Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Health and Rehabilitation Sciences

Collaborative Specialization

Musculoskeletal Health Research

Supervisor

Walton, David M.

Abstract

It is estimated that as many as 50% of people suffering from Whiplash Associated Disorders (WAD) may experience chronic alterations of their activities of daily living as much as 1-year post injury. Despite their burden, there is little to evidence to suggest why some people may be more likely to acquire WAD or develop chronic symptomology. Additionally, the link between biomechanical forces at the time of impact and symptom development or recovery is poor. As a result, interest in alternative theories such as stress system reactivity have received interest in recent literature, but empirical methods to test them has been lacking. Thus, the purpose of this thesis was to explore the relationship between stress and trauma using a known stressor and a newly developed virtual reality (VR)-based car crash simulator to better understand the immediate reaction to being involved in a motor vehicle crash (MVC). In Chapter 2, we evaluated conditioned pain modulation (CPM) in reaction to the cold pressor task and measured associations with indices of sympathetic and hypothalamic-pituitary-adrenal function. It was found that only 30% of participants experienced inhibitory CPM. Within this group, there was a positive moderate correlation between CPM and the absolute change in skin conductance pre-to-post cold pressor task. In Chapter 3, we explored the initial tolerability to a novel VR-based car crash simulator in healthy subjects and also evaluated sense of presence and simulator sickness. The system was well tolerated by a majority of participants, and it appeared that the sense of presence and simulator sickness shared an inverse relationship. In Chapter 4, we evaluated the pain and stress response to our VR-based car crash simulator in the form of pain pressure detection thresholds, CPM, heart rate variability, and salivary cortisol. Over 40% of participants were more sensitive to pain following the simulation, and this may have been associated with an increase in parasympathetic nervous system activity and salivary cortisol. These results may help to explain some of the heterogeneity of WAD presentations after a MVC and signify that the pain/stress response to simulated trauma is variable.

Summary for Lay Audience

While there has been much research over the last 20 years to understand car crashes, it remains unclear why some people develop neck pain and others do not. This collection of symptoms immediately after a car crash is referred to as Whiplash. Recent research has suggested that neck pain after a car crash could be due to high amounts of stress that are felt during a car crash. Unfortunately, until now there has been no way to test this theory. We recently created a new virtual reality based simulator that is designed to mimic the experience of being in a car crash without the physical injury. Thus, this research project was designed to examine how healthy people react to being involved in a virtual reality car crash.

The first project in this thesis was designed to look at how healthy people react to being stressed using a common way of generating stress. We did this by placing healthy people’s hands into cold water and measuring their nervous system activity and their pain before and after. It appeared that some people become less sensitive to pain and that this was associated with the ‘fight’ aspect of the fight or flight response. For the second project in this thesis, we wanted to see if healthy people could tolerate exposure to a virtual reality car crash. We also measured how much they felt like they ‘were actually there’ and if they became sick or not. Most people were able to tolerate this virtual reality car crash and that as the feeling of ‘being there’ increased, sickness decreased. The third project in this thesis looked how healthy people responded to a virtual reality car crash in terms of their pain and nervous system activity. We surprisingly found that some people become more sensitive to pain after a virtual car crash and that this was associated with the ‘flight’ aspect of the fight or flight response. With this information, we may be able to start better understanding why some people get neck pain after a car crash and some people do not.

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