Exercise intolerance

Exercise intolerance is a condition of inability or decreased ability to perform physical exercise at the normally expected level or duration for people of that age, size, sex, and muscle mass. It also includes experiences of unusually severe post-exercise pain, fatigue, nausea, vomiting, or other negative effects. Exercise intolerance is not a disease or syndrome in and of itself, but can result from various disorders. In most cases, the specific reason that exercise is not tolerated is of considerable significance when trying to isolate the cause down to a specific disease. Dysfunctions involving the pulmonary, cardiovascular or neuromuscular systems have been frequently found to be associated with exercise intolerance, with behavioural causes also playing a part.

Signs and symptoms

Exercise in this context means physical activity, not specifically exercise in a fitness program. For example, a person with exercise intolerance after a heart attack may not be able to sustain the amount of physical activity needed to walk through a grocery store or to cook a meal. In a person who does not tolerate exercise well, physical activity may cause unusual breathlessness (dyspnea), muscle pain (myalgia), tachypnoea (abnormally rapid breathing), inappropriate rapid heart rate or tachycardia (having a faster heart rate than normal), increasing muscle weakness or muscle fatigue; or exercise might result in severe headache, nausea, dizziness, occasional muscle cramps or extreme fatigue, which would make it intolerable. The three most common reasons people give for being unable to tolerate a normal amount of exercise or physical activity are: breathlessness – commonly seen in people with lung diseases or heart disease. fatigue – when it appears early in an exercise test, it is usually due to deconditioning (either through a sedentary lifestyle or while convalescing from a long illness), but it can indicate heart, lung or neuromuscular diseases. pain – potentially due to a variety of medical conditions, such as arthritis, claudication, peripheral vascular disease, or angina. Chronic pain that makes a person unwilling to undertake physical activity is not, by itself, a form of exercise intolerance.

Causes

Neurological disorders

Multiple sclerosis

Respiratory disorders

Cystic fibrosis: CF can cause skeletal muscle atrophy; however, more commonly it can cause exercise intolerance. The exercise intolerance is associated with reduced pulmonary function that is the origin of CF. Bronchiectasis

Post-concussion syndrome (PCS)

Individuals with postconcussion syndrome may also experience a level of exercise intolerance; however, there is little known comparatively about exercise intolerance in PCS patients.

Heart conditions

Angina pectoris Heart failure: exercise intolerance is a primary symptom of chronic diastolic heart failure. Cardiac arrhythmia Aortic valve insufficiency Pulmonary artery hypertension: PAH has the following symptoms – dyspnea and fatigue, these systems consequently contribute to exercise intolerance. Asymptomatic atrial septal defects: in the heart the right ventricular (RV) can have a volume overload which ultimately produces a pressure overload in the RV resulting in exercise intolerance as the RV is no longer able to control high pressure associated with exercise. Chronic heart failure Inappropriate sinus tachycardia Postural orthostatic tachycardia syndrome

Musculoskeletal disorders

Spinal muscular atrophy: symptoms include exercise intolerance, cognitive impairment and fatigue. Rhabdomyolysis: a condition in which muscle degrades, releasing intracellular muscle content into the blood as reflected by elevated blood levels of creatine kinase. Exercise tolerance is significantly compromised.

Low ATP reservoir in muscles (inherited or acquired)

Exercise tolerance reflects the combined capacity of components in the oxygen cascade to supply adequate oxygen for ATP resynthesis by oxidative phosphorylation. In individuals with diseases such as cancer, certain therapies can affect one or more components of this cascade and therefore reduce the body's ability to utilise or deliver oxygen, leading to temporary exercise intolerance. Abnormal thyroid function can cause hyperthyroid myopathy and hypothyroid myopathy by affecting myocardial oxygen function. Both include symptoms of muscle fatigue and muscle pain, with dyspnea (shortness of breath) presenting in hyperthyroid myopathy. Thyroxine (T4) deficiency leads to a reduced mitochondrial oxidative capacity, abnormal glycogenolysis and an insulin resistant state of the cell. Hypothyroid myopathy includes Kocher-Debre-Semelaigne syndrome (childhood-onset) and Hoffmann syndrome (adult-onset).

Intracranial hypertension

Individuals with elevated levels of cerebrospinal fluid can experience increased head pain, throbbing, pulsatile tinnitus, nausea and vomiting, faintness and weakness and even loss of consciousness after exercise or exertion.

Diagnosis

Objective tests for exercise intolerance normally involve performing some exercise. Common tests include stair climbing, walking for six minutes, a shuttle-walk test, a cardiac stress test, and the cardiopulmonary exercise test (CPET). In the six-minute walk test, the goal is to see how far the person can walk, with approximately 600 meters being a reasonable outcome for an average person without exercise intolerance. The CPET test measures exercise capacity and help determine whether the cause of exercise intolerance is due to heart disease or to other causes. People who experience significant fatigue before reaching the anaerobic threshold usually have a non-cardiac cause for exercise intolerance. Additionally, testing for exercise-induced asthma may be appropriate.

Hazards

Certain conditions exist where exercise may be contraindicated or should be performed under the direction of a licensed medical professional acting within their scope of practice. These conditions include, but are not limited to: Decompensated heart failure Recent myocardial infarction Hypertrophic cardiomyopathy or cardiomyopathy from recent myocarditis Active or suspected myocarditis or pericarditis Low left-ventricular ejection fraction (LVEF) Severe aortic stenosis Unstable ischemia Unstable arrhythmia Irregular or resting pulse greater than 100 bpm Resting systolic blood pressure >200 mm Hg or resting diastolic blood pressure >110 mm Hg Severe pulmonary hypertension Chronic fatigue syndrome Suspected or known dissecting aortic aneurysm Recent systemic or pulmonary embolus Pneumothorax and haemoptysis Thrombophlebitis Although it has not been shown to promote improved muscle strength, passive range-of-motion exercise is sometimes used to prevent skin breakdown and prevent contractures in patients who are unable to safely self-power.

References

Text derived from https://en.wikipedia.org/w/index.php?oldid=1378642794 under CC BY-SA 4.0; modifications have been made.

Names in other languages