Exercise and Spinal Muscular Atrophy
This short review article looks at studies from the past three years which investigated the effects of exercise on individuals with SMA and also refers to two less recent studies. There have been very few studies on this topic and there is no definitive conclusion as to the type or duration of exercise that should be recommended for individuals who have SMA. The purpose of this article is not to make specific recommendations of exercise routines, but to discuss the findings of studies that have investigated this subject.
The relationship between exercise and neuromuscular conditions has long been a debatable issue. In the past the advice given to individuals with neuromuscular conditions was to avoid or limit exercise to prevent damaging muscles. Recently it has been suggested that some exercise may be beneficial for some types of neuromuscular conditions.
Review of the last three years of studies into exercise and SMA
There are many difficulties in investigating SMA and the effects of exercise. SMA is considered a rare condition, and symptoms vary widely between different types of SMA; this means that the results of studies looking at SMA Type 2 may not necessarily be useful for people who have other types of SMA. Exercise is often more difficult for individuals with a neuromuscular condition; weakness, pain, fatigue and contractures make recruitment of individuals to studies harder. A lack of ability to walk and exercise may also contribute to weight gain, which in turn may make movement more difficult.
Broadly speaking, most types of exercise can be grouped into two categories: strength training – moving increasing weights (such as through lifting), and aerobic exercise – highly repetitive movements with no, or minimal weight added (such as swimming). It is unclear which type of exercise is most beneficial for neuromuscular conditions, and it is likely this will vary between different types of neuromuscular conditions.
Over the past three years, only two studies have been published which look specifically into SMA and exercise. One looks into strength training, and the other into aerobic exercise.
In 2012, Lewelt and colleagues1 from Utah University, USA, published a study which had investigated nine young people aged, on average, ten years old, who all had SMA Types 2 or 3. Each individual was checked beforehand to make sure they could perform the exercises according to the planned schedule. The study was looking at ‘Progressive resistance training’; an exercise plan performed at home which involves individuals pushing or pulling against weights in the form of weighted wrist bands which gradually get heavier. Children as young as five have used this exercise routine in other studies to increase muscle strength and lose weight. The exercises consisted of 45-60 minute sessions with a physiotherapist three times a week. Exercise days were spaced at least one day apart, with two sets of fifteen repetitions of the exercise carried out, and five minutes of break time in between. The young people started doing the same exercises without weights, then ankle and wrist weights were added once each individual managed to complete the two sets of exercises in a week. Over a twelve week period it was discovered that there was only a small improvement in muscle strength overall, particularly in individuals who already had significant muscle weakness. The authors did, however, find that there was a significant overall improvement in some of the measures of how well muscles do particular tasks that the physiotherapists asked the individuals to do. The authors of the study do point out that individuals may not notice this improvement as it was so small.
The study by Lewelt and colleagues shows positive results, but there are several drawbacks to the study: the small number of participants, the short period of time over which the study took place, and the lack of a group of young people to compare to (control group). Although the results are good, a bigger, longer study should take place to ensure that this type of exercise schedule would have the same effect reported in this study.
Madsen and colleagues from University of Copenhagen, Denmark, published a study in 20152 looking at six individuals with SMA Type 3, and compared these to nine individuals without SMA. Both groups rode special types of exercise bikes two to four times per week for twelve weeks. Sessions were thirty minutes long. Madsen and colleagues were interested in how much oxygen could be used by the body during exercise; in this study they refer to this measurement as ‘VO2 max’. This measurement is interested in how the body improves in taking in oxygen during exercise; if your breathing muscles are weak, as they might be in SMA Type 2, this would interfere with the results and you couldn’t be sure if the response was due to the exercise or improvement of breathing muscles. It is likely that individuals with SMA Type 3 were chosen to take part because they don’t get breathing muscle weakness until late in life, if at all. Madsen and colleagues showed a significant increase in how well individuals could exercise and take oxygen into the body during exercise but there was no change in individuals’ muscle strength or in their ability to perform tasks. A lot of the individuals with SMA also reported fatigue, but had no increase in blood test results that showed muscle damage. Overall the results of this study suggest that this form of exercise may provide some benefit to how much oxygen can be taken in to the body, but it was unclear how beneficial and noticeable this would be to individuals. Participants reported experiencing fatigue after the exercise, and this led to one individual leaving before the end of the study.
Other methods of exercise
One recent review by Anziska and colleagues3, which looks at exercise and its role in neuromuscular conditions, suggested that ‘submaximal aerobic training’ (doing aerobic exercise but not quite as hard as you possibly can) should be advised in conditions like SMA, as individuals are more likely to damage muscles if they are pushing themselves to the limit of their abilities. The authors also suggested that it may be better to focus on training specific groups of muscles, by choosing carefully which exercises to concentrate on; although the authors of this review don’t suggest which specific muscle groups to focus on in the case of SMA.
No recent studies have looked at hydrotherapy and water based exercise in SMA specifically. Hydrotherapy has historically been suggested to help to prevent contracture development, and has been beneficial to individuals with other neuromuscular conditions. One study was published in 19964, which looked at the response of individuals with SMA Type 2 and 3 to hydrotherapy. The authors suggested that there was some stabilisation of muscle strength, and even improved strength reported in some individuals. There was also a reported improvement in activities of daily living. In this study, individuals had bi-weekly hydrotherapy sessions which lasted between 30-45 minutes. The provision of hydrotherapy in the UK is very variable, and individuals may not have access to these therapies as frequently as the participants did in this study.
Another method which has been trialled in other, similar conditions is direct electrical stimulation of muscle groups. In the past, this therapy has not been shown to be successful over a reasonably long period (1 year) at improving measures of muscle function in children with SMA Type 2 or 35.
Over the past decade, guidance on exercise in SMA has changed, with more studies showing that there may be beneficial effects of different types of exercise. The studies over the past three years have added to our knowledge of how exercise can affect individuals with SMA but there is much that is not yet known. Studies so far haven’t been big enough and may suggest potential benefits which may not make a big enough difference to be noticeable to individuals.
There is probably enough evidence now, that exercise is helpful for individuals with SMA, but the jury is still out on what type of exercise is best, how long to exercise for, and how best to avoid fatigue or pain. One thing that all of the authors of the studies above agree on is that individuals with SMA should discuss their plans with a physician or physiotherapist before beginning an exercise routine.
1. Lewelt A, Krosschell KJ, Stoddard GJ, Weng C, Xue M, Marcus RL, et al. Resistance Strength Training Exercise in Children with Spinal Muscular Atrophy. Muscle & nerve. 2015 Jan 19. PubMed PMID: 25597614. Pubmed Central PMCID: Pmc4506899. Epub 2015/01/20. Eng.
2. Madsen KL, Hansen RS, Preisler N, Thogersen F, Berthelsen MP, Vissing J. Training improves oxidative capacity, but not function, in spinal muscular atrophy type III. Muscle & nerve. 2015 Aug;52(2):240-4. PubMed PMID: 25418505. Epub 2014/11/25. eng.
3. Anziska Y, Sternberg A. Exercise in neuromuscular disease. Muscle & nerve. 2013;48(1):3-20.
4. Cunha MCB, Oliveira ASB, Labronici RHDD, Gabbai AA. Spinal muscular atrophy type II (intermediary) and III (Kugelberg-Welander): evolution of 50 patients with physiotherapy and hydrotherapy in a swimming pool. Arquivos de Neuro-Psiquiatria. 1996;54:402-6.
5. Fehlings DL, Kirsch S, McComas A, Chipman M, Campbell K. Evaluation of therapeutic electrical stimulation to improve muscle strength and function in children with types II/III spinal muscular atrophy. Developmental medicine and child neurology. 2002 Nov;44(11):741-4. PubMed PMID: 12418614. Epub 2002/11/07. eng.