Laura D. Ellingson

Physical Activity, Sustained Sedentary Behavior, and Pain Modulation in Women With Fibromyalgia

UNLABELLED Fibromyalgia (FM) has been conceptualized as a disorder of the central nervous system, characterized by augmented sensory processing and an inability to effectively modulate pain. We previously reported that physical activity is related to brain processing of pain, providing evidence for a potential mechanism of pain management. The purpose of this study was to extend our work by manipulating pain modulation and determining relationships to both physical activity and sustained sedentary behavior. Eleven women with FM completed accelerometer measures of physical activity and underwent functional magnetic resonance imaging of painful heat, administered alone and during distracting cognitive tasks. Results showed that physical activity was significantly (P < .005) and positively related to brain responses during distraction from pain in regions implicated in pain modulation including the dorsolateral prefrontal cortex (DLPFC), the dorsal posterior cingulate, and the periaqueductal grey. A significant negative relationship occurred in the left anterior insula. For sedentary time, significant negative relationships were observed in areas involved in both pain modulation and the sensory-discriminative aspects of pain including the DLPFC, thalamus, and superior frontal and pre- and post-central gyri. These results suggest that physical activity and sedentary behaviors are related to central nervous system regulation of pain in FM. PERSPECTIVE Our results support a promising benefit of physical activity and highlight the potentially deleterious effects of sustained sedentary behavior for pain regulation in FM. Studies aimed at increasing physical activity or reducing sedentary behavior and determining the impact of these on pain regulation are warranted.

Physical Activity Is Related to Pain Sensitivity in Healthy Women.

UNLABELLED There are many benefits associated with meeting current physical activity recommendations. At present, it is unknown whether a reduced sensitivity to pain is included among these benefits. PURPOSE The studys purpose was to assess the relationship between pain sensitivity and physical activity and sedentary behaviors in a sample of healthy women. METHODS Self-reported and accelerometer measures of physical activity and sedentary behavior were collected and compared with pain intensity and unpleasantness ratings to noxious thermal stimuli in a sample of 21 healthy women (age = 30.0 ± 5.8 yr). On the basis of accelerometer data, participants were classified into two groups: meets recommendations (n = 12) and insufficiently active (n = 9). Independent-samples t-tests were conducted to compare pain ratings and physical activity behaviors between groups, and correlation coefficients (Spearman ρ) were calculated between average minutes per day spent in moderate, vigorous, and sedentary behaviors, and average intensity and unpleasantness ratings. RESULTS Participants meeting physical activity recommendations had significantly lower unpleasantness ratings than their insufficiently active peers. Correlational analyses demonstrated a significant relationship between minutes spent in vigorous physical activity and both pain intensity and pain unpleasantness ratings. Relationships were not significant for moderate activity or sedentary behavior. CONCLUSIONS These results provide preliminary evidence that meeting current physical activity recommendations may be beneficial for pain in women. Moreover, participation in vigorous activity seems to account for the decreased pain sensitivity. In our sample, sedentary behavior did not seem to have a deleterious effect on pain. Results from this study have many potential applications including aiding our understanding of why exercise functions as a treatment for those with chronic pain conditions and providing a rationale for including physical activity assessment in pain research.

Exercise alters pain sensitivity in Gulf War veterans with chronic musculoskeletal pain.

UNLABELLED Since returning from the Persian Gulf, nearly 100,000 veterans of the first Gulf War (GVs) have reported numerous symptoms with no apparent medical explanation. A primary complaint of these individuals is chronic musculoskeletal pain (CMP). CMP symptoms in GVs are similar to those reported by patients with fibromyalgia (FM), but have not received equivalent scientific attention. Exercise research in CMP patients suggests that acute exercise may exacerbate pain while chronic exercise can reduce pain and improve other symptoms. However, the influence of exercise on GVs with CMP is largely unexplored. This study examined the impact of an acute bout of exercise on pain sensitivity in GVs with CMP. Thirty-two GVs (CMP, n = 15; Control, n = 17) were recruited to complete a series of psychophysical assessments to determine pain sensitivity to heat and pressure stimuli before and after exercise. In response to heat-pain stimuli, GVs with CMP reported higher pain intensity and affect ratings than healthy GVs and exhibited a significant increase in ratings following exercise. GVs with CMP rated exercise as more painful and effortful and were generally more sensitive to heat-pain stimuli than healthy GVs. These results are similar to what has been reported for acute exercise in patients with FM. PERSPECTIVE Gulf War veterans with CMP perceive exercise as more painful and effortful than healthy GVs and experience increased pain sensitivity following exercise. These results suggest that similar abnormalities in central nervous system processing of nociceptive information documented in FM may also be occurring in GVs with CMP.

Examination of the dose–response relationship between pain perception and blood pressure elevations induced by isometric exercise in men and women

The purpose of this study was to examine exercise-induced hypoalgesia (EIH) in men and women, and whether different magnitudes of BP elevations induced by isometric exercise systematically influenced pain perception. Twenty-five men and 25 women performed isometric exercise at 25% MVC for 1-min, 3-min, and 5-min while BP and pain perception were assessed. Results indicated that BP was significantly elevated (p<0.05) by isometric exercise in a dose-response manner. Pain thresholds were found to be elevated while pain ratings were lower (p<0.05) immediately following isometric exercise but not in a dose-response manner. It was concluded that isometric exercise produced EIH in men and women, and there was not a dose-response relationship between BP and EIH.

Does exercise induce hypoalgesia through conditioned pain modulation

Pain sensitivity decreases with exercise. The mechanisms that underlie this exercise-induced hypoalgesia (EIH) are unclear. Our purpose was to investigate conditioned pain modulation (CPM) as a potential mechanism of EIH. Sixteen women completed pain testing during three sessions: painful exercise, nonpainful exercise, and quiet rest. Intensity and unpleasantness ratings to noxious heat stimuli were assessed at baseline and during and following each session. Results showed that pain sensitivity decreased significantly during both exercise sessions (p < .05), but not during quiet rest. Effect size calculations showed that the size of the hypoalgesic response was greater following painful exercise than nonpainful exercise. Our results suggest that exercise-induced muscle pain may contribute to the magnitude of EIH. However, as pain sensitivity also decreased following nonpainful exercise, CPM is not likely the primary mechanism of EIH.

Exercise Strengthens Central Nervous System Modulation of Pain in Fibromyalgia

To begin to elucidate the mechanisms underlying the benefits of exercise for chronic pain, we assessed the influence of exercise on brain responses to pain in fibromyalgia (FM). Complete data were collected for nine female FM patients and nine pain-free controls (CO) who underwent two functional neuroimaging scans, following exercise (EX) and following quiet rest (QR). Brain responses and pain ratings to noxious heat stimuli were compared within and between groups. For pain ratings, there was a significant (p < 0.05) Condition by Run interaction characterized by moderately lower pain ratings post EX compared to QR (d = 0.39–0.41) for FM but similar to ratings in CO (d = 0.10–0.26), thereby demonstrating that exercise decreased pain sensitivity in FM patients to a level that was analogous to pain-free controls. Brain responses demonstrated a significant within-group difference in FM patients, characterized by less brain activity bilaterally in the anterior insula following QR as compared to EX. There was also a significant Group by Condition interaction with FM patients showing less activity in the left dorsolateral prefrontal cortex following QR as compared to post-EX and CO following both conditions. These results suggest that exercise appeared to stimulate brain regions involved in descending pain inhibition in FM patients, decreasing their sensitivity to pain. Thus, exercise may benefit patients with FM via improving the functional capacity of the pain modulatory system.

Active and Sedentary Behaviors Influence Feelings of Energy and Fatigue in Women.

PURPOSE The purpose of this study was to determine whether physical activity and sedentary behaviors interact to influence feelings of energy and fatigue in women. METHODS Feelings of energy and fatigue and physical activity and sedentary behaviors were assessed in 73 women (mean ± SD age = 37 ± 10) who were dichotomized based on physical activity status (meets physical activity recommendations [n = 40] vs insufficiently active [n = 33]) and the amount of uninterrupted sedentary time they accumulated (high [n = 38] vs low [n = 35]). Three 2 × 2 ANOVA were conducted to determine the relationships between physical activity and sedentary behaviors and between energy (vigor and vitality) and fatigue. RESULTS Results demonstrated a significant main effect for meeting physical activity recommendations for both vigor (P = 0.004) and vitality (P < 0.001). For fatigue, there was a significant interaction between physical activity and sedentary behaviors (P = 0.005). Analyses of simple main effects demonstrated that in women who were not meeting physical activity recommendations, those who were less sedentary had significantly lower levels of fatigue than their more sedentary peers (P = 0.003). CONCLUSIONS Our results suggest that meeting physical activity recommendations has benefits for energy and fatigue even when combined with an otherwise sedentary lifestyle. Moreover, in women who are insufficiently active, being less sedentary is associated with lower levels of fatigue that are comparable with women who are meeting recommendations.

Neural consequences of post-exertion malaise in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Post exertion malaise is one of the most debilitating aspects of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome, yet the neurobiological consequences are largely unexplored. The objective of the study was to determine the neural consequences of acute exercise using functional brain imaging. Fifteen female Myalgic Encephalomyelitis/Chronic Fatigue Syndrome patients and 15 healthy female controls completed 30min of submaximal exercise (70% of peak heart rate) on a cycle ergometer. Symptom assessments (e.g. fatigue, pain, mood) and brain imaging data were collected one week prior to and 24h following exercise. Functional brain images were obtained during performance of: 1) a fatiguing cognitive task - the Paced Auditory Serial Addition Task, 2) a non-fatiguing cognitive task - simple number recognition, and 3) a non-fatiguing motor task - finger tapping. Symptom and exercise data were analyzed using independent samples t-tests. Cognitive performance data were analyzed using mixed-model analysis of variance with repeated measures. Brain responses to fatiguing and non-fatiguing tasks were analyzed using linear mixed effects with cluster-wise (101-voxels) alpha of 0.05. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome patients reported large symptom changes compared to controls (effect size ≥0.8, p<0.05). Patients and controls had similar physiological responses to exercise (p>0.05). However, patients exercised at significantly lower Watts and reported greater exertion and leg muscle pain (p<0.05). For cognitive performance, a significant Group by Time interaction (p<0.05), demonstrated pre- to post-exercise improvements for controls and worsening for patients. Brain responses to finger tapping did not differ between groups at either time point. During number recognition, controls exhibited greater brain activity (p<0.05) in the posterior cingulate cortex, but only for the pre-exercise scan. For the Paced Serial Auditory Addition Task, there was a significant Group by Time interaction (p<0.05) with patients exhibiting increased brain activity from pre- to post-exercise compared to controls bilaterally for inferior and superior parietal and cingulate cortices. Changes in brain activity were significantly related to symptoms for patients (p<0.05). Acute exercise exacerbated symptoms, impaired cognitive performance and affected brain function in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome patients. These converging results, linking symptom exacerbation with brain function, provide objective evidence of the detrimental neurophysiological effects of post-exertion malaise.

Surveillance of Youth Physical Activity and Sedentary Behavior With Wrist Accelerometry

INTRODUCTION Accurate tracking of physical activity (PA) and sedentary behavior (SB) is important to advance public health, but little is known about how to interpret wrist-worn accelerometer data. This study compares youth estimates of SB and moderate to vigorous PA (MVPA) obtained using raw and count-based processing methods. METHODS Data were collected between April and October 2014 for the National Cancer Institutes Family Life, Activity, Sun, Health, and Eating Study: a cross-sectional Internet-based study of youth/family cancer prevention behaviors. A subsample of 628 adolescents (aged 12-17 years) wore the ActiGraph GT3X+ on the wrist for 7 days. In 2015-2016, SB and MVPA time were calculated from raw data using R-package GGIR and from activity counts data using published cutpoints (Crouter and Chandler). Estimates were compared across age, sex, and weight status to examine the impact of processing methods on behavioral outcomes. RESULTS ActiGraph data were available for 408 participants. Large differences in SB and MVPA time were observed between processing methods, but age and gender patterns were similar. Younger children (aged 12-14 years) had lower sedentary time and greater MVPA time (p-values <0.05) than older children (aged 15-17 years), consistent across methods. The proportion of youth with ≥60 minutes of MVPA/day was highest with the Crouter methods (~50%) and lowest with GGIR (~0%). CONCLUSIONS Conclusions about youth PA and SB are influenced by the wrist-worn accelerometer data processing method. Efforts to harmonize processing methods are needed to promote standardization and facilitate reporting of monitor-based PA data.

Psychobiological Responses to Preferred and Prescribed Intensity Exercise in Major Depressive Disorder.

Exercise acutely improves mood in major depressive disorder (MDD). However, it is unknown whether benefits differ depending on whether exercise intensity is self-selected or prescribed. PURPOSE This study aimed to compare psychological and biological responses to preferred and prescribed steady-state exercise intensities to a patient-selected preferred intensity. METHOD Female adults (N = 24, age = 38.6 ± 14.0 yr) diagnosed with MDD completed four 30-min sessions of cycling exercise at three prescribed intensities (RPE of 11, 13, and 15) and one session with a self-selected intensity (preferred). Order was randomized and counterbalanced. Depressed mood (DM) was evaluated before, 10 min, and 30 min postexercise using the Profile of Mood States. Serum brain-derived neurotrophic factor (BDNF) was measured before and within 10 min postexercise. Changes in BDNF and DM for the preferred session were compared with the following prescribed sessions: 1) performed at the most similar intensity (matched on RPE; closest) and 2) with the greatest improvement in DM (greatest). RESULTS Compared with the preferred session, improvement in DM was significantly larger after the greatest session (30 min postexercise: -11.8 ± 7.4 vs -3.4 ± 4.8), and the BDNF response was significantly greater after the closest session (5.4 ± 6.9 vs -1.4 ± 9.8 ng·mL). CONCLUSIONS Permitting patients to select their own exercise intensity did not maximize improvements in mood. Further, preferred intensity exercise was also associated with a smaller BDNF response. Overall, the results suggest that exercise undertaken to improve mood should be prescribed on an individual basis in MDD and not necessarily based on the patients preferred intensity. Clinicians, psychologists, and other practitioners should consider providing clear exercise intensity recommendations for symptom management in depression rather than allowing patients to self-select their intensity.