Blood Flow and Exercise in ME/CFS and Orthostatic Intolerance

Orthostatic intolerance (OI) is when people feel symptoms like light-headedness, dizziness, blurred vision, and sometimes fainting, especially when they stand up. This is because of instability in blood flow and pressure. Since 2003, recognizing these symptoms has been a key part of diagnosing ME/CFS (Myalgic Encephalomyelitis/Chronic Fatigue Syndrome), a condition where OI is quite common. In some cases, these symptoms in ME/CFS patients are due to reduced blood flow to the brain rather than changes in how blood circulates upon standing.

We hypothesize that people with ME/CFS and OI will be impacted more by upright exercise versus supine exercise. This will be observed by reduced blood flow to the brain and/or reduced blood pressure and/or increased heart rate during and after exercise. We suspect this could lead to more severe post-exertional malaise (PEM), which is a worsening of symptoms following physical activity.

Additionally, the study predicts that there will be observable differences in metabolic processes in ME/CFS and OI patients before and after exercise, particularly during PEM, and these differences will be more pronounced in patients with both conditions.