Functional ability is an important outcome measure in people with chronic low back pain (CLBP). It is predominantly measured using self-report and physical performance testing. Both methods have limitations, and neither provides an objective insight into a person's functional ability in everyday life. The purpose of this thesis was to investigate if free-living physical activity (PA) monitoring could be used as an objective marker of functional ability during everyday life in people with chronic low back pain (CLBP).

Low back pain affects a large proportion of the general population. For some individuals, back pain becomes chronic, complex and difficult to treat effectively, with patients reporting continued pain and disability. A biopsychosocial framework has been adopted within research and clinical practice, as psychosocial factors have been recognised to be important in terms of pain management and recovery from back pain. Coping-related factors have been identified as particularly important, however a comprehensive examination of a wide range of coping factors is missing from available literature. A systematic review of the published literature identified important psychological factors that are predictive of low back pain outcome. Several factors emerged as potentially important, but fear avoidance beliefs appeared to be the most consistent predictor. Very few studies were found that investigated the role of behavioural coping, therefore a new measurement instrument was developed to aid further research. A detailed analysis of the Coping Strategies Questionnaire-24 was undertaken. Exploratory and confirmatory factor analyses were used and it was concluded that the measure was appropriate for use within this thesis. Data from a large cohort of primary care low back pain patients (n = 1,591) was used for analysis. Cross-sectional analyses revealed potential confounders of the relationship between coping and outcome at 12 months follow-up, which were controlled for within the longitudinal analyses. Only five coping variables were independently predictive of outcome – anxiety, depression, catastrophizing, self-efficacy and passive behavioural coping – along with pain duration and employment status. Change in coping over time predicted low back pain outcome, and it was found that coping worsening was particularly important. Coping worsening also partially mediated the relationship between pain duration and outcome. The major thesis findings were integrated into an overall conceptual model of coping, and key implications of this for clinical practice and research were discussed.