Patients with multiple sclerosis often ask about exercises that may improve their condition, according to research. Here is a review of studies in endurance training, aquatic fitness programs, and progressive resistance exercises to help answer their questions.
Patients with multiple sclerosis often ask about exercises that may improve their condition, according to research. Here is a review of studies in endurance training, aquatic fitness programs, and progressive resistance exercises to help answer their questions. Multiple sclerosis (MS) is the most common demyelinating disease of the CNS. In the United States, approximately 400,000 persons have a diagnosis of MS, with as many as 200 persons receiving the diagnosis every week.1 There is no known cure for MS, but the life expectancy of patients with the disease has been described as close to that of the general population.1,2 Rates of death caused by coronary heart disease, cancer, and stroke in adults with MS are similar to those in the general population.3 Although most adults with MS have the ability to ambulate 25 years after diagnosis,2 many reduce their physical activity levels to below that of sedentary adults.4 Demyelination of nerve tissue causes a variety of symptoms that may affect levels of physical activity. These symptoms include excessive muscle fatigue,5 muscular weakness,6 spasticity, impaired balance, and impaired autonomic cardiovascular control.7,8 Symptoms may lead to abnormal gait or immobility and are frustrating for patients with MS to the extent that they negatively affect daily activities. Other symptoms such as idiopathic lassitude, or MS fatigue,9 are also of concern and, combined with inactivity, may lead to increased levels of muscular weakness and deconditioning. This vicious cycle may be stopped when physical activity replaces inactivity. Although the American College of Sports Medicine has exercise guidelines available for adults with MS,10 the recommendations are developed from research that has been based primarily on aerobic exercise. Heat intolerance,11 another MS symptom, may make aerobic exercise difficult because of the continuous nature and duration of typical exercise programs (10 to 30 minutes). Research examining resistance exercise in patients with MS has progressed from a descriptive nature, comparing subjects with and without MS, to intervention studies, using pro- gressive resistance exercise in many forms. Studies so far suggest that patients with MS may benefit from low- to moderate-intensity resistance training. The results of some of these studies also show functional benefits for patients with MS.12,13 Functional benefits, including improved mobility, have frequently been assessed using timed tasks (up and go). An isokinetic dynamometer has the ability to measure force and the effects of resistance training more accurately. This apparatus uses peak torque as a measure of muscular strength, and total work output during 30 or 50 repetitions as a measure of muscular endurance. Isokinetic dynamometry used during research has not increased MS-related symptoms nor caused any exacerbations (an episode of inflammation caused by the immune system attacking myelin). Although the appropriate number of familiariza- tion periods (before data collection) has been debated, both of the studies that examined reliability found that at least 1 familiarization period should be performed,14 and others have suggested 1 or 2 sessions.15 ADULTS WITH MS Many studies have focused on the differences in muscular strength and endurance between adults with MS and adults without MS matched for age, gender, and body mass.14,15 In one study, 10 participants with MS were shown to have significantly lower values for peak torque of the knee flexor and knee extensor muscles at all velocities (0 to 275 per second), compared with 10 age- and gender-matched controls.15 Ponichtera-Mulcare and colleagues16 also found that 9 ambulatory adults with MS had significantly less concentric peak torque (at 30, 60, and 90 per second) in both the quadriceps and hamstrings than the matched group. The difference in average peak torque ranged from 25% to 29% for the quadriceps and from 19% to 22% for the hamstrings. In contrast, there were no significant differences in peak torque between groups for either speed during eccentric contractions of quadriceps and hamstrings. A similar study examined the muscular strength, muscular endurance, and fatigue index in 15 adults with MS and 15 adults without MS. After adjusting for body mass and age, Lambert and colleagues14 found differences in concentric peak torque for the dominant flexors (25.7%), the nondominant flexors (20.8%), and the extensors (16.9%) at speeds of 30, 60, 90, 120, and 180 per second between subjects with MS and without MS. There also were significant differences between groups for muscular endurance and fatigue index (work during last 15 contractions/work during first 15 contractions). Therefore, adults with MS may have less muscular strength and muscular endurance and may experience greater muscle fatigue than adults without MS. A key finding of this study is that after adjusting for age and fatfree mass, adults with MS were weaker than controls, suggesting that they may have a reduced ability to activate muscle fibers and/ or that the level of force per unit of muscle mass they can generate is lower. Most of the research regarding the rate of muscle tension development and peak torque in adults with MS compared with controls has found similar results. 17 Another study found that adults with MS had reduced maximum motor neuron firing rates compared with controls (47% vs 93%).18 Activities such as chair raises, for which a large percentage of muscle fibers may be needed, may take longer for adults with MS to perform. EXERCISE INTERVENTIONS One of the first exercise intervention studies to be reported examined the effects of a 10-week aquatic fitness program on upper and lower extremity muscular force, torque, fatigue, and work in 10 adults with MS.19 Participants performed freestyle swimming and shallow-water calisthenics 3 times per week for 1 hour. Peak torque during knee extension was significantly greater after 5 weeks, compared with baseline, whereas there were no differences in knee flexion. Lower extremity fatigue (percent of peak torque decline) and muscular endurance improved at the end of 10 weeks, as did upper extremity power, work, and force measurements. An endurance-training program of the knee flexors in 5 adults with MS was initiated in a clinical setting.20 The 5 participants used weight cuffs, a pulley apparatus, or an isokinetic dynamometer 2 or 3 days per week for 4 to 8 weeks. After training, peak torque, general well-being (fatigue, health, physical fitness, somatic health, and mood), and perception of fatigue had improved for 3 of the 5 participants. A point of interest was the fact that this study used both isokinetic dynamometry and typical weight training equipment as part of the intervention program. A similar study examined the effects of progressive resistance exercise on muscular strength in 5 adults with relapsing-remitting MS (see National Multiple Sclerosis Society. Just the Facts: 2004- 20051 for an explanation of the disease categories). The 10-week, community-based exercise program used machine-based resistance and free weights 2 days per week for 1 hour. The results of the study indicated that the participants improved the average peak torque of their knee flexors/extensors by 16% to 57%, elbow flexors/ extensors by 6% to 29%, and shoulder abductors/adductors by 3% to 11%. The authors concluded that although some participants did not have improvement, the results indicate that the majority of the participants improved their muscular strength.21 Kraft and colleagues22 also examined the effect of 12 weeks of progressive resistance exercise on measures of strength in ambulatory adults with MS. Three times per week, 4 adults with mild MS and 4 adults with moderate levels of MS exercised in a university-based human performance laboratory. The adults with mild MS (mean Expanded Disability Status Scale [EDSS] score, 3) had greater levels of improvement for the quadriceps, hamstrings, triceps, and biceps than those with moderate levels of MS (mean EDSS score, 6). Persons with moderate levels of MS significantly improved the strength of their biceps, triceps, and hamstrings.22 Another research study used resistance exercise but focused on the functional skill improvements of these participants.12 The results of the study indicated that adults with both mild and moderate levels of MS significantly improved their self-selected stair-climbing speed. Improvements were also made in the "up and go" mobility test,23 as well as in scores on the psychosocial and physical dimensions of the Sickness Impact Profile. 24 Participants reported feeling typical activity-related fatigue that subsided within 24 to 48 hours, and no participant experienced an MS exacerbation during the 12- week program. The results of these studies are important because they included both objective measures of strength and improvements related to functional daily activities. When one examines research in this area, it becomes apparent that sample sizes have been small and experimental designs have not included control groups. One study randomized 37 participants into exercise and control groups.25 It assessed the effect of an 8-week, home-based resistance exercise program on lower extremity power, functional mobility, and balance in ambulatory adults with MS. Twenty-nine women and 8 men were adjusted for disability level and age and then randomized into exercise (n = 19) and control (n = 17) groups. The lower extremity strength training intervention used weighted vests and functional exercises (chair raises, forward lunges, step-ups, toe raises, and leg curls). The exercise group participated in 6 instructional sessions before implementation of the 8- week home-based exercise program, while those in the control group maintained their current levels of physical activity. Weekly phone contact and bimonthly home visits increased compliance with self-reported exercise (95% of exercise sessions were completed). General fatigue was recorded daily using a visual analog scale. The results of the study indicate that leg extensor power improved significantly in the exercise group, although improvements in balance and mobility did not reach statistical significance. Anterior-posterior sway decreased by 10.3% and mediolateral sway decreased by 4% in the exercise group, whereas the control group had increases in both areas. In the "up and go" test, patients in the exercise group decreased their average time by 12.7%, while the control group showed little improvement (1% decrease). After regression for daily fatigue over time to yield a fatigue slope for both groups, no significant differences in fatigue between groups were found.26 The authors concluded that this type of resistance exercise might be a feasible way for adults with MS to improve lower extremity power without increasing fatigue, using a model accessible to many. LIMITATIONS Although research suggests that resistance exercise is safe and beneficial, most of the studies have used small sample sizes and lacked control groups. In addition, intensity of exercise, in relation to muscular weakness and fatigue, has not been examined in adults with MS. It has been shown that persons with stroke and muscular dystrophy have experienced greater levels of fatigue and weakness after intense exercise in muscles with neurogenic disturbance.27,28 Specifically, it has been shown that weak respiratory muscles generated greater levels of muscle fatigue in children with muscular dystrophy.27 In patients with stroke, researchers found lower levels of peak torque and decreased work capacity in the stroke-affected leg than in the unaffected leg during high-intensity eccentric-concentric contractions of the plantar flexors. 28 This indicates that muscle groups with neuromuscular weakness may respond to high-intensity resistance exercise differently and/or respond to fatigue more quickly than nonaffected muscle groups. It also is not known whether high-intensity exercise would damage these muscle groups over time. RECOMMENDATIONS Health professionals should use low- to moderate-intensity resistance exercise when training patients with MS. This decrease in intensity may be offset with an increase in repetitions, which may have a carryover effect of improving muscular endurance and duration of repetitive movements and activities such as walking and gardening. A second recommendation is that health professionals carefully monitor patients' exertional fatigue and recovery from exercise. A third recommendation is to provide ongoing systematic evaluation during exercise. Finally, resistance exercise should be implemented by trained health professional who is understanding of and sensitive to the specific needs of each person with MS. The best approach to improving the health and wellness of adults with MS may be to use a community- based team of practitioners. Exercise and resistance training is a very important component of the overall program and should not be overlooked, but physicians, therapists, and other health professionals need to keep current on ongoing research regarding exercise and MS. In addition, all professionals on the team should make themselves aware of adequately staffed community- or university-based programs available in the area. Many adults with MS are interested in exercise, yet they often have difficultly finding available, low-cost, community-based programs with support staff trained to provide guidance. Transportation also may be difficult for adults with diseaserelated vision impairments or paralysis. Patients who are still working part-time and/or raising children may find it difficult to commit to an exercise program in the community. Thus, home-based exercise may be an appropriate tool for many adults with MS. The frustrating conundrum is that therapists regularly prescribe home exercises only to have patients fail to exercise at home. A possible solution may involve monthly phone calls to maintain contact and promote compliance with home-based exercise programs. Participants could even return to the clinical setting for retesting and updates to their programs. CONCLUSION Exercise prescription remains a topic on which adults with MS most frequently ask for more information from health professionals. 29 Studies have shown that adults with both mild and moderate levels of MS may improve their upper and lower body fitness with exercise. Progressive resistance exercise may improve muscular strength and endurance and lower extremity power, balance, and mobility and may decrease muscle fatigue. 12,14,19-22,25,30 These changes can occur without increasing or exacerbating MS symptoms or increasing daily fatigue.25 Aquatic fitness programs and programs in traditional rehabilitation centers, physical therapy clinics, and universitybased settings have all been successful at improving muscular strength and endurance in these adults. ? Editor's Note: A previous version of this article appeared in the November-December 2004 issue of BioMechanics. 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