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Exercise as it relates to Disease/Exercising with muscular dystrophy

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Comparison of normal muscle tissue and muscle tissue affected by muscular dystrophy

What is muscular dystrophy (MD)?

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Muscular dystrophy is a progressive disorder where muscle function is gradually lost.[1][2] It is an inherited disease where there are abnormalities in the X-linked gene[3] leaving a deficiency of the muscle protein dystrophin.[4][5] Dystrophin plays a vital role in the sarcolemma membrane of the muscle fibres by protecting the muscle fibres from being damaged while the body is under mechanical stress.[6]

With over 30 different categories of muscular dystrophies, all can be characterised by wasting and weakness.[2] Despite the numerous categories, the majority of the muscular dystrophy types have overlying medical measures, generally allowing a more simple diagnosis and easier treatment.[7][8] Major forms of MD include:

Forms Differentiating factor
Myotonic Men and women both affected, after mechanical stress muscles may experience period of spasms or stiffening [9]
Duchenne Most known in children appear between 2 and 6 years old, affecting only males. Muscle weakens and decreases in size. Leads to wheelchair dependency early years. Limb deformities and some cognitive impairment[9]
Becker Milder. Symptoms later in life and with slower progression. Only affects males [9]
Limb-Girdle Males and females, originates in hips and develops to shoulders, arms, and legs, walking becomes challenging.[9]
Facioscapulohumeral Face, shoulder blade, upper arm bone. Advancement is slow. Short periods of rapid deterioration and weakness. Mild to completely disabling.[9]
Congenital Present at birth, females and males, muscle weakness and sever and early contractures. Abnormalities in brain and often seizures in Fukuyama cogenital MD [9]
Oculopharyngeal Eye and throat, later years of life (40's+), slow progression with weakness in the muscles of the eye and face leading to swallowing difficulties, pelvic and shoulder weaknesses later prevalent [9]
Distal Men and women, distal muscles, less severe, slow progression, affects fewer muscles than other dystrophies [9]
Emery-Dreifuss Rare form, only males, childhood to early teens,shoulders, upper arms and lower legs, life-threatening heart problems,muscle shortening, spread across body [9]

Epidemiology

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Muscular dystrophy generally affects younger people which could be the reason why patients generally have a shorter lifespan, along with other complications.[1][2] Though recently due to interventions, life expectancy is increasing.[8] With the increasing life expectancy of this symptomatic disease, new symptoms are becoming identified.[8] prevalence of this disease is around 1 in 17000 live births, with 1 in 4200 life-born boys being affected by Duchenne muscular dystrophy (DMD) specifically. 20-40% of young boys affected by DMD are found to lose their ability to walk by fractures in the lower body. .[1] Individuals with MD generally find many tasks challenging, including simple daily activities like walking and working; however, without exercise, patients may progress to physical deconditioning which may further their challenge for everyday activities.[1][7]

Exercise prescription: Aerobic vs. resistance exercise

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Although many muscular dystrophy patients are fearful of exercising with their condition, there is evidence that exercising with muscular dystrophy can have some positive benefit.[5][7][8] Benefits include, increasing muscle and cardiorespiratory function as well as slowing atrophy, which all affects daily activities and overall quality of life [8] With aerobic exercises being encouraged, there has been evidence that shows that resistance training my also being beneficial and harmless.[7]

Exercise type Frequency Duration Intensity Type
Resistance 2–3 days/week [7] No more than 60 minutes[7] 1 set of 8–10 exercises, 8–12 repetitions. 45–50% 1RM (rep max) Frail: 10-15 repetitions with lower resistance [7] Specific to severity [7]
Aerobic 3–5 days/week[7] 20–60 minutes continuously or 10-minute stints [7] 55–90% maximal heart rate [7] Larger muscle group activities, rhythmic [7]

Aerobic exercise is shown to to have a positive effect towards muscle strength and fatigue.[5][8] Endurance was also shown improve with dynamic exercise.[7] Resistance programs should be greatly specific to the individual, which needs to take into account the type of muscular dystrophy and the severity of their disease.[8] Individuals should avoid heavy resistance and eccentric training to ensure muscles do not undergo intense mechanical stress.[5] Exercises should be altered between upper and lower body exercise for ideal benefits. In both aerobic and resistance exercise, programs should be done with caution using supervision and aids to ensure safety.[7][8]

Exercise can also be undertaken for patients that are already wheelchair-dependent, which can give benefits to the wellbeing of the individual. These exercises may include passive exercises that are assisted from either supervisors or machines.[8] Training intensity differs for individuals in wheelchairs and should be based on rate of perceived exertion.[8]

MD cannot be stopped, only slowed; therefore it is vital to this disease to aim towards maintaining independence and delaying the loss of functional capacities.[2][8] Saying this, MD patients that do not undertaken exercise may find themselves with other complications such as chronic deconditioning and cardiovascular health risks.[1][8] An early decrease in physical activity can greatly enhance this deconditioning and loss of muscle function leading to faster onset of wheelchair dependency, therefore exercise should be readily initiated at the onset of MD when trainable muscle tissues are still present.[5]

Further reading

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References

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  1. ↑ a b c d e Becker's Muscular Dystrophy. Hartree, Dr Naomi. s.l. : patient.co.uk, 2013, Vol. 23.
  2. ↑ a b c d Efficacy of Muscle Exercise in Patients with Muscular Dystrophy: A Systematic Review Showing a Missed Opportunity to Improve Outcomes. Silvia Gianola, Valentina Pecoraro, Simone Lambiase, Robertp Gatti, Giuseppe Banfi, Lorenzo Moja. 6, s.l. : PLoS ONE , 2013, Vol. 8.
  3. ↑ X-linked gene
  4. ↑ dystrophin
  5. ↑ a b c d e Muscle training in muscular dystrophies. Ansved, T. 2001, Acta Physiol Scand, pp. 359–366.
  6. ↑ Local restoration of dystrophin expression with the morpholino oligomer AVI-4658 in Duchenne muscular dystrophy: a single-blind, placebo-controlled, dose-escalation, proof-of-concept study. Maria Kinali*, Virginia Arechavala-Gomeza*, Lucy Feng, Sebahattin Cirak, David Hunt, Carl Adkin, Michela Guglieri, Emma Ashton, Stephen Abbs,. 2009.
  7. ↑ a b c d e f g h i j k l m n Strength training and aerobic exercise training for muscle disease. Voet NBM, van der Kooi EL, Riphagen II, Lindeman E, van Engelen BGM, Geurts ACH. 1, s.l. : JohnWiley & Sons, Ltd., 2010.
  8. ↑ a b c d e f g h i j k l Rehabilitation in Muscular Dystrohies: Changing Approach. Imelda J.M. de Groot, Nicoline B.N. Voet, Merel Janse and Lenie van den Engle-Hoek. s.l. : InTech, 2012.
  9. ↑ a b c d e f g h i Understanding Muscular Dystrophy - the Basics. Benaroch, Roy. s.l. : WebMD, 2013.
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