McArdle disease is a rare disease of muscle metabolism. Affected people cannot use a starch-like substance called glycogen which is stored in muscle and used for energy at the beginning of activity and during strenuous exercise. The effects of the condition are fatigue and cramping within a few minutes of starting an activity, which can potentially lead to acute muscle damage. After about seven or eight minutes of exercise the muscle can start to use alternative sources of energy from fats and sugars supplied from the liver and so the symptoms ease. This phenomenon is called the 'second wind'. In healthy people, aerobic training is known to improve the ability of muscle to burn fats for energy during exercise. In theory then, aerobic training could be beneficial to people with McArdle disease, as their muscles might be trained to use fats earlier and more efficiently during exercise. The purpose of this review was to identify any randomised controlled trials of aerobic training and assess its effects in people with McArdle disease. There were no randomised controlled trials of aerobic training in people with McArdle disease. There were, however, three small uncontrolled studies (the largest included nine participants). The studies showed that it is possible for people with McArdle disease to undergo exercise training and there were no harmful effects. Whether or not training is beneficial for people with McArdle disease needs further investigation, with randomised controlled trials including larger numbers of people with the condition.