the aim to improve its outcomes and to reduce the related individual and societal burdens.

Reductions in kinesiophobia and distress after pain neuroscience education and exercise lead to favourable outcomes: a secondary mediation analysis of a randomized controlled trial in primary care

ABSTRACT

Pain neuroscience education combined with exercise (PNE + exercise) is an effective treatment for patients with chronic spinal pain. Yet, however, little is known about its underlying therapeutic mechanisms. Thus, this study aimed to provide the first insights by performing a novel mediation analysis approach in a published randomized controlled trial in primary care where PNE + exercise was compared with standard physiotherapy. Four mediators (catastrophizing, kinesiophobia, central sensitization-related distress, and pain intensity) measured at postintervention and 3 outcomes (disability, health-related quality of life, and pain medication intake) measured at 6-month follow-up were included into the analysis. The postintervention measure of each outcome was also introduced as a competing candidate mediator in each respective model. In addition, we repeated the analysis by including all pairwise mediator-mediator interactions to allow the effect of each mediator to differ based on the other mediators' values. Postintervention improvements in disability, medication intake, and health-related quality of life strongly mediated PNE + exercise effects on each of these outcomes at 6-month follow-up, respectively. Reductions in disability and medication intake were also mediated by reductions in kinesiophobia and central sensitization-related distress. Reductions in kinesiophobia also mediated gains in the quality of life. Changes in catastrophizing and pain intensity did not mediate improvements in any outcome. The mediation analyses with mediator-mediator interactions suggested a potential effect modification rather than causal independence among the mediators. The current results, therefore, support the PNE framework to some extent as well as highlight the need for implementing the recent approaches for mediation analysis to accommodate dependencies among the mediators.

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.

Higher intensity exercise reduces disability more than lower intensity exercise in adults with chronic low back pain: A systematic review and meta-analysis

BACKGROUND

Intensity is an important determinant of physiological adaptations and health benefits of exercise, but the role of exercise intensity on improving outcomes in people with chronic low back pain (CLBP) is unclear. This systematic review aimed to determine the effect of higher versus lower intensity exercise intensity on pain, disability, quality of life and adverse events in people with CLBP.

METHODS

Six databases and four clinical trial registries were searched from inception to 21 December 2022, for randomised controlled trials that compared two or more exercise intensities in adults with CLBP. Data were analysed using random-effects meta-analysis for disability and synthesised narratively for pain, quality of life and adverse events due to limited studies. Risk of bias was assessed using the Cochrane tool and certainty of evidence was evaluated using Grading of Recommendations, Assessment, Development and Evaluations framework.

RESULTS

Four trials (n = 214 participants, 84% male) reported across five studies were included. Higher intensity exercise reduced disability more than lower intensity exercise at end-treatment (SMD [95% CI] = -0.39 [-0.56 to -0.22]; very low certainty) but not at 6-month follow-up (SMD [95% CI] = -0.20 [-0.53 to 0.13]; very low certainty). Higher intensity exercise did not reliably improve pain and quality of life more than lower intensity exercise. Adverse events did not differ between exercise intensities. All studies were at high risk of bias.

CONCLUSION

Based on very low certainty evidence from a limited number of studies, exercise intensity does not appear to meaningfully influence clinical outcomes in people with CLBP.

Physical exercise recommendations for patients with polycythemia vera based on preferences identified in a large international patient survey study of the East German Study Group for Hematology and Oncology (OSHO #97)

BACKGROUND

Exercise therapy during cancer treatment reduces symptom burden and improves quality of life (QoL). Polycythemia vera (PV) is a myeloproliferative neoplasia associated with good overall survival (up to decades) but a significant symptom burden, including thromboembolic events and dysesthesias. There are no specific exercise recommendations for patients with PV. Thus, we aimed to determine the exercise preferences of patients with PV and to derive specific recommendations based on the most commonly reported symptoms.

METHODS

This multicenter survey included patients with PV ≥18 years old. Demographic, clinical, and disease burden data were collected. The severity of selected symptoms was assessed using the adapted Myeloproliferative Neoplasms Symptom Assessment Form: 0 (absent), 1-30 (mild), 31-70 (moderate), or 71-100 (severe). The patients' information needs about physical activity (PA) and exercise preferences were recorded depending on their motivation and analyzed with regard to demographic aspects.

RESULTS

The sample comprised 182 patients (68% female, 61 ± 12 years). The prevalence of moderate-to-severe symptoms was 60% for fatigue, 44% for concentration problems, and 35% for bone/muscle pain. Other commonly reported symptoms included skin reactions (49%), splenomegaly (35%), and increased bleeding tendency (28%). Overall, 67% of respondents requested more information regarding PA. Patients with PV preferred individual training (79%) located outdoors (79%) or at home (56%). Regarding the amount of training, sports-inactive patients preferred a frequency of 1-2 times/week and session durations of 15-45 min, whereas sports-active patients preferred 3-4 times/week and 30-60 min (p < 0.001). Higher sport-inactiveness was observed in patients with lower educational level compared to patients with higher educational level (69% vs. 50%, p = 0.021). For beginners, combined resistance-endurance (circuit) training two times/week, which can be performed outdoors or at home, should be recommended. In the case of splenomegaly or bleeding symptoms, exercises with a low injury risk should be chosen.

CONCLUSION

PA is important for patients with PV; therefore, counseling should be integrated into the treatment plan. Specifically, patients with low educational level should be addressed. Prospective studies are warranted to evaluate the effects of the novel exercise recommendations.

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 Effect of Exercise on Pain in People with Cancer: A Systematic Review with Meta-analysis

INTRODUCTION

Cancer-related pain is common and undertreated. Exercise is known to have a pain-relieving effect in non-cancer pain.

OBJECTIVES

This systematic review aimed to evaluate (1) the effect of exercise on cancer-related pain in all cancers, and (2) whether the effect of exercise differed according to exercise mode, degree of supervision, intervention duration and timing (during or after cancer treatment), pain types, measurement tool and cancer type.

METHODS

Electronic searches were undertaken in six databases to identify exercise studies evaluating pain in people with cancer, published prior to 11 January 2023. All stages of screening and data extraction were conducted independently by two authors. The Cochrane risk of bias tool for randomised trials (RoB 2) was used and overall strength of evidence was assessed using the GRADE approach. Meta-analyses were performed overall and by study design, exercise intervention and pain characteristics.

RESULTS

In total, 71 studies reported in 74 papers were eligible for inclusion. The overall meta-analysis included 5877 participants and showed reductions in pain favouring exercise (standardised mean difference - 0.45; 95% confidence interval - 0.62, - 0.28). For most (> 82%) of the subgroup analyses, the direction of effect favoured exercise compared with usual care, with effect sizes ranging from small to large (median effect size - 0.35; range - 0.03 to - 1.17). The overall strength of evidence for the effect of exercise on cancer-related pain was very low.

CONCLUSION

The findings provide support that exercise participation does not worsen cancer-related pain and that it may be beneficial. Better pain categorisation and inclusion of more diverse cancer populations in future research would improve understanding of the extent of benefit and to whom.

PROSPERO REGISTRATION NUMBER

CRD42021266826.

Cervical musculoskeletal impairments and pain sensitivity in migraine patients

INTRODUCTION

Currently, examination of migraine patients relies on a clinical interview investigating symptoms characteristics. Despite this, to help identify distinct migraine subtypes and allow a personalized treatment approach, biomarkers to profile distinct migraine subtypes should be utilized in clinical and research settings. Therefore, there is a need to include physical and psychophysical examinations aimed at assessing migraine features quantitatively.

PURPOSE

This paper aimed to discuss if increased pressure pain sensitivity and impaired cervical musculoskeletal function could be considered 1) as quantitative features of migraine and 2) if they could be used as biomarkers to profile migraine patients in distinct subtypes.

IMPLICATION

Increased pain sensitivity and cervical musculoskeletal impairments have been suggested as quantitative biomarkers to phenotype and subgroup migraine patients in clinical and research settings. This could provide the first step for a mechanistically-driven and personalized treatment approach according to migraine phenotypes.

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.

Acute exercise of painful muscles does not reduce the hypoalgesic response in young healthy women - a randomized crossover study

OBJECTIVES

Exercise-induced hypoalgesia (EIH) is characterized by an increase in pain threshold following acute exercise. EIH is reduced in some individuals with chronic musculoskeletal pain, although the mechanisms are unknown. It has been hypothesized that this may relate to whether exercises are performed in painful or non-painful body regions. The primary aim of this randomized experimental crossover study was to investigate whether the presence of pain per se in the exercising muscles reduced the local EIH response. The secondary aim was to investigate if EIH responses were also reduced in non-exercising remote muscles.

METHODS

Pain-free women (n=34) participated in three separate sessions. In session 1, the maximal voluntary contraction (MVC) for a single legged isometric knee extension exercise was determined. In sessions 2 and 3, pressure pain thresholds (PPT) were assessed at the thigh and shoulder muscles before and after a 3-min exercise at 30 % of MVC. Exercises were performed with or without thigh muscle pain, which was induced by either a painful injection (hypertonic saline, 5.8 %) or a non-painful injection (isotonic saline, 0.9 %) into the thigh muscle. Muscle pain intensity was assessed with an 11-point numerical rating scale (NRS) at baseline, after injections, during and after exercises.

RESULTS

PPTs increased at thigh and shoulder muscles after exercise with painful (14.0-24.9 %) and non-painful (14.3-19.5 %) injections and no significant between-injection EIH differences were observed (p>0.30). Muscle pain intensity was significantly higher following the painful injection compared to the non-painful injection (p<0.001).

CONCLUSIONS

Exercising painful muscles did not reduce the local or remote hypoalgesic responses, suggesting that the pain-relieving effects of isometric exercises are not reduced by exercising painful body regions.

ETHICAL COMMITTEE NUMBER

S-20210184.

TRIAL REGISTRATION NUMBER

NCT05299268.

Effects of a foot-ankle muscle strengthening program on pain and function in individuals with knee osteoarthritis: a randomized controlled trial

BACKGROUND

Foot-ankle exercises could improve pain and function of individuals with KOA and need to be tested.

OBJECTIVE

To investigate whether an 8-week foot-ankle muscle strengthening program is effective for individuals with KOA to reduce pain and improve function.

METHODS

In this randomized controlled trial, individuals diagnosed with clinical and radiographic KOA were randomized into the intervention (supervised foot-ankle strengthening exercise program three times a week for 8 weeks) or control (usual care and recommendations of the healthcare team) group. Effectiveness was assessed by changes in clinical and functional outcomes between baseline and 8 weeks with pain as the primary outcome. ANCOVA tests using the intervention group as a reference and sex, body mass index, and baseline values as covariates assessed between-group differences.

RESULTS

The intervention group showed lower pain scores (-4.4 units; 95%CI = -7.5, -1.1), better function (-7.1 units; 95%CI = -12.7, -1.4), higher total functional score (-11.9 units; 95%CI = -20.7, -3.1), with confidence intervals indicating a potential for the differences to be clinically meaningful, and better scores for the 30-s chair stand test (2.7 repetitions; 95%CI = 1.1, 4.1), with a confidence interval indicating a moderate clinically meaningful difference, compared to the controls.

CONCLUSION

The 8-week foot-ankle exercise program showed positive, and potentially clinically meaningful, effects on knee pain and physical function among individuals with KOA, when compared to usual care.

TRIAL REGISTRATION

NCT04154059. https://clinicaltrials.gov/ct2/show/NCT04154059.

Physical therapist perceptions and use of clinical pain mechanism assessment in the musculoskeletal setting: a survey analysis

BACKGROUND

A mechanism-based approach to the evaluation and management of pain has been suggested across disciplines in contemporary research. However, the translation of pain mechanism assessment strategies in research to clinical practice is unclear. This study sought to explore perceptions and use of clinical pain mechanism assessment by physical therapists managing musculoskeletal pain.

METHODS

This was an electronic cross-sectional survey. After initial development, refinement, and piloting for comprehensiveness, comprehensibility and relevance, the survey was disseminated to members of the Academy of Orthopaedic Physical Therapy via email listserv. Data was maintained anonymously using the online database REDCap. Descriptive statistics and Spearman's correlations for non-parametric data were analyzed for frequencies and associations across variables.

RESULTS

In total, 148 respondents completed all aspects of the survey. Respondent age ranged from 26 to 73 years, with a mean (SD) of 43.9 (12.0). Most respondents (70.8%) reported performing clinical pain mechanism assessments at least 'sometimes'. A majority (80.4%) believed clinical pain mechanism assessments are useful in guiding management strategies while 79.8% reported specifically choosing interventions to alter aberrant pain mechanisms. The most commonly used pain severity, physical examination testing and questionnaires were the numeric pain rating scale, pressure pain thresholds and pain diagrams, respectively. However, the vast majority of instruments to clinically assess pain mechanisms were performed by a small proportion of respondents (< 30%). There were no significant correlations between age, years of experience, highest earned degree, completion of advanced training or specialist certification and testing frequency.

CONCLUSION

The evaluation of pain mechanisms involved in the pain experience is becoming common in research. The clinical application of pain mechanism assessment is unclear. Based on the results of this survey, physical therapists in the orthopedic setting believe pain mechanism assessment is useful, but data suggests it is infrequently performed. Additional research to uncover clinician motivation related to pain mechanism assessment is warranted.

Central sensitization in adolescents with hypermobility spectrum disorder or hypermobile Ehlers-Danlos syndrome-a feasibility study

BACKGROUND

Pain is a major symptom in adolescents with hypermobility spectrum disorder or hypermobile Ehlers-Danlos syndrome. Although the underlying mechanism causing generalized pain in children with hypermobility spectrum disorder or hypermobile Ehlers-Danlos syndrome is unclear, central sensitization has been suggested as a possible explanation. The aim of this study was to explore the feasibility of a study protocol for a future case-control study, investigating features of central sensitization in adolescents with hypermobility spectrum disorder or hypermobile Ehlers-Danlos syndrome.

METHODS

Central sensitization features were measured in ten patients and nine healthy controls aged 13-17 years via experimental pain measurement quantifying primary and secondary hyperalgesia, endogenous pain modulation, and exercise-induced hyperalgesia. Descriptive statistics were used. Frequency, median, and range values were calculated.

RESULTS

Eleven out of 57 patients chose to participate. No control could be recruited through public schools. Therefore, a convenience sampling strategy was used for the recruitment of the control group. The process of assessing primary and secondary hyperalgesia, endogenous pain modulation, and exercise-induced hyperalgesia was well tolerated by all participants (patients and controls). When assessing endogenous pain modulation via conditioned pain modulation, two participants in the patient group and three in the control group did not achieve a pain experience ≥ 3 on the numerical rating scale when immersing their hands in cold water.

CONCLUSION

This study investigated the feasibility, safety, and toleration of experimental pain measurements in adolescents with hypermobility spectrum disorder or hypermobile Ehlers-Danlos syndrome. Although the test protocol proved to be sufficiently feasible for use with the participant group, it will need to be adapted in the main study in order to obtain more reliable data. Recruitment, especially of participants for the control group, can be a major obstacle for future studies and requires careful planning.

TRIAL REGISTRATION

Researchweb.org, 270,501. Registered on 9 May 2019.

Analgesic Effect of Passive Range-of-Motion Exercise on the Healthy Side for Pain after Total Knee Arthroplasty: A Prospective Randomized Trial

Background

Exercise can reduce the pain threshold momentarily and induce analgesia, which is called exercise-induced hypoalgesia (EIH). Exercise therapy for inducing EIH may be an effective treatment option for pain. We aimed at investigating whether continuous passive motion (CPM) on both healthy and affected sides could induce EIH and reduce pain in the operated knee in patients after unilateral total knee arthroplasty (TKA). Patients and Methods. In this prospective randomized controlled trial, participants were randomly assigned to two groups: a bilateral group that received bilateral exercise on the operated and healthy sides and a unilateral group that received exercise therapy only on the affected side. We enrolled 40 patients aged ≥60 years who were scheduled to undergo unilateral TKA. Visual analogue scale (VAS) scores and range of motion (ROM) on the operated side were measured immediately before and after CPM on postoperative days 2, 4, 7, and 14. The primary outcome was the difference in the VAS scores before and after CPM on postoperative day 14. The secondary outcome was the difference in the ROM before and after CPM on postoperative day 14.

Results

Comparison of VAS scores before and after CPM showed no significant intergroup differences on all measurement dates. However, there was a significant difference in values on day 14 (P < 0.05). Both groups showed an increase in ROM after CPM, with significant increments observed on days 2 and 4 in the bilateral group and on day 14 in the unilateral group. There was no significant difference in values on postoperative day 14.

Conclusion

Post-TKA pain was reduced by performing the same exercise on the healthy knee during CPM therapy. This could be due to EIH, and the results indicated that EIH can also influence postoperative pain immediately after surgery.

Effects of a videoconference-based therapeutic exercise intervention on the musculoskeletal pain of eldercare workers: protocol for the ReViEEW randomized controlled trial

BACKGROUND

Prevalence of musculoskeletal pain is high among eldercare workers, and therapeutic exercise has shown to be effective for its management. Although telerehabilitation is an increasingly used alternative for delivering therapeutic exercise, no studies have assessed synchronous group telerehabilitation interventions for the management of musculoskeletal disorders. Thus, the aim of this article is to describe the protocol of a randomized controlled trial that will assess the effects of a videoconference-based group therapeutic exercise intervention on the musculoskeletal pain of eldercare workers.

METHODS

This multicenter trial will randomly assign 130 eldercare workers to either a control or experimental group. Participants in the control group will not receive any intervention, and participants in the experimental group will take part in a 12-week remote supervised videoconference-based intervention, consisting of 2 weekly 45-min group sessions. Each session will include 4 sets of 6 progressive resistance exercises for the lower limbs, upper limbs and trunk, performed with bodyweight and elastic bands at moderate-high intensity. Following the 12 weeks, participants in the experimental group will be provided with material for autonomously carry on the therapeutic exercises and advised to continue performing 2 weekly sessions on their own until a 48-week follow-up. Assessments will be performed at baseline, 12 and 48 weeks. Primary outcome will be average pain intensity in the low back during the last 7 days, measured by the 0-10 Numerical Rating Scale. Secondary outcomes will include additional measures of musculoskeletal pain, psycho-affective state, work-related variables, and physical fitness.

DISCUSSION

This will be the first trial, to our knowledge, assessing whether a remote delivery of a group therapeutic exercise intervention via videoconference is effective for reducing the musculoskeletal pain, improving the psycho-affective state and physical fitness, and enhancing the work-related parameters in eldercare workers. If successful, this study will provide innovative tools for implementing effective, scalable and affordable interventions to tackle musculoskeletal disorders in the workplace. It will also highlight the utility of telehealth, and address the importance of therapeutic exercise to manage musculoskeletal pain in a critical population for the future of the aging societies as it is the eldercare workers.

TRIAL REGISTRATION

The study protocol was prospectively registered at ClinicalTrials.gov (registration number: NCT05050526) on September 20, 2021.

Effect of exercise on chronic neck pain and central sensitization: A protocol for a randomized crossover trial

Exercise-induced hypoalgesia (EIH) has been found to vary widely within individuals with chronic neck pain (NP). Research has suggested that the presence of central sensitization within a subgroup of individuals with chronic NP might be a mediating factor to explain the relationship between exercise and improvements in patient-reported outcomes. Furthermore, recent work has found that lactate might play a role in the development and maintenance of chronic pain. The immediate effect of a single bout of physical exercise on central sensitization in individuals with chronic NP and the relationship between lactate concentration, central sensitization and pain sensitivity are to be investigated. Eighty adult participants with chronic NP will be recruited for this randomized crossover trial. Outcome measures, including temporal summation, conditioned pain modulation, EIH and lactate concentration, will be assessed before and after low- and high-intensity bicycling exercise. The outcomes of this study will provide new insights into the mechanistic effect of exercise on central sensitization in individuals with chronic NP and have the potential to add important information to the current exercise prescription guidelines for individuals with chronic NP. This study has been approved by the Human Research Ethics Committee, The University of Adelaide (H-2022-082) and registered in the Australian New Zealand Clinical Trials Registry (ACTRN12622000642785p).

Task-based measures of sensitivity to physical activity predict daily life pain and mood among people living with back pain

BACKGROUND

Clinical interventions aim to improve the daily life experiences of patients. However, past research has highlighted important discrepancies between commonly used assessments (e.g. retrospective questionnaires) and patients' daily life experiences of pain. These gaps may contribute to flawed clinical decision-making and ineffective care. Recent work suggests that real-time, task-based clinical assessments may help reduce these discrepancies by adding predictive value in explaining daily life pain experiences. This study aimed to investigate these relationships by evaluating whether task-based measures of sensitivity to physical activity (SPA) predict daily life pain and mood, beyond traditional pain-related questionnaires.

METHODS

Adults with back pain (<6-month onset) answered pain-related questionnaires and completed a standardized lifting task. SPA-Pain, SPA-Sensory and SPA-Mood were, respectively, assessed as task-evoked changes in pain intensity, pressure pain threshold (back, hands), situational catastrophizing. Over the next 9 days, daily life pain and mood were assessed using smartphone-based ecological momentary assessment (EMA-Pain and EMA-Mood, respectively) with stratified random sampling. Data analyses estimated fixed effects (b) using multilevel linear modelling with random intercepts.

RESULTS

Median EMA completion per participant was 66.67% (n = 67 participants). After controlling for covariates, SPA-Pain was associated with EMA-Pain (b = 0.235, p = 0.002) and SPA-Psych approached significance with EMA-Mood (b = -0.159, p = 0.052).

CONCLUSIONS

Task-based assessment of SPA helps explain daily life pain and mood among adults with back pain, beyond traditional questionnaires. Adding task-based assessment of SPA may achieve a more complete picture of pain and mood in daily life, offering clinicians better guidance when prescribing activity-based interventions that are designed to modify daily life behaviour, such as graded activity.

SIGNIFICANCE

This study found that, among people with back pain, task-based measures of sensitivity to physical activity contribute additional predictive value for daily life pain and mood beyond self-report questionnaires. Findings suggest that real-time, task-based measures may help mitigate some of the shortcomings that are commonly associated with retrospective questionnaires.

Low-Intensity Blood Flow Restriction Exercises Modulate Pain Sensitivity in Healthy Adults: A Systematic Review

Low-intensity exercise with blood flow restriction (LIE-BFR) has been proposed as an effective intervention to induce hypoalgesia in both healthy individuals and patients with knee pain. Nevertheless, there is no systematic review reporting the effect of this method on pain threshold. We aimed to evaluate the following: (i) the effect of LIE-BFR on pain threshold compared to other interventions in patients or healthy individuals; and (ii) how different types of applications may influence hypoalgesic response. We included randomized controlled trials assessing the effectiveness of LIE-BFR alone or as an additive intervention compared with controls or other interventions. Pain threshold was the outcome measure. Methodological quality was assessed using the PEDro score. Six studies with 189 healthy adults were included. Five studies were rated with 'moderate' and 'high' methodological quality. Due to substantial clinical heterogeneity, quantitative synthesis could not be performed. All studies used pressure pain thresholds (PPTs) to assess pain sensitivity. LIE-BFR resulted in significant increases in PPTs compared to conventional exercise at local and remote sites 5 min post-intervention. Higher-pressure BFR results in greater exercise-induced hypoalgesia compared to lower pressure, while exercise to failure produces a similar reduction in pain sensitivity with or without BFR. Based on our findings, LIE-BFR can be an effective intervention to increase pain threshold; however, the effect depends on the exercise methodology. Further research is necessary to investigate the effectiveness of this method in reducing pain sensitivity in patients with pain symptomatology.

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.

The effects of a 15-week physical exercise intervention on pain modulation in fibromyalgia: Increased pain-related processing within the cortico-striatal- occipital networks, but no improvement of exercise-induced hypoalgesia

Dysfunctional top-down pain modulation is a hallmark of fibromyalgia (FM) and physical exercise is a cornerstone in FM treatment. The aim of this study was to explore the effects of a 15-week intervention of strengthening exercises, twice per week, supervised by a physiotherapist, on exercise-induced hypoalgesia (EIH) and cerebral pain processing in FM patients and healthy controls (HC). FM patients (n = 59) and HC (n = 39) who completed the exercise intervention as part of a multicenter study were examined at baseline and following the intervention. Following the exercise intervention, FM patients reported a reduction of pain intensity, fibromyalgia severity and depression. Reduced EIH was seen in FM patients compared to HC at baseline and no improvement of EIH was seen following the 15-week resistance exercise intervention in either group. Furthermore, a subsample (Stockholm site: FM n = 18; HC n = 19) was also examined with functional magnetic resonance imaging (fMRI) during subjectively calibrated thumbnail pressure pain stimulations at baseline and following intervention. A significant main effect of exercise (post > pre) was observed both in FM patients and HC, in pain-related brain activation within left dorsolateral prefrontal cortex and caudate, as well as increased functional connectivity between caudate and occipital lobe bordering cerebellum (driven by the FM patients). In conclusion, the results indicate that 15-week resistance exercise affect pain-related processing within the cortico-striatal-occipital networks (involved in motor control and cognition), rather than directly influencing top-down descending pain inhibition. In alignment with this, exercise-induced hypoalgesia remained unaltered.

Exercise-induced hypoalgesic effects of different types of physical exercise in individuals with neck pain: A systematic review and meta-analysis

OBJECTIVE

To evaluate the exercise-induced hypoalgesic (EIH) effects of different types of physical exercise in individuals with neck pain.

DESIGN

Systematic review with meta-analysis.

LITERATURE SEARCH

An electronic search of six databases was completed to include studies assessing EIH effects on neck pain.

STUDY SELECTION CRITERIA

Randomized controlled trials, controlled trials, and observational studies that assessed before and immediate after-effects of a single session of physical exercise in people with neck pain were included. Two reviewers independently screened records, extracted outcomes, assessed the risk of bias, and rated the quality of evidence using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

DATA SYNTHESIS

EIH is characterized by increased pain threshold, pain tolerance, and/or decreased sensitivity to painful stimuli or unpleasantness, which may last up to 30 min after a single bout of exercise. EIH is usually measured with quantitative sensory testing (QST) and is mostly taken as the difference between pre- and postexercise pressure pain threshold (PPT). Data were pooled and analyzed using a fixed-effect meta-analysis.

RESULTS

Eleven articles were included in this review; nine with low risk of bias and two with some concerns about the risk of bias. Three studies with chronic whiplash-associated disorders (WAD) were included in the meta-analysis; isometric exercise had a larger EIH effect at the local testing site compared with submaximal aerobic exercises (MD = -0.21, [95% CI = -0.43, 0.00], p = 0.05, I²  = 92%), submaximal aerobic and isometric exercises had equal EIH effects at the remote testing site (MD = 0.01, [95% CI = -0.33, 0.35], p = 0.95, I²  = 0%), and submaximal aerobic exercises exerted comparably larger EIH effect at the remote testing site than local testing site (MD = -0.01, [95% CI = -0.20, 0.18], p = 0.93, I²  = 56%). The certainty of evidence (GRADE) for these analyses was low to very low. According to the descriptive analysis of the studies of chronic nonspecific neck pain, isometric and range of motion (ROM) exercises have shown EIH effects. Active stretching exercises have illustrated contradictory effects.

CONCLUSION

Isometric and ROM exercises exerted hypoalgesia at local and remote sites. A larger EIH effect following submaximal aerobic exercises was exerted at the remote testing site compared with the local site.

Perceived Pain in Athletes: A Comparison between Endurance Runners and Powerlifters through a Cold Experimental Stimulation and Two Sessions of Various Physical Activation

Few studies in the literature have illustrated cold hypoalgesia induced by strength training. Objectives of this contribution were to compare the ratings of perceived pain in endurance running (n = 22) and powerlifting (n = 22) male athletes and controls (n = 22) at baseline and after two bouts of 40 min aerobic/strength training respectively, using the Cold Pressor Test (CPT) and simultaneously monitoring changes in blood pressure (BP), heart rate (HR), and body temperature. A two-way repeated measures ANOVA was conducted to examine the effects of training sessions in endurance runners vs. powerlifting athletes vs. controls on the intensity of perceived pain at CPT. A statistically significant two-way interaction between the group and training resulted in p < 0.001, ηp2 = 0.513. A simple main effects analysis showed that as the participants went through the strength training session, pain perception at CPT was significantly lower in powerlifters compared to runners and controls. Considering the physiological parameters, powerlifters reported significantly higher values of BP and HR. This difference was present at baseline but after training as well, and before and after CPT, despite a slight hypotensive effect. The differences reported after CPT at baseline, but very significantly after the strength activation session in the powerlifters, provide interesting insights into the hypoalgesic effect of high-intensity strength training.

Exercised-Induced Hypoalgesia following An Elbow Flexion Low-Load Resistance Exercise with Blood Flow Restriction: A Sham-Controlled Randomized Trial in Healthy Adults

We aimed to evaluate the hypoalgesic effect of an elbow flexion low-load resistance exercise with blood flow restriction (LLRE-BFR) when compared to high-load resistance exercise (HLRE) with sham-BFR in healthy individuals. Forty healthy young adults (17 women), with a mean age ± SD: 26.6 ± 6.8 years, and mean body mass index ± SD: 23.6 ± 2.7 were randomly assigned to either an LLRE-BFR (30% 1 repetition maximum, RM) or an HLRE with sham-BFR group (70% of 1 RM). Blood pressure and pressure pain thresholds (PPTs) were measured pre- and post-exercise intervention. The rating of perceived exertion (RPE) was recorded after each set. There were non-significant between-group changes in PPT at the dominant biceps (-0.61, 95%CI: -1.92 to 0.68) with statistically significant reductions between pre- and post-exercise in LLRE-BFR (effect size, d = 0.88) and HLRE-BFR (effect size, d = 0.52). No within- or between-group differences were recorded in PPT at non-exercising sites of measurement. No mediating effects of changes in blood pressure or RPE on the changes in pressure pain threshold were observed. LLRE-BFR produced a similar hypoalgesic effect locally compared to HLRE and can be used as an alternative intervention to decrease pain sensitivity when HLRE is contraindicated or should be avoided.

Effects of Exercise-Induced Hypoalgesia at Different Aerobic Exercise Intensities in Healthy Young Adults

PURPOSE

Exercise-induced hypoalgesia (EIH) is a reduction in pain sensitivity that occurs following a single bout of exercise. However, little research has compared the EIH effects of exercise at different intensities, including low intensity, in the same participant. It is unclear as to which exercise intensities demonstrate EIH more effectively. The aim of this study was to examine and compare the effect of different intensities of exercise on pain sensitivity in the same participant.

METHODS

We included 73 healthy young adult volunteers (35 female and 38 male) in this experimental cross-over study. Each participant completed four experimental sessions of 30 min, consisting of aerobic exercise at 30% heart rate reserve (HRR), aerobic exercise at 50% HRR, aerobic exercise at 70% HRR, and quiet rest. EIH was assessed using the pressure pain threshold (PPT) and temporal summation of pain (TSP) in the quadriceps, biceps, and trapezius.

RESULTS

Low- and moderate-intensity exercise increased the multisegmental PPT and reduced TSP (all P < 0.05). High-intensity exercise increased the multisegmental PPT (all P < 0.05), but decreased TSP in only the quadriceps and biceps (P < 0.05), not the trapezius (P = 0.13). We found no difference in relative PPT and TSP changes between exercise intensities (P > 0.05) except for relative PPT change at the quadriceps (P < 0.05).

CONCLUSION

Our results show that not only moderate- and high-intensity exercise, but also low-intensity exercise can produce a hypoalgesic response.

Physical activity, self-efficacy and quality of life in patients with chronic pain, assessed during and 1 year after physiotherapy rehabilitation - a prospective follow-up study

PURPOSE

The aim of this prospective cohort study was to evaluate the level of physical activity, self-efficacy and health-related quality of life in patients with chronic pain, at baseline and one year after physiotherapy rehabilitation at a specialist pain clinic.

MATERIALS AND METHODS

All patients who underwent rehabilitation at the physiotherapy unit at the Pain Centre at Sahlgrenska University Hospital/Östra in Gothenburg during a nine-month period were asked to participate in the study. The participants were evaluated regarding self-efficacy, health-related quality of life (HRQoL) and physical activity during physiotherapy treatment and one year later. Physical activity was measured both subjectively (self-reported physical activity) and objectively (accelerometer).

RESULTS

Out of 42 patients who participated in the baseline evaluation, 28 (19 women and nine men) were included in the one-year follow-up. The patients had increased levels of vigorous physical activity at one-year follow-up, without deterioration of pain. There were no significant changes regarding self-efficacy and HRQoL. Levels of physical activity and perceived physical function may be associated to levels of physical activity 1 year after rehabilitation.

CONCLUSION

Patients with chronic pain can increase their level of vigorous physical activity after a period of rehabilitation without deterioration of pain.IMPLICATIONS FOR REHABILIATIONPhysical activity is an important part of rehabilitation for chronic pain patients, but many patients expect more pain after exercise, which they fear may affect performance and maintenance of physical activity.Patients with chronic pain at a specialist clinic increased their level of vigorous physical activity one year after physiotherapist led rehabilitation without deterioration of pain.Levels of physical activity and perceived physical function during rehabilitation may predict levels of physical activity 1 year after rehabilitation.Physiotherapist led rehabilitation seems to be beneficial for long-term improved physical activity in patients with chronic pain.

Effects of Self-Efficacy and Outcome Expectations on Motor Imagery-Induced Thermal and Mechanical Hypoalgesia: A Single-Blind Randomised Controlled Trial

The main aim of this study was to assess whether self-efficacy (SE) and outcome expectations (OEs) modulate the hypoalgesic effect induced by motor imagery (MI). A total of 75 asymptomatic participants were randomly assigned to the positive (SE+, OE+), negative (SE-, OE-) or non-expectation (CG) groups. Heat pain threshold (HPT) and pain pressure threshold (PPT) were the main variables. Cold detection threshold (CDT), warm detection threshold (WDT), heart rate (HR) and perceived fatigue were the secondary variables. The variables were assessed preintervention, immediately postintervention and 10 min postintervention, except for HR, which was measured continuously during the intervention. Regarding HPT, significant within-group pre-post differences were found in the OE+ group, with a low effect size (p = 0.01, d = -0.39). With regard to ΔPPT, significant intergroup differences were found in Δpost-pre between the SE+ and CG groups (p = 0.012, d = 1.04) and also between SE+ and OE- (p = 0.006, d = 1.08), both with a large effect size. CG, SE-, and OE- groups had poorer CDT and WDT. Regarding HR, significant intergroup differences were found in the postintervention measurement between OE+ and SE-, with a large effect size (p = 0.016, d = 1.34). Lastly, no between-group differences were found regarding perceived fatigue (p > 0.05). The results obtained showed that positive expectations have a slight influence on the increase in heat and mechanical pain detection thresholds. Positive and non-expectancy groups showed an autonomic activation. The results also showed that negative expectations led to poorer perceptual processes.

Hypoalgesia after exercises with painful vs. non-painful muscles in healthy subjects - a randomized cross-over study

OBJECTIVES

Exercise-induced hypoalgesia (EIH) is a decrease in the pain sensitivity after exercise. Individuals with chronic pain show less EIH after one exercise session compared with pain-free individuals possibly due to pain in exercising muscles. The primary aim of this randomized controlled cross-over study was to compare the EIH response at the exercising thigh muscle following exercises performed with painful vs. non-painful muscles. Secondary aims were to explore if a reduced EIH response was confined to the painful muscle, and whether the muscle pain intensity and the EIH responses were negatively associated.

METHODS

In two sessions, 34 pain-free participants received a painful (hypertonic saline, 5.8%) injection and a control (isotonic saline, 0.9%) injection in the right thigh muscle before performing a 3 min isometric wall squat exercise. Pressure pain thresholds (PPTs) were assessed at both thighs and the left neck/shoulder at baseline, after injections and after exercise. Pain intensities in the thighs were rated on numerical rating scales (NRS: 0-10).

RESULTS

Hypertonic saline induced moderate thigh pain at rest (NRS: 4.6 ± 2.1) compared to the control injection (NRS: 0.3 ± 0.4; p<0.001). EIH at the thighs and neck/shoulder were not different between sessions (Injected thigh: 0 kPa; 95% CI: -51 to 52; Contralateral thigh: -6 kPa; 95% CI: -42 to 30; neck/shoulder: 19 kPa; 95% CI: -6 to 44). No significant associations between pain intensity ratings immediately after the Painful injection and EIH responses at any assessment sites were found (right thigh: β=0.08, 95% CI: -12.95 to 20.64, p=0.64, left thigh: β=-0.33, 95% CI: -27.86 to 0.44, p=0.06; neck/shoulder: β=-0.18, 95% CI: -15.11 to 4.96, p=0.31).

CONCLUSIONS

Pain in the area of an exercising muscle did not reduce local or systemic EIH responses.

TRIAL REGISTRATION NUMBER

NCT04354948.

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-Related Post-Exertional Malaise in Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS) and Fibromyalgia: A Systematic Review and Three-Level Meta-Analysis

OBJECTIVE

Myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS) and fibromyalgia (FM) are two debilitating, moderately comorbid illnesses in which chronic musculoskeletal pain symptoms are prevalent. These individuals can experience post-exertional malaise (PEM), a phenomenon in which symptom severity is worsened for 24 hours or longer after physical stress, but the pain-related component of PEM is not well characterized.

DESIGN

Systematic review and meta-analysis.

METHODS

Case-control studies involving adults with ME/CFS or FM and measuring pain symptoms before and after exposure to a standardized aerobic exercise test were included. Hedges' d effect sizes were aggregated with random-effects models, and potential moderators were explored with meta-regression analysis. Results were adjusted for nesting effects with three-level modeling.

RESULTS

Forty-five effects were extracted from 15 studies involving 306 patients and 292 healthy controls. After adjusting for nesting effects, we observed a small to moderate effect indicating higher post-exercise pain in patients than in controls (Hedges' d = 0.42; 95% confidence interval [CI]: 0.16-0.67). The mean effect was significantly moderated by pain measurement time point (b = -0.19, z = -2.57, P = 0.01), such that studies measuring pain 8-72 hours after exercise showed larger effects (d = 0.71, 95% CI = 0.28-1.14) than did those measuring pain 0-2 hours after exercise (d = 0.32, 95% CI = 0.10-0.53).

CONCLUSIONS

People with ME/CFS and FM experience small to moderate increases in pain severity after exercise, which confirms pain as a component of PEM and emphasizes its debilitating impact in ME/CFS and FM. Future directions include determining mechanisms of pain-related PEM and developing exercise prescriptions that minimize symptom exacerbation in these illnesses.

The effect of prolonged experimental neck pain on exercise-induced hypoalgesia

ABSTRACT

Neck pain is a common musculoskeletal problem often accompanied by reduced exercise-induced hypoalgesia (EIH) or hyperalgesia compared to an asymptomatic population. This study investigated EIH in a healthy population during experimental neck pain. Forty participants were randomized into this double-blinded parallel-group study. On four separate test days (Day0, Day2, Day4, Day15), participants completed the Neck Disability Index (NDI) and scored neck pain intensity during head movements on a numerical rating scale (NRS). At the end of Day0 and Day2, Nerve Growth Factor (NGF) or isotonic saline (control) was injected into the right splenius capitis muscle. Pressure pain thresholds (PPTs) were recorded bilaterally over splenius capitis (neck), temporalis (head) and tibialis anterior (leg) muscles on all days. On Day0, Day4 and Day15, PPTs were recorded before and after a hand-bike exercise. EIH was defined as the PPT increase caused by the exercise. Compared with the control-group, the NGF-group demonstrated higher NDI scores at Day2 and Day4 (P<0.001,η2>0.557) and higher NRS scores (P<0.03,η2>0.09) along with reduced neck PPTs (P<0.01,d>0.44) at Day2(Right:95%CI[26.0,54.0];Left:95%CI[6.8,26.9]), Day4(Right:95%CI[40.5, 67.9];Left:95%CI[6.9,28.2]) and Day15(Right:95%CI[5.6,37.2];Left:95%CI[6.9,34.8]). Across days, the EIH-effect was reduced at the neck site in the NGF-group compared to the control-group (P<0.001,η2P=0.367,95%CI[-34.5,-13.7]). At the head and leg sites, the NGF-group showed reduced EIH-effect compared to the control-group (P<0.05,d>0.43) on Day4(Head:95%CI[-61.4,-22.9];Leg:95%CI[-154.7,-72.4]) and Day15(Head:95%CI[-54.3,-7.6];Leg:95%CI[-122.7,-34.4]). These results indicate that a few days of clinically comparable neck pain and hyperalgesia might have a negative impact on EIH-responses and may help explain why some neck pain patients do not experience immediate positive effects of exercise.

[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.

Pain and executive function: no association between remote exercise-induced hypoalgesia and cognitive inhibition in pain-free participants

OBJECTIVES

Cognitive inhibition, which denotes the ability to suppress predominant or automatic responses, has been associated with lower pain sensitivity and larger conditioned pain modulation in humans. Studies exploring the association between cognitive inhibition and other pain inhibitory phenomena, like exercise-induced hypoalgesia (EIH), are scarce. The primary aim was to explore the association between cognitive inhibition and EIH at exercising (local) and non-exercising (remote) muscles after isometric exercise. The secondary aim was to explore the association between cognitive inhibition and pressure pain sensitivity.

METHODS

Sixty-six pain-free participants (28.3 ± 8.9 years old, 34 women) completed two cognitive inhibition tasks (stop-signal task and Stroop Colour-Word task), a 3-min isometric wall squat exercise, and a quiet rest control condition with pre- and post-assessments of manual pressure pain thresholds at a local (thigh) and a remote site (shoulder). In addition, cuff pressure pain thresholds, pain tolerance and temporal summation of pain were assessed at baseline.

RESULTS

No association was found between remote EIH and cognitive inhibition (Stroop interference score: r=0.12, [-0.15; 0.37], p=0.405, BF01=6.70; stop-signal reaction time: r=-0.08, [-0.32; 0.17], p=0.524, BF01=8.32). Unexpectedly, individuals with worse performance on the Stroop task, as indicated by a higher Stroop interference score, showed higher local EIH (r=0.33; [0.10; 0.53], p=0.007, BF01=0.29). No associations were observed between pain sensitivity and any of the cognitive inhibition performance parameters.

CONCLUSIONS

The present findings do not support previous evidence on positive associations between exercise-induced hypoalgesia and cognitive inhibition, as well as baseline pain sensitivity and cognitive inhibition.

Aerobic exercise with blood flow restriction causes local and systemic hypoalgesia and increases circulating opioid and endocannabinoid levels

This study examined the effect of aerobic exercise with and without blood flow restriction (BFR) on exercise-induced hypoalgesia and endogenous opioid and endocannabinoid systems. In a randomized crossover design, pain-free individuals performed 20 min of cycling in four experimental trials: 1) low-intensity aerobic exercise (LI-AE) at 40% V̇o_2max; 2) LI-AE with low-pressure BFR (BFR40); 3) LI-AE with high-pressure BFR (BFR80); and 4) high-intensity aerobic exercise (HI-AE) at 70% V̇o_2max. Pressure pain thresholds (PPTs) were assessed before and 5 min postexercise. Circulating concentrations of beta-endorphin and 2-arachidonoylglycerol were assessed before and 10 min postexercise. In the exercising legs, postexercise PPTs were increased following BFR40 and BFR80 compared with LI-AE (23-32% vs. 1-2% increase, respectively). The increase in PPTs was comparable to HI-AE (17-20% increase) with BFR40 and greater with BFR80 (30-32% increase). Both BFR80 and HI-AE increased PPTs in remote areas of the body (increase of 26-28% vs. 19-21%, respectively). Postexercise circulating beta-endorphin concentration was increased following BFR40 (11%) and HI-AE (14%), with the greatest change observed following BFR80 (29%). Postexercise circulating 2-arachidonoylglycerol concentration was increased following BFR40 (22%) and BFR80 (20%), with the greatest change observed following HI-AE (57%). Addition of BFR to LI-AE can trigger both local and systemic hypoalgesia that is not observed follow LI-AE alone and activate endogenous opioid and endocannabinoid systems of pain inhibition. Compared with HI-AE, local and systemic hypoalgesia following LI-AE with high-pressure BFR is greater and comparable, respectively. LI-AE with BFR may help pain management in load-compromised individuals.NEW & NOTEWORTHY We have shown that performing blood flow restriction (BFR) during low-intensity aerobic exercise can trigger local and systemic hypoalgesia, which is not typically observed with this intensity of exercise. High-pressure BFR triggers greater and comparable hypoalgesia than high-intensity aerobic exercise in the exercising limbs and remote areas of the body, respectively. Performing BFR during low-intensity aerobic exercise activates the opioid and endocannabinoid systems, providing novel insight into potential mechanisms of hypoalgesia with BFR exercise.

Making exercise count: Considerations for the role of exercise in back pain treatment

INTRODUCTION

Chronic low back pain (CLBP) is pain that has persisted for greater than three months. It is common and burdensome and represents a significant proportion of primary health presentations. For the majority of people with CLBP, a specific nociceptive contributor cannot be reliably identified, and the pain is categorised as 'non-specific'. Exercise therapy is recommended by international clinical guidelines as a first-line treatment for non-specific CLBP.

AIM

This comprehensive review aims to synthesise and appraise the current research to provide practical, evidence-based guidance concerning exercise prescription for non-specific CLBP. We discuss detailed initial assessment and being informed by patient preferences, values, expectations, competencies and goals.

METHODS

We searched the Cochrane Database of Systematic Reviews, PubMed and the Physiotherapy Evidence Database (PEDro) using broad search terms from January 2000 to March 2021, to identify the most recent clinical practice guidelines, systematic reviews and randomised controlled trials on exercise for CLBP.

RESULTS/DISCUSSION

Systematic reviews show exercise is effective for small, short-term reductions in pain and disability, when compared with placebo, usual care, or waiting list control, and serious adverse events are rare. A range of individualised or group-based exercise modalities have been demonstrated as effective in reducing pain and disability. Despite this consensus, controversies and significant challenges remain.

CONCLUSION

To promote recovery, sustainable outcomes and self-management, exercise can be coupled with education strategies, as well as interventions that enhance adherence, motivation and patient self-efficacy. Clinicians might benefit from intentionally considering their own knowledge and competencies, potential harms of exercise and costs to the patient. This comprehensive review provides evidence-based practical guidance to health professionals who prescribe exercise for people with non-specific CLBP.

The Prospective Prognostic Value of Biopsychosocial Indices of Sensitivity to Physical Activity Among People With Back Pain

OBJECTIVES

Many people living with musculoskeletal pain conditions experience a range of negative biopsychosocial responses to physical activity, referred to as increased sensitivity to physical activity (SPA), that may undermine successful rehabilitation. This exploratory study aims to provide the first prospective analysis of the potential prognostic value of 3 biopsychosocial indices of SPA in relation to rehabilitation outcomes. This study also aimed to shed light on the cross-sectional interrelationships between these 3 biopsychosocial indices of SPA.

MATERIALS AND METHODS

Adults with back pain were evaluated upon starting physical therapy and then again 3 months later. The initial testing session consisted of self-reported pain-related questionnaires and assessment of activity-related changes in pressure pain thresholds (SPA-Sensory), pain intensity ratings (SPA-Pain), and situational catastrophizing (SPA-Psych). The 3-month follow-up consisted of self-reported disability and pain questionnaires. Correlational and hierarchical linear regression analyses were conducted.

RESULTS

A total of 97 participants completed both the initial visit and 3-month follow-up. The SPA-Pain index and the SPA-Psych index were significantly intercorrelated, but neither were correlated with the SPA-Sensory index. The SPA-Sensory index was not correlated with outcomes. The SPA-Pain index was correlated only with cross-sectional disability and pain outcomes. The SPA-Psych index was the only SPA index significantly correlated with outcomes both cross-sectionally and at 3-month follow-up. After controlling for baseline pain/disability and pain catastrophizing, SPA-Psych was no longer a significant prognostic factor for pain, but remained a significant prognostic factor for disability at 3-month follow-up (β=0.272, t=2.674, P=0.008, R2 Δ=5.60%).

DISCUSSION

This study highlights the importance of conceptualizing and measuring SPA as a biopsychosocial (rather than unidimensional) construct and points toward the added prognostic value of this construct. Implications for future research and practice are discussed.

The effect of exercise intensity on exercise-induced hypoalgesia in cancer survivors: A randomized crossover trial

Pain is experienced by people with cancer during treatment and in survivorship. Exercise can have an acute hypoalgesic effect (exercise-induced hypoalgesia; EIH) in healthy individuals and some chronic pain states. However, EIH, and the moderating effect of exercise intensity, has not been investigated in cancer survivors. This study examined the effect of low- and high-intensity aerobic exercise on EIH in cancer survivors after a single exercise session as well as a brief period of exercise training (2-weeks, three exercise sessions per week). Participants (N = 19) were randomized to low- (30%-40% Heart Rate Reserve (HRR) or high- (60%-70% HRR) intensity stationary cycling for 15-20 min. Pressure pain thresholds (PPT) were assessed over the rectus femoris and biceps brachii before and after a single exercise session and again after a short training period at the assigned intensity. Then, following a 6-week washout period, the intervention was repeated at the other intensity. After the first exercise session, high-intensity exercise resulted in greater EIH over the rectus femoris than low intensity (mean difference ± SE: -0.51 kg/cm2  ± 0.15, Cohen's d = 0.78, p = 0.004). After a 2-week training period, we found no difference in EIH between intensities (0.01 kg/cm2  ± 0.25, d = 0.00 p = 0.99), with comparable moderate effect sizes for both low- and high-intensity exercise, indicative of EIH. No EIH was observed over the biceps brachii of the arm at either low or high intensity. Low-intensity exercise training may be a feasible option to increase pain thresholds in cancer survivors.

Pressure pain thresholds in individuals with knee pain: a cross-sectional study

Background

Knee osteoarthritis (KOA), chronic widespread pain (CWP) and overweight/obesity are public health problems that often coincide, and there is a multifactorial and unclear relationship between them. The study aimed to (1) investigate pain sensitivity, assessed by pressure pain thresholds (PPTs), among women and men with knee pain and (2) associations with, respectively, radiographic KOA (rKOA), CWP, and overweight/obesity.

Methods

Baseline data from an ongoing longitudinal study involving 280 individuals with knee pain in the 30–60 age group. Pain sensitivity was assessed by PPTs on eight different tender points using a pressure algometer. The participants’ knees were x-rayed. Self-reported CWP and number of pain sites were assessed with a pain figure, and overweight/obesity was measured using body mass index (BMI), visceral fat area (VFA), and body fat percentage, assessed with a bioimpedance. Associations were analysed using regression analyses.

Results

Women reported lower PPTs than men (p < 0.001), but no PPTs differences were found between those with and without rKOA. Low PPTs was associated with female sex, more pain sites, CWP, and a higher VFA and body fat percentage. The tender points second rib and the knees were most affected. The prevalence of CWP was 38 %.

Conclusions

The modifiable factors, increased VFA, and body fat could be associated with increased pain sensitivity among individuals with knee pain. Longitudinal studies are needed to further investigate the associations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04408-0.

Strength training in addition to neuromuscular exercise and education in individuals with knee osteoarthritis-the effects on pain and sensitization

BACKGROUND

There is a lack of evidence of the relative effects of different exercise modes on pain sensitization and pain intensity in individuals with knee osteoarthritis (KOA).

METHODS

Ninety individuals with radiographic and symptomatic KOA, ineligible for knee replacement surgery, were randomized to 12 weeks of twice-weekly strength training in addition to neuromuscular exercise and education (ST+NEMEX-EDU) or neuromuscular exercise and education alone (NEMEX-EDU). Outcomes were bilateral, lower-leg, cuff pressure pain- and tolerance thresholds (PPT, PTT), temporal summation (TS), conditioned pain modulation (CPM), self-reported knee pain intensity and number of painful body sites.

RESULTS

After 12 weeks of exercise, we found significant differences in increases in PPT (-5.01 kPa (-8.29 to -1.73, p = .0028)) and PTT (-8.02 kPa (-12.22 to -3.82, p = .0002)) in the KOA leg in favour of ST+NEMEX-EDU. We found no difference in effects between groups on TS, CPM or number of painful body sites. In contrast, there were significantly greater pain-relieving effects on VAS mean knee pain during the last week (-8.4 mm (-16.2 to -0.5, p = .0364) and during function (-16.0 mm (-24.8 to -7.3, p = .0004)) in favour of NEMEX-EDU after 12 weeks of exercise.

CONCLUSION

Additional strength training reduced pain sensitization compared to neuromuscular exercise and education alone, but also attenuated the reduction in pain intensity compared to neuromuscular exercise and education alone. The study provides the first dose- and type-specific insight into the effects of a sustained exercise period on pain sensitization in KOA. Future studies are needed to elucidate the role of different exercise modes.

SIGNIFICANCE

This study is an important step towards better understanding the effects of exercise in pain management of chronic musculoskeletal conditions. We found that strength training in addition to neuromuscular exercise and education compared with neuromuscular exercise and education only had a differential impact on pain sensitization and pain intensity, but also that regardless of the exercise mode, the positive effects on pain sensitization and pain intensity were comparable to the effects of other therapeutic interventions for individuals with knee osteoarthritis.

Exercise-induced hypoalgesia and pain reduction following blood flow restriction: A brief review

OBJECTIVE

To review past literature regarding exercise-induced hypoalgesia and pain reduction following blood flow restriction interventions, and to discuss potential mechanisms as well as future considerations towards the efficacy of blood flow restriction in pain reduction following exercise.

METHODS

To be eligible for inclusion, studies had to include acute exercise, or long-term training interventions, with blood flow restriction, along with including pre and post intervention pain measurements.

RESULTS

A total of 13 studies met the inclusion criteria. Among these 13 studies, 3 studies examined exercise-induced hypoalgesia after an acute bout of resistance exercise with blood flow restriction, and 10 studies investigated pain reduction following long-term blood flow restriction training.

CONCLUSIONS

Existing literature suggests that low load resistance exercise with blood flow restriction may serve as an effective pain management method for those who are unable or unwilling to train with high loads. Several potential mechanisms have been suggested, however, the roles of these mechanisms are still unclear and require further clarification. Future research should consider implementing different methods of blood flow restriction application, and research study design to clarify the utility and efficacy of blood flow restriction as a pain management tool, by itself or in combination with exercise.

Should Exercises be Painful or not? Effects on Clinical and Experimental Pain in Individuals with Shoulder Pain

Exercise can reduce pain, however the effect of painful versus non-painful exercises is uncertain. The primary aim of this randomized crossover study was to compare the effect of painful versus nonpainful isometric shoulder exercises on pain intensity after exercise in individuals with rotator cuff-related shoulder pain. Secondary exploratory aims were to describe the effects on pressure pain thresholds (PPTs), conditioned pain modulation (CPM) and muscle strength. On separate days, 35 individuals performed painful isometric shoulder exercises (external rotation; 20% above pain threshold), nonpainful isometric shoulder exercises (external rotation; 20% below pain threshold), and a rest condition, in randomised order. Shoulder pain intensity, PPTs, CPM, and external rotation strength were assessed before, immediately after and 45 minutes after conditions. No significant differences were observed between painful and nonpainful exercises. Visual analogue scale scores increased immediately after both painful and non-painful exercises compared with rest (P = .047, partial ƞ² = .07), but were similar to preexercise levels after 45 minutes. No changes in PPTs, CPM, or muscle strength after exercises compared with rest were observed. Painful and non-painful isometric exercises caused a moderate but short-lasting increase in shoulder pain in individuals with RCRSP. Isometric exercises had no effect on pain sensitivity and shoulder muscle strength or CPM. Perspective: This study evaluated for the first time in individuals with rotator cuff-related shoulder pain the effects of painful versus non-painful isometric exercises on different pain-related outcome measures. Both painful and non-painful isometric exercises caused a moderate but relatively short-lasting increase in shoulder pain in individuals with rotator cuff-related shoulder pain. Trial registration number: (ClinicalTrials.gov) NCT03675399.

Movement-induced hypoalgesia: behavioral characteristics and neural mechanisms

Pain is essential for our survival because it helps to protect us from severe injuries. Nociceptive signals may be exacerbated by continued physical activities but can also be interrupted or overridden by physical movements, a process called movement-induced hypoalgesia. Several neural mechanisms have been proposed to account for this effect, including the reafference principle, non-nociceptive interference, and top-down descending modulation. Given that the hypoalgesic effects of these mechanisms temporally overlap during movement execution, it is unclear whether movement-induced hypoalgesia results from a single neural mechanism or from the joint action of multiple neural mechanisms. To address this question, we conducted five experiments on 129 healthy humans by assessing the hypoalgesic effect after movement execution. Combining psychophysics and electroencephalographic recordings, we quantified the relationship between the strength of voluntary movement and the hypoalgesic effect, as well as the temporal and spatial characteristics of the hypoalgesic effect. Our findings demonstrated that movement-induced hypoalgesia results from the joint action of multiple neural mechanisms. This investigation is the first to disentangle the distinct contributions of different neural mechanisms to the hypoalgesic effect of voluntary movement, which extends our understanding of sensory attenuation arising from voluntary movement and may prove instrumental in developing new strategies for pain management.

Acute Effects of a Brief Physical Exercise Intervention on Somatosensory Perception, Lumbar Strength, and Flexibility in Patients with Nonspecific Chronic Low-Back Pain

BACKGROUND

Evidence-based clinical guidelines consider physical exercise one of the best nonpharmacological interventions for low-back pain (LBP), but it is necessary to clarify the exercise-induced hypoalgesia effect of different modalities of exercise in chronic pain populations.

PURPOSE

This study focused on exploring acute changes in tactile and pressure-pain perception and lumbar strength and flexibility in patients with nonspecific chronic LBP (NSCLBP) after performing one of three 20-minute physical exercise modalities.

METHODS

A total of 81 patients with NSCLBP were pseudorandomly distributed into three groups of 20-minute physical exercise - 1) aerobic (n=21, mean age 42±9.72 years, nine men), 2) stretching (n=21, mean age 40±11.37 years, ten men), and 3) strengthening (n=20, mean age 35.80±11.56 years, ten men) - and 4) a control group (n=19, mean age 38.64±10.24 years, eight men), and completed self-reported questionnaires during the same period. Tactile and pressure-pain thresholds and isometric lumbar muscle endurance and flexibility were assessed before and after this brief exercise-based intervention.

RESULTS

All groups were comparable in terms of sociodemographic and clinical data, cardiovascular capacity, and self-reported data onphysical disability, mood, motivation, psychological response to stimulus properties of physical exercise, and physical activity enjoyment. Our analyses revealed higher tactile sensitivity (p<0.001) and pressure-pain thresholds (p<0.001) at the forefinger than other body locations. We also found lower pain sensitivity (p=0.010) and pressure pain-intensity ratings (p=0.001) and higher lumbar flexibility (p<0.001) after intervention. After calculation of absolute pre-post differences, higher tactile sensitivity was observed at the gluteus medius muscle than the erector spinal muscle only after aerobic intervention (p=0.046).

CONCLUSION

These results add some evidence about different modalities of exercise-induced hypoalgesia in NSCLBP. However, the fact that we also found improvements in the control group limits our conclusions.