Purpose of review: This review provides an up-to-date overview of the evidence relating to how physical inactivity ameliorates cancer-related fatigue. A summary of the postulated biological mechanisms underpinning the relationship is presented.
Recent findings: Systematic reviews and meta-analyses synthesising the results of randomised controlled trials of physical activity interventions to reduce fatigue broadly conclude that aerobic and combination exercise may be the most helpful, while resistance training alone is less efficacious. Further, light- and moderate-intensity physical activity interventions appeared to reduce fatigue, whereas vigorous-intensity activity may exacerbate the condition. Physical activity interventions result in greater reductions in cancer-related fatigue when delivered post-treatment. Biological mechanisms that may explain how physical activity can improve different elements of cancer-related fatigue include inflammation; the hypothalamic-pituitary-adrenal (HPA) axis and circadian rhythm dysregulation; serotonin dysregulation; and alterations in ATP and muscle metabolism. Physical activity is well tolerated by cancer survivors and results in modest improvements in cancer-related fatigue. Much of the research in this field has been from small-scale feasibility trials. In order to help clinicians and allied health professionals tailor exercise prescriptions to individual needs, further research is required. New trials in this field should implement rigorous inclusion criteria, be fully powered to detect effects in sub-group analyses, incorporate multiple sites, and have well-defined control conditions. There is also a need to better understand how physical activity affects different subtypes of cancer-related fatigue.
Keywords: Biological mechanisms; Cancer survivorship; Cancer-related fatigue; Exercise; Interventions; Physical activity.