Exercise

Exercise and the immune system
In healthy people, exercise induces a variety of temporary changes to immune markers. Immediately after exercise, natural killer cell activity is decreased and Leukotriene B4 (LTB4) increase, along with the LTB4/PGE2 ratio. Exercise elevates levels of prostaglandin E2 (PGE2) for up to five days.

Post Exertional Malaise
ME/CFS patients who exercise are likely to experience Post-exertional malaise.

Musculature
Exercise has also been found to induce both early and excessive lactic acid formation in the muscles with reduced intraceullar concentrations of ATP and acceleration of glycolysis. Several studies have found abnormal increases in plasma lactate following short period of moderate exercise that cannot be explained by deconditioning.

There is evidence of loss of capacity to recover from acidosis on repeat exercise.

There is evidence of abnormalities of AMPK activation and glucose uptake in cultured skeletal muscle cells in ME/CFS patients.

There is evidence of Abnormalities in pH handling by peripheral muscle.

Gene Expression
There is evidence of increased gene expression following muscular exertion.

Examples of Clinical Recommendations
While there has been no research on physical therapy alternatives to graded exercise, many clinicians recommend some exercise or strength training for patients who are able. Dr. Sarah Myhill recommends patients who are well enough engage in strength training, specifically Body by Science created by Dr Doug McGuff and John Little. "If muscle strength is correctly developed, this automatically translates into cardiovascular fitness and increased numbers of mitochondria". Dr Myhill has a page on her web site detailing her recommendations.

Dr. Lucinda Bateman encourages her patients to find a way to exercise: "we try to focus on maintaining or improving muscle strength, flexibility and also bit of cardiovascular exercise". She discusses exercise and gene expression in an interview. Dr. Nancy Klimas recommends patients engage in exercise or movement without exceeding a certain heart rate, a proxy for an individual's anaerobic threshold, as established by a VO2 max test.

British patient Sally Burch has written about the The UK National Institute for Health and Care Excellence (NICE) guidelines on maintaining a lower heart rate.