Glossary

A glossary of *key* ME-related terms.

C

crash - (noun) -- see post-exertional malaise

H

Heart rate monitor (HRM) - (noun) a device that measures your heart rate / pulse. Typically a chest strap, wrist strap, or mobile phone app. See also Pacing with a heart rate monitor

Heart rate variability (HRV) - a measurement of the specific changes in time (or variability) between successive heart beats. This is related to autonomic and cardiovascular function. See also Pacing with a heart rate monitor

O

orthostatic intolerance (OI) -- is the development of symptoms when standing upright which are relieved when reclining

P

post-exertional malaise (PEM)- (noun) a worsening of ME symptoms due to physical or cognitive exertion

post-exertional neuroimmune exhaustion -- see post-exertional malaise

T

Two-day cardiopulmonary exercise test

flare-up A symptoms flare in ME/CFS is a temporary increase in symptoms, alternatively known as experiencing post-exertional malaise. May be referred to as a "crash" or "collapse".

post-exertional malaise (PEM) - A notable exacerbation of symptoms brought on by small physical or cognitive exertions. PEM may be referred to as a "crash" or "collapse" and can last for days or weeks. Symptoms can include cognitive impairments, muscle pain, trouble remaining upright (orthostatic intolerance), sleep abnormalities, and gastro-intestinal impairments, and others.

heart rate monitor (HRM) - A device that measures your heart rate (pulse rate). Heart rate monitors may come as a chest strap, wrist strap, smartwatch, or even as a mobile phone app. Heart rate monitors are often used by ME/CFS patients to pace their exertion, in order to avoid post-exertional malaise (PEM). For more information, see pacing with a heart rate monitor.

heart rate (HR) - the number of times the heart beats within a certain time period, usually a minute

heart rate variability (HRV) - A measurement of the variability of the heart rate over time. When the heart rate is consistent, there will be a low heart rate variability. When the heart rate is constantly changing, there will be a high heart rate variability. Heart rate variability is often used by ME/CFS patients to monitor their autonomic nervous system, as high heart rate variability is associated with the sympathetic nervous system and low heart rate variability is associated with the parasympathetic nervous system.

orthostatic intolerance (OI) - The development of symptoms when standing upright, where symptoms are relieved upon reclining. Patients with orthostatic intolerance have trouble remaining upright for more than a few seconds or a few minutes, depending upon severity. In severe orthostatic intolerance, patients may not be able to sit upright in bed. Orthostatic intolerance is often a sign of dysautonomia. There are different types of orthostatic intolerance, including postural orthostatic tachycardia syndrome (POTS).

post-exertional malaise (PEM) - A notable exacerbation of symptoms brought on by small physical or cognitive exertions. PEM may be referred to as a "crash" or "collapse" and can last for days or weeks. Symptoms can include cognitive impairments, muscle pain, trouble remaining upright (orthostatic intolerance), sleep abnormalities, and gastro-intestinal impairments, and others.

cognition Thought processes, including attention, reasoning, and memory.