Participant A exhibited normal, linear increases in heart rate and oxygen consumption in the initial GXT (Table 1). Her blood pressure measurements also were normal. The GXT was terminated at volitional exhaustion when she could no longer maintain the test pedal speed (Table 1). Participant A did not meet objective criteria for a true maximal test. Ms. A's initial aerobic capacity (VO2peak = 23.4 ml/kg/min) was higher than the mean aerobic capacity reported for 61 women with MS (21.7 ± 5.5 ml/kg/min), the majority of whom, similar to Ms. A, exhibited mild disability.22 In the latter study, 51 of the 61 subjects had EDSS scores less than or equal to 3.5/10. However, her initial VO2 peak was below the 50th percentile (30.9 ml/kg/min) for healthy women in her age group.19
Spasticity in Participants B's right ankle plantar flexor musculature interfered with her ability to ride the bicycle ergometer. Foot straps, toe clips, and a low seat height were used to maintain her right foot on the pedal. Similarities existed between preintervention performances of the case subjects. Like Participant A, Participant B displayed normal heart rate and blood pressure responses during the initial GXT (Table 2). Furthermore, her GXT was stopped at volitional exhaustion and she also did not meet objective criteria for achieving maximal effort (Table 2). Ms B's initial VO2peak (17.6 ml/kg/min) was very low and met criteria established by the Social Security Administration for disability (18 ml/kg/min).19
Participant A's LT expressed as VO2 at LT (11.70 ml/kg/min or 3.34 METs) occurred at 50% of her VO2peak (Table 1). Ms A's LT was sufficient for walking at normal speed (ie, 3 mph) and for performing most daily activities but not large enough to perform moderately vigorous activities of daily living (such as climbing stairs which requires 4 METs) without breathlessness and accumulation of metabolic products associated with muscle fatigue.23
Participant B's preintervention LT (Table 2), expressed as VO2 at LT (7.32 ml/kg/min or 2.09 METS), was equivalent to the value considered necessary for performing light housework or walking about 2 mph.23 Her low LT and low VO2peak at baseline indicated that she was significantly deconditioned and, as a result, exercise beyond light house work or slow walking would be difficult for her.
Te initial FSS scores for our participants (Participant A = 5.4/7, Participant B = 5.6/7) were both above the mean score reported for healthy women of the same age and equivalent to means reported for individuals with MS and a similar EDSS ranking.4,24
EVALUATION AND DIAGNOSIS
Te Guide to Physical Therapist Practice Pattern 6B: Impaired Aerobic Capacity/Endurance Associated with Deconditioning served as an outline for management of the case participants.25 Both participants exhibited a low level of disability as defined by their EDSS scores. However, tests of cardiovascular fitness revealed that they both had impaired endurance large enough to impact their daily and recreational activity.
Te PT diagnosis for both participants was impaired endurance resulting in functional limitations and disability. Te prognosis for improvement in aerobic capacity following the intervention (an 8-week aqua aerobics class for people with MS) was good for both participants. It seemed plausible, based on the fact that individual A had not trained at a high enough intensity and individual B was deconditioned, that aqua aerobics at an appropriate exercise dose (similar bicycle ergometry) would increase cardiovascular fitness and may reduce fatigue.
Exercise Mode, Frequency, and Duration
Each participant attended an aqua aerobics class for people with MS. Te class was held 1 hour, 2 times per week for 8 weeks. Each class consisted of a 10-minute warm-up, 30 minutes of aerobic exercise, followed by a 20-minute cool-down period. Te warm-up and cool-down period included low-intensity aerobic exercises. Te cool-down also included resistance exercises in the pool. Te duration and structure of each class were based upon guidelines for exercise prescription with modifications specific for MS.16,26 Te number of classes per week and the program duration, 8 weeks, were determined by availability of the facility and staff. A physical therapist assistant with a certification in aqua aerobics served as the class leader and a physical therapist monitored the participants' exercise intensity.
During the 30 minute aerobic portion of the class, the participants exercised at an intensity equal to their LT. Training at LT overloads the peripheral vasculature and active muscles and increases the steady-state workload a person can perform without fatigue. This would appear to be beneficial for patients with MS and reduced activity level due to fatigue. Measurements of gas exchange, used to determine participants' LT, were not practical while exercising in the pool. Therefore, during the 30-minute aerobic portion of the class the participants were instructed to exercise at a heart rate equal to their heart rate at LT previously determined in their preintervention examination. This practical method for training at LT (ie, using heart rate at LT) is commonly used by competitive distance runners27 and has been employed in a bicycle ergometer training study involving patients with MS.4
Published guidelines for individualizing exercise intensity for people with MS (barring symptoms that require modification of the prescription intensity) are an intensity equivalent to (1) 50% to 70% of VO2peak or (2) 65% to 75% of HRpeak determined in a maximal graded exercise test.16,26 There are no specific guidelines related to the use of LT in individualizing exercise intensity for patients with MS. Te prescribed exercise intensity for Participant A (HR at LT = 115 bpm) occurred at 75% of her HRpeak and 50% of her VO2peak (Table 1). Te prescribed intensity for Participant B occurred at 72% of HRpeak and 41.3% of her VO2peak (Table 2). For both participants the prescribed exercise intensity was within existing guidelines.
VO2peak for Participant A
Similar to the pretest, in the post test Participant A exhibited normal cardiovascular responses (ie, heart rate, blood pressure, and oxygen consumption) to graded exercise (Table 3). Te amount of time Participant A was able to bicycle before reaching volitional exhaustion increased following the intervention and she achieved a higher fnal workload in the post-test (Table 3). Participant A's VO2 peak increased 11.4% from the pre- to the post-test (Table 3). However, despite improvement, Ms. A's VO2peak was still below the 50th percentile for healthy women in her age group.19
VO2peak for Participant B
Like Participant A, Participant B displayed normal cardiovascular responses during the post-test (Table 4). After training, Participant B was able to bicycle at a higher work load before reaching volitional exhaustion. Her post intervention VO2peak (20.60 ml/kg/min) was still slightly below the mean value reported for women with MS22 and was well below the 50th percentile for healthy women the same age range (28.2 ml/kg/min).19 Te intervention, however, increased her VO2peak 14.6% and to a value above the criteria for disability.
After intervention, LT increased for both individuals (Tables 3 and 4). Participant A's LT (15.7 ml/kg/min or 4.5 METs) had improved to the level required to comfortably sustain moderately vigorous daily and recreational activities.23 Participant B's LT (11.2 ml/kg/min or 3.18 METS) had improved to the level considered necessary for walking at a normal speed (ie, 3 mph).23
Fatigue Severity Scale
Te case subjects' scores on the FSS before and after training were as follows: Participant Abefore = 5.4/7, Participant Aafter = 3.6/7; Participant Bbefore = 5.6/7, and Participant Bafter = 5.6/7. Participant A reported a decrease in fatigue following endurance training, while Participant B reported no change in fatigue. After training, the participants FSS scores were still above the mean score reported for healthy women of the same age and equivalent to means reported for individuals with MS with similar EDSS rankings.24
This case report illustrates the use of metabolic and cardiovascular data obtained during a maximal GXT to (1) measure maximal aerobic capacity and estimate lactate threshold at baseline, (2) establish an appropriate exercise training intensity using HR at LT, and (3) measure the effects of an 8-week aqua aerobics class on indicators of cardiovascular fitness in 2 individuals with MS. Baseline exercise testing showed that both participants had a low aerobic capacity. Participant B's aerobic capacity was lower than Participant A's aerobic capacity. Participant B's higher level of disability, greater number of comorbidities, and lower level of physical activity, compared to A, likely accounted for her lower aerobic capacity. In general, people with MS, even people with low disability, have reduced aerobic capacity compared to healthy people.11,22 Furthermore, the magnitude of disparity between healthy people and people with MS appears to be related to the severity of MS.22,28 In addition to disability, factors such as comorbidities and participation in exercise may influence aerobic capacity.22
Following the 8-week aqua aerobics class, each participant's cardiovascular fitness increased as demonstrated by VO2peak and LT. Increases in VO2peak observed in this case report (11.4% for Participant A and 14.6% for Participant B) enabled the participants to perform more vigorous daily and recreational activities without breathlessness. The observed increases were within the range expected for sedentary healthy adults following land and aquatic exercise training (ie, 10% to 20%).29 For the MS population, improvements in VO2peak following land-based bicycle training have ranged from 10% to 22%.1–3,5,6 Table 5 summarizes studies that have measured cardiovascular adaptations to bicycle training in the MS population. The largest training effects were observed in studies involving combined leg and arm bicycle ergometer training, a higher training frequency (3 days per week vs. 2 days per week) and a longer training duration (> 8 weeks). In one bicycle training study involving 21 subjects with mild to moderate disability, the mean increase in aerobic capacity was 22%.2 The study subjects performed 30 minutes of combined leg and arm bicycle ergometry at 60% of VO2max 3 days a week for 15 weeks. In another training study, the investigators reported a 21% improvement in 13 subjects with MS and mild to moderate disability range following 15 weeks of training including 40 minutes of leg/arm ergometry at 60% of VO2max 3 times a week.1 The mean increase in aerobic capacity was 10% in the study in which 15 subjects with MS performed leg-only bicycle training at 60% of VO2max 2 times per week for 8 weeks.6
Since the principle of specificity of testing was not followed in this report (ie, the mode of exercise for testing and training were different), improvements achieved by the case subjects were expected to be less than improvements reported in previous studies in which subjects were tested and trained on a bicycle ergometer. Standardized protocols exist for testing aerobic capacity on land (eg, bicycle, treadmill, and step tests) but there are no tests that mimic aqua aerobics. Increasing the frequency and duration of the aqua aerobics class in this case report may produce even larger gains in aerobic capacity.
Information regarding exercise training and LT in individuals with MS is limited. Mostart and Kesselring4 showed that 4 weeks of aerobic training in an inpatient rehabilitation setting increased LT in subjects with MS. In their study 26 people with MS (EDSS range = 2.5 to 6.5) were randomly assigned to an exercise or non-exercise group. The exercise group performed five, 30-minute sessions of stationary bicycling per week in addition to physical rehabilitation. The non-exercise group performed physical rehabilitation only. Like the subjects in the present case report, the exercise group trained at an intensity equivalent to their heart rate at LT. The exercise group (n = 13) experienced a mean 12% increase in LT and a trend toward less fatigue (as determined by the FSS).4 There were no changes in LT or fatigue in the non-exercise group. Improvements in LT for our subjects (A= 33.8% and B= 53%) were much higher than the mean improvement reported by Mostart and Kesselring.4 Preintervention values for LT for participants in this case report (Tables 1 and 2) were below the baseline mean (14.29 ml/kg/min) for subjects in the experimental study.4 The case participants lower initial LT levels may explain larger improvements in LT observed in this report. The results of an investigation of the physiological responses of low fit older women to a 12-week aquatic exercise program lends support to this contention.30 Training resulted in a mean 20% increase in LT and furthermore, based upon the standard deviations reported for the mean LT before and after training, improvements as high as 49% may have been seen.30 Although the method used for determining LT in this case report is reliable in healthy individuals20, 31 the reproducibility in patients with MS is unknown. Therefore, a possible limitation of this case report is that random measurement error may also have contributed to the observed large improvements in LT.
Participant A's contention that her previous exercise class was ‘too easy’ was supported by her inability at the beginning of the current class to maintain the prescribed exercise intensity (HR at LT) and by her anecdotal comparisons of intensity of the 2 classes. When the current class began she was not accustomed to exercising at an intensity needed for her to achieve a cardiovascular training effect. Unfortunately exercise testing is not a routine component of community exercise classes in which people with chronic diseases and low disability (like Participant A) may elect to participate. The findings in this case report illustrate the benefits of baseline exercise testing to develop individualized exercise prescriptions and follow-up testing to monitor the effectiveness of an aerobic exercise regimen.
Physical therapists who prescribe cardiovascular exercise for patients with MS typically do not have access to the equipment used in this case report to directly measure maximal aerobic capacity (ie, metabolic cart). Alternatively, physical therapists can estimate aerobic capacity using bicycle exercise testing procedures (recommended for patients with MS) that involve determining the peak workload that the patient can achieve and the patient's heart rate at their peak workload.26 Furthermore, the HR obtained in the final workload can be used to establish an appropriate individualized training intensity.26 Use of age-predicted maximum heart rate (APMHR) to individualize intensity (rather than the actual HR response to graded exercise) is not recommended for the MS population.16,26 In patients who exhibit a blunted HR response to exercise resulting from a cardiovascular autonomic dysfunction use of the APMHR may result in a higher than indicated exercise intensity.16,32
Improvements in VO2 peak and LT in the present report were associated with decreased fatigue in Participant A but not Participant B. A limitation of the present case report is reliance on the FSS and the lack of additional instruments to measure fatigue, such as the SF-36 vitality subscale. The FSS discriminates between levels of fatigue in healthy and patient populations;18 however, the FSS may not be sensitive enough to assess changes in fatigue over time in patients with MS. Anecdotally Participant B said that the intervention made her feel more energetic and she was doing more activities at home. Use of a standardized assessment of self-reported physical activity would have augmented this case report.
The effects of training on fatigue differed for Participants A and B and may be an important factor related to exercise adherence for people with MS. Roehrs and Karst13 found that their 12-week aquatic aerobic program resulted in a significant decrease in fatigue (measured with the fatigue subscale of the Multiple Sclerosis Quality of Life Inventory) in 19 patients with MS (EDSS range = 1.5 to 8). They noted that only 19 of 31 adults with MS who agreed to participate in their study completed at least 25% of the exercise sessions. Issues related to withdrawal or sporadic attendance included poor bladder control, lack of transportation to the pool, and impaired mobility to get from the pool to the bathroom. Likewise, transportation and mobility issues impacted attendance in our aqua aerobics classes. Addressing these barriers appears to be important to promote adherence to aquatic exercise programs for people with MS.
Physical therapists often encourage people with MS to participate in aquatic aerobic exercise; however, little research has been conducted on the efficacy of aquatic aerobic exercise in improving the cardiovascular fitness of patients with MS. In this case report an 8-week aqua aerobic training program whose intensity was determined by exercise testing resulted in improvements in cardiovascular fitness in 2 individuals with multiple sclerosis.
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Keywords:© 2006 Neurology Section, APTA
ultiple sclerosis; aquatic exercise; cardiovascular fitness