OVERVIEW OF MULTIPLE SCLEROSIS
Multiple sclerosis (MS) is a chronic neurologic disease affecting approximately 2.5 million and 400,000 individuals worldwide and within the United States, respectively (2). Most patients are commonly diagnosed between the ages of 20 and 40 (2,3,6). MS affects 2-3 times as many women as men (2). MS is characterized by random (affecting various sites in the body including the eyes, skeletal muscles, the bladder, etc) autoimmune attacks of and damage to the insulating myelin sheath (demyelinization) of the central nervous system and to motor (effector) axons (nerve fibers). Lesions in myelin can be present in the cerebral hemispheres, brainstem, and spinal cord. Loss of myelin negatively affects rapid smooth coordinated movement (2). Table 1 describes the common disease courses of MS and their prevalence. Persons with MS typically assume a more sedentary lifestyle than apparently healthy individuals (5).
There are a number of MS symptoms, which can negatively alter an individual's ability to perform physical activities and to exercise. Table 2 describes common signs and symptoms of MS.
MS is commonly diagnosed by patient history of attacks, magnetic resonance imaging of the brain and spinal cord, and analysis of spinal fluid during disease flare-ups for specific antibodies (2,6).
Life expectancy is linked to disability level. Most deaths are secondary to other non-MS-related complications like heart disease, hypertension, and diabetes (6). Disease-specific disability and severity are measured during a clinical examination with the Kurtzke expanded disability status scale (EDSS) (1,8).
To establish realistic physical activity goals, exercise professionals should know the ambulatory and functional status of their clients with MS before working with them. The EDSS is a 10-step scale with steps 1.0-4.5 referring to fully ambulatory status and steps 5.0-9.5 referring to increasing levels of ambulatory impairment.
EFFECTS OF MS ON THE EXERCISE RESPONSE
Exercise tolerance is reduced for people with MS, and maximal exercise capacity appears to be inversely related to EDSS level, with individuals who have a higher EDSS score possessing lower maximal and submaximal aerobic exercise (AE) capacities (2,4,12). Persons with MS have been observed to be more sedentary than apparently healthy age-matched individuals (5). Persons with MS generate 20-68% less power during leg cycling or combined leg-arm exercise testing protocols than healthy individuals (8). Maximal aerobic power (POmax) has been reported to be 31 and 24% lower on treadmill and bicycle ergometer testing, respectively, compared with healthy individuals (8). Nonspecific physical deconditioning is known to contribute to fatigue and general poor health in persons with MS (5). In addition, maximal muscle force measured during isokinetic testing has been shown to be consistently lower when matched to controls (2). Potential mechanisms for these observed deficiencies could include the following:
- Spasticity and/or cocontraction of opposing muscles
- Conduction block of demyelinated fibers
- Reduced muscle metabolic responses during voluntary exercise
- Muscle weakness because of fiber atrophy
- Sensory deficits (2).
MEDICATIONS ASSOCIATED WITH MS
Several medications are used to modify and/or reduce the severity of the disease and number of exacerbations and to help manage symptoms of MS. Exercise response and tolerance can be altered by these medications (3). Table 3 describes commonly used medications and their potential side effects (3,6).
EXERCISE BENEFITS AND RISKS FOR PERSONS WITH MS
Previously, exercise was not often prescribed for persons with MS because it was believed to exacerbate symptoms and fatigue (1). Disease stage and severity determine individual responses to exercise. Although exercise training has no direct effects on prognosis or progression of MS, it may improve short-term and long-term physical fitness and functional performance (e.g., strength, endurance, aerobic fitness, fatigability, and mobility (3)). More recent studies indicate that moderate-intensity AEs improve physical fitness (1), mobility (4,11), walking speed (10) and capacity, exercise tolerance (9); reduce fatigue (5,7); and decrease disability (4,9). Improvements of 14.7, 18.2, and 27.7% in V̇o2peak, peak workload, and anaerobic threshold, respectively, have been observed in persons with MS participating in a supervised AE program (1).
Recent evidence suggests that resistance training (RT) is a safe effective form of exercise for persons with MS with mild to moderate disability (EDSS < 5) (5,10,12). Subjects engaged in an 8-week RT program consisting of 1 set of 10-15 repetitions at 70% of maximal voluntary contraction strength improved knee extension, plantarflexion, and stepping performance by 7.4, 52, and 8.7%, respectively (12). After participating in a 6-month, randomized, controlled exercise program consisting of 1 AE and 3 RT sessions per week, participants demonstrated significant improvements in walking speed, knee flexion strength, and upper extremity muscle endurance (10). In another study, participants engaging in a 3-month combined group and home RT program demonstrated significant improvements in exercise capacity, quality of life, and fatigue scores (5).
Because some persons with MS are at an increased fall risk and their symptoms and energy levels can vary daily, AE and RT sessions should be supervised, individualized, and frequently modified. In addition, heat sensitivity, spasticity, sensory deficits, muscle weakness, and fatigue can preclude upright activities like walking and running and reduce tolerated exercise intensity and duration (2,3,6).
EXERCISE GOALS FOR PERSONS WITH MS
Exercise professionals should provide clients with MS close supervision and help reduce their fall risk both during exercise sessions and daily activities. They should monitor their clients for signs of fatigue and heat intolerance and encourage proper hydration. Exercise sessions should be modified as necessary to accommodate any fluctuations in client's symptoms and energy level (2,3,6). Table 4 describes general exercise program goals for persons with MS.
Participants showing signs/symptoms of worsening disease or physical activity intolerance should be referred to their physician or health care provider. They should not resume their exercise program until their symptoms are under control and they have received medical clearance to do so.
Exercise professionals can help persons with MS, who have been cleared by their physicians, engage in safe and effective exercise programs. Both AE and RT exercise programs can improve physical fitness, balance, mobility, performance of activities of daily living, and quality of life. The reader is directed to the “one on one” column for specific exercise programming guidelines, interventions, and strategies for persons with MS.
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