Impact of Exercise on Targeted Secondary Conditions
James H. Rimmer and Swati S. Shenoy*
Regular exercise has been recognized as one of the most important health behaviors for reducing the risk of chronic diseases and improving overall health.19 There is strong evidence that exercise leads to improved physiologic fitness; extends longevity; and protects against the development of coronary heart disease, hypertension, type 2 diabetes, obesity, osteoporosis, colon cancer, breast cancer, lung cancer, and clinical depression.13 As a result of this supportive literature base, regular exercise is considered one of the most essential health behaviors for reducing the risk of various health conditions and is listed as one of the primary target goals in the U.S. Department of Health and Human Services’ Healthy People 2010, a document that identifies preventable threats to the nation’s health and sets goals for reducing these threats.18
Less is known about the potential benefits of exercise in reducing secondary conditions in people with disabilities. The epidemiologic work that has confirmed the benefits of exercise in the general population has typically excluded individuals with physical, cognitive, and sensory disabilities. This has left an enormous gap in the literature in terms of understanding if
similar “doses” of exercise can have the same health benefits for people with disabilities.
In recent years there has been a modest but growing increase in the number of exercise-related studies that have targeted people with disabilities. Although the majority of these studies are not randomized controlled trials (RCTs) and had limited sample sizes, they are part of a growing effort among researchers to understand the effects of exercise in improving health among people with disabilities.1,2,5,6,7,8,9 However, there is a limited amount of data on the effects of exercise in reducing or mitigating specific secondary conditions that are related to a primary disabling condition.10,15
This paper reviews 10 RCTs that tested an exercise intervention to ameliorate the following secondary conditions: deconditioning, fatigue, and pain. Two primary disabling conditions were targeted: multiple sclerosis and spinal cord injury. A glossary at the end of this paper describes the assessment instruments used in the studies reviewed. To identify relevant studies, we conducted a literature search for the period from 1990 to 2005. The databases searched were PubMed/MEDLINE and Cumulative Index to Nursing and Allied Health Literature (CINAHL). The keywords used to identify peer reviewed articles were “exercise,” “physical activity,” “secondary conditions,” “disability,” “multiple sclerosis,” and “spinal cord injury.” The studies selected had to fulfill the following criteria: (1) the enrolled subjects had to have a spinal cord injury or multiple sclerosis; (2) the intervention targeted deconditioning, fatigue, or pain; (3) the trial involved a prospective randomization methodology; (4) the treatment involved some type of exercise regimen; and (5) the study was published in English. A total of 10 articles satisfied the inclusion criteria.
Deconditioning is associated with low levels of physical fitness (e.g., low levels of aerobic power and muscle strength and endurance, higher fat to lean muscle ratio, and poor flexibility) and often occurs as a result of high levels of sedentary behavior. It leads to a loss of cardiorespiratory endurance and musculoskeletal function, subsequently reducing a person’s ability to perform various physical tasks, including activities of daily living, such as dressing and bathing, and instrumental activities of daily living, such as transfers, rolling up ramps, walking, and wheeling.
Six RCTs examined the effects of exercise on deconditioning in individuals with spinal cord injuries (one study) or multiple sclerosis (five stud-
ies). A brief review of each study is described below, followed by a summary of the overall findings.
Hicks and colleagues9 conducted an RCT of supervised progressive exercise training in 34 subjects with spinal cord injuries (time postinjury, >1 year; age range, 19 to 65 years; lesion level, C4 or below; intervention group, 21 subjects; control group, 13 subjects) to examine the effects of a long-term exercise training protocol on strength and cardiovascular endurance. Subjects in the exercise intervention group trained 90 to 120 minutes per day, 2 days per week. The training protocol included a warm-up consisting of wheeling around an indoor track or low-intensity arm ergometry and gentle upper-extremity stretching. The aerobic portion involved arm ergometry for 15 ± 30 minutes at an intensity level of approximately 70 percent maximum heart rate (a rating of 3 to 4 on the 11-point Borg rating scale). Initially, the subjects performed two arm ergometry bouts of 5 ± 10 minutes, which were gradually increased to two bouts of 15 ± 20 minutes as the training progressed. These two bouts were interspersed with resistance training exercise. The resistance training component consisted of exercises with a wall pulley, free weights, and an Equalizer weight machine. The subjects performed their resistance exercises in a circuit system, which consisted of two sets of each exercise (50 percent of 1-RM, which is the maximum amount of weight that can be lifted one time by a particular study subject) and which then progressed to three sets (70 to 80 percent of 1-RM) after the fourth week. The resistance loads were reassessed approximately every 6 weeks to ensure a constant training intensity. A wide variety of exercises targeted the upper torso (i.e., forearm-wrist, biceps, back, chest, abdominals, shoulder, triceps, and legs). Subjects in the control group were offered a bimonthly education session (together with the exercise group) on topics that included exercise physiology for individuals with spinal cord injuries, the occurrence of osteoporosis after a spinal cord injury, and relaxation techniques. Control subjects were also given the opportunity to join the exercise program once the 9-month study ended. The evaluations for 1-RM strength and arm ergometry were obtained at 3, 6, and 9 months, respectively. The results indicated that a 9-month training program of structured exercise two times per week produced significant increases in submaximal power output (81 percent; p < 0.05) and significant increases in upper body muscle strength (19 to 34 percent; p < 0.05). The exercise group was able to perform significantly more work at a given heart rate compared with the amount of work performed at baseline. The implications of these findings were that subjects could perform certain physical tasks much easier after this 9-month training program, which would hypothetically lead to greater independence. However, this association was never tested.
Petajan and colleagues15 conducted a 15-week RCT involving aerobic
exercise with 46 individuals with multiple sclerosis. Subjects were randomly assigned to an exercise group (n = 21) or a nonexercise (control) group (n = 25). Six subjects were excluded for reasons unrelated to the study, and two subjects were dropped because of an exacerbation. Outcome measures included maximal aerobic capacity; isometric strength; body composition; blood lipids; performance in daily activities; mood, fatigue, and disease status as measured by the Profile of Mood States (POMS), Fatigue Severity Scale (FSS), and Sickness Impact Profile (SIP); the Kurtzke Expanded Disability Status Scale (EDSS); and neurological examination. The subjects trained 3 days per week for 40 minutes per session using a combination of arm/leg cycling on a stationary bicycle. Exercise sessions consisted of a warm-up (5 minutes) and cool down (5 minutes); 30 minutes of cycling at 60 percent of VO2max; and 5 to 10 minutes of stretching that focused on the posterior muscles of the lower leg, thigh, and back. Compared with values at baseline, the exercise group demonstrated significant increases in VO2max (22 percent), physical work capacity (48 percent), upper- and lower-extremity strength, skin fold thickness and triglyceride levels. The results of EDSS were unchanged except for improved bowel and bladder function. The exercise group showed improved SIP scores (physical dimension) in ambulation, mobility, body care, and movement. The investigators noted that the gains in fitness were associated with enhanced social integration and improvements in physical and psychological functions.
Mostert and Kesselring11 conducted a 4-week aerobic exercise training program with 37 subjects who had one of the following types of multiple sclerosis: relapsing-remitting, chronic-progressive, or relapsing-progressive. All subjects were in an inpatient rehabilitation program. Subjects with multiple sclerosis were randomly assigned to an exercise training group (MS-ET) or a nonexercise training or nonintervention (MS-NI) group. The subjects in the latter group received physical therapy but did not engage in any other physical activity. Another control group consisted of 26 subjects without multiple sclerosis matched with the MS-ET and the MS-NI groups by age, gender, and activity level. Eleven of the 37 subjects with multiple sclerosis were excluded or dropped out of the study, leaving a total of 13 subjects in each group (the MS-ET and MS-NI groups). Subjects performed a graded exercise test to measure peak aerobic capacity (VO2peak). The training component consisted of five 30-minute sessions of stationary cycling per week for 3 to 4 weeks. The results indicated that there were no changes in peak aerobic capacity (VO2peak), although the maximum work rate did improve (+11 percent) in the training group. The investigators noted that the low training volume (3 to 4 weeks) might not have been high enough to improve fitness. Other improvements included increased health perception (vitality, +46 percent; social interaction, +36 percent) and activity level (+17 percent). No changes in these measures were observed in the MS-NI group or the control
group without multiple sclerosis. Overall, the researchers considered the rate of compliance with the training program to be low (65 percent).
Romberg and colleagues16 conducted an RCT with subjects with multiple sclerosis to evaluate the effects of a progressive 6-month exercise training program consisting of 3 weeks of inpatient rehabilitation and 23 weeks of home exercise on walking and other aspects of physical function. The subjects (n = 114; age range, 30 to 55 years) had mild to moderate multiple sclerosis on the basis of their EDSS scores, which were between 1.0 and 5.5. The subjects were randomly assigned to either the exercise group (n = 56) or the control group (n = 58). The outcome measures included walking speed (7.62- and 500-meter-walk tests), maximal isometric torque of knee extensor and flexor muscles (dynamometer), upper-extremity endurance (weightlifting test), peak oxygen uptake, and static balance. The groups were evaluated at baseline and 6 months. Data for only 95 subjects were included in the analyses because of withdrawals or exclusion because of illness. The intervention consisted of inpatient rehabilitation (weeks 1 to 3), followed by a progressive home-based exercise program (weeks 4 to 26). Ten supervised strength training and aerobic exercise sessions were conducted during the inpatient rehabilitation. Trained physiotherapists instructed the patients individually on the home exercise program. Aerobic training during weeks 1 to 3 consisted of aquatic training, and during weeks 4 to 26 the subjects were encouraged to continue with aquatic training or with their earlier mode of aerobic exercise (the specific modes were not reported). The results indicated that 91 (96 percent) of the 95 subjects who enrolled in the study were able to complete it. However, this was after a screening process that identified 276 eligible subjects, 162 of whom were not eligible for the study for several reasons, including the fact that they were out of the age range of the study, their EDSS score was out of the range for the study, they had some other disease or medical condition, they could not be contacted, or they did not want to participate. Walking speed improved significantly on both the 7.62-meter-walk (p = 0.04) and the 500-meter-walk (p = 0.01) tests. In the 7.62-meter-walk test, the exercise group had a 12 percent decrease in time, whereas the controls had a 6 percent decrease. On the 500-meter-walk test, the exercise group decreased their time by 6 percent and there was no change for the controls. There were no reported changes in lower-extremity strength, VO2peak, static balance, or manual dexterity. Even though the researchers concluded that exercise had a significant effect on increasing functional performance and was considered safe by individuals with mild to moderate multiple sclerosis, the measures typically improved in exercise trials (i.e., VO2peak and lower extremity strength) were not demonstrated.
DeBolt and McCubbin5 conducted an RCT to examine the effects of an 8-week home-based resistance exercise program on balance, power, and
mobility in adults with multiple sclerosis. The subject pool consisted of 29 women with multiple sclerosis (mean age, 50.3 ± 8.5 years) and 8 men with multiple sclerosis (mean age, 51.1 ± 7.1 years). The subjects were stratified by disability level, as determined by EDSS, and age and were randomized into an intervention group (n = 19) or a control group (n = 17). The intervention consisted of 5 to 10 minutes of warm-up activities (walking) and stretches, 25 to 30 minutes of strengthening exercises, and 5 to 10 minutes of whole-body stretching. The exercises included chair raises, forward lunges, step-ups, heel-toe raises, and leg curls. Weighted vests were used to increase the intensity of the training regimen. The progression of intensity was based on the strength training periodization model: the initial vest resistance was set at 0.5 percent of body weight and increased by percentages of body weight (0.05 to 1.5 percent) every 2 weeks. During weeks 1 and 3 the participants were instructed to perform two sets of 8 to 12 repetitions of each exercise, and during weeks 2 and 4 they were instructed to perform three sets of 8 to 12 repetitions of each exercise (hypertrophy phase). During weeks 5 to 8, the participants decreased the number of exercises to two sets of 8 to 10 repetitions (strength and power phase). The control group members were given the opportunity to learn the homebased resistance exercises at the end of posttesting and were also given a home exercise video. Bimonthly home visits and weekly phone contacts were conducted for both groups. The results indicated a significant improvement in leg extensor power in the exercise group (p < 0.004). However, measures of balance and mobility did not show any changes.
Patti and colleagues14 conducted an RCT to evaluate the effects of a 12-week comprehensive outpatient rehabilitation program on the quality of life in individuals with multiple sclerosis. Individuals with multiple sclerosis (n = 111) were recruited from a sample of 407 eligible subjects on the basis of the following inclusion criteria: laboratory-confirmed multiple sclerosis, an EDSS score between 4.0 and 8.0, and age between 18 and 65 years. The eligible subjects were randomly assigned to the treatment group (n = 58) or a control group on a treatment waiting list (n = 53). The intervention consisted of a comprehensive outpatient rehabilitation program (6 weeks), followed by a 6-week self-initiated home exercise program. The control group on the waiting list was offered the comprehensive outpatient rehabilitation program at the end of 12 weeks. The outcome measures were the EDSS, the SF-36 health-related quality of life survey, the Beck Depression Inventory (BDI), the Tempelaar Social Experience Checklist (SET), and the Fatigue Impact Scale (FIS). The results indicated that the EDSS score remained unaffected in both groups. For the treatment group, all health-related quality-of-life components on the various components of the SF-36 improved significantly, including physical functioning, bodily pain, general health, and social functioning (p < 0.001) and vitality and emotional and
mental health (p < 0.05). Additionally, there was a significant reduction in fatigability and a significant improvement in social functioning and depression, as measured by FIS, SET and BDI, after the 12-week intervention (p < 0.001).
In summary, the six RCTs reported on in this section targeted improvements in physical fitness (i.e., aerobic power, muscle strength, and endurance) or physical function (measures of mobility), with the intent ot reduce the effects of deconditioning. The total aggregate sample that participated in the intervention arm was 21 subjects with spinal cord injuries and 156 subjects with multiple sclerosis. The sample sizes in the intervention arm ranged from 13 to 58. All of the studies reported positive findings on one or more outcome measures associated with deconditioning, but there were wide variations between studies. This may be related to the substantial heterogeneity in age, gender, and level of disability. The studies of individuals with multiple sclerosis indicated that individual patterns of disease progression may or may not have matched well between the control and the experimental groups. Similarly, all of the studies included subjects with various types and severities of multiple sclerosis. With small sample sizes, this becomes an even greater issue because alterations in health or function could skew the findings for either the control group or the experimental group. Only two studies reported a power analysis,5,16 and one of those studies indicated that the power was less than 80 percent.26 One study performed an intention-to-treat analysis,16 but the other studies reported their findings only for subjects who remained in the study. It is possible that subjects who agreed to participate in an exercise trial may have had higher levels of baseline function or health, which may limit the findings to a subgroup of the targeted population. Several participants dropped out of each of the studies because of compromised health status, a lack of interest, or other factors.
Fatigue is a common secondary condition that affects individuals with multiple sclerosis. It can be expressed as general or systemic fatigue; muscle fatigue without exercise; and cognitive fatigue, which is indicated by reduced attention, memory, and information processing. Only four RCTs that targeted fatigue reduction in individuals with multiple sclerosis were identified.
Surakka and colleagues17 conducted an RCT consisting of a 3-week supervised exercise program followed by 23 weeks of home exercise to examine the effects of aerobic and strength training on motor fatigue of knee flexor and extensor muscles in individuals with multiple sclerosis. The subject pool consisted of 95 subjects with mild to moderate disability who
were randomly assigned to an exercise group (n = 47) or a control group (n = 48). The outcome measures were the Fatigue Index, subjective fatigue measured by the Fatigue Severity Scale (FSS) and EDSS. The intervention phase consisted of five supervised resistance exercise sessions and five aerobic exercise sessions. The resistance exercise was conducted in a circuit training format, beginning with a 10-minute warm-up, followed by 10 exercises with 10 to 15 repetitions in two sets. The exercises were performed with pressurized air resistance machines, with weight stack machines, or against gravity. The exercise load was 50 to 60 percent of 1-RM. The load was increased or decreased on the basis of the evaluation at the end of the third session. The aerobic program consisted of a variety of gymnastic exercises in shoulder-deep water with the temperature maintained at 28°C (82.4°F). The session started with a 5- to 7-minute warm-up, followed by 20 to 25 minutes of aerobic exercise, and ended with a 5- to 8-minute cool down. The exercise intensity was maintained at 65 to 70 percent of the age-predicted maximum heart rate (MHR). If the subject was unable to participate in the aquatic program, a 30- to 35-minute stationary cycling program was used.
The home exercise program lasted 23 weeks, with four exercise sessions per week during weeks 1 to 17 and five exercise sessions per week during weeks 18 to 23. The subjects were provided with two different elastic therabands for the upper and the lower extremities that were used for training. The participants in the control group were asked to continue with their normal daily routine. The results showed decreases in the AFI in the exercise group (p < 0.007) and a reduction in motor fatigue in knee flexion (p < 0.001) but not in extension in female subjects only after 6 months of exercise training.
Oken and colleagues12 conducted a 6-month parallel-group (two or more different groups of patients) RCT to determine the effects of yoga and aerobic exercise on fatigue in 69 individuals with multiple sclerosis (12 subjects did not complete the study, leaving a total of 57 subjects). The subjects were randomly assigned to one of three groups: (1) Iyengar yoga (n = 22) (a form of hatha yoga that focuses on physical alignment of the body in various poses) with home practice, (2) aerobic exercise (n = 15) on a recumbent or dual-action stationary cycle with a home program, and (3) a control group on a waiting list (n = 20). The Iyengar yoga intervention was performed 1 day a week for 90 minutes. The subjects were trained in 19 poses (not all poses were completed each week), which were performed in a chair, against the wall, or while the subject was sitting on the floor. Each pose was held for approximately 10 to 30 seconds, with rest periods between poses of 30 seconds to 1 minute. The aerobic exercise sessions were held 1 day a week, along with home exercise, and consisted of bicycling on
a recumbent or dual-action (arms and legs) stationary cycle. All exercises started and ended with a 5-minute stretching routine that involved the cycling muscles. The heart rate (HR) was not recorded, and the subjects were instructed to exercise at a very light to moderate intensity (modified Borg Rating of Perceived Exertion of 2 to 3). Outcomes measures for fatigue at baseline and at the end of 6 months were measured with the Multidimensional Fatigue Inventory (MFI); POMS, which includes measures of fatigue and vigor; and SF-36. The results indicated that both intervention groups showed a significant improvement on the general fatigue component of the MFI (p < 0.01) and the energy and fatigue component of the SF-36 energy and vitality dimension (p < 0.001).
Petajan and colleagues15 conducted a 15-week RCT of aerobic training with 54 individuals with multiple sclerosis who were randomly assigned to an exercise group or a control group (see the study design discussed above in the section on deconditioning). For the exercise group, POMS depression and anger scores were significantly reduced at weeks 5 and 10, and fatigue was reduced at week 10. The exercise group improved significantly on all components of the physical dimension of SIP and showed significant improvements for social interaction, emotional behavior, home management, total SIP score, and recreation and pastimes. No changes on the FSS were observed for the exercise or the no-exercise control group. Exercise also had a positive impact on factors related to quality of life.
Mostert and Kesselring11 conducted a 4-week aerobic exercise training program with 26 subjects (13 experimental and 13 control) involved in an inpatient rehabilitation program (see the study design discussed above in the section on deconditioning). The results indicated that, compared with the level of fatigue at baseline, the participants in the training group demonstrated a tendency toward less fatigue, although the researchers noted that the difference was not significant.
Pain is one of the most common secondary conditions reported by people with disabilities.3 In particular, musculoskeletal pain in the neck and shoulder region are commonly observed in individuals with spinal cord injuries and is exacerbated by wheelchair transfers and propulsion.1,2,3,4 Only four exercise-related RCTs that targeted pain reduction in individuals with spinal cord injuries were identified.
Hicks and colleagues9 targeted reduction in pain as one of their primary outcomes (see the study design discussed above in the section on deconditioning). The results indicated that a 9-month training regimen consisting of cardiorespiratory endurance and resistance exercise decreased
the level of self-reported pain in individuals with spinal cord injuries. The researchers suggested that exercise be used as a prophylactic measure for improving pain tolerance in this population.
Ginis and colleagues8 conducted an RCT of aerobic and resistance training with 34 individuals with traumatic spinal cord injuries (23 men and 11 women; mean age, 38.6 ± 11.7 years; average duration postinjury, 10.4 years; 14 had complete spinal cord injuries and 13 had incomplete spinal cord injuries). The participants were matched for years postinjury and relative mortality risk and were then randomly assigned to either an exercise group (n = 21) or a control group (n = 13), a ratio of 2:1. The treatment group trained two times per week in small groups of three to five participants. Each session included a 5-minute stretching routine, 15 to 30 minutes of arm ergometry exercise, and 45 to 60 minutes of resistance exercise. Initially, the exercise intensity for the aerobic component was 70 percent of MHR, but this was progressively increased on the observation of a decrease in perceived exertion or HR. The results indicated that there were significant improvements (p < 0.05) in perceived quality of life and better physical self-concept and a significant decrease (p < 0.05) in pain compared with the findings for the controls.
Patti and colleagues14 (as discussed above) evaluated the effects of a comprehensive outpatient rehabilitation program on the quality of life in individuals with multiple sclerosis. All health-related quality-of-life components—physical functioning, role limitations due to physical health problems (role physical), bodily pain, general health, and social functioning—significantly improved in the treatment group (p < 0.001).
Curtis and colleagues4 analyzed the effectiveness of a 6-month exercise protocol on shoulder pain in wheelchair users (n = 42). The subject pool consisted of a cluster sample recruited from the community. The average age was 35 ± 8 years, and the average duration of wheelchair use was 14 ± 9 years. The subjects were randomly assigned to a treatment group (n = 21) or a control group (n = 21). The subjects in the treatment group received 60 minutes of educational training that instructed them in five daily shoulder exercises. These exercises consisted of two static stretching exercises to increase the flexibility of the anterior shoulder muscles and three resistive strengthening exercises for the posterior shoulder muscles. The subjects performed all exercises independently while they were seated in their wheelchairs, and lightweight elastic exercise bands were used for resistance. The subjects with tetraplegia used wrist straps to accommodate a weak or absent grasp response. An instructional session was included to provide an overview of functional shoulder anatomy, the purpose of the exercises, and a demonstration of each exercise. The treatment group was instructed to perform stretching exercises twice daily, five times each, with a 20- to 30-second hold of each position for a prolonged stretch and to perform the
strengthening exercises once daily with three sets of 15 repetitions. Bi-weekly phone calls were made to monitor performance and problems. The Wheelchair Users Shoulder Pain Index (WUSPI) was used to evaluate pain at baseline and at bimonthly intervals. The results showed that 75 percent of the subjects reported a history of shoulder pain since the initiation of wheelchair use. The average initial performance-corrected WUSPI (PC-WUSPI) score for the 42 subjects was 17.7 ± 21.3 with a range of 0 to 103.2. (A low score on the PC-WUSPI indicates lower levels of pain intensity.) More than 83 percent of the subjects (35 of 42) completed the 6-month study. The subjects in the treatment group decreased their PC-WUSPI scores by an average of 39.9 percent, whereas the decreases for the control group were only 2.5 percent. The study demonstrated that a small number of flexibility and resistive exercises had a positive effect on the reduction of shoulder pain in a population of wheelchair users.
SUMMARY OF STUDIES REVIEWED
The studies that we have reviewed used various methodologies, assessment tools, and exercise doses to address various health issues associated with people with multiple sclerosis and spinal cord injuries: deconditioning, fatigue, and pain. The studies reported under deconditioning used quality of life as their primary endpoint, which included both physiological and psychological measures. In the future, a more focused research agenda should use specific doses and modalities of exercise to address specific secondary conditions. Moreover, studies should be more homogeneous in terms of the age, health status, and functional levels of the study subjects and should use a consistent methodology and training dose to enhance the generalizability of the findings to certain subgroups of disabilities.
All of the studies reviewed in this paper had several different outcomes (e.g., physical and emotional well-being, quality of life, reduced fatigue, and increased fitness), used a variety of interventions and doses of exercise (length of study, frequency, duration, intensity, and modality), and had widely different inclusion and exclusion criteria within each disability group. A few studies included individuals in a wide age range and with a wide range of functional levels. This may have attenuated the potential effects of the intervention on a certain subgroup within the larger sample (e.g., younger versus older subjects). Although the use of heterogeneous populations makes it easier to recruit subjects (e.g., by including individuals with paraplegia and tetraplegia in the same study) and obtain higher levels of statistical power, generalizability is limited because of variations in the levels of health and function within disability groups.
It has become widely accepted that exercise promotes good health and reduces the risk of chronic conditions. However, it is less clear what doses
of exercise are effective for reducing or mitigating the effects of various secondary conditions in people within different disability types and, within a certain disability, between individuals with different functional levels.
The lack of data pertaining to the frequency, intensity, duration, and modality components of an exercise prescription for individuals with various disabilities has limited the utility of exercise as a viable treatment for secondary conditions. While exercise is presumed to be beneficial for all individuals (with or without a disability), data on dose-response are critical for understanding and providing appropriate, targeted interventions that have a clinically meaningful effect in reducing the risk of, minimizing, or eliminating certain secondary conditions.
Researchers must also explore the possibility that certain individuals with the same disability may require a greater dose or a lower dose of exercise, depending on their genetic history, functional level, and the severity of the secondary condition being targeted (e.g., pain, fatigue, depression, and deconditioning). Some individuals may not respond favorably to a certain dose of exercise or physical activity, whereas others may drop out because of an injury or exacerbation. In one of the RCTs reviewed in this paper,9 10 of 21 subjects (47.6 percent) who were randomized to the exercise arm dropped out of the study because of illness, transportation difficulties, or time conflicts. This is a major concern in research with disabled populations and should be addressed in future clinical trials.
SPECIFIC RESEARCH RECOMMENDATIONS
1. Prospective observational studies should be conducted to determine the frequency, intensity, and duration of physical activity associated with reducing the symptoms of targeted secondary conditions (e.g., deconditioning, fatigue, and pain). Epidemiological studies will offer greater opportunities to obtain an understanding of the effects of various forms of structured exercise and general physical activity on the incidence, risk, or reduction of secondary conditions in individuals with disabilities.
2. The heterogeneity between and within disability groups and the low incidence of many disabilities make it extremely difficult to obtain adequate sample sizes when subjects are recruited from one setting. Multi-center trials are necessary to achieve adequate statistical power and to be able to generalize the findings of those trials to certain subgroups within the targeted disability (e.g., older versus younger individuals, individuals with higher levels of functioning versus those with lower levels of functioning, male versus female subjects, individuals with paraplegia versus those with tetraplegia, and individuals with progressive multiple sclerosis versus those with relapsing-remitting multiple sclerosis). A structured protocol that tar-
gets a homogeneous subset of the population identified (e.g., young adults with paraplegia) and that employs the same testing instruments, procedures, and training regimen must be established.
3. RCTs are needed to examine exercises of various types and doses (by frequency, intensity, and duration). There is still a lack of information on what types of programs or interventions are the most effective for ameliorating specific secondary conditions. Evidence-based practice guidelines must be established from well-designed studies.
4. Group versus individual exercise, such as tai chi or yoga, may have an additional social benefit, which may improve outcomes but which may also confound the benefit of the specific dose of exercise. Future studies should control for the social aspect of exercise to obtain accurate data on the exercise regimen itself versus the social benefits associated with exercising in a group.
5. Numerous self-report assessment tools have been developed to measure changes in deconditioning, fatigue, and pain. It is difficult to make comparisons between studies when the instruments are not the same or are not explained in detail to make critical comparisons between them. The use of a consistent set of instruments that measure the reductions in specific secondary conditions should be explored so that data from various studies can be compared.
6. Although the studies reviewed here were mostly supportive of the role of exercise in reducing deconditioning, fatigue, and pain, none explained the physiological, musculoskeletal, or neurological mechanisms associated with these changes. With more sophisticated imaging and laboratory techniques, it may now be possible to identify the more subtle biological changes associated with exercise training.
7. Innovative strategies for the recruitment of individuals who generally do not volunteer for research studies must be explored. Because most experimental research is conducted with volunteers, it is difficult to generalize the study’s findings to the entire subgroup. People who volunteer for exercise-related research may generally be younger or may have a higher functional level. This is a common problem in experimental research, but it may be an even greater problem for people with disabilities because sample selection is limited to a small subset of the population and barriers such as transportation limit opportunities for participation in clinical research.
8. Several studies emphasized the unique aspects of improving social integration and quality of life. It would be helpful to understand how these self-report measures are associated with more objective measures, such as quantitative assessment of an increase in community participation (i.e., an increased number of out-of-home social activities, a greater amount of time engaging in social events, increased rates of employment, and more social
contacts). The idea that exercise can improve psychological functioning and quality of life is an intriguing one, and should be measured with more objective monitoring techniques.
9. Specific secondary conditions, such as deconditioning, fatigue, and pain, must be more clearly defined. There are various types of deconditioning (e.g., low muscle strength, poor cardiorespiratory endurance, and lack of flexibility or balance), fatigue (e.g., physical and mental), and pain (e.g., neurogenic and musculoskeletal). Researchers targeting the reduction of these secondary conditions must be certain that the sample groups are similar on the basis of the defined characteristics of the secondary conditions.
10. There needs to be stronger collaboration between researchers whose work focuses on a specific disability group or secondary condition. Government funding agencies that support model systems involved in tracking the health status of a specific disability group (e.g., spinal cord injury, traumatic brain injury), should consider funding similar networks that conduct intervention research aimed at reducing specific secondary conditions.
Very few RCTs have targeted the reduction of secondary conditions in people with disabilities. There is a strong need for a new frontier of research that identifies the effective doses of structured exercise regimens and general physical activity needed to reduce various physical, psychological, social, and environmental secondary conditions in individuals with disabilities.
Understanding how exercise can affect various secondary conditions is a line of research that must be given a higher priority among funding agencies, in the same regard that other prophylactic measures, such as the use of medication and assistive technology, are scientifically supported with public and private funding. Evidence-based exercise guidelines associated with the reduction of various secondary conditions will require more empirical evidence before private and public health insurers will pay for these programs or services.
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GLOSSARY OF ASSESSMENT INSTRUMENTS USED IN THE STUDIES REVIEWED
AFI: Ambulatory Fatigue Index
AFI is a 500-meter walking test. Subjects are asked to walk at their maximum speed.
BDI: Beck Depression Inventory
BDI is a self-administered 21-item self-report scale that measures the supposed manifestations of depression and takes approximately 10 minutes to complete.
EDSS: The Kurtzke Expanded Disability Status Scale
EDSS is a method of quantifying disability in individuals with multiple sclerosis. EDSS quantifies disability in eight functional systems and allows neurologists to assign a functional system score in each of the eight areas. The functional systems are pyramidal, cerebellar, brainstem, sensory, bowel, bladder, visual, and cerebral. EDSS steps 1.0 to 4.5 refer to people with multiple sclerosis who are fully ambulatory. EDSS steps 5.0 to 9.5 are defined by impairment related to ambulation.
FI: Fatigue Index
FI is the ratio between the integral of muscle strength decay over time and maximal voluntary contraction using a knee muscle dynamometer. The fatigue index was defined as the ratio of the force F at time t (Ft) to the maximum force during stimulation (Fmax): FI = Ft/Fmax.
FIS: Fatigue Impact Scale
FIS evaluates the impact of fatigue on physical function (10 items), cognitive function (10 items), and psychosocial function (20 items).
FSS: Fatigue Severity Scale
FSS is designed to measure the impact of fatigue on function using nine statements for which subjects rate their level of agreement.
MFI: Multidimensional Fatigue Inventory
The MFI self-assessment questionnaire measures five dimensions of fatigue: general fatigue, physical fatigue, reduced activity, reduced motivation, and mental fatigue.
MOS SF-36 Health Survey: the Medical Outcomes Study 36-Item Short-Form Health Survey
Same instrument as the SF-36. Initially, the SF-36 was developed to
survey health status in the Medical Outcomes Study. It is a measure of health status designed for use in clinical practice, research, health policy evaluations, and general population surveys. It includes eight scales that assess the following general health concepts: physical functioning, role limitations due to physical health problems (role physical), bodily pain, general health perceptions, vitality, social functioning, role limitations due to emotional problems (role emotional), and mental health.
MSIS-29:29-item Multiple Sclerosis Impact Scale
MSIS-29 can be used to measure therapeutic outcomes in persons with multiple sclerosis. It consists of 29 items: (1) 3 items dealing with limited abilities and (2) 26 items related to the symptoms or the consequences of the illness.
MSWS-12:12-item Multiple Sclerosis Walking Scale
MSWS-12 is a questionnaire that asks the patient to self-rate the degree of limitation in walking due to multiple sclerosis experienced in the prior 2 weeks for each of 12 activities.
POMS: Profile of Mood States
The POMS provides a method to assess transient, fluctuating mood states. The key areas measured are tension-anxiety, anger-hostility, fatigue-inertia, depression-dejection, vigor-activity, and confusion-bewilderment.
SIP: Sickness Impact Profile
SIP describes relative functional limitations across 12 specific areas: ambulation, body care and movement, mobility, emotional behavior, social interaction, alertness behavior, communication, work, sleep and rest, eating, home management, and recreation and pastimes.