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.

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

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

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Pathology of knee osteoarthritis pain: contribution of joint structural changes and pain sensitization to movement-evoked pain in knee osteoarthritis

Introduction

Movement-evoked pain (MEP) is the primary symptom in patients with knee osteoarthritis (KOA).

Objectives

This study aimed to investigate the contribution of joint structural changes and pain sensitization to the mechanisms of MEP in patients with KOA.

Methods

A total of 86 patients were assessed for demographic characteristics, osteoarthritis severity, Whole-Organ Magnetic Resonance Imaging Score-Hoffa synovitis and bone marrow lesions, pressure pain threshold and temporal summation of pain at the knee and forearm, Central Sensitization Inventory-9, and MEP. In measure of MEP, knee pain was scored using a numerical rating scale (NRS, 0-10) before and every minute during a 6-minute walking test (6MWT), and the MEP index was defined as the change in NRS pain score from baseline to the sixth minute of walking.

Result

On average, pain during 6MWT increased by 1.4 ± 1.5 points on the NRS relative to baseline, with 30.2% of patients showing an increase of 2 points or more. The hierarchical linear regression analysis revealed that Hoffa synovitis, pressure pain threshold at the forearm, and temporal summation of pain at the knee were associated with the MEP index.

Conclusion

The findings of this study suggest that both synovitis and neural mechanisms, such as pain sensitization, play a role in the development of MEP in KOA.

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

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

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

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

Does Exercise-Induced Hypoalgesia Depend on Exercise Duration?

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

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.

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Are endogenous opioid mechanisms involved in the effects of aerobic exercise training on chronic low back pain? A randomized controlled trial

Aerobic exercise is believed to be an effective chronic low back pain (CLBP) intervention, although its mechanisms remain largely untested. This study evaluated whether endogenous opioid (EO) mechanisms contributed to the analgesic effects of an aerobic exercise intervention for CLBP. Individuals with CLBP were randomized to a 6-week, 18-session aerobic exercise intervention (n = 38) or usual activity control (n = 44). Before and after the intervention, participants underwent separate laboratory sessions to assess responses to evoked heat pain after receiving saline placebo or intravenous naloxone (opioid antagonist) in a double-blinded, crossover fashion. Chronic pain intensity and interference were assessed before and after the intervention. Endogenous opioid analgesia was indexed by naloxone-placebo condition differences in evoked pain responses (blockade effects). Relative to controls, exercise participants reported significantly greater pre-post intervention decreases in chronic pain intensity and interference (Ps < 0.04) and larger reductions in placebo condition evoked pain responsiveness (McGill Pain Questionnaire-Short Form [MPQ]-Total). At the group level, EO analgesia (MPQ-Total blockade effects) increased significantly pre-post intervention only among female exercisers (P = 0.03). Dose-response effects were suggested by a significant positive association in the exercise group between exercise intensity (based on meeting heart rate targets) and EO increases (MPQ-Present Pain Intensity; P = 0.04). Enhanced EO analgesia (MPQ-Total) was associated with a significantly greater improvement in average chronic pain intensity (P = 0.009). Aerobic exercise training in the absence of other interventions appears effective for CLBP management. Aerobic exercise-related enhancements in endogenous pain inhibition, in part EO-related, likely contribute to these benefits.

New Factor Structure of the Tampa Scale for Kinesiophobia in Older Japanese Adults After Lumbar Surgery

Purpose

The Tampa Scale for Kinesiophobia (TSK) has been used worldwide as a measure of kinesiophobia, but its factor structure in older Japanese adults after lumbar surgery is unknown. The purpose of this study was to fill this research gap by identifying the factors that comprise TSK in older Japanese adults after lumbar surgery.

Patients and Methods

Participants were older Japanese adults who had undergone surgery for lumbar spinal stenosis. Clinicodemographic data, TSK, intensity of low back pain and leg pain, dysesthesia (using an 11-point numerical rating scale), and HRQOL (using the EQ-5D-5L) were collected. After supplementing the missing values by the multiple assignment method, the hypothetical model of TSK was developed by categorical exploratory factor analysis (weighted least squares method, promax rotation). Confirmatory factor analysis (WLSMV method, promax rotation) was used to compare the hypothetical model and the traditional one-factor and two-factor models. Furthermore, we confirmed the relationship between factors extracted from the hypothetical model and HRQOL, pain, and dysesthesia.

Results

Questionnaires were mailed to 302 individuals, and responses were obtained from 211 (72.4±4.2 years [range: 65–88]; 115 men and 96 women; 804±343.1 [380–1531] days after surgery; 137 who had undergone decompression and fixation surgery, 74 who had undergone decompression surgery) (response rate: 69.9%). The hypothesized model consisted of “somatic focus,” “activity avoidance,” and “efficacy of physical activities,” all of which were highly consistent. The fit of the hypothetical model was slightly inferior to that of the traditional two-factor model, but the hypothetical model met the criteria for fit. Somatic focus in the hypothetical model was significantly associated with HRQOL, pain, and dysesthesia.

Conclusion

In older Japanese adults after lumbar surgery, the goodness of fit of the TSK model was maintained by adding efficacy of physical activities as a third factor to the traditional two factors.

Impaired exercise-induced hypoalgesia in individuals reporting an increase in low back pain during acute exercise

OBJECTIVES

Exercise therapy is recommended for low back pain (LBP) although the immediate effects on pain are highly variable. In 96 individuals with LBP this cross-sectional study explored (a) the magnitude of exercise-induced hypoalgesia (EIH) and (b) measures of pain sensitivity and clinical pain manifestations in individuals reporting a clinical relevant increase in back pain during physical activity compared with individuals reporting low or no increase in back pain during physical activity.

METHODS

Cuff algometry was performed at baseline on the leg to assess pressure pain threshold (cPPT), tolerance (cPTT) and temporal summation of pain (cTSP). Manual PPTs were assessed on the back and leg before and after a 6-min walk test (6MWT). Back pain was scored on a numerical rating scale (NRS) after each minute of walking. The EIH-effect was estimated as the increase in PPTs after the walk exercise.

RESULTS

Twenty-seven individuals reported an increase of ≥2/10 in pain NRS scores during walking and compared with the individuals with <2/10 NRS scores: cPPT and EIH-effects were lower whereas cTSP, pain intensity and disability were increased (p < 0.03). Baseline NRS scores, EIH and pain thresholds were associated with the likelihood of an increase of ≥2/10 in back pain intensity during walking (p < 0.05).

CONCLUSIONS

Pain flares in response to physical activity in individuals with LBP seem to be linked with baseline pain sensitivity and pain intensity, and impair the beneficial EIH. Such information may better inform when individuals with LBP will have a beneficial effect of physical activity.

SIGNIFICANCE

Pain flares in response to physical activity in individuals with LBP seem to be linked with baseline pain sensitivity and pain intensity, and impair the beneficial exercise-induced hypoalgesia. Such information may better inform when individuals with LBP will have a beneficial effect of physical activity.

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

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

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