Exercise intolerance is a common symptom among those who suffer from heart disease, mitochondrial disease or metabolic disorders. In such cases, the normal conversion of food or oxygen into energy is disrupted, leaving the patient without an adequate supply. Degrees of exercise intolerance can vary: it can exhibit itself after the mildest exertions or require more sustained effort to be recognized. Likewise, it can afflict the sufferer during exercise or later. Learning to identify its signs is essential.
For even the physically fit, vigorous exercise taxes the organs and muscles of the respiratory system. When exhaustion is reached, continued effort can lead to shortness of breath and dizziness. These sensations signal that oxygen no longer is being processed efficiently and rest is required. In the case of an exercise intolerant individual, the exhaustion threshold may show within minutes of starting physical activity. Worse, fatigue can be induced by seemingly innocuous activity such as eating or writing.
Muscle cramps happen to elite athletes, so why should they signal exercise intolerance? The difference lies in the amount of exertion necessary to produce the cramps and the duration of their presence. A sufferer -- assuming adequate stretching -- may endure only a few minutes of training before experiencing pain and stiffness, which can last for several days. Alternately, the pain can develop in the exercise intolerant hours later, perhaps when asleep.
Insufficient Heart Rate
Metabolic researchers cite chronotropic incompetence as a sign of exercise intolerance in some patients. This phenomenon occurs when the heart rate does not rise to the level necessary to meet the metabolic needs of increased activity. Though many factors affect heart rate -- weight, age and history, for example -- the inability to reach the rate that would be normal for a given profile is a possible flag for exercise intolerance.
Heightened activity can produce mental and emotional malaise in those afflicted with exercise intolerance. Insidiously, the depression can rob them of more energy, creating a vicious cycle. Facing physically debilitating limitations takes a toll on the psyche, manifesting itself in anxiety, despondence, disorientation and irritability. Taken together with other symptoms, depression is a common characteristic of exercise intolerance.
Marked changes in blood pressure can occur in people with exercise intolerance. Standing up and walking across the room is sometimes all it takes. The "Hypertension Reseach" journal published a 2007 study showing a correlation between hypertensive response and exercise intolerance. After six minutes of exercise, those with the intolerance had higher jumps in blood pressure than the control group.
Discoloration of the extremities and face, appearing as a bluish pallor, can indicate abnormally oxygenated blood. This is a very visible sign of exercise intolerance but also a serious call for intervention. Sufferers should seek medical attention in the event of a serious blood-flow disruption.