The University of Notre Dame Australia ResearchOnline@ND Theses 2016 Does temporarily altering visual perception of limb size have a modulatory effect on deep-tissue pain? A repeated-measures within-subjects randomised study M van Selm Follow this and additional works at: https://researchonline.nd.edu.au/theses Part of the Physical Therapy Commons, and the Physiotherapy Commons COMMONWEALTH OF AUSTRALIA Copyright Regulations 1969 WARNING The material in this communication may be subject to copyright under the Act. Any further copying or communication of this material by you may be the subject of copyright protection under the Act. Do not remove this notice. Publication Details van Selm, M. (2016). Does temporarily altering visual perception of limb size have a modulatory effect on deep-tissue pain? A repeated-measures within-subjects randomised study (Master of Philosophy (School of Physiotherapy)). University of Notre Dame Australia. https://researchonline.nd.edu.au/theses/133 This dissertation/thesis is brought to you by ResearchOnline@ND. It has been accepted for inclusion in Theses by an authorized administrator of ResearchOnline@ND. For more information, please contact [email protected]. Does temporarily altering visual perception of limb size have a modulatory effect on deep- tissue pain? A repeated-measures within-subjects randomised study. Megan van Selm BSc Physiotherapy (Hons), Grad Dip OMT School of Physiotherapy The University of Notre Dame Australia, Fremantle Master of Philosophy 2016 i Abstract Previous research has suggested that looking at a painful body part has an analgesic effect on experimental pain. Furthermore, it has been demonstrated that magnifying the size of the viewed part has a greater analgesic effect, while minifying the perceived size of the body part reduces the analgesia. These studies involved the application of a noxious stimulus to the skin, inducing pain that is perceived superficially. It is believed that most clinical pain is likely contributed to by noxious information from deep tissues and is certainly more commonly perceived as deep (below the skin surface). Research on clinical populations has also supported the idea that visualisation of the painful body part is analgesic, however the effects of magnification and minification are opposite to those seen with an experimental pain paradigm. While a number of mechanisms might explain these differences it is possible that the modulatory effect of vision is different for pain that is perceived superficially to that which is perceived deeply. Here we explore the effects of visualisation and visual enlargement on experimental deep tissue pain of the anterior thigh. All participants undertook a bout of high load eccentric exercise to induce delayed onset muscle soreness. Twenty four hours later those participants who reported at least a moderate level of muscle soreness were tested in a four phase randomised cross-over experiment. We measured pain intensity during the performance of a standardised quadriceps contraction under four different visual conditions, namely: normal visualisation of the thigh; magnified visualisation of the thigh; visualisation of the contralateral uninjured thigh and visualisation of a neutral object. Contrary to previous research on superficially perceived pain, we found no difference in pain intensity across any of the four conditions. These results demonstrate that visualisation does not have an analgesic effect on experimental deep tissue pain, suggesting that different modulatory factors exist for superficial and deep experimental pain. It also proposes the notion that visualisation may only have a modulatory effect on experimental pain when visual feedback offers a significant contribution to the perception of safety of the ii stimulated structure. Visualisation provides clear information that all is well with the skin but less credible evidence that all is well with deep structures, however this hypothesis remains to be tested. iii Acknowledgements I would like to acknowledge the support of my supervisors Professor Ben Wand and Dr Will Gibson. They have guided me through this process with the perfect amount of assistance - enough to enable me to explore, discover, find my feet and make mistakes, keep me going, encourage me and point me in the right direction. This has resulted in a rich learning experience for me, through which I have slowly developed confidence in my research skills, oral and written presentation delivery, and in my knowledge of the subject material. I appreciate their patience with me and all the time they have dedicated to this project. I am truly grateful to both Ben and Will! I would also like to thank my husband, Rob, for his support. Not only has he helped look after our children, Emma and Natalie, which has allowed me to spend time on this project, but he has been a sounding board when I have come up against stumbling blocks, a guinea pig while I was trialling various methods of inducing DOMS, and a handy-man constructing wooden frames and mirror boxes for the pilot study. A big thank you to my mother, Pam Rodwell, for her encouragement and endless support. I am so appreciative of her help. Thank you to Professor Max Bulsara for his help with the statistics. I would also like to acknowledge Professor Peter Hamer’s input, particularly with regard to his extensive knowledge of DOMS. I also appreciate his constant support of my study. Finally, I would like to thank my friends and extended family who kindly took the time to subject themselves to a nasty dose of DOMS during my pilot study. They provided a useful contribution to my study but also great entertainment value. I owe you!! v List of Contents Abstract .....................................................................................................................................ii Declaration of Authorship ........................................................................................................ iv Acknowledgements ................................................................................................................... v List of Contents ........................................................................................................................ vi List of Figures ............................................................................................................................ x List of Tables ............................................................................................................................ xi CHAPTER ONE: INTRODUCTION ............................................................................................... 1 1.1 Topic and Purpose .................................................................................................... 1 1.2 Background .............................................................................................................. 3 1.3 Development of this Research Study ....................................................................... 6 1.4 Potential Significance ............................................................................................... 8 CHAPTER TWO: LITERATURE REVIEW ...................................................................................... 9 2.1 Past Concepts of Pain ............................................................................................... 9 2.2 The Neuroanatomical Pathways of Nociception ................................................... 10 2.2.1 Peripheral nociception. .................................................................................. 10 2.2.2 Spinal cord. ..................................................................................................... 14 2.2.3 Brain structures involved in pain perception. ................................................ 16 2.3 Modulation of Pain ................................................................................................ 20 2.3.1 Peripheral modulation of pain. ...................................................................... 20 2.3.2 Modulation of pain in the spinal cord. ........................................................... 21 2.3.3 Supraspinal modulation of pain. .................................................................... 28 2.4 Interaction between Pain and Emotional Factors ................................................. 30 2.5 Interaction between Pain and Cognitive Factors ................................................... 32 vi 2.6 Multisensory Integration ....................................................................................... 35 2.6.1 Modulatory effects of tactile activity on pain perception. ............................ 35 2.6.2 Modulatory effects of nociceptive activity on pain perception. .................... 35 2.6.3 Modulatory effects of auditory activity on pain perception.......................... 35 2.6.4 Modulatory effects of olfaction on pain perception. .................................... 38 2.6.5 Modulatory effects of gustation on pain perception. .................................... 39 2.6.6 Modulatory effects of vision on pain perception. ......................................... 40 2.7 Deep versus Superficial Pain .................................................................................. 50 2.8 Summary of Literature Review .............................................................................. 52 CHAPTER THREE: PILOT STUDY .............................................................................................