A 37-year-old man reported exercise/activity-related muscle pain and fatigue from early childhood. His symptoms were labelled as "growing pains" by different medical professionals, and he was often called "a lazy child". He had difficulties to keep up with his friends and family when walking. He reported physical education classes and school games as bad experiences. Throughout his life he continued to avoid activities that provoked muscle symptoms. Despite not being aware of the second wind phenomenon, he used strategies such as slowing down or stopping and restarting when symptoms eased off. He reported pain in his muscles within a few minutes or sometimes seconds of initiating physical activity, particularly noticeable when walking upstairs, walking up hills, and carrying shopping bags. He had a previous medical history of four episodes of myoglobinuria triggered by playing football or lifting heavy items. He was diagnosed with McArdle disease at the age of 20 years based on an abnormal muscle biopsy. He was later confirmed to have a homozygous mutation (p.Gln567Pro) in PYGM.
Physical examination at the age of 29 revealed rounded shoulders with hypertrophy of deltoid, biceps, and calf muscles. He had significantly wasted pectoralis muscles and bilateral scapular winging, but muscle strength was normal. When diagnosed he had been advised to complete at least three sessions of walking 30 minutes per week. However, he did not change his physical activity levels and did not report changes in his quality of life.
After graduation he started his first office job. He became more sedentary, his weight increased, and symptoms worsened. He reported difficulties in walking short distances. Everyday tasks such as vacuuming and cutting grass became more difficult.
He joined a local gym, where he has been a member for approximately 9 years. Initially exercises included walking on a treadmill and cycling on a stationary bike. He tried resistance machines but was not confident in using them. Four years ago, he approached a personal trainer, who took the time to learn about his metabolic condition. He suggested that weight lifting could be safe and effective if using principles of strength training after considering the pathophysiology of McArdle disease.
Initial phase of training consisted of gentle 15-20 minutes aerobic exercise to warm up and get into second wind (walking on a treadmill, cycling on a stationary bike) followed by learning strengthening exercise techniques using body weight and very light weights. Training intensity gradually progressed towards mobility movements (e.g., Turkish get ups, walking lunges), increasing resistance as well as adding high intensity interval training (HIIT) protocol on the rowing ergometer at the end of the session. Strength exercises were mainly performed using compound movements with free weights rather than resistance machines. Currently, he performs a 15-20 minute aerobic warm up. He performs 1-5 repetitions with 2-5 minutes rest in between sets depending on the % of one repetition max (1RM). He also tried a different protocol involving four repetitions with 30 seconds rest followed by another four repetitions of the same weight. He has been doing two sessions with the personal trainer and two sessions on his own each week. When without the trainer, he only performs exercises he is familiar with.
Over the past four years of strength training his weight increased from 65kg to 70kg; body composition dramatically changed by significantly increasing muscle bulk, in particular of his quadriceps, gluteus, pectoralis, deltoids, and trapezius muscles. His waist remained the same; collar size increased from size 14.5 to 15.5/16.0. He had to purchase new clothing due to dramatic change in body composition. Importantly, his muscle strength increased significantly as described in Table 1.
He also performed other exercises, including lateral pull downs, TRX rows, TRX pull-ups, body weight pull-ups from jumps, Olympic lifting movements, box jumps, medium height approx. 45cm, and pistol squats.
He has never experienced any McArdle symptoms during or after strength training and has not had myoglobinuria following his gym sessions. His serum CK level varied as expected in McArdle disease, with a decreasing trend (average CK in 2011-2014: 3,006 IU/L, average in 2015-2017: 1,029 IU/L; last measured in July 2017: 941 IU/L; reference range: up to 240 IU/L). Improvement in McArdle symptoms was described as a delayed onset of skeletal muscle symptoms, which now occurs at much higher physical activity intensity. Reaching the second wind is more efficient. In general, his quality of life improved significantly. He has been eating high protein diet with a bigger portion of carbohydrates on training days. He autonomously chose not to take any supplements containing glucose pre- or intra-training sessions.