Exercise intolerance

• Multiple sclerosis

• 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.[4]
• Bronchiectasis

• Post-exertional malaise is one of the main symptoms of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).[5] PEM can be described as "a delayed and significant exacerbation of ME/CFS symptoms that always follows physical activity and often follows cognitive activity".[6]
• Orthostatic intolerance (OI) occurs in CFS. OI includes exercise intolerance as one of the main symptoms. It also includes fatigue, nausea, headaches, cognitive problems and visual disturbances as other less major symptoms.[7]

• Exercise intolerance is present in those with PCS however their intolerance to exercise may reduce over time.[8]
• Individuals with postconcussion syndrome may also experience a level of exercise intolerance, however there is little known comparatively about exercise intolerance in PCS patients.[9]

• Angina pectoris
• Heart failure: Exercise intolerance is a primary symptom of chronic diastolic heart failure.[10]
• Cardiac arrhythmia
• Aortic valve insufficiency
• Pulmonary artery hypertension: PAH has the following symptoms; dyspnea and fatigue, these systems consequently contribute to exercise intolerance.[11]
• 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.[12]
• Chronic heart failure

• Spinal muscular atrophy: symptoms include exercise intolerance, cognitive impairment and fatigue.[13]
• Rhabdomyolysis: a condition in which muscle degrades, releasing intracellular muscle content into the blood as reflected by elevated blood levels of creatine kinase.[14] Exercise tolerance is significantly compromised.[15]

• 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.[16]
• Abnormal thyroid function can cause hyperthyroid myopathy and hypothyroid myopathy by affecting myocardial oxygen function.[17] Both include symptoms of muscle fatigue and muscle pain, with dyspnea (shortness of breath) presenting in hyperthyroid myopathy.[18] Thyroxine (T4) deficiency leads to a reduced mitochondrial oxidative capacity, abnormal glycogenolysis and an insulin resistant state of the cell.[19] Hypothyroid myopathy includes Kocher-Debre-Semelaigne syndrome (childhood-onset) and Hoffmann syndrome (adult-onset).[20]

Metabolic myopathies are inherited inborn errors of metabolism that affect the ability of the muscle to produce ATP, either aerobically (cellular respiration) or anaerobically (glycolysis and lactic acid fermentation). The common symptom that they share is exercise intolerance, due to the low ATP reservoir within muscle cells. Depending on the enzymatic or transport protein defect, symptoms may show only upon exertion or both at rest and upon exertion. Metabolic myopathies are further categorized by the system that they affect: inborn errors of carbohydrate metabolism (including muscle GSDs), inborn errors of lipid metabolism (fatty acid metabolism disorder), inborn error of purine–pyrimidine metabolism (such as AMP deaminase deficiency), and those involving enzymes or transport proteins within the mitochondrion (mitochondrial myopathies and disorders of citric acid cycle and electron transport chain). (See metabolic myopathies for more details.)

• • Mitochondrial complex III: One of the metabolic myopathies, currently it is suggested that there are 27 different mutations identified in cytochrome b (mitochondrial complex III is one of those mutations). This mutation can often lead to skeletal muscle weakness and as a result exercise intolerance.[21]
  • A complex of Coenzyme Q10: One of the metabolic myopathies, Coenzyme Q10 deficiency includes the symptom of exertional fatigue.[22]
  • Skeletal muscle respiratory chain defect (electron transport chain [ETC]): A type of metabolic myopathy, this can result in severe exercise intolerance which is manifested by the following symptoms of skeletal muscle respiratory chain defect; muscle fatigue and lactic acidosis.[23]
  • Riboflavin-responsive exercise intolerance caused by mutations of the SLC25A32 gene
  • Glycogen storage disease type V, one of the metabolic myopathies, is caused by mutations of the gene encoding myophosphorylase.

Cytochrome b mutations can frequently cause isolated exercise intolerance and myopathy and in some cases multisystem disorders. The mitochondrial respiratory chain complex III catalyses electron transfer to cytochrome c. Complex III is embedded in the inner membrane of the mitochondria and consists of 11 subunits. Cytochrome b is encoded by the mitochondrial DNA which differs from all other subunits which are encoded in the nucleus. Cytochrome b plays a major part in the correct fabrication and function of complex III.

This mutation occurred in an 18-year-old man who had experienced exercise intolerance for most of his adolescence. Symptoms included extreme fatigue, nausea, a decline in physical activity ability and myalgia.

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.

A person who is not physically fit due to a sedentary lifestyle may find that vigorous exercise is unpleasant.

Certain conditions exist where exercise may be contraindicated or should be performed under the direction of an experienced and licensed medical professional acting within his or her scope of practice. These conditions include:

The above list does not include all potential contraindications or precautions to exercise. 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 unable to safely self-power.