What causes exercise intolerance in ME/CFS, David Systrom? (Interview 2025)

Prof David Systrom is an assistant professor of medicine at Brigham and Women's Hospital and the director of the Massachusetts General Hospital Cardiopulmonary Laboratory in Boston, USA. Prof Systrom is also an assistant professor of medicine at Harvard Medical School, where he leads the Dyspnea Clinic and the Advanced Cardiopulmonary Exercise Testing Program. For the past 10 years, he has been using invasive cardiopulmonary exercise testing (iCPET) to investigate the mechanisms underlying fatigue, shortness of breath, and orthostatic intolerance in ME/CFS and, more recently, Long COVID/post-COVID syndrome. His recent work points to commonalities between both conditions, particularly neurovascular dysregulation and associated hyperventilation underlying symptoms during physical exertion. Prof Systrom is the principal investigator of several ongoing studies, including research into mitochondrial dysfunction of limb skeletal muscles, as well as clinical trials for pharmacological treatment of ME/CFS, carried out with the support of the Open Medicine Foundation (OMF).

In the video, he answers the following questions:

• How do you characterise and measure the physiological causes of exercise intolerance in ME/CFS?

• Why do you think medications like Mestinon could help and what are the results of initial studies?

• Is it possible to recognise that in your iCPET diagnosis?

• What are the next steps in your research to better characterise the ME/CFS subtypes identified using iCPET?