Andrea Polli1, Jessica Van Oosterwijck2, Jo Nijs3, Uros Marusic4, Inge De Wandele5, Lorna Paul6, Mira Meeus7, Greta Moorkens8, Luc Lambrecht9, Kelly Ickmans3. 1. Pain in Motion International Research Group, Belgium(12); Department of Physiotherapy, Human Physiology and Anatomy, Faculty of Physical Education & Physiotherapy, Vrije Universiteit Brussel, Brussels, Belgium; Research Foundation-Flanders (FWO), Brussels, Belgium. Electronic address: andrea.polli@vub.be. 2. Pain in Motion International Research Group, Belgium(12); Research Foundation-Flanders (FWO), Brussels, Belgium; Department of Rehabilitation Sciences and Physiotherapy, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium; Department of Rehabilitation Sciences and Physiotherapy, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium. 3. Pain in Motion International Research Group, Belgium(12); Department of Physiotherapy, Human Physiology and Anatomy, Faculty of Physical Education & Physiotherapy, Vrije Universiteit Brussel, Brussels, Belgium; Department of Physical Medicine and Physiotherapy, University Hospital Brussels, Brussels, Belgium. 4. Institute for Kinesiology Research, Science and Research Centre Koper, Koper, Slovenia; Department of Health Sciences, Alma Mater Europaea-ECM, Maribor, Slovenia. 5. Department of Rehabilitation Sciences and Physiotherapy, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium. 6. School of Health and Life Sciences, Glasgow Caledonian University, Glasgow, United Kingdom. 7. Pain in Motion International Research Group, Belgium(12); Department of Rehabilitation Sciences and Physiotherapy, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium; Department of Rehabilitation Sciences and Physiotherapy, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium. 8. Department of Internal Medicine, University Hospital Antwerp (UZA), Antwerp, Belgium. 9. Private Practice for Internal Medicine, Ghent, Belgium.
Abstract
PURPOSE: Oxidative stress has been proposed as a contributor to pain in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). During incremental exercise in patients with ME/CFS, oxidative stress enhances sooner and antioxidant response is delayed. We explored whether oxidative stress is associated with pain symptoms or pain changes following exercise, and the possible relationships between oxidative stress and parasympathetic vagal nerve activity in patients with ME/CFS versus healthy, inactive controls. METHODS: The present study reports secondary outcomes from a previous work. Data from 36 participants were studied (women with ME/CFS and healthy controls). Subjects performed a submaximal exercise test with continuous cardiorespiratory monitoring. Levels of thiobarbituric acid-reactive substances (TBARSs) were used as a measure of oxidative stress, and heart rate variability was used to assess vagal activity. Before and after the exercise, subjects were asked to rate their pain using a visual analogic scale. FINDINGS: Significant between-group differences in pain at both baseline and following exercise were found (both, P < 0.007). In healthy controls, pain was significantly improved following exercise (P = 0.002). No change in oxidative stress level after exercise was found. Significant correlation between TBARS levels and pain was found at baseline (r = 0.540; P = 0.021) and after exercise (r = 0.524; P = 0.024) in patients only. No significant correlation between TBARS and heart rate variability at baseline or following exercise was found in either group. However, a significant correlation was found between exercise-induced changes in HRV and TBARS in healthy controls (r = -0.720; P = 0.001). IMPLICATIONS: Oxidative stress showed an association with pain symptoms in people with ME/CFS, but no exercise-induced changes in oxidative stress were found. In addition, the change in parasympathetic activity following exercise partially accounted for the change in oxidative stress in healthy controls. More research is required to further explore this link.
PURPOSE: Oxidative stress has been proposed as a contributor to pain in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). During incremental exercise in patients with ME/CFS, oxidative stress enhances sooner and antioxidant response is delayed. We explored whether oxidative stress is associated with pain symptoms or pain changes following exercise, and the possible relationships between oxidative stress and parasympathetic vagal nerve activity in patients with ME/CFS versus healthy, inactive controls. METHODS: The present study reports secondary outcomes from a previous work. Data from 36 participants were studied (women with ME/CFS and healthy controls). Subjects performed a submaximal exercise test with continuous cardiorespiratory monitoring. Levels of thiobarbituric acid-reactive substances (TBARSs) were used as a measure of oxidative stress, and heart rate variability was used to assess vagal activity. Before and after the exercise, subjects were asked to rate their pain using a visual analogic scale. FINDINGS: Significant between-group differences in pain at both baseline and following exercise were found (both, P < 0.007). In healthy controls, pain was significantly improved following exercise (P = 0.002). No change in oxidative stress level after exercise was found. Significant correlation between TBARS levels and pain was found at baseline (r = 0.540; P = 0.021) and after exercise (r = 0.524; P = 0.024) in patients only. No significant correlation between TBARS and heart rate variability at baseline or following exercise was found in either group. However, a significant correlation was found between exercise-induced changes in HRV and TBARS in healthy controls (r = -0.720; P = 0.001). IMPLICATIONS: Oxidative stress showed an association with pain symptoms in people with ME/CFS, but no exercise-induced changes in oxidative stress were found. In addition, the change in parasympathetic activity following exercise partially accounted for the change in oxidative stress in healthy controls. More research is required to further explore this link.