For many of us who have no difficulties in walking, the privilege of being able to ambulate freely rarely registers as a privilege at all; it is simply a fact of life, neither to be celebrated nor scorned. However, for patients with diseases such as Duchenne muscular dystrophy (DMD), in which the loss of ambulation is a sad fact of life, the ability to move about freely and independently is a gift that is exceedingly cherished. 

There has been much movement in the research world with regards to using gene therapy to treat DMD; we know the genetic defect that causes it, so it makes perfect sense to target the heart of the problem. However, the reality of the matter is that gene therapy is (still) a budding field of medical research — the hype surrounding it has largely remained unvalidated. 

In view of this, physicians are turning their attention to the age-old prescription for improving mobility: physiotherapy and exercise. Physiotherapy and exercise have been a mainstay of the recovery process for patients who have experienced a stroke or been in a vehicle accident. The logic of this practice is obvious: train and build on what has weakened, and what is weakened will eventually become strong again. 


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Nevertheless, physiotherapy and exercise has suffered from a poor reputation among some members of the medical community, simply because its progress in improving mobility has been viewed as too slow, almost arcane. Many physicians would rather have at their disposal a wonder drug that improves mobility without the hassle of months or years of physiotherapy. 

In the case of DMD, in which the eventual loss of mobility is an inevitable fact of the disease, physicians would be wise to give greater weight to this legitimate form of therapy that incurs very little costs and risks. Let’s examine the case for physiotherapy and exercise for patients with DMD. 

Small Steps, Big Change 

In Muscle & Nerve, Lott and colleagues conducted a study of the value of walking activities in a cohort of boys with DMD. 

“Step activity and community ambulation data have recently been recognized as being both valid and sensitive real-world measures that can be of utility as outcome measures in clinical trials for Duchenne muscular dystrophy,” they wrote. “In unaffected individuals, walking and step activity are important variables for assessing fitness and overall health.” 

For their study, they recruited ambulatory boys with DMD as well as healthy individuals for control. The boys with DMD recruited must be able to walk 100 m independently, as well as climb 4 steps. Participants were asked to wear an activity monitor (accelerometer) for all walking hours for 7 consecutive days. 

To assess their functional ability, they were asked to perform 3 functional tasks: 10-meter walk, ascending 4 stairs, the 6-minute walk test, and rising from the floor (supine up). In addition, the strength of their isometric peak torque of the knee extensor and plantar flexor muscle groups of the right leg were assessed using a dynamometer. 

The results demonstrated that the 6-minute walk test was a sensitive indicator of functional mobility, and that step activity was positively correlated with walking distance. In addition, there was a significant relationship between steps per day and 10-meter walk results and knee extensor strength. 

On the key takeaway of this study, the researchers wrote, “Step activity for DMD is related to and predictive of functional declines, which may be useful for clinical trials.” 

The findings of this study echo that of one conducted by Lott and colleagues on the safety, feasibility, and efficacy of strengthening exercises in boys with DMD. This study, also published in Muscle & Nerve, sought to determine the impact, if any, of the role of strengthening exercises on the ambulatory strength and function of boys with DMD. 

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The first part of the study involved participants exercising for 3 sessions at an intensity of 30% and 50% baseline maximal volitional contraction (MVC). The second part of the study involved participants performing the prescribed exercise training program for 6 weeks at 50% MVC. All the participants (except for 1 who chose to opt out) then performed 12 weeks of in-home strengthening exercises of moderate intensity. 

The results demonstrated that 12 weeks of training produced significant improvements in muscle strength and function. In addition, the exercise program was safe (no muscle damage was recorded), even when conducted at home. 

“Being able to maintain and/or improve leg strength and walking ability may be the most important rehabilitation goals for ambulatory children with DMD,” Lott et al wrote. “Boys who completed the exercise program had significantly greater leg strength and improved ability to descend stairs.”

Back to Basics 

In light of the evidence surrounding physiotherapy and exercise in patients with DMD, physicians should see these tools as an integral part of the treatment process. Patients and their families should be encouraged that the persistent commitment to an exercise program can slow down disease progression and preserve ambulation for longer — perhaps even long enough for new and more potent therapeutics to be introduced. 

References

Lott DJ, Taivassalo T, Senesac CR, et al. Walking activity in a large cohort of boys with Duchenne muscular dystrophyMuscle Nerve. Published online November 14, 2020. doi:10.1002/mus.27119

Lott DJ, Taivassalo T, Cooke KD, et al. Safety, feasibility, and efficacy of strengthening exercise in Duchenne muscular dystrophyMuscle Nerve. Published online December 8, 2020. doi:10.1002/mus.27137