Marie K. Hoeger Bement

Dose response of isometric contractions on pain perception in healthy adults.

INTRODUCTION The purpose of the study was to compare pain ratings and thresholds in men and women before and after isometric contractions of varying intensity and duration performed with the elbow flexor muscles. METHODS Pain perception was assessed, using a pressure device applied to the contralateral finger, before and after the following isometric contractions: 1) three brief maximal voluntary contractions (MVC), 2) 25% MVC sustained until task failure, 3) 25% MVC sustained for 2 min, and 4) 80% MVC sustained until task failure. RESULTS High-intensity and long-duration, low-intensity isometric contractions produced an analgesic response. The greatest change in pain threshold and pain ratings, when pressure was applied to the contralateral finger, was after the long-duration, low-intensity contraction sustained until failure. Sex differences were present with women reporting 1) lower pain thresholds and higher pain ratings during quiet rest and 2) higher pain ratings before and after isometric contractions. CONCLUSION These results suggest that activation of high-threshold motor units is involved in exercise-induced analgesia.

Pain Perception after Isometric Exercise in Women with Fibromyalgia

OBJECTIVE The purpose of this study was to identify exercise protocols incorporating isometric contractions that provide pain relief in women with fibromyalgia. DESIGN A before-after trial. SETTING A physical therapy department in an academic setting. PARTICIPANTS Fifteen women (mean ± SD, 52±11y) with fibromyalgia. INTERVENTIONS Subjects completed 4 sessions: 1 familiarization and 3 experimental. The following randomized experimental sessions involved the performance of isometric contractions with the elbow flexor muscles that varied in intensity and duration: (1) 3 maximal voluntary contractions (MVCs), (2) 25% MVC held to task failure, and (3) 25% MVC held for 2 minutes. MAIN OUTCOME MEASURES Experimental pain (pain threshold and pain rating), Fibromyalgia Impact Questionnaire, and fibromyalgia pain intensity (visual analog scale). RESULTS After all 3 isometric contractions, there was considerable variability between subjects in the pain response. Based on the changes in experimental pain, subjects were divided into 3 groups (increase, decrease, no change in pain). Multiple regression analysis revealed that age, baseline experimental pain, and change in fibromyalgia pain intensity were significant predictors of the experimental pain response after the isometric contractions. CONCLUSIONS We identified subgroups of women with fibromyalgia based on how they perceived pain after isometric contractions. The greatest pain relief for women with fibromyalgia occurred at a younger age and in women with the greatest experimental pain before exercise. Additionally, we established a link between experimental and clinical pain relief after the performance of isometric contractions.

Conditioned pain modulation predicts exercise-induced hypoalgesia in healthy adults.

INTRODUCTION Conditioned pain modulation (CPM) is the concept that pain inhibits pain and has potential rehabilitation implications for exercise prescription. The purpose of this study was to determine whether changes in pressure pain perception after a thermal conditioning stimulus (i.e., CPM) was attenuated with aging and whether CPM predicted pain relief after exercise (exercise-induced hypoalgesia (EIH)) in healthy young and older adults. METHODS Twenty young (21.9 ± 3.3 yr, 10 men) and 19 older (72.0 ± 4.5 yr, 10 men) adults participated in three sessions: one familiarization and two experimental (EIH and CPM) sessions. Pressure pain perception was assessed using a weighted Lucite edge placed on the right index finger for 1 min. EIH was determined by measuring pressure pain perception before and after prolonged submaximal isometric contraction of the elbow flexors. CPM was assessed by measuring pressure pain perception at the finger while the foot was immersed in neutral water versus painful ice water. RESULTS Young, but not older, adults reported a decrease in pressure pain at the finger while their foot was immersed in the ice water bath compared with the neutral bath (i.e., CPM, trial-age: P = 0.001). Pressure pain ratings decreased after exercise (P = 0.03) that was perceived as painful (peak arm pain, 7.0 ± 3.3) for both young and older adults. Regression analysis showed that after controlling for age and baseline pain, CPM predicted EIH (model adjusted R = 0.23, P = 0.007). CONCLUSIONS CPM was attenuated in older adults, as measured with a noxious pressure stimulus after a thermal conditioning stimulus, and adults with greater CPM were more likely to report greater EIH.

FATIGUE AND RECOVERY FROM DYNAMIC CONTRACTIONS IN MEN AND WOMEN DIFFER FOR ARM AND LEG MUSCLES

Introduction: Whether there is a gender difference in fatigue and recovery from maximal velocity fatiguing contractions and across muscles is not understood. Methods: Sixteen men and 19 women performed 90 isotonic contractions at maximal voluntary shortening velocity (maximal velocity concentric contractions, MVCC) with the elbow flexor and knee extensor muscles (separate days) at a load equivalent to 20% maximal voluntary isometric contraction (MVIC). Results: Power (from MVCCs) decreased similarly for men and women for both muscles (P > 0.05). Men and women had similar declines in MVIC of elbow flexors, but men had greater reductions in knee extensor MVIC force and MVIC electromyogram activity than women (P < 0.05). The decline in MVIC and power was greater, and force recovery was slower for the elbow flexors compared with knee extensors. Conclusions: The gender difference in muscle fatigue often observed during isometric tasks was diminished during fast dynamic contractions for upper and lower limb muscles. Muscle Nerve 48: 436–439, 2013

Anxiety and stress can predict pain perception following a cognitive stress

Hoeger Bement, M.K., A. Weyer, M. Keller, A. Harkins, and S.K. Hunter. Anxiety and stress can predict pain perception following a cognitive stressor. PHYSIOL BEHAV 000-000. The purpose of this study was to investigate the influence of a cognitive stressor on pain perception and determine individual characteristics that may predict the pain response. Twenty-five subjects participated in three sessions: one familiarization and two experimental. The experimental sessions involved measurement of pain perception before and after 1) mental math tasks (stressor session) and 2) quiet rest (control session). Pain threshold and ratings were assessed with a mechanical noxious stimulus. Changes in stress and anxiety were examined with self-reported and physiological measures including questionnaires, visual analogue scales, and salivary cortisol levels. During the control session, stress and anxiety decreased and pain reports remain unchanged. During the stressor session, stress and anxiety increased and pain reports were variable among subjects. Based on the pain response to mental math, subjects were divided into three groups (increase, decrease or no change in pain). The increase-pain group (n=8) had lower baseline stress and anxiety, lower baseline pain reports, and large anxiety response following the mental math. In contrast, the decrease-pain group (n=9) had higher baseline stress and anxiety levels, higher baseline pain reports, and a large increase in cortisol levels. Thus, the differential response in the changes in pain perception was related to anxiety and stress levels prior to and during the cognitive stressor, indicating that psychosocial characteristics can help determine the stress-induced pain response.

Fatiguing exercise attenuates pain-induced corticomotor excitability

The purpose of this study was to assess net corticomotor excitability during a painful stimulus before and after exercise. In the first study, 25 subjects participated in three sessions: one familiarization session and two experimental sessions. The two experimental sessions were randomized and involved measurement of pain perception before and after (1) a submaximal isometric fatiguing contraction with the left elbow flexor muscles and (2) 30 min of quiet rest. Pain perception was assessed using a pressure device applied to the right index finger for 2 min. Motor evoked potentials (MEPs) of the left brachioradialis muscle were measured following transcranial magnetic stimulation (TMS) which was delivered before, during, and after the 2 min pain test. In the second study, 12 subjects participated in one session which involved application of TMS to elicit MEPs at the same time points as in study one, before and after a submaximal fatiguing contraction, but in the absence of pain. In the absence of the mechanical noxious stimulus, MEP amplitude was reduced following the fatiguing contraction and unchanged over this time period. In study one, pain threshold increased and pain ratings decreased following the isometric contraction but not after 30 min of quiet rest. During application of the mechanical noxious stimulus to the right index finger, MEP amplitude of the left brachioradialis muscle increased indicating an increase in net corticomotor excitability. The pain-induced increase in MEPs was attenuated following the isometric fatiguing contraction and this occurred in parallel with the decrease in pain.

The role of the menstrual cycle phase in pain perception before and after an isometric fatiguing contraction

The purpose of this study was to compare exercise-induced analgesia in young women after a fatiguing isometric contraction during different phases of the menstrual cycle. Twenty female subjects performed a submaximal (25% maximal voluntary contraction) isometric contraction until task failure during both the mid-follicular and mid-luteal phases of their menstrual cycle. Pain perception (i.e., pain threshold and pain ratings) was measured before and after the isometric fatiguing contraction. Other measures included mean arterial pressure, heart rate, and anxiety levels. Time to task failure of the fatiguing contraction was similar for the two phases of the menstrual cycle. Following the performance of the isometric contraction: (1) pain thresholds increased and pain ratings decreased; (2) anxiety levels increased; and (3) mean arterial pressure and heart rate increased. These changes were not dependent on the phase of the menstrual cycle. Thus, the menstrual cycle phase does not influence the magnitude of exercise-induced analgesia.

Pain relief after isometric exercise is not task-dependent in older men and women.

INTRODUCTION This study assessed the effect of isometric contractions that varied in intensity and duration on pain perception in adults older than 60 yr. METHODS Pain perception was measured in 24 men and women (mean ± SD age = 72.2 ± 6.2 yr) using a pressure pain device applied to the right index finger before and after isometric contractions of the left elbow flexor muscles of the following doses: 1) three brief maximal voluntary contractions (MVC), 2) 25% MVC held for 2 min, and 3) 25% MVC held to task failure. RESULTS Older adults reported increased pain thresholds (58 s vs 49 s, P < 0.001) and decreased pain ratings (2.8 vs 3.4, P < 0.001) after exercise, and these changes were similar across all three tasks (P = 0.94 and P = 0.55, respectively). Sex differences were identified with older women reporting greater pain sensitivity (lower pain thresholds [P = 0.01] and higher pain ratings [P = 0.004]) and larger reductions in pain ratings than men (23% vs 9%, P = 0.003) after isometric contractions. CONCLUSIONS Older adults experienced similar reductions in pain after several different intensities and durations of isometric contractions. Both older men and women experienced increases in pain threshold, but only older women experienced reductions in pain ratings.

Co-localization of p-CREB and p-NR1 in spinothalamic neurons in a chronic muscle pain model

Activation of the cAMP pathway is an important mediator of chronic muscle pain. This study examined phosphorylation of the transcription factor cAMP-response-element-binding protein (p-CREB) and the NR1 subunit of the NMDA receptor (p-NR1) in the spinal cord. Bilateral mechanical hyperalgesia of the paw was induced by administering two injections of acidic saline, 5 days apart, into the gastrocnemius muscle of male Sprague-Dawley rats. The proportion of spinothalamic neurons that expressed p-NR1 or p-CREB did not change in the dorsal horn 24h after the second intramuscular acid injection compared with animals that received pH 7.2 injections. This lack of change in spinothalamic neurons in the dorsal horn may be due to increases in individual spinothalamic neurons or increases in non-spinothalamic neurons. There was an increase in the proportion of spinothalamic neurons expressing p-NR1 in lamina X. These findings suggest that there are region-specific changes in spinothalamic neurons that express p-NR1 and lamina X may play an important role in the modulation of chronic muscle pain.

An Interprofessional Consensus of Core Competencies for Prelicensure Education in Pain Management: Curriculum Application for Physical Therapy

Core competencies in pain management for prelicensure health professional education were recently established.1 These competencies represent the expectation of minimal capabilities for graduating health care students for pain management and include 4 domains: multidimensional nature of pain, pain assessment and measurement, management of pain, and context of pain (Appendix 1). The purpose of this article is to advocate for and identify how core competencies for pain can be applied to the professional (entry-level) physical therapist curriculum. By ensuring that core competencies in pain management are embedded within the foundation of physical therapist education, physical therapists will have the core knowledge necessary for offering best care for patients, and the profession of physical therapy will continue to stand with all health professions engaged in comprehensive pain management. One hundred million adults in America have chronic pain.2 This statistic is greater than the number of individuals affected by diabetes, cancer, and heart disease combined.2,3 Chronic pain management costs the United States more than