Exercise intolerance in Glycogen Storage Disease Type III: Weakness or energy deficiency?

► Metabolism during exercise and exercise tolerance were examined in the patients. ► The peak oxidative capacity was abnormally low. ► Exercise intolerance with excessive fatigue was evident in the patients. ► However, a glucose infusion significantly improved exercise capacity. ► GSD type IIIa thus includes dynamic exercise-related symptoms of muscle fatigue. ► This is due to insufficient energy production in skeletal muscle during exercise.