Exercise Intolerance is a medical symptom used when describing why people are not performing in the exercise state as they should. The exerciser may experience other symptoms that cause him or her to stop exercising prematurely or they may simply "run out of steam" too soon.
This is a slippery term, as it encompasses a lot of other terminology, and is easily misapplied. Exercise intolerance is not a disease or syndrome in and of iteself, but a symptom.
It is not fatigue, it is not myalgia, nor is it weakness. Any of these symptoms could be a cause of Exercise Intolerance.
Many diseases have Exercise Intolerance as one of the only symptoms, as in the case of some of the less severe Metabolic Myopathies . Nonspecific fatigue or pain syndromes such as Chronic Fatigue, Fybromyalgia and Overtraining Syndrome are all collections of symptoms, one of which is likely to be exercise intolerance.
