Chronic Fatigue Syndrome, Exercise & the Heart "When it comes to chronic fatigue syndrome (CFS or ME/CFS), exercise is a contentious subject. That's because of a symptom called post-exertional malaise; exertion makes symptoms worse." "Dr. A. Martin Lerner, an infectious disease specialist who himself recovered from ME/CFS, says anything that raises the heart rate of someone with this condition is dangerous, unless they're well on their way to recovery (at a 7 on his EIPS chart.) He says this is because, in his practice, he's seen that ME/CFS does involve the heart. Dr. Lerner says people with ME/CFS have a rapid heart rate when they're at rest, on top of low blood volume. As the disease progresses, he says, the heart muscle becomes weaker." "For those in the early stages of recovery, Dr. Lerner says, "Certainly, it is helpful to not just let the muscles atrophy, but sitting up is actually a muscular activity." He adds, "Walk, live, but no exercise until you're at a 7, because if you exercise before that you're going to go backwards."