The phenomenon of post-exertional malaise (PEM), in which an ME/CFS patient's symptoms are elevated following even low-level exertion, is a hallmark feature of the disease. The cause of PEM, like the cause of ME/CFS, is not understood. This study aims to utilize a two-day CPET to invoke PEM. This provides a unique opportunity to collect data on how key outcome measures or disease parameters are altered during elevated symptoms relative to baseline within each patient by gathering information before and after symptom provocation.

A total of 90 participants and 90 controls will undergo CPET testing. Participation will be split amongst three different sites (Ithaca, NY, New York, NY, and Los Angeles, CA). Subjects will be located in urban and rural areas to establish relatively diverse study populations.

This study is a component of the Cornell ME/CFS Collaborative Research Center (CRC). Blood samples taken before and after CPET will be utilized in associated projects with the Cornell ME/CFS CRC. CPET data along with the analysis of blood samples has great potential to reveal why exercise negatively affects ME/CFS patients and thus perhaps why patients are also impaired even before increasing their activity level.