The Effects Of Exercise On Individuals With Muscular Dystrophy 

Muscular dystrophy (MD) is an inherited disease that causes a mutation in the dystrophin protein found in the muscles. This disease breaks down skeletal muscles causing them to weaken and waste away over time. MD is usually diagnosed in early childhood, and is seen more often in males than females. There are different types that can affect the body; the most common being Duchenne (DMD) and Becker (BMD). Both are inherited through the X chromosome, but Duchenne is more intense and progressive. This diagnoses has a shorter lifespan and typically the child is in a wheelchair by age ten to twelve. In figure one, the data shows the percentage of males at each age that use a wheelchair. Becker has a slower progression, but the end result is the same. Another diagnoses is limb girdle (LGMD). This diagnoses is only about 25-50% inherited, and affects the muscles of the limbs; including the deltoids, pectoralis, quadriceps and hip flexors. When an individual has MD, they have high creatine kinase enzymes due to the excessive muscle breakdown, a test that confirms MD. Unfortunately, there is no cure for MD. However; it has been proven that engaging in aerobic and resistance training can improve the independency of an individual that lives with this disease. Table one shows the number of males who are diagnosed with MD. (Center for Disease Control and Prevention, 2019)

Review of Literature

Anti-gravity treadmill. Bethelsen et al. , 2014 did a study on 8 individuals with Becker and limb girdle muscular dystrophy. The purpose was to test if individuals who were too weak to participate in aerobic training alone could benefit from aerobic and strength training. The study was done to see if using an antigravity treadmill would improve walking capacity and postural balance in patients with muscular dystrophy. Anti-gravity treadmills allow patients to control the pressure inside the chamber; which can reduce the bodyweight of the individual who is using it to below 30% of their normal body weight. This is an effective machine for individuals who have muscular dystrophy or another degenerative disease. Eight individuals, between the ages of 32-40, went through a ten-week training program. Five men had Becker muscular dystrophy (BMD), and one man and two women had Limb Girdle muscular dystrophy (LGMD). All of the patients had a sedentary lifestyle to be included in the study. The ten-week training program consisted of one-on-one training with a coach. They trained three times per week for 40 minutes each session. Aerobic and strength training was divided equally amongst these days. For aerobic training, they did interval training; which consisted of 1-2 minutes of active exercise and a one-minute rest. The workload was at about 50% of their bodyweight support, but intensity was individualized depending on what the person could handle. They did walking, jogging, running and high knee lift exercises. For resistance training, they did weight support inside of the anti-gravity treadmill. The treadmill was at a standstill, and they performed movements that worked major muscle groups of the lower limbs; including squats, lunges, and calf-raises. For the squats and lunges, they did three sets of 12 repetitions. For calf-raises, they did three sets of 15-20 repetitions. The 6-minute walk test (6MWT) and the dynamic postural balance test was conducted before; both at the half way mark and at the end of their training program. Their plasma creatine kinase (CK) levels and their steady state heart rate (HR) were also tested. The results supported their hypothesis in that training does improve walking capacity and postural balance. The 6MWT had an 8-10 % distance improvement (see figure 2). The dynamic postural balance test had a 13-17% improvement (see figure 3). Their steady state heart rate had a 10-14% drop during exercise, which is beneficial to their cardiovascular system. Their plasma CK levels had no change, which is also beneficial because in individuals with muscular dystrophy; their plasma CK levels remain high due to continuous muscular breakdown. With no change in those levels, it proved the benefit of aerobic and resistance training on individuals who were too weak to perform those movements on their own, as well as the fact that it actually does not progress muscular damage.

Aquatic Exercises. Hakan Atamturk and Arda Atamturk (2018) took a different approach, and studied the therapeutic effects of aquatic exercises on a boy with Duchenne muscular dystrophy. All individuals benefit from physical activity socially, psychologically, and physically; so it is a precise way to test the needs of an individual. This study was done to see how aquatic training would help a boy both psychologically as well as physically; ultimately improving his quality of life. Swimming is a perfect form of exercise because is seen as a recreational activity and is not as demanding on the muscles and joints. A lot of DMD patients are told by their doctors to participate in swimming in hopes of strengthening their muscles without further breaking them down. This study was done on one six-year-old boy who was diagnosed with DMD when he was three. The training was set up for eight weeks, with 45 minute sessions two days a week. Each session consisted of a warm up, respiratory breathing exercises, movements that engaged large muscle groups, and a cool down. The set up was more similar to a game than a training program; not exceeding the difficulty level that a six-year-old could handle. During the exercises he was allowed to take any break he needed which lasted two minutes each time. The results stated that this training program benefited the individual in regards of socialization, relaxation, quality of life, and his self-perception.

Protein-carbohydrate supplements. Not only do both aerobic resistance training and aquatic exercises benefit individuals with muscular dystrophy, but so do protein-carbohydrate supplements after endurance training. Andersen et al. , 2014 did a study to see if protein-carbohydrate supplements improve muscle protein balance after endurance training in muscular dystrophy patients. It is widely known that after training it is beneficial to consume protein and carbohydrates to replenish the muscle proteins and glycogen stores. This study tested the muscle protein balance before, during, and after exercise; as well as the effect of protein-carbohydrate (PC) supplementation. The study involved 17 patients; including seven women and ten men between ages 22-44. Seven patients had myotonic dystrophy type 1 (DM1), six had facioscapulohumeral muscular dystrophy, two had BMD, and two patients had LGMD. To test muscle protein balance; exercise and testing was done on one leg. A maximal exercise test was done for single legs; increasing intensity every minute until exhaustion. This test was used to get a 70% maximal oxygen uptake (VO2peak). Aerobic training was done on a single-leg bike ergometer at 60 kicks per minute. The Borg scale was used to test exertion every other minute during testing. The individuals had to come in for two testing days. One day there was no PC supplement, and on the second day there was. The exercise was the same on each day, and three days before each test they consumed a heavy carbohydrate diet. Each test that was conducted in the morning required fasting. On testing day one, two hours after the stable isotope infusion, the subject kicked for 40 minutes at their 70% VO2peak. On testing day two, the same procedure was done, but five minutes after the kicking the PC supplementation drink was consumed (see figure 4). The drink was “40 grams 50/50 ProMax powder dissolved in 0. 4 liter skim milk, thus containing 32. 8g protein, 36. 6g carbohydrate, 1. 4g fat and 1238kJ in total” (Andersen et al. , 2014, R124). The results indicated that leg phenylalanine uptake was the same at both rest and post exercise; but there was an increase in leg phenylalanine for the non-supplementation day during recovery. This was not present on testing day with the PC supplementation, meaning that a protein-carbohydrate supplementation reduced muscle protein breakdown in the individuals with muscular dystrophy.

References

1. Andersen, G. , Orngreen, M. C. , Preisler, N. , Jeppesen, T. D. , Krag, T. O. , Hauerslev, S. , et al. , (2014). Protein-carbohydrate Supplements Improve Muscle Protein Balance in Muscular Dystrophy Patients After Endurance Exercise: a placebo-controlled crossover study. American Journal of Physiology, 308(2), R123-130. DOI: 10. 1152/ajpregu. 00321. 2014
2. Atamturk, H. , & Atamturk. A. , (2018). Therapeutic Effects of Aquatic Exercises on a Boy with Duchenne Muscular Dystrophy. Journal of Exercise Rehabilitation, 14(5), 877-882. DOI: 10. 12965/jer. 1836408. 204
3. Berthelson, M. P. , Husu, E. , Christensen, S. B. , Prahm, K. P. , Vissing, J. , & Jensen, B. R. , (2014). Anti-gravity Training Improves Walking Capacity and Postural Balance in Patients with Muscular Dystrophy. Science Direct, 24(6), 492-498. DOI: 10. 1016/j. nmd. 2014. 03. 001
4. Center for Disease Control and Prevention (2019). Muscular Dystrophy. Retrieved October 16, 2009, from: https://www. cdc. gov/ncbddd/musculardystrophy/data. html