At the start of exercise, when pain occurs, slow right down or stop until the pain has subsided, then try again. Sustained or severe exercise, such as weight lifting, or sprinting, must be avoided because of the high risk of muscle damage. Continuing to exercise in the presence of severe pain will also result in muscle damage and myoglobinuria, which will in turn increase the risk of acute renal failure.
Many different diets and supplements have been tested in McArdle disease such as high protein diet, vitamin B6 and creatine supplements, as yet there is insufficient evidence to suggest that any of these benefit people with McArdle disease.
There is some evidence to suggest that a sugary drink prior to planned exercise might help. This however, needs to be balanced against excessive weight gain, which should be avoided at all cost. Carrying increased weight will lower your body’s aerobic threshold and make exercise more difficult.
Keeping aerobically fit is the best way to condition McArdle muscles to improve performance and improve quality of life.
What happens if myoglobinuria occurs?
Most people with McArdle disease will develop myoglobinuria at some time in their lives. Myoglobinuria is a dark discolouration of the urine from a red- brown colour (mild) to a brown-black colour (severe). This is a warning sign for acute renal failure, which can occur if severe muscle damage has occurred. If this happens the kidneys stop producing urine because the draining tubules become blocked with the products of muscle breakdown.
If the episode of pain and contracture was not too severe myoglobinuria will be transient and lighter in colour. After more severe episodes the muscles may be swollen and tender and there may be flu like symptoms.
Minor symptoms are managed by increasing fluid intake to maintain a good urine output. More severe episodes will require an admission to hospital for intravenous fluids and if kidney failure occurs, a period of dialysis may be required.
Kidney failure is almost always reversible, but expert treatment is required immediately to prevent complications during the acute stage. It is, therefore, very important to seek medical help early should any of these symptoms occur.
Are there any other precautions?
There is a reported risk of acute muscle damage, with certain general anaesthetics (usually muscle relaxants and inhaled anaesthetics), although in practice problems appear to be very rare. The anaesthetist should be made aware of the diagnosis of McArdle disease, and may choose to avoid certain anaesthetic agents.
Tourniquets should not be used during operative procedures in patients with McArdle disease.
Affected women do not seem to be disadvantaged by pregnancy or childbirth. A natural childbirth is a realistic possibility for women with McArdle disease.