Self-regulation, physical activity and unexplained chronic fatigue : from determinants to interventions

Unexplained Chronic Fatigue (CF) is of unknown aetiology, but research suggests a multifactorial nature in which biological/physical, psychological and social fators interact. Treatment approaches for CF target mainly perpetuating factors of fatigue chronicity, such as lack of physical activity. This thesis describes a brief self-regulation-based intervention targeting physical activity for patients with CF. Prior to this intervention study we conducted a series of studies that were important for the development of the trial: (1) a validation of a measure of fatigue severity for the language and population in which we intended to implement the intervention, (2) a comparison of clinical characteristics and behavioural and cognitive determinants of CFS in a Dutch and a Portuguese patient sample, and (3) a systematic review and meta-analysis of behavioural interventions with a graded activity component conducted with CF patients. In a randomized controlled trial (n=91), the self-regulation based intervention led to significant sustained effects (1 year) on fatigue severity, quality of life and physical activity. Sustained benefits on fatigue severity were partially explained by progress on a personal physical activity goal, and use of self-regulation skills. Findings are discussed in terms of its implications for practice, methodological considerations and avenues for future research