18.8: Conclusion

Fatigue is a symptom common across several diseases and disorders. The etiology of fatigue likely differs between each disease, although often the precise causes are unknown. However, the experience and overall impact of chronic fatigue can be similar across different diseases and conditions. For several clinical populations, exercise is a recommended therapy to improve health and quality of life. There is also some evidence that exercise alleviates chronic fatigue in some diseases. Indeed, even when the evidence base is poor, such as in stroke, exercise may still be recommended due to numerous other benefits to physical and mental health. However, as we have also shown in the case of ME/CFS, extreme caution is required when recommending exercise to people with chronic fatigue. Without knowing the causes of the symptom, it is possible that a therapy that alleviates fatigue in one set of patients may worsen it in another. It is often said that exercise is medicine (Pedersen & Saltin, 2015). For this to be true, then much like a drug, it is vital that we understand the mechanisms of action and the dose of exercise that is safe and beneficial. With these caveats in mind, in certain people, such as those who have been diagnosed with cancer or MS, exercise seems to be an effective and safe method to alleviate fatigue. In these people, a cautious prescription of exercise is likely warranted. Often, specific guidelines for the prescription of exercise in a clinical population have already been developed, and these can help the exercise scientist when designing and implementing an exercise program (Billinger et al., 2014; Campbell et al., 2019; Latimer-Cheung et al., 2013). However, much more research is required before we can fully understand if, how, and why exercise can be used to treat chronic fatigue.