Exercise-Induced Hypoalgesia in Healthy Individuals and People With Chronic Musculoskeletal Pain: A Systematic Review and Meta-Analysis

Reliability of Pain Thresholds and Exercise-Induced Hypoalgesia Following 45-Degree Roman Chair Exercise

Background

Acute exercise may induce a reduction in pain sensitivity, termed exercise-induced hypoalgesia (EIH). The 45-degree Roman Chair (low back extension) is a dynamic resistance exercise that may be beneficial for low back pain as it allows for direct overload of the spinal flexors and extensors. However, the ability of this exercise to reliably produce EIH has not been examined.

Purpose

The purposes of this study were to determine the reliability of heat pain threshold (HPT) and pressure pain threshold (PPT) measures, examine local and systemic EIH effects after a 45-degree Roman chair exercise, and determine if EIH was produced reliably between sessions.

Study Design

Observational Cohort, Crossover.

Methods

Thirty-five healthy participants (mean(SD) age: 21(1.39) years, 16 male) completed two identical sessions at least two days apart. HPT and PPT at the upper trapezius (UT) and low back (LB) were assessed pre/post quiet rest to examine reliability of these measures. HPT and PPT were repeated pre/post one set of the Roman chair exercise until failure to examine reliability of EIH. Intraclass Correlation Coefficients (ICC) examined reliability, and a three-way repeated measures ANOVA compared changes in HPT and PPT among quiet rest and exercise conditions.

Results

HPT and PPT demonstrated good (HPT: ICC3,1 >0.741) to excellent reliability (PPT: ICC3,1 >0.810). Significant EIH as assessed by PPT was demonstrated at both sites (p UT<0.025, LB<0.001) with larger effect sizes at the LB (ηp² >0.413). When assessed with HPT, significant EIH was observed over the LB (p<0.002) but not the UT (p=0.059) EIH can be reliably induced across sessions over the LB (ICC3,1 HPT=0.903, PPT=0.815)(r HPT=0.903, PPT=0.814) and UT (ICC3,1 HPT=0.867, PPT=0.729)(r HPT=0.877 and PPT=0.744).

Conclusion

The 45-degree Roman Chair may reliably induce significant hypoalgesia over the LB assessed with HPT and PPT in healthy participants.

Level of Evidence

3.

The influence of education on pain during and following acute exercise in people with knee osteoarthritis: A randomised controlled trial

BACKGROUND

Explicit education about exercise-induced hypoalgesia (EIH) reduces experimental pain after a single exercise session in pain-free individuals. However, the effect in people with chronic pain is unclear. This study aimed to determine the effect of EIH education on pain during and following exercise in people with knee osteoarthritis (OA).

METHODS

All procedures were administered online. Participants were randomised to receive 15-min of explicit EIH education or 15-min of general education about knee OA. Participants then completed a questionnaire on their beliefs about exercise and pain, followed by a bout of home-based lower limb resistance exercise. Pain intensity (0-10) was assessed before, during and immediately after exercise.

RESULTS

40 participants completed the study (67.3 ± 10.8 years old, 73 % female). Participants only somewhat agreed pain could be reduced following a single session of exercise and that the education changed what they thought about exercise and pain, but these beliefs were not significantly different between groups (p = 0.053 and p = 0.104, respectively). Pain was similar between groups (adjusted mean difference [95 % CI]) during exercise (0.51 [-0.72 to 1.74], p = 0.410) and following exercise (-0.75 [-1.62 to 1.11], p = 0.087. Compared to baseline, pain (mean difference [95 % CI]) was lower during exercise (-1.01 [-1.66 to -0.36], p = 0.003) and following exercise (-0.96 [-1.5 to -0.42], p < 0.001).

CONCLUSION

A single exercise session reduces pain in people with knee OA, but this was not influenced by pre-exercise education about EIH. Further research is needed to understand if and how EIH can be modulated in people with knee OA.

Ten Minutes of Core Stabilisation Exercise Result in Local Exercise-Induced Hypoalgesia in Patients With Chronic Unspecific Low Back Pain

BACKGROUND

Core stabilisation training is known to be effective in managing pain in patients suffering from chronic low back pain (CLBP). Yet, acute effects of core stabilisation exercise on exercise-induced hypoalgesia (EIH) are largely unknown. This study aimed to examine the EIH effects of an easy-to-perform core stabilisation exercise in CLBP patients and to explore associations between EIH and potential influencing factors (i.e., physical activity, catastrophizing, kinesiophobia, subjective pain state and exercise exertion).

METHODS

Thirty patients with unspecific CLBP finished this randomised controlled crossover trial. Patients performed a 10-min isometric core stabilisation exercise and a 10-min control session. Before and after, pain sensitivity was measured via pressure pain thresholds [Newton/cm2] locally (low back; PPTlocal) and remotely (forehead, thumb; PPTremote). Correlation analyses were performed between EIH and influencing factors.

RESULTS

A 'Time' × 'Intervention' interaction (p < 0.001) was observed for PPTlocal with post hoc analysis revealing higher values post exercise (p < 0.001; pre: 56.6 ± 20.6, post: 67.5 ± 26.1). No differences were observed for the control session (p = 0.894; pre: 58.5 ± 24.0, post: 58.4 ± 23.3). No such effect was observed for PPTremote (p = 0.014). Post hoc analyses showed no differences following the exercise session (p = 0.103; pre: 41.3 ± 12.5, post: 42.5 ± 13.6), while lower PPTremote post values were observed post control compared to pre values (p = 0.031; 42.5 ± 14.5, post: 41.3 ± 13.7). The only significant moderate correlation was observed between ΔPPTlocal of the exercise session and catastrophizing with rho = -0.381.

CONCLUSION

A 10-min isometric core stabilisation exercise results in local lumbar EIH, while no systemic effects are observed. A higher degree of catastrophizing is associated with lower hypoalgesic responses.

SIGNIFICANCE

This study shows for the first time that a brief and easy-to-perform 10-min core stabilisation exercise produces significant local pain relief (EIH) in patients with unspecific CLBP. The effect is localised to the lumbar region, with no observed impact on remote sites. Higher pain catastrophizing seems to be linked to reduced hypoalgesic response. These findings support the use of short core stabilisation exercises as an effective, immediate, non-pharmacological pain management strategy for these patients.

Understanding Exercise-Induced Hypoalgesia: An Umbrella Review of Scientific Evidence and Qualitative Content Analysis

Background and Objectives: Exercise-induced hypoalgesia (EIH) is a topic of interest in the scientific community. This umbrella review aimed to analyze EIH research and compare it with public dissemination on X. Materials and Methods: We selected relevant EIH reviews that included a healthy population or patients with pain and studied exercise interventions. A systematic literature search was carried out in PubMed, Web of Science, SciELO, PEDro, and Google Scholar, employing the Population, Intervention, Comparison, and Outcome strategy. Data were extracted and summarized, and methodological quality was assessed with the Quality Assessment Scale for Systematic Reviews, and risk of bias with the Risk of Bias in Systematic Reviews tool. The Physical Activity Guidelines Advisor Committee was employed for evidence synthesis. Simultaneously, advanced X website searches gathered EIH-related content for analysis. Information from posts on X was qualitatively analyzed and contrasted with evidence in the literature. Results: We included nine systematic reviews and 17 narrative reviews. Systematic reviews presented high methodological quality. However, half had low risk of bias, while the other half presented high risk of bias. The EIH in healthy participants was controversial for some exercise modalities, such as aerobic exercise, and the influence of psychological variables. Modalities, such as isotonic resistance exercise, showed favorable effects on hypoalgesia. However, in patients with musculoskeletal pain, different exercise modalities did not generate EIH. X analysis unveiled a considerable representation of science-related content, although with prevalent misinterpretations of scientific evidence. Conclusions: EIH has been extensively studied, yet the certainty of evidence remains limited. While some exercise modalities demonstrate hypoalgesic effects in asymptomatic individuals, these effects remain unverified in patients with musculoskeletal pain. Moreover, the analysis of social media content highlights frequent misinterpretations of scientific evidence, particularly conflating hypoalgesia with analgesia. This underscores the need for more precise, evidence-based communication on social media platforms.

Beneficial Effects of Exercise in Neuropathic Pain: An Overview of the Mechanisms Involved

Neuropathic pain is a prevalent issue that often arises following injuries to the peripheral or central nervous system. Unfortunately, there is currently no definitive and flawless treatment available to alleviate this type of pain. However, exercise has emerged as a promising nonpharmacological and adjunctive approach, demonstrating a significant impact in reducing pain intensity. This is why physical therapy is considered a beneficial approach for diminishing pain and promoting functional recovery following nerve injuries. Regular physical activity exerts its hypoalgesic effects through a diverse array of mechanisms. These include inhibiting oxidative stress, suppressing inflammation, and modulating neurotransmitter levels, among others. It is possible that multiple activated mechanisms may coexist within an individual. However, the priming mechanism does not need to be the same across all subjects. Each person's response to physical activity and pain modulation may vary depending on their unique physiological and genetic factors. In this review, we aimed to provide a concise overview of the mechanisms underlying the beneficial effects of regular exercise on neuropathic pain. We have discussed several key mechanisms that contribute to the improvement of neuropathic pain through exercise. However, it is important to note that this is not an exhaustive analysis, and there may be other mechanisms at play. Our goal was to provide a brief yet informative exploration of the topic.

Aerobic Exercise Prescription for Pain Reduction in Fibromyalgia: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVE

Fibromyalgia is a condition characterised by disabling levels of pain of varying intensity. Aerobic exercise may play a role in reducing pain in these patients. The aim of this review is to assess the dose of aerobic exercise needed, based on the frequency, intensity, type, time, volume and progression (FITT-VP) model, to obtain clinically relevant reductions in pain.

DATABASES AND DATA TREATMENT

A systematic review and meta-analysis of randomised clinical trials was conducted in the Web of Science (WoS), PEDro, PubMed and Scopus databases, the search having been conducted between July and October of 2023. Risk of bias was assessed with the Cochrane Risk of Bias assessment tool 2.

RESULTS

Seventeen studies were included. The risk of bias varied, with six studies showing low risk; five, some concerns; and six, high risk. Aerobic exercise interventions were analysed using the FITT-VP model. Frequency ranged from 1 to 10 times per week, intensity varied from light to vigorous, and the types of exercise included music-based exercise, interval training, pool-based exercise, stationary cycling, swimming and walking. The intervention durations ranged from 3 to 24 weeks, with session lengths ranging from 10 to 45 min. Most of the studies presented significant differences, favouring aerobic exercise (MD -0.49; CI [-0.90, -0.08; p = 0.02]), with moderate to low heterogeneity in subgroup analyses.

CONCLUSIONS

The study findings underscore the efficacy of aerobic exercise in alleviating pain among fibromyalgia patients, advocating for tailored exercise dosing to optimise adherence and outcomes.

SIGNIFICANCE STATEMENT

Individuals with fibromyalgia should engage in aerobic exercises two to three times weekly, for twenty-five to forty minutes in each session, aiming for more than a hundred minutes per week. They should start at low intensity, gradually increasing to higher intensities over six to twelve weeks, for optimal pain management. Exercise types should be selected in collaboration with the patient and based on personal preferences and accessibility, such as walking, and swimming, to ensure long-term adherence to the regimen.

Conservative Management of Occipital Neuralgia Supported by Physical Therapy: A Review of Available Research and Mechanistic Rationale to Guide Treatment

PURPOSE OF REVIEW

Conservative management is consistently recommended as a first line intervention for occipital neuralgia (ON); however, there is limited clinical research regarding conservative intervention for ON. This lack of research may lead to underutilization or unwarranted variability in conservative treatment. This article provides mechanism-based guidance for conservative management of ON as a component of a multimodal treatment approach, and discusses the role of the physical therapist in the care team. It also highlights opportunities for further research to refine conservative management of this condition.

RECENT FINDINGS

Published research on conservative interventions specific to ON is limited to very low-quality evidence for the use of TENS. The contemporary shift toward precision pain management emphasizing treatment based on a patient's constellation of clinical features-a phenotype-rather than solely a diagnosis provides more personalized and specifically targeted pain treatment. This paradigm can guide treatment in cases where diagnosis-specific research is lacking and can be used to inform conservative treatment in this case. Various conservative interventions have demonstrated efficacy in treating many of the symptoms and accepted etiologies of ON. Conservative interventions provided by a physical therapist including exercise, manual therapy, posture and biomechanical training, TENS, patient education, and desensitization have mechanistic justification to treat symptoms and causes of ON. Physical therapists have adequate time and skill to provide such progressive and iterative interventions and should be included in a multimodal treatment plan for ON. Further research is required to determine appropriate dosing, sequencing, and progression of conservative treatments.

Opposite effects of isometric exercise on pain sensitivity of healthy individuals: the role of pain modulation

Introduction

Exercise-induced hypoalgesia (EIHypo) among healthy individuals is well documented; however, the opposite effect of exercise, ie, exercise-induced hyperalgesia (EIHyper), has mainly been described in patients with chronic pain or after intense/painful exercise.

Objectives

We investigated the extent to which EIHypo and/or EIHyper occur among healthy participants and whether these responses are associated with individuals' pain modulation capacity.

Methods

Fifty-seven participants (mean age 29.20 ± 5.21 years) underwent testing of pressure pain threshold as an index of EIHypo/EIHyper: pain adaptation, offset analgesia (OA), and conditioned pain modulation as indices of pain modulation, prior to and immediately postsubmaximal isometric exercise (n = 40) or rest (n = 17, control group). Body awareness and exercise-evoked stress were also evaluated. Test-retest repeatability of the pain modulation indices was performed as well.

Results

Twenty-four participants (60%) exhibited EIHypo, whereas 16 (40%) exhibited EIHyper. Pressure pain threshold did not change in the control group. Baseline (preexercise) OA efficacy predicted EIHypo/EIHyper. Furthermore, OA significantly decreased postexercise in the EIHyper subgroup and slightly increased in the EIHypo subgroup. Exercise-induced hypoalgesia was associated with magnitude of daily exercise while EIHyper was associated with increased exercise-evoked stress and body awareness.

Conclusion

Submaximal isometric exercise can induce opposite effects on pain sensitivity among healthy participants-EIHypo or EIHyper. Descending pain inhibition pathways, and top-down influences over these pathways, seem to be involved in EIHypo/EIHyper effects. As such isometric exercise is often preferred in early stages of rehabilitation, preliminary screening individuals' vulnerability to this exercise is important; OA test may be used for this purpose.

Potential adjunct therapies for the management of temporomandibular disorders: An evidence-based review

OBJECTIVE

The aim was to review the role of adjuvant therapies that may potentially contribute toward the management of temporomandibular disorders (TMD).

METHODS

The addressed focused question was, "Are there any adjuvant therapies that may contribute toward the management of TMD?". Indexed databases were searched up to June 2021. The eligibility criteria were the following: (a) original clinical studies and (b) randomized controlled clinical trials (RCTs).

RESULTS

Adjuvant therapies were comprised of acupuncture, manual therapy, jaw exercises, dietary modifications, botulinum toxin therapy, and photobiomodulation. Short-term follow-up results from each of these RCTs showed beneficial effects in terms of pain reduction and improvements in jaw movement among patients with TMD. There are no long-term follow-up results in this regard.

CONCLUSION

The most effective adjunct treatment for managing TMD remains unknown, primarily due to a lack of sufficient scientific evidence.

Effects of Apnea-Induced Hypoxia on Hypoalgesia in Healthy Subjects

INTRODUCTION

Exercise-induced hypoalgesia is a phenomenon in which exercise bouts induce a reduction in pain sensitivity. Apnea training involves similar characteristics that could potentially induce hypoalgesia.

OBJECTIVES

The objectives of this study are to explore the effect of apnea training on hypoalgesia; assess the correlation between conditioned pain modulation (CPM) response and apnea-induced hypoalgesia; and examine the association between hypoalgesia with hypoxemia, and heart rate (HR) during apnea.

METHODS

A randomized controlled trial was conducted comparing a walking protocol employing intermittent apnea compared with normal breathing in healthy volunteers. Hypoalgesia was tested with pressure pain thresholds (PPTs) and CPM. Oxygen saturation (SpO2) and HR were also tested.

RESULTS

Relevant but not significant changes were detected in the thumb (MD = 0.678 kg/cm2), and tibialis (MD = 0.718 kg/cm2) in favor of the apnea group. No significant differences were detected in CPM. The apnea group presented lower SpO2, but HR values similar to those of the control group during the intervention. Basal CPM and intrasession hypoxemia significantly correlated with the PPT response. However, HR did not correlate with the PPT response.

CONCLUSIONS

The current results suggest a trend, though not statistically significant, toward an improvement in the PPT in favor of apnea training compared to normal breathing. Nevertheless, subjects who presented greater basal CPM and lower oxygen saturation during the session presented a greater PPT response, suggesting the possibility of mediators of response. Future investigations should clarify this phenomenon.

Hypoalgesia and Conditioned Pain Modulation in Blood Flow Restriction Resistance Exercise

We compared the magnitude of exercise-induced hypoalgesia and conditioned pain modulation between blood-flow restriction (BFR) resistance exercise (RE) and moderate-intensity RE. Twenty-five asymptomatic participants performed unilateral leg press in two visits. For moderate-intensity RE, subjects exercised at 50% 1RM without BFR, whereas BFR RE exercised at 30% 1RM with a cuff inflated to 60% limb occlusion pressure. Exercise-induced hypoalgesia was quantified by pressure pain threshold changes before and after RE. Conditioned pain modulation was tested using cold water as the conditioning stimulus and mechanical pressure as the test stimulus and quantified as pressure pain threshold change. Difference in conditioned pain modulation pre- to post-RE was then calculated. The differences of RE on pain modulations were compared using paired t-tests. Pearson's r was used to examine the correlation between exercise-induced hypoalgesia and changes in conditioned pain modulation. We found greater hypoalgesia with BFR RE compared to moderate-intensity RE (p=0.008). Significant moderate correlations were found between exercise-induced hypoalgesia and changes in conditioned pain modulation (BFR: r=0.63, moderate-intensity: r=0.72). BFR RE has favorable effects on pain modulation in healthy adults and the magnitude of exercise-induced hypoalgesia is positively correlated with conditioned pain modulation activation.

Effects of motor imagery using virtual reality on pain sensitivity and affect in healthy individuals: a prospective randomized crossover study

OBJECTIVE

Exercise induces a hypoalgesic response and improves affect. However, some individuals are unable to exercise for various reasons. Motor imagery, involving kinesthetic and visual imagery without physical movement, activates brain regions associated with these benefits and could be an alternative for those unable to exercise. Virtual reality also enhances motor imagery performance because of its illusion and embodiment. Therefore, we examined the effects of motor imagery combined with virtual reality on pain sensitivity and affect in healthy individuals.

DESIGN

Randomized crossover study.

SETTING

Laboratory.

SUBJECTS

Thirty-six participants (women: 18) were included.

METHODS

Each participant completed three 10-min experimental sessions, comprising actual exercise, motor imagery only, and motor imagery combined with virtual reality. Hypoalgesic responses and affective improvement were assessed using the pressure-pain threshold and the Positive and Negative Affect Schedule, respectively.

RESULTS

All interventions significantly increased the pressure-pain threshold at the thigh (P < .001). Motor imagery combined with virtual reality increased the pressure-pain threshold more than motor imagery alone, but the threshold was similar to that of actual exercise (both P ≥ .05). All interventions significantly decreased the negative affect of the Positive and Negative Affect Schedule (all P < .05).

CONCLUSIONS

Motor imagery combined with virtual reality exerted hypoalgesic and affective-improvement effects similar to those of actual exercise.

CLINICAL TRIALS REGISTRATION

The study was enrolled in the UMIN Clinical Trials Registry (registration number: UMIN000046095). The website for registration information is https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000052614.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

SIGNIFICANCE STATEMENT

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

General exercises are not superior to specific exercises for pain and functional disability in individuals with chronic nonspecific neck pain. A systematic review and meta-analysis

OBJECTIVE

To compare the effectiveness of general exercises with specific exercises for pain and functional disability of individuals with chronic nonspecific neck pain.

METHOD

This systematic review of clinical trials searched MEDLINE, CINAHL, Embase, CENTRAL, and PEDro databases with no date or language restriction. Methodological quality of evidence were assessed using the PEDro scale and GRADE, respectively. Pain and functional disability were the primary outcomes.

RESULTS

This review included 14 articles from 12 studies, from which nine were included in meta-analyses. Data were from 926 individuals with chronic nonspecific neck pain, comparing specific exercises with mind-body and aerobic exercises (general exercises). Pain intensity was not different between aerobic and specific exercises, with a mean difference (MD) of 0.95 points (95% CI -1.62 to 3.51) in the medium-term and 0.32 points (95% CI -1.05 to 1.68) in the long-term. Mind-body exercises were not better than specific exercises for pain intensity in medium- (MD 0.54 points; 95% CI 0.00 to 1.08) or long-term (MD 0.06 points; 95% CI -0.59 to 0.46). Also, mind-body exercises did not improve functional disability compared with specific exercises in medium- or long-term (MD 0.01 points; 95% CI -0.25 to 0.27). The quality of evidence among studies ranged from very low to low across all comparisons.

CONCLUSION

General exercises are not superior to specific exercises for pain and functional disability in individuals with chronic nonspecific neck pain.

Exercise induced hypoalgesia after a high intensity functional training: a randomized controlled crossover study

BACKGROUND

Acute physical activity often induces an acute reduction in pain sensitivity known as exercise induced hypoalgesia (EIH). The aim of this study was to investigate the effects of a high intensity functional training (HIFT) on EIH compared to a control session.

METHODS

50 (age: 26.0 ± 2.7; 23 female) participants successfully conducted this study consisting of a pre-experimental test as well as a 12-minute HIFT (body-weight exercises) and a 12-minute control (supervised breathing) session in a randomized crossover design. Pre and post, pressure pain thresholds (PPT) were measured at the ankles, knees, elbows, and forehead.

RESULTS

The HIFT resulted in a relative maximum and average heart rate of 96.2% (± 3.6%) and 91.1% (± 4.2%), respectively, and maximum and average RPE values of 19.1 (± 1.2) and 16.2 (± 1.4), respectively. Results reveal a significant 'Intervention' × 'Time point' interaction (p < 0.001) for PPT (pooled for one average value) with hypoalgesia observed following the HIFT (p < 0.001; pre: 56.0 ± 16.8, post: 61.6 ± 19.0 [Newton]) and no change following the control (p = 0.067; pre: 56.6 ± 18.4, post: 55.3 ± 18.9 [Newton]). Further, a significant 'Time' × 'Intervention' × 'Landmark' interaction effect (p = 0.024) is observed and all landmarks showed significant hypoalgesia following HIFT (p < 0.01), except for the right elbow and forehead. Following control, no hypoalgesia was observed at any landmark. Analysing male and female participants separately, it was observed that EIH occured only in men.

CONCLUSION

A HIFT using bodyweight exercises reduces pain sensitivity. Hence, combining strength and aerobically demanding exercises in a short but high intensity manner, as done in HIFT, can be seen as a usable tool to induce hypoalgesia. Yet, these results were observed only in male participants, necessitating future sex-specific research.

TRIAL REGISTRATION

DRKS00034391, retrospectively registered on the 4th of June 2024.

The Effect of Combining Spinal Manipulation and Dry Needling in Individuals With Nonspecific Low Back Pain

Low back pain (LBP) is one of the most common and costly musculoskeletal conditions impacting health care in the United States. The development of multimodal strategies of treatment is imperative in order to curb the growing incidence and prevalence of LBP. Spinal manipulative therapy (SMT), dry needling (DN), and exercise are common nonpharmacological treatments for LBP. This study is a 3-armed parallel-group design randomized clinical trial. We enrolled and randomized 96 participants with LBP into a multimodal strategy of treatment consisting of a combination of DN and SMT, DN only, and SMT only, followed by an at-home exercise program. All participants received 4 treatment sessions in the first 2 weeks followed by a 2-week home exercise program. Outcomes included clinical (Oswestry Disability Index, numeric pain intensity rating) and mechanistic (lumbar multifidus, erector spinae, and gluteus medius muscle activation) measures at baseline, 2, and 4 weeks. Participants in the DN and SMT groups showed larger effects and statistically significant improvement in pain and disability scores, and muscle percent thickness change at 2 weeks and 4 weeks of treatment when compared to the other groups. This study was registered prior to participant enrollment. PERSPECTIVE: This article presents the process of developing an optimized multimodal treatment plan utilizing SMT, DN, and exercise to address the burden of LBP for impacted individuals and the health care system. This method could potentially help clinicians who treat LBP to lower initial pain and increase exercise compliance. (clinicaltrials.gov NCT05802901).

Biopsychosocial contributors to irritability in individuals with shoulder or low back pain

OBJECTIVES

Irritability is a foundational clinical reasoning concept in rehabilitation to evaluate reactivity of the examination and treatment. While originally theorized to reflect tissue damage, a large body of evidence supports pain is a biopsychosocial experience impacted by pain sensitivity and psychological factors. Therefore, the purpose of this study was to examine biopsychosocial contributors to irritability.

METHODS

40 patients with shoulder (n = 20) and low back (n = 20) pain underwent Quantitative Sensory Testing (QST) (Pressure Pain Threshold, Heat Pain Threshold, Conditioned Pain Modulation, Temporal Summation), completed pain-related psychological questionnaires, an Exercise-Induced Hypoalgesia protocol, and standardized irritability assessment based on Clinical Practice Guidelines. Participants were then categorized as irritable or not irritable based on Maitland's criteria and by irritability level based on Clinical Practice Guidelines. An independent samples t-test examined for differences in QST and psychological factors by irritability category. A MANOVA examined for differences in QST and psychological factors by irritability level (high, moderate, low).

RESULTS

Significantly lower heat and pressure pain thresholds at multiple locations (p < 0.05), as well as less efficient conditioned pain modulation (p = 0.02), were demonstrated in individuals categorized as irritable. Heat and pressure pain thresholds were also significantly lower in patients with high irritability compared to other levels. Significantly higher depression and anger, as well as lower self-efficacy, were reported in individuals with an irritable presentation.

DISCUSSION/CONCLUSION

Biopsychosocial factors, including widespread hyperalgesia and elevated psychological factors, may contribute to an irritable presentation.

Quality of life and level of physical activity of individuals with temporomandibular disorders with and without otological symptoms: Secondary analysis of a cross-sectional study

BACKGROUND AND PURPOSE

Otological symptoms (OS) are highly prevalent in individuals with temporomandibular disorders (TMD). Individuals with TMD and OS have more neck disability and decreased deep neck muscles endurance when compared to individuals without OS. However, no studies have evaluated whether OS is associated with lower Quality of Life (QoL) and worse levels of physical activity. This study aimed to evaluate the QoL and level of physical activity of individuals with TMD with and without OS.

METHODS

In this cross-sectional study, 62 individuals with TMD were allocated into 2 groups: TMD with OS (n = 36) or TMD without OS (n = 26). Self-reported complaints of dizziness, vertigo, tinnitus, earache, ear fullness, or hypoacusis were considered as OS. QoL was assessed with the WHOQOL-Bref and physical activity with the IPAQ-SF. Independent t-test and chi-squared test were used for analysis between-groups. Effect sizes were reported using Cohen's d. A Pearson correlation was used to compare the number of OS and QoL scores. A significance level of p < 0.05% and 95% confidence intervals were considered statistically significant.

RESULTS

The total generic scores for QoL were not different between-groups (p = 0.076), but individuals with TMD with OS had lower satisfaction (p = 0.015; d: 0.63) and physical domain (p = 0.015; d: 0.64) scores with a moderate effect size. In TMD with OS, 69.4% of individuals were irregularly active and 50% for the TMD without OS, with no statistical significance (p > 0.05). The number of OSs was inversely and weakly associated with the QoL total score.

CONCLUSION

Individuals with TMD and OS are associated with worsened QoL (physical domain and satisfaction) when compared to individuals with TMD without OS. The higher the number of OS, the worse the QoL score. Individuals with TMD with and without OS had similar levels of physical activity, but a high prevalence of irregularly active and sedentary individuals within TMD diagnosed population was found.

Efficacy of various exercise interventions for migraine treatment: A systematic review and network meta-analysis

OBJECTIVE

To compare various exercise modalities' efficacy on migraine frequency, intensity, duration, and disability.

BACKGROUND

Exercise has been shown to be an effective intervention to reduce migraine symptoms and disability; however, no clear evidence exists regarding the most effective exercise modalities for migraine treatment.

METHODS

A systematic review was performed in PubMed, PEDro, Web of Science, and Google Scholar. Clinical trials that analyzed the efficacy of various exercise modalities in addressing the frequency, intensity, duration, and disability of patients with migraine were included. Eight network meta-analyses based on frequentist (F) and Bayesian (B) models were developed to estimate the direct and indirect evidence of various exercise modalities. Standardized mean difference (SMD) and 95% confidence (CI) and credible intervals (CrI) were calculated for each treatment effect based on Hedge's g and p scores to rank the modalities.

RESULTS

We included 28 studies with 1501 migraine participants. Yoga (F: SMD -1.30; 95% CI -2.09, -0.51; B: SMD -1.33; 95% CrI -2.21, -0.45), high-intensity aerobic exercise (F: SMD -1.30; 95% CI -2.21, -0.39; B: SMD -1.17; 95% CrI -2.20, -0.20) and moderate-intensity continuous aerobic exercise (F: SMD -1.01; 95% CI -1.63, -0.39; B: SMD -1.06; 95% CrI -1.74, -0.38) were significantly superior to pharmacological treatment alone for decreasing migraine frequency based on both models. Only yoga (F: SMD -1.40; 95% CI -2.41, -0.39; B: SMD -1.41; 95% CrI -2.54, -0.27) was significantly superior to pharmacological treatment alone for reducing migraine intensity. For diminishing migraine duration, high-intensity aerobic exercise (F: SMD -1.64; 95% CI -2.43, -0.85; B: SMD -1.56; 95% CrI -2.59, -0.63) and moderate-intensity continuous aerobic exercise (SMD -0.96; 95% CI -1.50, -0.41; B: SMD -1.00; 95% CrI -1.71, -0.31) were superior to pharmacological treatment alone.

CONCLUSION

Very low-quality evidence showed that yoga, high- and moderate-intensity aerobic exercises were the best interventions for reducing migraine frequency and intensity; high- and moderate-intensity aerobic exercises were best for decreasing migraine duration; and moderate-intensity aerobic exercise was best for diminishing disability.

Muscle activity and hypoalgesia in blood flow restricted versus unrestricted effort-matched resistance exercise in healthy adults

This study assessed muscle activity (root mean square, RMS, and median frequency, MDF) to evaluate the acute response to blood flow restriction (BFR) resistance exercise (RE) and conventional moderate intensity (MI) RE. We also performed exploratory analyses of differences based on sex and exercise-induced hypoalgesia (EIH). Fourteen asymptomatic individuals performed four sets of unilateral leg press with their dominant leg to volitional fatigue under two exercise conditions: BFR RE and MI RE. Dominant side rectus femoris (RF) and vastus lateralis (VL) muscle activity were measured using surface electromyography (sEMG) through exercise. RMS and MDF were calculated and compared between conditions and timepoints using a linear mixed model. Pressure pain thresholds (PPT) were tested before and immediately after exercise and used to quantify EIH. Participants were then divided into EIH responders and nonresponders, and the differences on RMS and MDF were compared between the two groups using Hedges' g. RMS significantly increased over time (RF: p = 0.0039; VL: p = 0.001) but not between conditions (RF: p = 0.4; VL: p = 0.67). MDF decreased over time (RF: p = 0.042; VL: p < 0.001) but not between conditions (RF: p = 0.74; VL: p = 0.77). Consistently lower muscle activation was found in females compared with males (BRF, RF: g = 0.63; VL, g = 0.5. MI, RF: g = 0.72; VL: g = 1.56), with more heterogeneous findings in MDF changes. For BFR, EIH responders showed greater RMS changes (Δ RMS) (RF: g = 0.90; VL: g = 1.21) but similar MDF changes (Δ MDF) (RF: g = 0.45; VL: g = 0.28) compared to nonresponders. For MI, EIH responders demonstrated greater increase on Δ RMS (g = 0.61) and decrease on Δ MDF (g = 0.68) in RF but similar changes in VL (Δ RMS: g = 0.40; Δ MDF: g = 0.39). These results indicate that when exercising to fatigue, no statistically significant difference was observed between BFR RE and conventional MI RE in Δ RMS and Δ MDF. Lower muscle activity was noticed in females. While exercising to volitional fatigue, muscle activity may contribute to EIH.

Treadmill running on neuropathic pain: via modulation of neuroinflammation

Neuropathic pain is a type of chronic pain caused by an injury or somatosensory nervous system disease. Drugs and exercise could effectively relieve neuropathic pain, but no treatment can completely stop neuropathic pain. The integration of exercise into neuropathic pain management has attracted considerable interest in recent years, and treadmill training is the most used among exercise therapies. Neuropathic pain can be effectively treated if its mechanism is clarified. In recent years, the association between neuroinflammation and neuropathic pain has been explored. Neuroinflammation can trigger proinflammatory cytokines, activate microglia, inhibit descending pain modulatory systems, and promote the overexpression of brain-derived neurotrophic factor, which lead to the generation of neuropathic pain and hypersensitivity. Treadmill exercise can alleviate neuropathic pain mainly by regulating neuroinflammation, including inhibiting the activity of pro-inflammatory factors and over activation of microglia in the dorsal horn, regulating the expression of mu opioid receptor expression in the rostral ventromedial medulla and levels of γ-aminobutyric acid to activate the descending pain modulatory system and the overexpression of brain-derived neurotrophic factor. This article reviews and summarizes research on the effect of treadmill exercise on neuropathic pain and its role in the regulation of neuroinflammation to explore its benefits for neuropathic pain treatment.

The effect of resistance exercise on multimodal pain thresholds in local and systemic muscle sites

Dynamic resistance exercise may produce reductions in pain locally at the exercising muscle and systemically at non-exercising sites. However, limited research has examined these changes with multiple noxious stimuli. This study examined changes in heat pain threshold (HPT) and pressure pain threshold (PPT) on different musculature after an upper and lower body exercise to compare local and systemic effects. A crossover design with 28 participants (mean age: 21 ± 4 years, 21 female) completed three sessions. Visit one included baseline quantitative sensory testing and 5-repetition maximum (RM) testing for upper (shoulder press) and lower (leg extension) body. In subsequent sessions, participants performed upper or lower body exercises using an estimated 75% 1-RM with pre/post assessment of HPT and PPT at three sites: deltoid, quadriceps, and low back. A significant three-way interaction was observed for HPT (F (1.71, 3.80) = 2.19, p = 0.036, η2p = 0.12) with significant increases in HPT over the quadriceps (p = 0.043) after leg extension and over the deltoid (p = 0.02) after shoulder press. Significant systemic changes were not observed for HPT or PPT. Local but not systemic effects were demonstrated after an acute bout of exercise. Peripheral pain sensitivity may be more responsive to heat stimuli after resistance exercise.

The Effect of Myofascial Stretching on Mechanical Nociception and Contributing Neural Mechanisms

Myofascial stretching is often prescribed in the management of musculoskeletal pain. However, the neural mechanisms contributing to a decrease in pain are unknown. Stretching produces a sensation that may act as a conditioning stimulus in a conditioned pain modulation response. The purpose of this study was to compare immediate changes in pressure pain thresholds (PPTs) during a low-intensity stretch, moderate-intensity stretch, and cold water immersion task. A secondary purpose was to examine if personal pain sensitivity and psychological characteristics were associated with the responses to these interventions. Twenty-seven (27) healthy participants underwent a cross-over study design in which they completed a cold water immersion task, upper trapezius stretch to the onset of the stretch sensation, and a moderate-intensity stretch. A significant condition x time effect was observed (F (8,160) = 2.85, p < 0.01, partial eta2 = 0.13), indicating reductions in pain sensitivity were significantly greater during a cold water immersion task compared to moderate-intensity stretching at minutes two and four. Widespread increases in heat pain threshold and lower pain-related anxiety were moderately correlated with the response to the cold water immersion task but not stretching. Moderate-intensity stretching may not elicit a conditioned pain modulation response possibly because the stretch was not intense enough to be perceived as painful.

Chronic Pain Self-Management Strategies for Older Adults: An Integrative Review

INTRODUCTION

Due to the complex nature of chronic pain, especially in older adults, a biopsychosocial approach is more effective than an isolated approach for its management. Furthermore, when patients are actively engaged in their pain management, they are more likely to be successful than relying totally on others.

OBJECTIVE

To analyze the self-management strategies currently used by older adults with chronic pain.

METHOD

An integrative review was conducted through seven online databases, searching for scientific studies on this topic published in the last 10 years.

RESULTS AND CONCLUSION

Fifty-eight studies were included in the final sample. Research on chronic pain self-management for older adults has increased in recent years. Although a diversity of chronic physical painful conditions are being investigated, many conditions are still under-investigated. Online and in-person strategies are currently adopted, demonstrating similar results. Positive results are evidenced by strategies including health promotion, mind control, social participation and take-action fields. Major results come from a combination of strategies focusing on biopsychosocial aspects of pain management. Results include not only the reduction of pain itself, but increased self-efficacy, adoption of health behaviors and improvement of functionality, among others, i.e., improved QoL, despite pain.

Acute hypoalgesic, neurophysiological and perceptual responses to low-load blood flow restriction exercise and high-load resistance exercise

This study compared the acute hypoalgesic and neurophysiological responses to low-load resistance exercise with and without blood flow restriction (BFR), and free-flow, high-load exercise. Participants performed four experimental conditions where they completed baseline measures of pain pressure threshold (PPT), maximum voluntary force (MVF) with peripheral nerve stimulation to determine central and peripheral fatigue. Corticospinal excitability (CSE), corticospinal inhibition and short interval intracortical inhibition (SICI) were estimated with transcranial magnetic stimulation. Participants then performed low-load leg press exercise at 30% of one-repetition maximum (LL); low-load leg press with BFR at 40% (BFR40) or 80% (BFR80) of limb occlusion pressure; or high-load leg press of four sets of 10 repetitions at 70% one-repetition maximum (HL). Measurements were repeated at 5, 45 min and 24 h post-exercise. There were no differences in CSE or SICI between conditions (all P > 0.05); however, corticospinal inhibition was reduced to a greater extent (11%-14%) in all low-load conditions compared to HL (P < 0.005). PPTs were 12%-16% greater at 5 min post-exercise in BFR40, BFR80 and HL compared to LL (P ≤ 0.016). Neuromuscular fatigue displayed no clear difference in the magnitude or time course between conditions (all P > 0.05). In summary, low-load BFR resistance exercise does not induce different acute neurophysiological responses to low-load, free-flow exercise but it does promote a greater degree of hypoalgesia and reduces corticospinal inhibition more than high-load exercise, making it a useful rehabilitation tool. The changes in neurophysiology following exercise were not related to changes in PPT.

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.

Exercise induced hypoalgesia during different intensities of a dynamic resistance exercise: A randomized controlled trial

INTRODUCTION

Exercise produces an immediate lessening of pain sensitivity (Exercise-Induced Hypoalgesia (EIH)) in healthy individuals at local and distant sites, possibly through a shared mechanism with conditioned pain modulation (CPM). Dynamic resistance exercise is a recommended type of exercise to reduce pain, yet limited research has examined the effects of intensity on EIH during this type of exercise. Therefore, the primary purpose of this study is to compare changes in PPT at a local and distant site during a leg extension exercise at a high intensity, a low intensity, or a quiet rest condition. A secondary purpose is to examine if CPM changes after each intervention. The final purpose is to examine if baseline pain sensitivity measures are correlated with response to each intervention.

METHODS

In a randomized controlled trial of 60 healthy participants, participants completed baseline pain sensitivity testing (heat pain threshold, temporal summation, a cold pressor test as measure of CPM) and were randomly assigned to complete a knee extension exercise at: 1) high intensity (75% of a 1 Repetition Maximum (RM), 2) low intensity (30% 1RM), or 3) Quiet Rest. PPT was measured between each set at a local (quadriceps) and distant (trapezius) site during the intervention. CPM was then repeated after the intervention. To test the first purpose of the study, a three-way ANOVA examined for time x site x intervention interaction effects. To examine for changes in CPM by group, a mixed-model ANOVA was performed. Finally, a Pearson Correlation examined the association between baseline pain sensitivity and response to each intervention.

RESULTS

Time x site x intervention interaction effects were not significant (F(5.3, 150.97) = 0.87, p = 0.51, partial eta2 = 0.03). CPM did not significantly change after the interventions (time x intervention F(1,38) = 0.81, p = 0.37, partial eta2 = 0.02. EIH effects at the quadriceps displayed a significant, positive moderate association with baseline HPT applied over the trapezius (r = 0.61, p<0.01) and TS (r = 0.46, p = 0.04).

DISCUSSION

In healthy participants, PPT and CPM did not significantly differ after a leg extension exercise performed at a high intensity, low intensity, or quiet rest condition. It is possible pre-intervention CPM testing with a noxious stimuli may have impaired inhibitory effects frequently observed during exercise but future research would need to examine this hypothesis.

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

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

Exercise-induced hypoalgesia in chronic neck pain: A narrative review

Chronic neck pain (CNP) is a worldwide health problem with several risk factors. One of the most widely used treatments for managing this condition is therapeutic exercise, which could generate a response called exercise-induced hypoalgesia (EIH). There is no consensus on the best exercise modality to induce hypoalgesia. Therefore, this review aims to analyze and synthesize the state-of-the-art about the hypoalgesic effect of exercise in subjects with CNP. We included articles on EIH and CNP in patients older than 18 years, with pain for more than three months, where the EIH response was measured. Articles that studied CNP associated with comorbidities or measured the response to treatments other than exercise were excluded. The studies reviewed reported variable results. Exercise in healthy subjects has been shown to reduce indicators of pain sensitivity; however, in people with chronic pain, the response is variable. Some investigations reported adverse effects with increased pain intensity and decreased pain sensitivity, others found no clinical response, and some even reported EIH with decreased pain and increased sensitivity. EIH is an identifiable, stimulable, and helpful therapeutic response in people with pain. More research is still needed on subjects with CNP to clarify the protocols and therapeutic variables that facilitate the EIH phenomenon. In addition, it is necessary to deepen the knowledge of the intrinsic and extrinsic factors that influence EIH in people with CNP.

Pain Science in Practice (Part 6): How Does Descending Modulation of Pain Work?

SYNOPSIS

To understand the neuroscience of pain relief, one must know about the descending pain modulatory system. Neuronal pathways that originate in the brainstem and project to the spinal cord to modulate spinal neuronal activity provide a well-documented perspective on the mechanisms of analgesia that underpin pharmacological and nonpharmacological treatment options for people with musculoskeletal pain. Peripheral stimuli or signals from the cortex and subcortical regions of the brain can trigger the descending pain modulatory system (DPMS). The system helps explain how counter-stimulation techniques (eg, acupuncture and manual therapy), the patients' expectations and beliefs, and social or contextual factors could influence how people experience pain. J Orthop Sports Phys Ther 2024;54(2):1-4. doi:10.2519/jospt.2024.12112.

Exercise-Induced Hypoalgesia in Patients with Chronic Whiplash-Associated Disorders: Differences between Subgroups Based on the Central Sensitization Inventory

BACKGROUND

Physical exercise is an important element in the rehabilitation of chronic whiplash-associated disorders, with the physiological process underlying pain reduction called exercise-induced hypoalgesia. In chronic whiplash-associated disorders, exercise-induced hypoalgesia appears impaired, and the research suggests a relationship with symptoms of dysfunctional nociceptive processing, such as central sensitization. This study improves our understanding of exercise-induced hypoalgesia in chronic whiplash-associated disorders by examining the differences between the extent of exercise-induced hypoalgesia in subgroups based on scores on the central sensitization inventory (CSI).

METHODS

Data were collected from 135 participants with chronic whiplash-associated disorders who completed a set of questionnaires. Pain pressure thresholds and temporal summations were assessed before and after a submaximal aerobic bicycle exercise test.

RESULTS

We observed no interaction effect between exercise-induced hypoalgesia and the CSI scores for both pain pressure threshold and temporal summation. No overall statistical effect was measured in the analysis of the effect of time. The pain pressure threshold significantly related to the CSI. The temporal summation showed no correlation.

CONCLUSIONS

During this study, we did not find evidence for a difference in the presence of exercise-induced hypoalgesia when the subgroups were created based on the central sensitization cluster calculator. Limited evidence was found for the influence of CSI scores on the delta pain pressure threshold.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Efficacy of combined strategies of physical activity, diet and sleep disorders as treatment in patients with chronic shoulder pain. A systematic review

Introduction: The objective of this systematic review was to analyze the existing scientific evidence on the influence of dietary strategies, exercise, and sleep disorders on the symptomatology of patients with chronic shoulder pain, as well as to assess the methodological quality of the literature collected. Methods: The selection criteria were as follows: we included randomized controlled clinical trials written in English that investigated the effects of such interventions in patients with chronic shoulder pain and excluded studies where pre-operative rehabilitation or rehabilitation combined with corticosteroid injections was performed. We searched six databases Pubmed, Cochrane Library, Web of Science, CINAHL, Sportdiscus and Scopus, using the keywords "shoulder pain," "fasting," "physical therapy modalities," "rehabilitation," "exercise," "circadian clocks," and "chronic pain" to select randomized controlled clinical trials conducted in humans and written in English. The last search was conducted on 24/01/2023. (PROSPERO:CRD42023379925). Results: We used the tool proposed by the Cochrane Handbook to assess the risk of bias in the included studies of the 17 studies included, nine had a high risk of bias, two studies had an unclear risk of bias, and the remaining six studies had a low risk of bias. A total of 17 articles were selected, including 10 studies that showed a positive influences of exercise on chronic shoulder pain and five studies that showed a negative influence of sleep disorders on this patient profile. The remaining two articles analyzed the influence of nutritional strategies and metabolic problems in patients with chronic shoulder pain. The total sample size of the 17 included articles amounted to 9,991 individuals. Discussion: Studies confirm that exercise generates a hypoalgesic effect that improves chronic shoulder pain, functionality, and quality of life. Although dietary strategies and sleep disorders are known to influence chronic shoulder pain, there is a lack of studies that conduct interventions on these problems to assess how chronic shoulder pain varies.

Autonomic responses to aerobic and resistance exercise in patients with chronic musculoskeletal pain: A systematic review

BACKGROUND

It is unknown whether patients with chronic musculoskeletal pain (CMP) show autonomic dysregulation after exercise, and the interventional effects of exercise on the autonomic dysregulation have not been elucidated. The objectives of this study were to reveal acute autonomic responses after aerobic and resistance exercises and the interventional effects of both exercises on autonomic dysregulation in patients with CMP.

METHODS

A systematic search using nine electronic databases was performed based on three key search terms: "chronic musculoskeletal pain," "autonomic nervous system," and "exercise." Data were extracted from measurements of the autonomic nervous system and pain.

RESULTS

We found a total of 1170 articles; 17 were finally included, incorporating 12 observational and five interventional studies. Although a comparator has not been specified, healthy controls were compared to patients with CMP in observational studies. Three of five interventional studies were pre-post study with healthy controls as a comparator or no controls. The other two interventional studies were randomized controlled trial with a different treatment e.g., stretching. There were four good, 10 fair, and three poor-quality articles. The total number of participants was 617, of which 551 were female. There was high heterogeneity among the five disease conditions and nine outcome measures. Following one-time exposure to aerobic and resistance exercises, abnormal autonomic responses (sympathetic activation and parasympathetic withdrawal), which were absent in healthy controls, were observed in patients with CMP. The effects of aerobic and resistance exercise as long-term interventions were unclear since we identified both positive effects and no change in the autonomic activities in patients with CMP.

CONCLUSIONS

This study indicates dysfunctional autonomic responses following one-time exposure to exercise and inconsistent interventional effects in the autonomic activities in patients with CMP. Appropriate therapeutic dose is necessary for studying the management of autonomic regulation and pain after exercise.

Pain intensity and pain sensitivity are not increased by a single session of high-intensity interval aerobic exercise in individuals with chronic low back pain: A randomized and controlled trial

BACKGROUND

Evidence on the acute impact of high-intensity interval aerobic exercise on pain is scarce. This type of exercise might be perceived as increasing pain intensity and pain sensitivity negatively impacting adherence. More evidence on the acute effects of high-intensity interval aerobic exercise in individuals with low back pain (LBP) is needed.

OBJECTIVES

To compare the acute effects of a single session of high-intensity interval aerobic exercise, continuous moderate-intensity aerobic exercise, and no exercise on pain intensity and pain sensitivity in patients with chronic non-specific LBP.

DESIGN

Randomized controlled trial with three arms.

METHOD

Participants were randomly assigned to one of three groups (i) continuous moderate-intensity aerobic exercise, ii) high-intensity interval aerobic exercise, and iii) no intervention. Measures of pain intensity and pressure pain threshold (PPT) at the lower back and at a distant body site (upper limb) were taken before and after 15 min of exercise.

RESULTS

Sixty-nine participants were randomized. A significant main effect of time was found for pain intensity (p = 0.011; η2p = 0.095) and for PPT at the lower back (p < 0.001; η2p = 0.280), but not a time versus group interaction (p > 0.05). For PPT at the upper limb, no main effect of time or interaction was found (p > 0.5).

CONCLUSIONS

Fifteen minutes of high-intensity interval aerobic exercise does not increase pain intensity or pain sensitivity compared to both moderate-intensity continuous aerobic exercise and no exercise, suggesting that high-intensity interval aerobic exercise can be used in clinical practice and patients reassured that it is unlikely to increase pain.

Mechanisms hypothesized for pain-relieving effects of exercise in fibromyalgia: a scoping review

Background

Exercise is one of the most recommended management strategies by treatment guidelines for fibromyalgia (FM); however, the mechanism through which exercise improves pain in FM is still unknown.

Objective

We aimed to summarize the hypothesized theoretical mechanisms for the pain-relieving effects of exercise in people with FM.

Eligibility Criteria

Randomized controlled trials (RCTs) in English reporting mechanisms for pain-relieving effects of exercise in the 'Introduction' and 'Discussion' sections and significant within- group or between-group effects of exercise interventions were included.

Sources of Evidence

We searched the databases Ovid MEDLINE(R), EMBASE, CINAHL, COCHRANE, Sports Discuss, and AMED with the keywords: exercise and fibromyalgia until December 2021.

Charting Methods

Two authors independently performed title/abstract, full-text review, and data abstraction using a data abstraction form. The hypothesized mechanisms from individual studies were grouped into three categories.

Results

The literature search resulted in 2147 studies, out of which 220 studies were considered for full-text review. A total of 50 RCTs proposing 29 unique mechanisms for the pain-relieving effects of exercise were included. These mechanisms were divided into three categories: physical, neuro-physiological, and psychological. The neuro-physiological category was further subdivided into exercise-induced hypoalgesia (EIH), pain sensitization, the autonomic system, the immune system, the endocrine system, and miscellaneous categories. The most frequently hypothesized mechanisms were EIH (n = 15), autonomic modulation (n = 7), improved sleep (n = 6), muscle oxygenation (n = 6), self-efficacy (n = 5), mental health (n = 4), and benefits of the aquatic environment (n = 12). While all exercise interventions involved FM patients, most of the supporting evidence for these mechanisms was cited from previous studies conducted on healthy samples. No studies performed analyses to demonstrate causal associations between the mechanisms and outcomes.

Conclusion

Multiple mechanisms were hypothesized for the positive influence of exercise in people with FM. Future studies using causal analyses, such as mediation analysis, are recommended to validate these mechanisms.

Effect of Type and Dose of Exercise on Neuropathic Pain After Experimental Sciatic Nerve Injury: A Preclinical Systematic Review and Meta-Analysis

This preclinical systematic review aimed to determine the effectiveness of different types and doses of exercise on pain behavior and biomarkers in preclinical models of focal neuropathic pain. We searched MEDLINE, EMBASE, Web of Science, PubMed, SCOPUS, CINAHL, and Cochrane library from inception to November 2022 for preclinical studies evaluating the effect of exercise compared to control interventions on neuropathic pain behavior after experimental sciatic nerve injury. If possible, data were meta-analyzed using random effect models with inverse-variance weighting. Thirty-seven studies were included and 26 meta-analyzed. Risk of bias (SYRCLE tool) remained unclear in most studies and reporting quality (CAMARADES) was variable. Exercise reduced mechanical (standardized mean differences [SMD] .53 (95% CI .31, .74), P = .0001, I2 = 0%, n = 364), heat (.32 (.07, .57), P = .01, I2 = 0%, n = 266) and cold hypersensitivity (.51 (.03, 1.0), P = .04, I2 = 0%, n = 90) compared to control interventions. No relationship was apparent between exercise duration or intensity and antinociception. Exercise modulated biomarkers related to different systems (eg, immune system, neurotrophins). Whereas firm conclusions are prevented by the use of male animals only, variable reporting quality and unclear risk of bias in many studies, our results suggest that aerobic exercise is a promising tool in the management of focal neuropathic pain. PERSPECTIVE: This systematic review and meta-analysis demonstrates that aerobic exercise reduces neuropathic pain-related behavior in preclinical models of sciatic nerve injury. This effect is accompanied by changes in biomarkers associated with inflammation and neurotrophins among others. These results could help to develop exercise interventions for patients with neuropathic pain.

Longitudinal relationships between habitual physical activity and pain tolerance in the general population

Physical activity (PA) might influence the risk or progression of chronic pain through pain tolerance. Hence, we aimed to assess whether habitual leisure-time PA level and PA change affects pain tolerance longitudinally in the population. Our sample (n = 10,732; 51% women) was gathered from the sixth (Tromsø6, 2007-08) and seventh (Tromsø7, 2015-16) waves of the prospective population-based Tromsø Study, Norway. Level of leisure-time PA (sedentary, light, moderate, or vigorous) was derived from questionnaires; experimental pain tolerance was measured by the cold-pressor test (CPT). We used ordinary, and multiple-adjusted mixed, Tobit regression to assess 1) the effect of longitudinal PA change on CPT tolerance at follow-up, and 2) whether a change in pain tolerance over time varied with level of LTPA. We found that participants with high consistent PA levels over the two surveys (Tromsø6 and Tromsø7) had significantly higher tolerance than those staying sedentary (20.4 s. (95% CI: 13.7, 27.1)). Repeated measurements show that light (6.7 s. (CI 3.4, 10.0)), moderate (CI 14.1 s. (9.9, 18.3)), and vigorous (16.3 s. (CI 6.0, 26.5)) PA groups had higher pain tolerance than sedentary, with non-significant interaction showed slightly falling effects of PA over time. In conclusion, being physically active at either of two time points measured 7-8 years apart was associated with higher pain tolerance compared to being sedentary at both time-points. Pain tolerance increased with higher total activity levels, and more for those who increased their activity level during follow-up. This indicates that not only total PA amount matters but also the direction of change. PA did not significantly moderate pain tolerance change over time, though estimates suggested a slightly falling effect possibly due to ageing. These results support increased PA levels as a possible non-pharmacological pathway towards reducing or preventing chronic pain.

[Blood flow restriction training as a treatment option for lateral elbow tendinopathy-a study presentation]

Blood flow restriction training, developed in 1966 in Japan, is a training modality that utilizes partial arterial and complete venous blood flow occlusion. Combined with low load resistance training, it aims to induce hypertrophy and strength gains. This makes it particularly suitable for people recovering from injury or surgery, for whom the use of high training loads is unfeasible. In this article, the mechanism behind blood flow restriction training and its applicability for the treatment of lateral elbow tendinopathy is explained. An ongoing prospective, randomized, controlled trial on the treatment of lateral elbow tendinopathy is presented.

Role of Immersive Virtual Reality in Motor Behaviour Decision-Making in Chronic Pain Patients

Primary chronic pain is a major contributor to disability worldwide, with an estimated prevalence of 20-33% of the world's population. The high socio-economic impact of musculoskeletal pain justifies seeking an appropriate therapeutic strategy. Immersive virtual reality (VR) has been proposed as a first-line intervention for chronic musculoskeletal pain. However, the growing literature has not been accompanied by substantial progress in understanding how VR exerts its impact on the pain experience and what neurophysiological mechanisms might be involved in the clinical effectiveness of virtual reality interventions in chronic pain patients. The aim of this review is: (i) to establish the state of the art on the effects of VR on patients with chronic pain; (ii) to identify neuroplastic changes associated with chronic pain that may be targeted by VR intervention; and (iii) to propose a hypothesis on how immersive virtual reality could modify motor behavioral decision-making through an interactive experience in patients with chronic pain.

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

Purpose

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

Methods

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

Results

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

Conclusion

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

The Effectiveness of Rehabilitation Interventions on Pain and Disability for Complex Regional Pain Syndrome: A Systematic Review and Meta-analysis

OBJECTIVES

To summarize and critically appraise the body of evidence on conservative management of complex regional pain syndrome (CRPS), we conducted a systematic review and meta-analysis of randomized controlled trials (RCTs).

METHODS

We conducted a literature search from inception to November 2021 in the following databases: Embase, Medline, CINAHL, Google Scholar, PEDRO, and Psychinfo. Two independent reviewers conducted risk of bias and quality assessment. Qualitative synthesis and meta-analysis were the methods for summarizing the findings of the RCTs. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach was used to rate the overall quality and certainty of the evidence on each treatment outcome.

RESULT

Through a database search, 751 records were found, and 33 RCTs were eligible for inclusion. Studies were published between 1995 and 2021. The overall risk of bias for 2 studies was low, 8 studies were unclear, and 23 studies were high.Low-quality evidence suggests that mirror therapy (as an addition to conventional stroke rehabilitation interventions) and graded motor imagery program (compared with routine rehabilitation interventions) may result in a large improvement in pain and disability up to 6-month follow-up in poststroke CRPS-1 patients. Low-quality evidence suggests that pain exposure therapy and aerobic exercises as an additive treatment to physical therapy interventions may result in a large improvement in pain up to a 6-month follow-up. The evidence is very uncertain about the effect of all other targeted interventions over conventional physical therapy or sham treatments on pain and disability.

DISCUSSION

There is an ongoing need for high-quality studies to inform conservative management choices in CRPS.

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 autonomic and nociceptive response to acute exercise is impaired in people with knee osteoarthritis

Objectives

An acute bout of exercise typically leads to short term exercise induced hypoalgesia (EIH), but this response is more variable in many chronic pain populations, including knee osteoarthritis (OA) and fibromyalgia (FM). There is evidence of autonomic nervous system (ANS) dysfunction in some chronic pain populations that may contribute to impaired EIH, but this has not been investigated in people with knee OA. The aim of this study was to assess the acute effects of isometric exercise on the nociceptive and autonomic nervous systems in people with knee OA and FM, compared to pain-free controls.

Methods

A cross-sectional study was undertaken with 14 people with knee OA, 13 people with FM, and 15 pain free controls. Across two experimental sessions, baseline recordings and the response of the nociceptive and autonomic nervous systems to a 5-min submaximal isometric contraction of the quadriceps muscle was assessed. The nociceptive system was assessed using pressure pain thresholds at the knee and forearm. The ANS was assessed using high frequency heart rate variability, cardiac pre-ejection period, and electrodermal activity. Outcome measures were obtained before and during (ANS) or immediately after (nociceptive) the acute bout of exercise.

Results

Submaximal isometric exercise led to EIH in the control group. EIH was absent in both chronic pain groups. Both chronic pain groups showed lower vagal activity at rest. Furthermore, people with knee OA demonstrated reduced vagal withdrawal in response to acute isometric exercise compared to controls. Sympathetic reactivity was similar across groups.

Discussion

The findings of reduced tonic vagal activity and reduced autonomic modulation in response to isometric exercise raise the potential of a blunted ability to adapt to acute exercise stress and modulate nociception in people with knee OA. The impairment of EIH in knee OA may, in part, be due to ANS dysfunction.

Effect and mechanisms of exercise for complex regional pain syndrome

Complex regional pain syndrome characterized by severe pain and dysfunction seriously affects patients' quality of life. Exercise therapy is gaining attention because it can effectively relieve pain and improve physical function. Based on the previous studies, this article summarized the effectiveness and underlying mechanisms of exercise interventions for complex regional pain syndrome, and described the gradual multistage exercise program. Exercises suitable for patients with complex regional pain syndrome mainly include graded motor imagery, mirror therapy, progressive stress loading training, and progressive aerobic training. In general, exercise training for patients with complex regional pain syndrome not only alleviates pain but also improves physical function and positive mental status. The underlying mechanisms of exercise interventions for complex regional pain syndrome include the remodeling of abnormal central and peripheral nervous system, the regulation of vasodilation and adrenaline levels, the release of endogenous opioids, and the increased anti-inflammatory cytokines. This article provided a clear explanation and summary of the research on exercise for complex regional pain syndrome. In the future, more high-quality studies with sufficient sample sizes may provide more exercise regimens and better evidence of efficacy.

Exercise-Induced Hypoalgesia Following Proprioceptive Neuromuscular Facilitation and Resistance Training Among Individuals With Shoulder Myofascial Pain: Randomized Controlled Trial

BACKGROUND

Various exercises can attenuate pain perception in healthy individuals and may interact with the descending pain modulation in the central nervous system. However, the analgesic effects of exercise in patients with myofascial pain can be disrupted by the pathological changes during chronic pain conditions. Thus, the exercises targeted on the facilitation of the sensory-motor interaction may have a positive impact on the restoration of the descending pain modulation and the analgesia effects.

OBJECTIVE

This paper estimates the effect of proprioceptive neuromuscular facilitation (PNF) and resistance training on exercise-induced hypoalgesia (EIH) and conditioned pain modulation (CPM) among patients with myofascial pain syndrome.

METHODS

A total of 76 female patients with myofascial pain syndrome (aged 18-30 years), with the pain in the upper trapezius and a visual analog scale score of greater than 30/100 mm, were enrolled in the study. Participants were randomly assigned into 3 intervention groups, including isometric (n=18, 24%), isotonic (n=19, 25%), and PNF (n=20, 26%) exercises, as well as 1 control group (n=19, 25%) with no intervention. Pressure pain threshold and the CPM responses at the myofascial trigger point, arm, and leg sites were assessed before and after the exercise session. The effective EIH response was reflected in the improvement of pressure pain thresholds.

RESULTS

There was an increase in pressure pain thresholds and CPM responses at trigger point (P<.001 and P<.001), arm (P<.001 and P<.001), and leg sites (P<.001 and P=.03) in participants who performed PNF and isotonic exercise, while the isometric exercise only increased pressure pain thresholds at leg sites (P=.03). Compared with the control group, both the isotonic (P=.02) and PNF (P<.001) groups showed greater EIH responses at the trigger points. In comparison to the control group, only the PNF exercise (P=.01) significantly improved pressure pain thresholds and CPM responses at arm and leg sites compared to the control group.

CONCLUSIONS

PNF, isotonic, and isometric exercises could lead to local and global EIH effects. The improvement in CPM response following PNF and isotonic exercises suggested that the EIH mechanisms of different resistance exercises may be attributed to the enhancement of the endogenous pain modulation via the motor-sensory interaction from the additional eccentric and dynamic muscle contraction.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCtr202111090819166165; https://tinyurl.com/2ab93p7n.

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.

The effect and mechanism of exercise for post-stroke pain

One of the common negative effects of a stroke that seriously lowers patients' quality of life is post-stroke pain (PSP). Thus, exercise in PSP management has become a hot research topic. The main advantages of exercise therapy are affordability and ease of acceptance by patients compared to other treatment methods. Therefore, this article reviews the effectiveness and possible mechanisms of exercise interventions for PSP. Exercise training for patients with PSP not only improves physical function but also effectively reduces pain intensity and attenuates the behavioral response to pain. In addition, exercise therapy can improve brain function and modulate levels of pro-inflammatory and neurotrophic factors to exert specific analgesic effects. Potential mechanisms for exercise intervention include modulation of synaptic plasticity in the anterior cingulate gyrus, modulation of endogenous opioids in vivo, reversal of brain-derived neurotrophic factor overexpression, inhibition of purinergic receptor (P2X4R, P2X7R) expression, and inhibition of microglia activation. However, current research on exercise for PSP remains limited, and the sustainable benefits of exercise interventions for PSP need to be further investigated.

Effects of a single exercise session on pain intensity in adults with chronic pain: a systematic review and meta-analysis

BACKGROUND

Chronic pain is prevalent amongst society, making it necessary to find strategies to manage chronic pain. Regular exercise is efficacious; however, pain is a barrier to initiating exercise. A single exercise session is also believed to acutely reduce pain, however, the evidence for this is less robust.

OBJECTIVES

This systematic review and meta-analysis aimed to identify the effect of a single exercise session on pain intensity in adults with chronic pain.

METHODS

We searched eight databases and trial registries to identify randomised controlled trials evaluating the effect of a single exercise session on pain intensity in adults with chronic pain compared to a non-exercise control. Literature screening, data extraction, risk of bias (Cochrane 2.0) and quality assessment (GRADE) were conducted independently and in duplicate. Random-effects meta-analyses were performed using the metafor package in R.

RESULTS

We included 17 trials (46 study arms with 664 adults [44% female]). There were no significant differences in pain intensity (mean difference on a 0-10 scale) immediately post-exercise -0.02 (95% CI = -0.06, 0.62; I² = 77.1%) or up to 45-min post-exercise -0.17 (95% CI = -0.49, 0.16; I² = 34.2%). All trials were at high risk of bias and the overall confidence in these findings was very low.

CONCLUSION

A single exercise session did not reduce pain intensity up to 1-h post-exercise. Notably, increases in pain were not observed either, suggesting that while pain can be a barrier to initiating exercise, clinicians can educate patients on the unlikelihood of exercise acutely increasing pain intensity.

Is low intensity exercise sufficient to induce exercise-induced pain threshold modulation in people with persistent pain?

OBJECTIVES

We investigated whether a 12-min walk test (12MWT) yielded exercise-induced pain threshold modulation (EIPM) within people with persistent pain and whether baseline self-report and pain sensitivity measures differed according to these responses.

DESIGN

Cross-sectional study.

METHODS

Two cohorts (tertiary/community) (n = 88) with persistent pain underwent pressure pain threshold (PPT) testing before and after a 12MWT to determine exercise-induced pain threshold modulation responses. Baseline self-report (pain severity, pain distribution, psychological distress, sleep) and baseline widespread pain sensitivity (WPS) (high/low) were recorded. Within and between-group differences were analysed using paired t-tests and repeated measure analyses of covariance. Individual EIPM responses were categorised as hyperalgesic, no change and hypoalgesic responses. Differences in baseline self-report and pain sensitivity measures between EIPM categories were investigated.

RESULTS

No significant within- or between-group differences in PPT following the 12MWT were detected (p > 0.05). Individual responses showed that up to 30% of the community and 44% of the tertiary cohort demonstrated >20% change in PPT (in either direction). Significant differences were shown in pain distribution (p = 0.002) and baseline WPS (p = 0.001) between people with hyperalgesic, no change, hypoalgesic responses. People with 4-5 pain regions were more likely hyperalgesic (χ2 = 9.0, p = 0.003); people with low baseline WPS were more likely to demonstrate no change (p = 0.002).

CONCLUSION

Low or self-selected intensity exercise was insufficient to induce exercise-induced pain modulation at group level. Individual responses were variable with pain distribution and baseline WPS differing between responses. Future research could evaluate responses and associated factors in larger samples with high baseline pain sensitivity specifically.