# Exercise as it relates to Disease/Benefits of physical exercise interventions for Myotonic Dystrophy patients

Myotonic Dystrophy is the most common form of Muscular Dystrophy. Characterized by wasting of the muscles and muscle weakness, Myotonic Dystrophy is a genetic disorder that affects approximately 1 in 8000 people worldwide. Myotonic Dystrophy differs from other forms of muscular dystrophies as it is associated with a number of other disorders including myotonia (delayed relaxation of muscles after contraction), endocrine changes , cataracts and heart conduction defects. There are two forms of myotonic dystrophy, including DM1 (type 1) and DM2 (type 2), both inherited but affecting a different gene.

### Symptoms.

Symptoms may occur from birth onwards but as the disease is slow progressing, it isn't usually until adulthood when signs become present. One of the first signs of myotonic dystrophy is muscle stiffness caused from myotonia. Other symptoms may include heart problems, breathing troubles, difficulty swallowing, excessive tiredness and digestive problems. Hormonal problems are also often related to the disease and may include reproductive abnormalities, diabetes and thyroid dysfunction .

### Cause

DM1 is caused by a genetic mutation of the DMPK gene found on chromosome 19. The DMPK gene contains an area where the three building blocks of DNA, CTG and genetic material are repeated. A normal gene will contain 5-35 repeats CTC repeats but an individual with Myotonic Dystrophy will have anywhere from 50 to 10,000 depending on the severity of the case.
DM2 is caused by a repeat of cytosine-cytosine-thymine-guanosine (CCTG) in the ZNF9 gene on chromosome 3. In DM2 the number of repeats is much larger, ranging from 75 to more than 11,000 but unlike in DM1 the number of repeats does not affect the severity of the disease.

## The Effects of Resistance Training

* Even though research surrounding DM is minimal, there is evidence to suggest a patient with DM can benefit from resistance training with no side effects.
* A study from the Departments of Neurology and Radiation Physics at the Karolinska Hospital in Stockholm, Sweden, illustrated that although resistance training will have no effect on isokinetic concentric and eccentric torque values, it can increase the muscular strength in patients suffering from myotonic dystrophy.
* The same study found not only can resistance training increase muscular strength, it can also prevent atrophy and in some cases even promote hypertrophy in type 1 fibers.
* Although their is sufficient evidence supporting the benefits of resistance training, some findings are controversial. It seems as if resistance training has beneficial short term effects but only if performed at near maximal levels. The long term effects are yet to be studied and their is cause for concern in patients who suffer a rapidly progressing form of the disease.
* Resistance programs should only be used in the early stages of the disease, when their is still a large amount of trainable muscle fibers.
* An increase in muscular strength and size in patients with DM may lead to improvement of symptoms including muscular pain, myotonia and poor balance, allowing patients to move more freely and improve their overall wellbeing.
* Although high intensity resistance training may benefit some patients, depending on the severity of the disease some patients may have no training potential.

## High Intensity Resistance Training

to be beneficial, training needs to be of high intensity. High intensity resistance training involves the combination of both training for strength and hypertrophy. The following table gives a basic guideline on training protocol.
| Rep Range | Percent of 1 Rep Max | Muscular Changes |
| 1-5 Reps | 85-100% | Strength |
| 9-12 Reps | 70-75% | Hypertrophy |
A high intensity resistance training program involves using this guideline, targeting each muscle group twice a week.

## Further reading

Myotonic dystrophy: Prognosis and managementThe Effects of High Resistance Training in Myotonic Dystrophy patients Effects of High Intensity Resistance Training in Patients with Myotonic Dystrophy Scand J Rehab Med 31: 9–16, 1999

## References

* ↑ Muscular Dystrophy Australia. 2013. MYOTONIC DYSTROPHY . [ONLINE] Available at: http://www.mda.org.au/disorders/dystrophies/myt.asp.
* ↑ Genetic Home Reference. 2010. What is myotonic dystrophy?. [ONLINE] Available at: http://ghr.nlm.nih.gov/condition/myotonic-dystrophy. [Accessed 29 September 14].
* ↑ Muscular Dystrophy Australia. 2013. MYOTONIC DYSTROPHY . [ONLINE] Available at: http://www.mda.org.au/disorders/dystrophies/myt.asp.
* ↑ Up to Date . 2013. Myotonic dystrophy: Prognosis and management. Available at: http://www.uptodate.com/contents/myotonic-dystrophy-prognosis-and-management.
* ↑ Day JW, Ricker K, Jacobsen JF, et al. (February 2003). "Myotonic dystrophy type 2: molecular, diagnostic and clinical spectrum". Neurology 60 (4): 657–64
* ↑ Tollba¨ck, A., Eriksson, S., Wredenberg, A., Jenner, G., Vargas, R., Borg, K., and Ansved, T. (1999) EFFECTS OF HIGH RESISTANCE TRAINING IN PATIENTS WITH MYOTONIC DYSTROPHY 31: 9–16
* ↑ Wiles CM, Busse ME, Sampson CM, et al. Falls and stumbles in myotonic dystrophy. J Neurol Neurosurg Psychiatry 2006; 77:393.
* ↑ 18.Voet NB, van der Kooi EL, Riphagen II, et al. Strength training and aerobic exercise training for muscle disease. Cochrane Database Syst Rev 2013; 7:CD003907.