McArdle disease is a metabolic myopathy mainly characterised by symptom onset during physical activities or isometric muscle contraction. Resistance (also termed strength) training is a type of physical exercise focusing on the use of resistance (e.g., lifting weights) to induce muscular contraction, which builds muscle mass and strength. Historically people with McArdle disease were advised to avoid resistance exercises and any other form of physical activity involving high mechanical loads such as prolonged isometric contraction. Paradoxically, a clinical trial exploring the benefits of strength training in this patient population was published. The theory supporting strength training relied on the use of the ATP molecule and the creatine phosphate (ATP-phosphocreatine system) as energy sources for skeletal muscles. Here, the authors present two people with McArdle disease who have been performing resistance training without experiencing McArdle-related injuries. Both showed positive results, such as increased strength, muscle hypertrophy, fat loss, and attenuation of McArdle symptoms, which substantially diminished after starting this form of training. They provide further safety evidence of this type of exercise in people with McArdle disease and emphasise the importance of using a specific protocol developed for people affected by this condition.
