Absolute and Relative Reliability of Pressure Pain Threshold Assessments in the Shoulder Muscles of Participants With and Without Unilateral Subacromial Impingement Syndrome

Spatiotemporal characterization of an experimental model of muscle pain in humans based on short-wave diathermy

BACKGROUND

Commonly used models for eliciting muscle pain involve the injection of algesic substances or the induction of delayed onset muscle soreness. The former require invasive procedures, and the time frame for pain induction and subsidence in the latter can be inconvenient. This study presents a detailed spatiotemporal characterization of a new experimental model of muscle pain based on short-wave diathermy (SWD), developed to overcome the limitations of existing models.

METHODS

The shoulder was selected as target site and the effects of the model were tested in two sessions to assess its reliability. Pain intensity profiles were recorded during the application of SWD, and changes in pressure pain threshold (PPT) in the infraspinatus muscle, together with pain intensity, duration, and quality were assessed 30 min after induction.

RESULTS

SWD-induced pain intensity scores averaged 4 points on a visual analogue scale, whereas PPT showed a consistent decrease of about 25% relative to baseline values. Pain was localized in the shoulder area, and was described as continuous, dull, well-delimited, heavy, and bearable. Pain lasted for an average of 145 min without requiring reinduction and was reliably elicited in both experimental sessions.

CONCLUSION

SWD can be used to elicit experimental muscle pain in a non-invasive, long-lasting, and reliable way and allows for repeated within- and between-session testing in the shoulder.

SIGNIFICANCE STATEMENT

SWD produces deep heating in muscles by converting electromagnetic energy to thermal energy. It was previously shown that it can be used to elicit experimental pain in the forearm muscles, and the present study demonstrates that this can be reliably generalized to other body sites, such as the shoulder. Furthermore, SWD application is non-invasive and presents a convenient time frame for pain induction and subsidence, thus overcoming limitations associated with traditional muscle pain models.

Regional and widespread pain sensitivity decreases following stretching in both men and women - Indications of stretch-induced hypoalgesia

INTRODUCTION

This study aimed to investigate the effect of sex on regional and widespread pain sensitivity following acute bouts of stretching and to investigate the acute effect of stretching on regional and widespread pain sensitivity following stretching.

METHODS

73 healthy adults (36 females; mean age 25.6 ± 6.7 years) with an age range from 19 to 62 years were recruited for this experimental study. Regional and distant pain pressure pain thresholds, passive knee extension range of motion and passive resistive torque were measured before and 30 s after four bouts of 30-s static muscle stretching of the knee flexors with 20-s rest between bouts.

RESULTS

No significant sex differences were found for pressure pain thresholds (p > 0.132), range of motion (p = 0.446) or passive resistive torque (p = 0.559) between pre-stretch and post-stretch measures. There were significant increases in pressure pain thresholds (p = 0.010), range of motion (p = 0.001) and passive resistive torque (p = 0.007) between pre-stretch and post-stretch measures.

CONCLUSION

Muscle stretching significantly decreased regional and widespread pain sensitivity, indicating that central pain-modulating mechanisms are engaged during muscle stretching, resulting in stretch-induced hypoalgesia. Moreover, the results showed that the effect of stretching on regional and widespread pain sensitivity is not sex-specific.

Test-Retest Reliability of Pain Sensitivity Measures in Individuals with Shoulder Pain

Background

Central sensitization (CS) has been proposed as a possible contributor to persistent shoulder pain. Measures of sensitivity, such as quantitative sensory tests (QSTs) and sensitivity to movements evoked pain (SMEP), have been increasingly used to investigate CS in a wide range of painful conditions. However, there is a lack of data on whether QST and SMEP are reliable among individuals with shoulder pain. Therefore, the present study aimed to investigate the intra-rater test-retest reliability of QST and SMEP in individuals with chronic shoulder pain.

Materials and Methods

Forty-seven individuals with chronic shoulder pain were enrolled in the study. The QST measures, including pressure pain threshold (PPT) and mechanical temporal summation (MTS), were tested, and SMEP was measured with a lifting task. Relative and absolute reliability were analyzed using intraclass correlation coefficients (ICC 3,1) and standard error of the measurement (SEM), respectively.

Results

The results showed that the ICC coefficients for all sensitivity measures were moderate to good, ranging from 0.63 to 0.86. The SEM% for the QST measures at all sites ranged from 21.4% to 36%, with TS at the forearm demonstrating a high SEM% (greater than 30%). The SMEP measure also showed a high SEM% (46%).

Conclusion

The results showed that the sensitivity measures had moderate to good reliability among individuals with shoulder pain. Acceptable limits of accuracy of measurements were demonstrated for TS and PPT measures, while SMEP demonstrated high error, highlighting the need for further refinement of this measure among these populations.

Blood Flow Restriction Training in Nonspecific Shoulder Pain: Study Protocol of a Crossover Randomised Controlled Trial

"Nonspecific shoulder pain" encompasses various non-traumatic musculoskeletal shoulder disorders, diverging from diagnostic terminologies that refer to precise tissue-oriented clinical diagnosis. Blood flow restriction (BFR) training, involving partial arterial inflow and complete venous outflow restriction, has exhibited acute hypoalgesic effects primarily in healthy populations by increasing their pain thresholds. This study aims to examine whether a single BFR session with low-load exercises can alleviate pain perception among nonspecific shoulder pain patients. Conducted as a single-blind crossover randomised clinical trial, 48 adults (age range: 18 to 40) presenting with nonspecific shoulder pain will partake in two trial sessions. Random assignment will place participants into BFR or sham BFR groups and ask them to perform one exercise with BFR. Subsequently, participants will complete a shoulder girdle loading regimen comprising six exercises. The second session will involve participants switching treatment groups. Pain pressure thresholds (PPTs), shoulder pain and disability via the shoulder pain and disability index (SPADI), maximal voluntary isometric contraction (MVIC) of shoulder external rotators, pain during active abduction, and peak pain during shoulder external rotation will be evaluated using the numeric pain rating scale (NPRS). Immediate post-exercise assessments will include patient-perceived pain changes using the global rating of change scale (GROC) and participant-rated perceived exertion (RPE), employing a modified Borg's scale (Borg CR10) post-BFR or sham BFR exercise session. Each session will encompass three assessment periods, and a combination of mixed-effect models and descriptive statistics will underpin the analysis. This protocol was approved by Cyprus National Bioethics Committee (ΕΕΒΚ/2023/48), and was registered in ClinicalTrials.gov (Registration number: NCT05956288). Conclusion: The anticipated outcomes of this study illuminated the acute effects of BFR training on pain perception within the context of nonspecific shoulder pain, potentially advancing strategies for managing pain intensity using BFR techniques.

Are clinical outcomes associated with baseline sensory profiles in people with musculoskeletal shoulder pain? Protocol for a prospective longitudinal observational study

BACKGROUND

Musculoskeletal shoulder pain is a common problem and its symptoms often become persistent. The experience of pain is multidimensional, and therefore, a range of patient characteristics may influence treatment response. An altered sensory processing has been associated with persistent musculoskeletal pain states and may contribute to outcomes in patients with musculoskeletal shoulder pain. The presence and potential impact of altered sensory processing in this patient cohort is not currently known. The aim of this prospective longitudinal cohort study is to investigate if baseline sensory characteristics are associated with clinical outcomes in patients presenting to a tertiary hospital with persistent musculoskeletal shoulder pain. If found, a relationship between sensory characteristics and outcome may lead to the creation of more effective treatment strategies and improvements in risk adjustment and prognosis.

METHODS

This is a single-centre prospective cohort study with 6-, 12- and 24-month follow-up. A total of 120 participants aged ≥18 years with persistent musculoskeletal shoulder pain (≥3 months) will be recruited from an Australian public tertiary hospital orthopaedic department. Baseline assessments, including quantitative sensory tests and a standardised physical examination, will be performed. In addition, information will be obtained from patient interviews, self-report questionnaires and medical records. Follow-up outcome measures will comprise information from the Shoulder Pain and Disability Index and a six-point Global Rating of Change scale.

ANALYSIS

Descriptive statistics will be used to report baseline characteristics and outcome measures over time. Change in outcome measures at the primary endpoint of six months from baseline will be calculated using paired t-tests. Associations between baseline characteristics and outcomes at a 6-month follow-up will be reported using multivariable linear and logistic regression models.

DISCUSSION

Understanding the relationship between sensory profile and the variable response to treatment in people with persistent musculoskeletal shoulder pain may enhance our understanding of the mechanisms contributing to the presentation. In addition, through better understanding of the contributing factors, the results of this study may contribute to the development of an individualised, patient-centred approach to treatment for people with this highly prevalent and debilitating condition.

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.

Intra-rater and inter-rater reliability of pressure pain threshold assessment in stroke patients

BACKGROUND

As pain is a common symptom following a stroke, pressure pain threshold (PPT) assessment can be used to evaluate pain status or pain sensitivity of patients. However, the reliability of PPT test in stroke patients is still unknown.

AIM

To examine the intra- and inter-rater reliability of PPT measurements in poststroke survivors and explore their factors.

DESIGN

An observational study.

SETTING

The setting of the study is a rehabilitation hospital.

POPULATION

The population of the study was represented by a total of 54 patients after stroke.

METHODS

The study included 16 measured points on the affected and unaffected sides. PPT was assessed by two raters in turn. Intra- and inter-rater reliability was evaluated by intraclass correlation coefficients (ICC).

RESULTS

All intra-rater (ICC=0.84-0.97) and inter-rater (ICC=0.83-0.95) reliability for PPT assessment were good or excellent in stroke patients. Of the 16 points, 12 showed higher intra-rater ICC values than inter-rater, whereas no evident difference was observed between the affected and unaffected sides. Furthermore, patients who were male, ischemic, or with higher motor function generally performed higher ICC values than those who were female (24 out of 32 results), hemorrhagic (28 out of 32 results), or mobility dysfunction (26 out of 32 results), respectively.

CONCLUSIONS

PPT assessment with good or excellent reliability can be used in stroke patients. Neither of the two sides (affected or unaffected) affects PPT reliability, and intra-rater reliability is better than inter-rater reliability. In addition, gender, stroke type, and motor function can affect the reliability of measuring mechanical pain threshold in poststroke survivors.

CLINICAL REHABILITATION IMPACT

The pressure algometer can be used as a reliable and portable tool to assess the mechanical pain tolerance and sensory function in stroke patients in clinics.

Evidence of Bilateral Localized, but Not Widespread, Pressure Pain Hypersensitivity in Patients With Upper Extremity Tendinopathy/Overuse Injury: A Systematic Review and Meta-Analysis

OBJECTIVE

The presence of altered nociceptive pain processing in patients with upper extremity tendinopathy/overuse injury is conflicting. Our aim was to compare pressure pain thresholds (PPTs) in symptomatic and distant pain-free areas between patients with upper extremity tendinopathy/overuse injury and controls.

METHODS

Five databases were searched from inception to October 15, 2020. The authors selected case-control studies comparing PPTs between individuals with upper extremity tendinopathy/overuse injury and pain-free controls. Data were extracted for population, diagnosis, sample size, outcome, and type of algometer. Results were extracted by 3 reviewers. The methodological quality/risk of bias (Newcastle-Ottawa Quality Assessment Scale) and evidence level (Grading of Recommendations Assessment, Development and Evaluation approach) were assessed. Meta-analyses of symptomatic, segment-related, and distant pain-free areas were compared.

RESULTS

The search identified 807 publications with 19 studies (6 shoulder, 13 elbow) eligible for inclusion. The methodological quality ranged from fair (48%) to good (37%). Patients exhibited lower bilateral PPTs than controls at the symptomatic area (affected side: MD = -175.89 kPa [95% CI = -220.30 to -131.48 kPa]; nonaffected side: MD = -104.50 kPa [95% CI = -142.72 to -66.28 kPa]) and the segment-related area (affected side: MD = -150.63 kPa [95% CI = -212.05 to -89.21 kPa]; nonaffected side: MD = -170.34 kPa [95% CI = - 248.43 to -92.25]) than controls. No significant differences in PPTs over distant pain-free areas were observed.

CONCLUSION

Low to moderate quality evidence suggests bilateral hypersensitivity to pressure pain at the symptomatic and contralateral/mirror areas in patients with upper extremity tendinopathies/overuse injury. Moderate quality of evidence supports bilateral pressure pain sensitivity in the segment-related area (neck) in lateral epicondylalgia, but not in subacromial impingement syndrome. No evidence of widespread pressure pain hyperalgesia was reported.

IMPACT

Early identification of people with altered pain modulation could guide clinicians in treatment strategies. This review shows that there is a complex interplay between peripheral and central pain mechanisms in upper extremity tendinopathies/overuse injuries and that there likely are different subgroups of patients with upper extremity conditions.

Hand-held dynamometer to measure pressure pain thresholds: A double-blinded reliability and validity study

BACKGROUND

Pain is the most common complaint reported in the musculoskeletal setting. Quantitative sensory testing (QST) assists with pain mechanism identification, although QST is typically performed in research settings. It is possible that clinical utilization of QST may improve if clinically accessible tools can be reliably and validly used.

OBJECTIVE

To determine if a hand-held dynamometer (HHD) can be a valid and reliable assessment of pressure pain threshold (PPT).

DESIGN

Double-blinded validation study.

METHODS

Eighteen healthy subjects (25.6 ± 3.4 years old) participated in this study. Two testers independently assessed PPT using a HHD and a digital algometer. Assessments followed previously described pressure algometry protocols. Testers and subjects were each blinded to data during assessments.

RESULTS

Intra- and inter-rater reliability were excellent for the foot and face for both devices (ICC's > 0.9). Bland-Altman plots and intraclass correlation coefficients revealed good-excellent agreement with minimal proportional bias when normalizing device force at pain threshold to the circumference of the device applicator (ICC 95%CI: 0.56-0.95). Only poor-good agreement (ICC 95% CI: 0.30-0.76) and significant proportional bias was observed when normalizing to area (pressure).

CONCLUSIONS

Based on the results of this study, when force is normalized by circumference of the applicator, a HHD was found to be a valid and reliable tool for measuring PPT. Clinicians may use HHD to detect relevant pain mechanisms at fault in their evaluation and treatment of pain. Additional research in various pathologic populations is warranted.