Exercise and Sports for Children with Neuromuscular Disease

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Exercise and Sports for Children with Neuromuscular Disease.

http://disability.ucdavis.edu/report_retrieve.php?Report=0007

By D. Kilmer, MD, and Craig M. Mc, MD.

Neuromuscular diseases (NMD) involve the anterior horn cell,

peripheral nerve, or muscle. They are uncommon causes of physical

impairment and disability in children. Because of this, many

physicians and physical educators have a poor understanding of

either the beneficial or detrimental effects of exercise in these

children. Excessive caution in the past has too often led to an

isolated, sedentary lifestyle. This caution has little scientific

support. However, those who deal with children with NMD need to be

aware of functional limitations so that expectations remain

appropriate.

Exercise Pathophysiology in NMD.

The ultimate cause of physical impairment in NMD is loss of normally

functioning muscle fibers. Thirty to fifty percent of muscle tissue

is lost before clinical weakness is appreciated, although exercise

performance may be compromised at a lower percentage of loss. In the

later stages of Duchenne Muscular Dystrophy (DMD) and Spinal

Muscular Atrophy (SMA), pulmonary or cardiac involvement become

additional factors which may influence exercise performance.

A major concern with exercise in individuals with NMD is overwork

weakness. Overwork weakness was first suggested in DMD by muscle

histologic examination, demonstrating that most degeneration occurs

in muscles typically used during sustained physical activity. Muscle

enzymes, used as a marker of muscle breakdown, were reduced by

bedrest in dystrophic patients and elevated to a greater degree than

normal controls after a vigorous strengthening program.

Exercise: Traditionally, high resistance exercise has been

discouraged in NMD due to fears of overworking the weakened muscle.

However, a survey of the research literature indicates studies with

results ranging from no untoward effects to beneficial effects, with

slowly progressive NMDs obtaining better results than DMDs. Stronger

muscles appear to strengthen more than very weak ones. Thus,

starting an exercise regimen early in the disease when muscle fiber

degeneration and weakness are minimal is generally recommended.

Measurement of exercise capacity is feasible in children and

adolescents with NMD if they are able to climb stairs with the aid

of a railing. In the absence of significant cardiac involvement,

oxygen delivery to the muscles should be intact in NMD, with the

exception of DMD. The limitation appears to be in oxygen uptake at

the muscle cell level, which is proportional to the loss of active

muscle tissue. Likewise, cardiac output seems to increase

proportionally to increased O2 consumption during exercise in

muscular dystrophies, as in normal individuals. Little work has been

done on the response of diseased muscle to endurance exercise. One

study showed that adaptations to endurance exercise in NMD may not

differ from that of normal individuals.

Respiratory Exercise: Several studies have indicated that

respiratory muscle training in NMD either improves or maintains

pulmonary function. While respiratory exercise training may have an

impact on respiratory endurance, there is no evidence that the

progressive course of restrictive lung disease in DMD can be delayed

with an exercise program. Similar to skeletal muscle training, we

would predict less improvement in patients with more advanced NMD. A

cautious approach seems warranted in the later stages of respiratory

weakness, since vigorous training may add to the work of breathing

in individuals with limited respiratory reserve.

Contractures: Muscle imbalance leading to contracture may be an

important factor in limiting performance. This is primarily a

concern in children with DMD, although children with early onset SMA

may also have significant contractures. Muscle shortened by

contracture develops less maximal tension and fatigues more rapidly

due to effects on the normal length-tension relationship of skeletal

muscle. Contractures may also contribute to the increased metabolic

costs of task performance due to activation of muscle groups not

usually needed.

General Exercise Precautions and Recommendations: Based on available

data, we recommend submaximal strengthening exercises for post-

pubertal and adult patients with slowly progressive NMD. Because

children normally increase strength more through the myogenic

(protein synthesis and hypertrophy) component of strength rather

than through the neurogenic (improved recruitment of motor units),

the response of growing diseased muscle to resistance training is

unknown. We feel that children should not focus on formal weight-

lifting programs.

Although the incidence and risk of overuse weakness are still

unclear, children with NMD should avoid exhaustive exercise, and

rest periods are encouraged. As a rule, if the child feels fatigued

or weak on the day following an exercise bout, the workload was

probably excessive. Occasionally the most deconditioned children

require a supervised exercise program to obtain a fitness level that

would allow participation in sports and games. In this situation, we

follow the general goal of 20-30 minutes of aerobic exercise 3 days

per week, monitoring for excessive fatigue or increased weakness.

If the child can participate in exercise for 10-15 minutes without

stopping, we would prefer exercise for enjoyment and socialization

rather than in a strictly supervised program. Choices of

recreational activity should provide a positive experience, be

sufficiently challenging, and offer some opportunity for success.

Potential Benefits of Exercise in Children with NMD: Although direct

benefits of exercise have not scientifically been proven, the

empirical benefits of improved socialization, self-esteem, and

independence cannot be minimized in NMDs. Lack of these often lead

to isolation and loneliness. Regardless of any deconditioning, these

components should respond to exercise. Adherence to a stretching

program for contractures may maintain joint range of motion and

should be made part of an enjoyable daily routine. Exercise during

the childhood and adolescent years has been shown to lead to a more

active lifestyle as an adult.

Exercise and Sports Programs for Children with NMD: Families and

physical educators need to learn about the effects of the disease.

Often there are fears and caution due to lack of knowledge and the

overriding concern of making impaired muscles even weaker.

Discussion of fears with the physician, who can provide guidelines

and support is most beneficial. The specific choice of activities

may involve discussions among the individual, family, physical

therapist, occupational therapist or adaptive physical education

teacher. The natural history of the disease needs to be considered,

so that an unexpected sense of loss does not occur with cessation of

ability to exercise. Consideration should be given to the

adaptability of sports to accommodate for increasing impairment.

Exercise Recommendations Based Upon Functional Level.

Known Presence of NMD but No Overt Sequelae with Routine Activities:

These children are less likely to require encouragement to

participate in sports, but may have difficulty experiencing success

and performing at peer level, particularly in activities with high

static or dynamic strength and endurance demands. Although there are

no obvious limitations, exercise capacity may be limited,

necessitating frequent rest breaks. Overwork weakness is a potential

concern in a nonsupervised setting, even at this mild level of

involvement. For this reason, competitive sports such as football,

distance running, sprinting or wrestling are not encouraged. Rather,

these children are more likely to experience success with peers in

sports such as golf, swimming or softball. A goal with this group is

to help the child with slowly progressive NMD choose a " lifetime

sport, " meaning one that could be performed into adulthood to

maintain fitness. Examples would be swimming or cycling. Children

and adolescents with Myotonic Muscular Dystrophy (MMD) may have

little weakness but demonstrate mild grip myotonia, often going

unnoticed by the patient. This may increase the difficulty of

activities requiring fine motor coordination, although exercise

warmup utilizing repetitive hand motion will often reduce the

myotonia. Sports using the larger muscle groups should be

emphasized.

Ambulatory Without Aids with Mild Muscular Fatigue, Mild

Contractures or Reduced Endurance: There is often a component of non-

myopathic disuse atrophy in this group because they have prematurely

curtailed activity due to fear, familial pressures, or simply the

inability to keep up with peers. With encouragement, children may

continue physical education which helps maintain social interaction.

Competitive sports are generally not possible but recreational ones

definitely are appropriate, although they should avoid exercise to

exhaustion and have frequent rest breaks. Professional supervision

is not always necessary if the child can be trusted not to " overdo "

it. Swimming and water games are ideal sports to provide resistance,

endurance and flexibility training in an enjoyable manner. Golf,

hiking, cycling or table tennis are examples of other activities

which may be popular among children with NMD. Children with reduced

endurance may enjoy tandem cycling, canoeing or rowing with a

parent, sibling or friend. These activities have reasonable

neuromuscular skill demands, static and dynamic demands, and upper

and lower body motion. We have found poor adherence to formal

stretching programs in this population unless parents are insistent.

This may become a control issue and increase stress at home. If the

stretching program can be made part of warmup for a game or sport,

cooperation may improve.

Ambulatory But Markedly Limited Due to Weakness, Advancing

Contractures, Braces, or Poor Endurance: Examples in this category

would be primarily the late childhood phase of DMD and some children

with SMA. These children often use braces for ambulation, are not

functional runners, and demonstrate marked inefficiency with gait

due to postural adaptations to compensate for weakness and

contractures. Because of the significant weakness, there may be

minimal strengthening response seen with conditioning activities.

Water sports are ideal to provide freedom of movement and maintain

fitness due to the elimination of gravity disadvantage. Support with

flotation devices may be necessary. Pool ball games, relay races,

tag and slalom walking in shallow water may be utilized.

In school, adaptive physical education is necessary, with stress on

individual sports alongside peers to maintain socialization and goal

oriented skills. In the proximally-affected syndromes, overhead

activities such as throwing and basketball may be quite difficult,

and sports with the arms maintained below the shoulders are more

appropriate. Unless contractures are severe, three-wheeled cycling

may be an enjoyable way for these children to remain active.

Functional Wheelchair User: This group is made up of adolescents

with DMD and the most severely affected children with SMA. The

period of time these children predominantly use a manual wheelchair

is usually less than 2-3 years. A powered chair is ultimately

required. Goals of an exercise program in this group include

prevention of disuse atrophy and functionally limiting contractures,

maintenance of proper posture in the wheelchair, and avoidance of

social isolation, which is common in this phase. Restrictive lung

disease and cardiomyopathy become concerns and any exercise program

begun in a previously deconditioned child will have to progress at a

very slow pace. The few muscle strengthening studies reported

demonstrated the least benefit in the weakest subjects. Thus,

patients in a wheelchair are not likely to realize significant

benefit from a resistive exercise program.

There are significant benefits to exercise and recreation in this

group, not the least of which include socialization and improved

self-concept. A recreational therapist or adaptive physical

education teacher can be very helpful with introducing a variety of

activities. Water activities usually require some combination of

flotation device and one-to-one assistance by a partner. The

buoyancy of the water provides freedom of movement for the child

that can be quite gratifying. Many can still participate in water

games such as those involving a lightweight ball. Occasionally

children requiring a wheelchair for mobility have been able to sit

ski. This requires the ability to long-sit in a sled and fairly

preserved upper extremity function. Boating in a sailboat, canoe,

kayak, or rowboat is also popular. Many activities can be performed

from a manual or power wheelchair including wheelchair bowling (with

a special wheelchair bowling ramp), wheelchair floor hockey (usually

played with manual or electric wheelchairs and special stick

attachments), fishing, hiking (at one of the wheelchair accessible

parks), wheelchair slalom events and relay races, miniature golf,

and tee-ball.

The Muscular Dystrophy Association (MDA) has an extensive summer

camp program with more than 90 camps nationwide. These sessions

offer a wide variety of activities specially designed for youngsters

who have limited mobility or who use wheelchairs. Activities range

from outdoor sports such as swimming, boating, baseball, and bowling

to less physically demanding programs like arts and crafts and

talent shows. These camps provide an introduction to many adaptive

recreational opportunities and provide an excellent avenue for

children to develop friendships, build self-confidence, and improve

self-esteem. (From Kilmer, D., and Mc, Craig M., chapter

for Sports and Exercise for Children With Chronic Health Conditions -

Human Kinetics, Publishers, 1995, Barry Goldberg, M.D., editor).