Chronic Pain and Exercise Studies on pain intensity, biochemistry, adherence and attitudes

.......................................................................................................................... 3 Svensk sammanfattning ................................................................................................. 5 List of papers .................................................................................................................. 7 List of abbreviations ....................................................................................................... 8 Background ............................................................................................ 9 Definitions ................................................................................................................... 9 Pain and chronic pain .............................................................................................. 9 Physical activity and physical exercise .................................................................... 9 Adherence ................................................................................................................ 9 Chronic pain and the biopsychosocial model ........................................................... 10 Epidemiology of chronic pain .................................................................................... 11 Pain physiology ......................................................................................................... 12 Psychological factors ................................................................................................. 15 Physical activity and exercise as treatment for chronic pain ................................... 17 Physical activity and exercise physiology .............................................................. 17 Physical activity and exercise, and pain inhibitory effect mechanisms ................... 19 Physical activity and exercise acute pain inhibitory mechanisms ..................... 19 Physical activity and exercise – long term pain inhibitory mechanisms ............. 20 Physical activity and exercise – psychological effects .......................................... 21 Application of physical activity and exercise as treatment for chronic pain ........... 21 Aim of the thesis ................................................................................... 23 Aims .......................................................................................................................... 24 Methods and materials ......................................................................... 25 Methods and materials (paper 1, 2 and 3) ................................................................ 25 Design and procedures .......................................................................................... 25 Participants ............................................................................................................... 26 Women with neckand shoulder pain (paper 1, 2 and 3) ..................................... 26 Pain-free women (paper 2).................................................................................... 26 Randomization and blinding (paper 1) .................................................................... 27 Completers and responders (paper 1 and 3) ............................................................ 29 Completer and non-completer .............................................................................. 29 Responder and non-responder ............................................................................. 29 Sample size ................................................................................................................ 29 The pysical activity and exercise intervention ......................................................... 30 Microdialysis (paper 2) ............................................................................................. 31 Procedure ............................................................................................................... 31 Chemical analyses .................................................................................................. 33 Outcome measurements ........................................................................................... 34 Pain perception and subjective pain related function .......................................... 34 (paper 1, 2 and 3) ................................................................................................... 34 Physical function (paper 1) .................................................................................... 34 Biochemical substances (paper 2) ......................................................................... 35 Psychological factors (paper 3) ............................................................................. 35 The trial setup and outcome measurement time-points .......................................... 37 Statistics .................................................................................................................... 38 Traditional statistics .............................................................................................. 38 Multivariate data analysis ..................................................................................... 38 Methods and materials (paper 4) ............................................................................. 39 Procedures ............................................................................................................. 39 Participants ............................................................................................................ 39 Interviews ..............................................................................................................40 Qualitative content analysis ..................................................................................40 Results .................................................................................................. 41 Home-based physical activity and exercise improves pain and function (paper 1) 41 4-6 month follow-up compared to baseline .......................................................... 42 12-month follow-up compared to baseline ........................................................... 43 Adherence to the physical activity and exercise intervention .............................. 44 Completers and responders................................................................................... 45 4-6 month follow-up for the completers and responders ..................................... 45 12-month follow-up for the completers and responders ...................................... 46 Physical activity and exercise alters pain modulatory substances in painful trapezius muscles (paper 2) ...................................................................................... 47 Results traditional statistics ................................................................................ 47 Substance P, beta-endorphin, and cortisol ........................................................... 47 Glutamate, lactate, and pyruvate .......................................................................... 49 Pain intensity ......................................................................................................... 50 Pressure pain thresholds ....................................................................................... 52 Results multivariate data analyses...................................................................... 53 Regression of group membership at baseline ....................................................... 53 Regression of pain intensity in participants with neckand shoulder pain at baseline .................................................................................................................. 53 Regressions of changes in aspects of pain ............................................................ 53 Regression of PPT of trapezius at baseline ........................................................... 54 Regression of changes in PPT of trapezius in participants with chronic neckand shoulder pain ......................................................................................................... 54 Psychological factors are associated with the results of physical activity and exercise as treatment for chronic pain (paper 3) ..................................................... 55 Completers and responders................................................................................... 55 Pain intensity, function, and psychological variables at baseline, 4-6 month follow-up, and at 12 month follow up ................................................................... 55 Regression analyses ............................................................................................... 57 Differences in pain intensity, disability, and psychological variables at baseline between participants who discontinued vs. participants who remained in the trial ................................................................................................................................ 59 Physical activity and exercise are valuable, but difficult to achieve (paper 4) ........60 Valuing a life with physical activity and exercise .................................................. 61 Physical activity and exercise – before and after pain .......................................... 61 A strive – difficulties and challenges .................................................................... 61 Enabling physical activity and exercise................................................................. 62 In contact with health care providers ................................................................... 63 Discussion ............................................................................................ 65 Methodological considerations ................................................................................. 75 Conclusions ............................................................................................................... 77 Clinical implications ................................................................................................. 78 Future research ......................................................................................................... 78 Acknowledgements ...................................................................................................... 79 References ............................................................................................ 81 Appendix; The physical activity and exercise intervention Appended papers 1 4