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

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

Cognitive Inhibition Correlates with Exercise-Induced Hypoalgesia After Aerobic Bicycling in Pain-Free Participants.

PURPOSE: Exercise-induced hypoalgesia (EIH) is the short-term reduction of pain sensitivity after a single bout of exercise. Descending pain inhibition has been proposed to at least partly underlie EIH. Cognitive inhibition is the ability to inhibit a pre-potent response and has in turn been associated with descending pain inhibition, as indexed by conditioned pain modulation. Therefore, we hypothesized that cognitive inhibition is associated with higher EIH. METHODS: In this cross-sectional study, 37 pain-free participants (16 male, age 27.75 ± 9.91) completed a stop-signal task assessing cognitive inhibition ability and a control condition in the first session. In the second session, pre-post-test design EIH was assessed by means of aerobic bicycling (15 min., 75% VO2max) and isometric knee extension (90 sec, 30% MVC). EIH was assessed with pressure pain thresholds (PPT) and temporal summation of pain (TSP), each at the hand and at the leg. Correlational analyses quantified the associations between cognitive inhibition and EIH change scores. RESULTS: Better cognitive inhibition correlated with EIH change scores in PPTs after aerobic bicycling at the hand (r = -0.35, 95% CI: -0.57; -0.08, p =0.021), but not at the leg (rho = -0.10, 95% CI: -0.36; 0.18, p = 0.277). No correlations between cognitive inhibition and change in PPTs after isometric knee extension at the hand (rho = -0.03, 95% CI: -0.30; 0.25, p = 0.857) nor at the leg (rho = -0.03, 95% CI: -0.25; 0.30, p = 0.857) were observed. There were no EIH effects after isometric exercise and, generally, no effects of exercise on TSP. CONCLUSION: This study provides preliminary evidence for the notion that cognitive inhibition might play a supportive role in EIH. Although these results are clearly in need of replication, they accord well with previously reported associations between cognitive inhibition, experimental pain and descending pain inhibition.

Kinesiophobia is associated with pain intensity but not pain sensitivity before and after exercise: an explorative analysis.

OBJECTIVE: To compare clinical pain intensity, exercise performance, pain sensitivity and the effect of aerobic and isometric exercise on local and remote pressure pain thresholds (PPTs) in patients with chronic musculoskeletal pain with high and low levels of kinesiophobia. DESIGN: An experimental pre-post within-subject study. SETTING: An exercise laboratory in a multidisciplinary pain clinic. PARTICIPANTS: Fifty-four patients with chronic musculoskeletal pain. INTERVENTIONS: Acute aerobic and isometric leg exercises. MAIN OUTCOME MEASURES: Clinical pain intensity (numerical rating scale, range 0 to 10), Tampa Scale of Kinesiophobia, aerobic and isometric exercise performances (intensity and maximal voluntary contraction), and PPTs at local and remote body areas before and after exercise conditions. RESULTS: Patients with a high degree of kinesiophobia demonstrated increased pain intensity compared with patients with a low degree of kinesiophobia [high degree of kinesiophobia: 7.3 (1.6) on NRS; low degree of kinesiophobia: 6.3 (1.6) on NRS; mean difference 1.0 (95% confidence interval 0.08 to 1.9) on NRS]. Aerobic and isometric exercises increased PPTs, but no significant group differences were found in PPTs before and after exercise. CONCLUSIONS: Clinical pain intensity was significantly higher in patients with a high degree of kinesiophobia compared with patients with a low degree of kinesiophobia. Despite a difference in isometric exercise performance, the hypoalgesic responses after cycling and isometric knee exercise were comparable between patients with high and low degrees of kinesiophobia. If replicated in larger studies, these findings indicate that although kinesiophobic beliefs influence pain intensity, they do not significantly influence PPTs and exercise-induced hypoalgesia in patients with chronic musculoskeletal pain.

Ten-year prevalence of mental disorders in patients presenting with chronic pain in secondary care: A register linkage cohort study.

BACKGROUND: Prevalence rates of mental disorders in patients with chronic pain vary and may be overestimated when assessed by screening instruments only. Objectives were to estimate the 10-year prevalence of different mental disorders diagnosed by psychiatrists in patients with chronic pain compared with the Danish general population. METHODS: Patients (n = 7197) consulted in the interdisciplinary Pain Clinic South at Odense University Hospital, Denmark, from 2005 to 2015 were included. Data from the Pain Clinic were linked to the Danish National Patient Register-Psychiatry and the Danish Civil Registration System. Age and gender standardized prevalence ratios (SPR) were calculated. RESULTS: In all, 17.8% of patients with chronic pain had been diagnosed with a mental disorder. The most frequent diagnoses were adjustment disorders (subcategory of anxiety disorders) (8.9%), depression (6.1%), personality disorders (3.8%), and substance abuse disorders (3.5%). Women and men with chronic pain had higher rates of anxiety disorders (SPR 3.1; 95% CI 2.9-3.4) and depression (SPR 2.5; 95% CI 2.3-2.8), whereas men had higher rates of substance abuse disorders (SPR 1.6; 95% CI 1.3-1.9) than found for the general population. CONCLUSIONS: Although depression and anxiety were noted more frequently among patients with chronic pain than the general population, prevalence rates were lower than previously reported. The most frequent diagnoses were adjustment disorders. SIGNIFICANCE: Prevalence rates of anxiety and depression diagnosed by psychiatrists in patients with chronic pain were found to be lower than previous findings using screening instruments. Adjustment disorders were the most frequent disorders diagnosed, as this study is the first to investigate.

Exercise increases pressure pain tolerance but not pressure and heat pain thresholds in healthy young men.

BACKGROUND: Exercise causes an acute decrease in the pain sensitivity known as exercise-induced hypoalgesia (EIH), but the specificity to certain pain modalities remains unknown. This study aimed to compare the effect of isometric exercise on the heat and pressure pain sensitivity. METHODS: On three different days, 20 healthy young men performed two submaximal isometric knee extensions (30% maximal voluntary contraction in 3 min) and a control condition (quiet rest). Before and immediately after exercise and rest, the sensitivity to heat pain and pressure pain was assessed in randomized and counterbalanced order. Cuff pressure pain threshold (cPPT) and pain tolerance (cPTT) were assessed on the ipsilateral lower leg by computer-controlled cuff algometry. Heat pain threshold (HPT) was recorded on the ipsilateral foot by a computer-controlled thermal stimulator. RESULTS: Cuff pressure pain tolerance was significantly increased after exercise compared with baseline and rest (p < 0.05). Compared with rest, cPPT and HPT were not significantly increased by exercise. No significant correlation between exercise-induced changes in HPT and cPPT was found. Test-retest reliability before and after the rest condition was better for cPPT and CPTT (intraclass correlation > 0.77) compared with HPT (intraclass correlation = 0.54). CONCLUSIONS: The results indicate that hypoalgesia after submaximal isometric exercise is primarily affecting tolerance of pressure pain compared with the pain threshold. These data contribute to the understanding of how isometric exercise influences pain perception, which is necessary to optimize the clinical utility of exercise in management of chronic pain. SIGNIFICANCE: The effect of isometric exercise on pain tolerance may be relevant for patients in chronic musculoskeletal pain as a pain-coping strategy. WHAT DOES THIS STUDY ADD?: The results indicate that hypoalgesia after submaximal isometric exercise is primarily affecting tolerance of pressure pain compared with the heat and pressure pain threshold. These data contribute to the understanding of how isometric exercise influences pain perception, which is necessary to optimize the clinical utility of exercise in management of chronic pain.

Isometric exercises reduce temporal summation of pressure pain in humans.

BACKGROUND: Aerobic and isometric exercises are known to decrease pain sensitivity. The effect of different types of exercise on central mechanisms such as temporal summation of pain (TSP) is less clear. This study hypothesized that both aerobic and isometric exercises would increase pressure pain tolerance (PTT) and reduce TSP with greater effects after higher-intensity exercises. METHODS: One hundred thirty-six healthy subjects (18-65 years; 68 women) participated in two randomized crossover experiments with trials on two different days. PTT and TSP were assessed before and after bicycling and a non-exercise condition (experiment 1), and after low- and high-intensity bicycling and low- and high-intensity isometric arm and leg exercises with the dominant arm/leg (experiment 2). PTT and TSP were assessed before and after each exercise condition on the non-dominant arm and leg by computer-controlled cuff algometry. TSP was assessed by visual analogue scale (VAS) scores of the pain intensity during sequential cuff-pressure stimulation at the pain tolerance intensity related to that specific time point. RESULTS: In experiment 1, bicycling, but not the non-exercise condition, slightly increased PTT when assessed at the leg (p < 0.05). In experiment 2, isometric arm and leg exercises increased PTT and reduced VAS scores to sequential stimulation at the arm and leg (p < 0.05). No systematic difference was found between low- and high-intensity exercises. CONCLUSIONS: Different manifestations of hypoalgesia between aerobic and isometric exercises were found. Isometric exercises reduced temporal summation illustrating the potential for exercise as a rehabilitation procedure also targeting the central mechanisms.