Men Report Greater Pain Relief Following Sustained Static Contractions Than Women When Matched for Baseline Pain

Similar effects of fatigue induced by a repetitive pointing task on local and remote light touch and pain perception in men and women

Background

Women involved in repetitive, fatiguing, jobs develop more neck and/or shoulder musculoskeletal disorders than men. Sex differences in the pain response to exercise could contribute to the higher prevalence of neck/shoulder musculoskeletal disorders in women. The objective of this study was to assess sex differences in pain sensitivity following a fatiguing upper limb task. Relationships between measures of fatigue and of the sensitivity to nociceptive and to non-nociceptive stimulations were also explored.

Methods

Thirty healthy adults (15 women) performed a fatiguing repetitive pointing task with their dominant arm. Upper limb electromyography was recorded from the dominant upper trapezius, anterior deltoid and bicep brachii and from the contralateral tibialis anterior. Before and immediately after the repetitive pointing task, pressure pain and light touch sensitivity thresholds were measured over the same muscles.

Results

Electromyographic signs of fatigue were observed only in the anterior deltoid and biceps brachii muscles. Pressure pain thresholds over both muscles increased slightly (effect size ≤ 0.34), but no changes occurred over the upper trapezius and the tibialis anterior. Light touch thresholds increased moderately to importantly after the repetitive pointing task over all four muscles (effect sizes = 0.58 to 0.87). No sex differences were observed in any sensory variable. Moreover, no or weak correlations (r = -0.27 to 0.39) were observed between electromyographical signs of fatigue, light touch threshold and pressure pain threshold variables.

Conclusions

We observed sex-independent effects of a repetitive upper limb task on the sensitivity to painful and to nonpainful stimuli. Moreover, the hypoalgesia induced by the repetitive pointing task was weak and localized, and did not directly correlate with the induced muscle fatigue. Results suggest that fatigue-related changes in the sensitivity to noxious and innocuous stimuli could not explain women’s greater prevalence of neck/shoulder musculoskeletal disorders.

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.

Sex differences in perceptual responses to experimental pain before and after an experimental fatiguing arm task

BACKGROUND

The incidence and prevalence of musculoskeletal disorders (MSDs) is about twice as high in women compared to men, and those of the neck/shoulder region are particularly high among women. Fatigue and responses towards pain are known risk factor for MSDs. However, women have been shown to be less fatigable than men, but more sensitive to experimental pain. From a general standpoint, sex differences in the relationships between the fatigue and pain pathways are poorly understood. This may be due to differences in how men and women conceptually define the sensations of fatigue and pain. The objective of this study was to compare physical and verbal descriptors of fatigue and pain between men and women undergoing an experimental protocol where fatigue and pain were manipulated.

METHODS

Healthy adult volunteers (14 men and 14 women) underwent experimental pain tests to identify pressure pain threshold (PPT) at biceps brachii (BIC), anterior deltoid (AD), and upper trapezius (UT) followed by the Short-form McGill Pain Questionnaire (SF-MPQ) and Pain Catastrophizing Scale (PCS) before and after a repetitive arm task performed at shoulder height until reaching a rating of neck/shoulder perceived exertion, using the Borg Category Ratio 10 (CR10), greater than 8/10. PPT and MPQ data were analyzed using repeated measures analyses of variance (ANOVA) (time × sex). Correlational analyses were used to investigate relationships between pain measures with time and fatigue.

RESULTS

UT PPT was reduced following the fatiguing task (p ≤ 0.01). Men overall reported higher AD PPT levels compared to women (p ≤ 0.05). MPQ and PCS magnification scores were significantly higher after the fatiguing task (p ≤ 0.05), with no sex differences. Time to fatigue correlated with changes in AD PPT in men and with PCS scores in women.

CONCLUSIONS

Findings suggest that mechanisms underlying the sensation of acute pain following a repetitive shoulder height task are closely linked with PPT changes in shoulder stabilizers (UT) irrespective of sex, and more so with physical pain responses in men and in attitudes towards pain in women. Sex differences in pain perception may contribute to a better understanding of sex-specific mechanisms underlying neck/shoulder MSDs.

Frequency of Shoulder Corticosteroid Injections for Pain and Stiffness After Shoulder Surgery and Their Potential to Enhance Outcomes with Physiotherapy: A Retrospective Study

Introduction

What is the rate of injecting patients with shoulder corticosteroid injections to alleviate excessive stiffness and pain within 6 months after shoulder surgery?

Methods

Retrospective 10-year review of a shoulder surgeon’s practice. Participants included 754 patients who had 945 non-arthroplasty shoulder surgeries. Outcome measures included the rate of injections, diagnoses, patient characteristics, and efficacy via questionnaire.

Results

Approximately one in five patients received a subacromial and/or glenohumeral corticosteroid injection. Over 95% of patients stated that the injections helped reduce shoulder pain and increased function 6 weeks post-injection. Twenty-two percent of cases (208/945) received glenohumeral and/or subacromial injections. The 208 injected cases had these diagnoses: rotator cuff tear (28% of injected patients), subacromial impingement (20%), glenohumeral instability (16%), subacromial impingement with acromioclavicular osteoarthritis (10%), adhesive capsulitis (7%), SLAP lesion (5%), biceps tendinopathy (3%), glenohumeral instability with subacromial impingement (3%), proximal humerus fracture (2%), calcific tendinitis (2%), and less common conditions (4%). Diagnoses among those with the highest rates of injected patients per diagnosis included: SLAP lesions (40%), calcific tendinitis (40%), adhesive capsulitis (29%), subacromial impingement (28%), proximal humerus fracture (24%), rotator cuff tear (19%), and glenohumeral instability (16%). Significant differences (p < 0.03) were found between patients who did and did not receive injections with respect to age (more likely younger patients with cuff tear) and sex (more likely female with subacromial impingement and instability) but not for diabetes or arthroscopic vs. open procedures.

Conclusion

This is the first study to establish the rates of postoperative shoulder corticosteroid injections within the first 6 months after various non-arthroplasty shoulder surgeries for patients with high pain/stiffness. These data will be useful for establishing guidelines for using corticosteroid injections along with physiotherapy.