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Effects of Aquatic Aerobic Exercise for a Child with Cerebral Palsy: Single-Subject Design

Retarekar, Runzun PT, MS; Fragala-Pinkham, Maria A. PT, MS; Townsend, Elise L. DPT, PhD

doi: 10.1097/PEP.0b013e3181beb039
Research Report

Purpose: The purpose of this study was to evaluate the effects of an aquatic aerobic exercise program for a child with cerebral palsy.

Methods: A 5-year-old girl with spastic diplegia classified at level III on the Gross Motor Function Classification System participated in this single-subject A-B-A design study. The aquatic aerobic exercise intervention was carried out 3 times per week for 12 weeks at an intensity of 50% to 80% of heart rate reserve. The Canadian Occupational Performance Measure, Gross Motor Function Measure, and 6-minute walk test were used as outcomes.

Results: Statistically significant improvements were found in the participation, activity, and body function components of the International Classification of Functioning, Disability, and Health model. Improvements in functional abilities and walking endurance and speed were recorded.

Conclusion: These findings suggest that an aquatic aerobic exercise program was effective for this child with cerebral palsy and support the need for additional research in this area.

This case study demonstrates improvements in activity, participation, and body function of a 5-year-old child following a 12-week aquatic exercise program.

Outpatient Physical Therapy, Spaulding Rehabilitation Hospital (R.R.), Boston, Massachusetts; Research Center for Children with Special Health Care Needs (M.A.F.-P.), Franciscan Hospital for Children, Brighton, Massachusetts; and Graduate Programs in Physical Therapy (E.L.T.), MGH Institute of Health Professions, Boston, Massachusetts

Address Correspondence to: Maria Fragala-Pinkham, PT, MS, Franciscan Hospital for Children, 30 Warren Street, Brighton, MA 02135. E-mail:

Grant Support: Supported by Marjorie K. Ionta Grant (to E.L.T.) and the John W. Alden Trust (to M.F.-P.).

This research was conducted in partial fulfillment of a Master of Science in Physical Therapy awarded to Runzun Retarekar by MGH Institute of Health Professions, Boston, MA.

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Routine moderate to vigorous physical activity is an important component in the prevention of disease and promotion of general well-being. The World Health Organization has emphasized the importance of physical activity as an influence on participation in the community.1 Children with cerebral palsy (CP) engage in less physically active play, participate less in playground activities, spend more time sitting, and take fewer steps per day than peers without disabilities.2–4 Reduction in physical activity levels in children with CP leads to low endurance and deconditioning.5 Children with CP have increased heart rates and energy costs with activity and tend to be less physically fit compared with their peers without disabilities.6

Cardiorespiratory endurance is an integral component of physical fitness and has been identified as the most important fitness component associated with health and mortality.7 Children with CP have decreased cardiorespiratory endurance, which may be limited by respiratory, cardiovascular, and skeletal muscle systems.5 With increasing evidence suggesting that children with CP have decreased levels of cardiorespiratory endurance compared with same-age peers, physical therapists have identified improving aerobic fitness as an important rehabilitation goal.8

Preliminary research suggests that aerobic exercise programs may improve cardiorespiratory endurance and other physiological responses of children and youths with CP.9,10 Although aerobic exercise has a positive effect on physiological outcomes for children with CP, the effects on activity and participation components are unknown.11 Effective modes for cardiorespiratory training include running overground, treadmill training, cycle ergometer, and aquatic activities. Because of muscle weakness, poor joint alignment, and contractures, children with CP are at risk for overuse syndromes or other chronic conditions.12 Low-impact aerobic exercise programs may provide children with CP the opportunity to improve cardiorespiratory endurance while at the same time avoiding further joint trauma and potential injury. Aquatic exercise is a form of low-impact exercise in which joint-loading forces are greatly reduced compared with land-based exercise.12 At the same time, however, water provides resistance that may be used to increase muscle strength and aerobic capacity.

Evidence supporting the benefits of aquatic exercise for children with CP is limited.12 The strongest evidence comes from a nonrandomized control trial evaluating the effects of a 6-month program of individual swimming activities and land-based movement exercise for 5- to 7-year-old children with CP.13 Significant improvements in vital capacity and swimming skills were observed for the intervention group. Because both land- and aquatic-based activities were included in the intervention, it is unclear how aquatic activities influenced outcomes. Additionally, no information was provided about the aquatic program training intensity, specific activities, or effect of improved vital capacity on functional abilities.

In a case series, 7 children with CP participated in a 3 times per week aquatic exercise program lasting 10 weeks.14 The sessions consisted of 15 minutes of trunk and lower extremity stretching, 20 minutes of lower extremity resistive exercises, and 10 to 15 minutes of water walking, running, or other endurance-promoting activities. Improvements in gross motor function and floor-to-stand transfers were observed. The changes in aerobic capacity were not measured; however, this case series demonstrates that children with CP were able to participate successfully in an aquatic exercise program with an aerobic exercise component.

In a more recent A-B design study, children with CP and other disabilities demonstrated significant improvements in cardiorespiratory endurance after a 14-week aquatic aerobic exercise program held twice per week.15 Children swam laps and participated in aquatic games and activities with a focus of maintaining a defined target heart rate (THR). In this group aquatic exercise program, a 1:2 coach-to-child ratio was used to promote safety and participation. Although this study also provides preliminary information about the effects of aquatic aerobic exercise on children with CP, results are inconclusive because only 2 children in this study had a diagnosis of CP.

From the available literature, it is evident that the effects of aquatic aerobic exercise on children with CP have not been thoroughly investigated. Additional research is needed to examine whether aquatic aerobic exercise has a positive effect on submaximal exercise tolerance, functional abilities, and participation on land. The purpose of this study was to evaluate the effects of an aquatic aerobic exercise program on participation, gross motor function, walking endurance, and energy expenditure in a child with CP who was ambulatory.

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A 5-year-old girl with spastic diplegic CP met inclusion criteria and participated in this study. She was classified at level III on the Gross Motor Functional Classification System (GMFCS). She used a posterior rolling walker and bilateral hinged ankle-foot orthoses for walking and a stroller for longer community distances. She was medically able to participate in an exercise program, had no history of orthopedic surgery or botulinum toxin injections, and was not receiving an intervention that focused on improving aerobic capacity. The child did not have passive range of motion limitations. She presented with hypotonia in her trunk muscles and spasticity in her hip adductors and extensors, hamstrings, and plantar flexors, with Modified Ashworth scores ranging from 1 (catch and minimal resistance through less than half of the range) to 2 (resistance through more than half of the range but limb easily moved). Her trunk and lower extremity strength was not formally assessed, although screening revealed muscle weakness with an inability to perform a sit-up or move from supine to sitting position without upper extremity support and difficulty in moving her legs during transitional movements such as rolling and getting up from the floor. She had no swallowing problems or risk for aspiration and was not fearful of the pool. The child and her mother signed informed assent/consent forms approved by the Institutional Review Board at Franciscan Hospital for Children.

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A single-subject A1-B-A2 design was used (Table 1). The baseline phase (A1) consisted of 6 data collection points at 1-week intervals for 6 weeks before the aquatic aerobic intervention. Phase B, the intervention phase, consisted of 2 to 9 data collection points over 13 weeks. The A2 phase constituted the second baseline phase or follow-up, lasted 13 weeks, and consisted of 2 to 3 data collection points. A single-subject design was used to gather preliminary data because of its feasibility in a clinical setting and plausibility to replicate in other clinical settings. Although single subject designs have methodological limitations, their use can also provide valuable clinical information,16 particularly when used to study a population with a heterogeneous clinical presentation such as CP. To strengthen the study design and to evaluate the stability of the outcome measures, 6-week baseline (A1) and 3-month follow-up (A2) phases were used, with the child acting as her own control. The child received physical therapy in school 2 times per week for 30 minutes per session and physical education 1 time per week for 30 minutes. The frequency of these services remained constant across the study period. She did not attend other after-school activities.

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Aerobic Exercise Intervention (B)

The study plan was to conduct intervention sessions 3 times per week for 12 continuous weeks, with at least 1 day of rest between sessions. To accommodate the family’s schedule, rest days between sessions were not always possible. In addition, because of family illness, week 11 occurred after a 1-week break. The intervention sessions were carried out in an 8 × 12-ft therapeutic pool at a pediatric rehabilitation hospital. The pool temperature ranged from 86°F to 90°F and was equipped with an underwater treadmill with variable speed and water height. A physical therapist was in the pool with the participant at all times.

The aims of the aquatic aerobic intervention were to increase: (1) duration of time that the participant spent exercising in her THR zone; (2) duration of continuous exercise without a rest break; and (3) treadmill walking speed. The intervention began with a 5-minute warm-up, included a 30- to 40-minute aerobic exercise program, and ended with a 5-minute cool down. Activities were chosen to emphasize larger muscle groups and also fun for the participant (Table 2). Throughout the aerobic exercise phase, the child was encouraged to work as hard as possible to maintain her heart rate within the THR zone. A Polar E200 monitor (Polar Electro, Inc., Lake Success, NY) was used to record the child’s heart rate. The child rested when she became tired and could not sustain exercise.

To establish an initial aerobic exercise prescription (treadmill speed, exercise duration, and training heart rate range), we used a progressive submaximal treadmill test. Because a progressive submaximal treadmill protocol for an aquatic environment has not been established, we used a land-based protocol for guidance.17 Given the drag force of water, walking in the aquatic environment is more effortful than on land, and this difficulty increases further at higher speeds.13 Because the participant was classified at level III on GMFCS, the aquatic submaximal treadmill test was initiated at a lower speed of 13.4 m/min and progressed by 5.4 m/min every 2 minutes. Testing was terminated after 12 minutes at the speed of 40.2 m/min, or when the participant began to hang on the support bar and could no longer initiate steps. The highest heart rate corresponding to this speed was 135 beats per minute (bpm). We began aerobic training on the treadmill at 24.1 m/min because this speed corresponded to 50% of her heart rate reserve. The THR zone was calculated using the heart rate reserve or Karvonen’s formula18 and was further adapted for an aquatic environment by subtracting 17 beats: [(200 − age) − RHR] × 50 − 80% + (RHR) − 17 = THR, where RHR is the resting heart rate.19 The THR zone ranged from 135 to 165 bpm for the participant. Working heart rate (WHR) in the aquatic environment is adjusted because heart rates are lower in water with the same benefits for similar work levels on land, given increased heat dissipation, lesser effects of gravity, compression due to hydrostatic pressure, and more efficient transfer of oxygen.20

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Outcome Measures

A variety of outcome measures were chosen to document changes across components of the World Health Organization International Classification of Functioning, Disability, and Health (ICF).1 Testing was conducted by 2 physical therapists (R.R. and M.F.P.), who were also involved in the intervention. Established protocols were used for administration and scoring. Tests were conducted in a standardized order across sessions, on the same day of the week and time of day in the physical therapy (PT) clinic setting. During phase B, testing was done before the pool training sessions.

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Canadian Occupational Performance Measure (COPM).

The COPM is a valid and reliable clinical measure of a child’s or parent’s perception of performance and satisfaction in the areas of self-care, productivity, and leisure.21,22 The COPM identifies restrictions in participation as perceived by the patient/parent and therefore can be used to measure changes in the participation component of the ICF.22 This measure has also been shown to be responsive in measuring the effects of short-term interventions for children.23 Minimal detectable change values (MDC90) for the COPM have been established: 1.8 points for performance and 2.1 points for satisfaction.22 MDC90 is the magnitude of change over and above the error of measurement of repeated measures at the 90% confidence interval. 24

The COPM was administered to the participant’s mother by a therapist (R.R.). The mother initially identified the following 5 activities as the most important things for her child to accomplish as a result of intervention: (1) walk outdoors longer distances with a walker, (2) pull up her pants without help while standing, (3) use her hands to play with toys while standing, (4) sit independently without arm support, and (5) stand up from a sitting position. The parent graded the child’s performance and her satisfaction of the performance for each activity on a scale of 1 (lowest performance/satisfaction) to 10 (highest performance/satisfaction). The parent chose these tasks because they were important to life situations, and the parent considered the child’s involvement in life situations when grading these 5 tasks. For example, for “walking outdoors longer distances,” the participant’s mother considered the child’s ability to walk around the neighborhood with the rest of the family in the evening after dinner. “Pulling pants up while standing” was considered important to child and parent because independence in this task would allow the child to go on play dates to other children’s homes. Finally, better standing and sitting ability would allow the child to play more easily with other children of her age.

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Gross Motor Function Measure.

The Gross Motor Function Measure-66 (GMFM-66) was designed to evaluate change in gross motor function in children with CP.25 It provides information for the activity component of the ICF. The GMFM-66 has also been used to examine the relationship between cardiorespiratory function and gross motor function in children with CP.6,26 The GMFM-66 has been shown to be a reliable measure, with excellent test-retest reliability (ICC = 0.9932).27 It is responsive to change in children with CP over a mean interval of 3.5 months with an MDC95 of 1.58 points.28 The measure was administered by a physical therapist (R.R.) while another therapist (M.F.P.) observed and recorded item scores. The GMFM-66 testing was video recorded and later scored for reliability by a third therapist (E.L.T.) not involved in treating the child. Videos were randomly coded to mask the scorer to testing sequence. The scoring by M.F.P. was used for all data analysis.

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6-Minute Walk Test.

The 6-minute walk test (6MWT) is a clinical measure of submaximal functional exercise capacity. It provides information for the activity component of the ICF. High test-retest reliability (ICC = 0.98) and MDC95 values (47.4 m) were recently established for children aged 4 to 18 years with CP and GMFCS Level III.29 The 6MWT was administered according to the American Thoracic Society guidelines with modifications to keep the child focused.30 A therapist walked alongside the child and provided frequent verbal encouragement throughout the task. Before the start of the 6MWT, the child sat and rested for 3 minutes, and the RHR was recorded every 10 seconds during the last 30 seconds of the 3-minute rest. For the last 30 seconds of the walk, the heart rate was recorded every 10 seconds and then averaged to obtain a WHR. The distance that the child walked in 6 minutes was recorded. The first 2 testing sessions in the A1 phase were considered as practice sessions and were excluded from data analyses because the child required physical assistance to turn around at the endpoints. Other researchers have used 2 practice sessions for children performing the 6MWT.31

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Modified Energy Expenditure Index.

Energy expenditure index (EEI) has been validated as a measure of energy expenditure during walking for children with CP.32,33 Excellent test-retest reliability has been established in adolescents with CP (ICC = 0.94).34 EEI scores are influenced by the RHR, WHR, and walking speed of the child. RHR has been shown to be unstable in young children and can be influenced both by the child’s comfort level with testing35 and ability to maintain a resting position. This child had difficulty sitting still during the 3-minute sitting-rest period, making the RHR variable. Therefore, we calculated a modified EEI (MEEI) using WHR and walking speed, eliminating the unstable RHR variable, as modeled in a previous study.36 Test-retest reliability of the MEEI for children and youth without disabilities is high (ICC = 0.83). MEEI was calculated using data from the 6MWT and the following equation: MEEI = WHR/Speed.4,37 MEEI provides information for the body function component of the ICF.

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Physical Activity Questionnaire.

The child’s mother completed a physical activity questionnaire while the child performed the 6MWT. This questionnaire included one question from a patient-centered assessment of physical activity (“How many days per week did your child participate in 60 minutes or more of moderate to vigorous physical activity over the past 7 days?”).38 In a study by Pate et al,39 it was found that 96.3% of children engage in physical activity of moderate intensity for an average of an hour per day, 5 or more times per week. Because children with CP at GMFCS level III often have decreased physical activity levels,3 we also added a second question to capture any potential changes in physical activity: “How many days per week did your child participate in 20 minutes of moderate to vigorous physical activity over the past 7 days?” Moderate to vigorous was defined, and examples of physical activities were provided. A question about the frequency, duration, and activities of the PT sessions at school was also included. This questionnaire was not a primary outcome measure but was used to evaluate trends in this child’s physical activity level over this 32-week study.

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Statistical Analyses

Data were analyzed using the 2 standard deviation (SD) band method.16 Two consecutive points in the intervention phase outside the 2SD bandwidth of the baseline phase suggest an effective intervention and constitute statistical significance.

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The participant attended 34 of the 36 planned sessions. Improvements in all 3 components of the ICF were observed for this child after she participated in an aquatic aerobic exercise program. In the participation component, improvements on the COPM-performance component were evident. Beginning in week 4 of phase B, COPM-performance was consistently above the +2SD band, suggesting a significant increase in the child’s mobility performance in her home and community environments as perceived by the parent (Fig. 1). This improvement was maintained during the A2 phase. A similar pattern of results was observed for the COPM-satisfaction component, suggesting that the parent became more satisfied with the child’s mobility performance at home and in the community with intervention (Fig. 2). Improvements in both components of the COPM exceeded the MDC90 values of 1.8 points for performance and 2.1 points for satisfaction.22

In the activity component of the ICF, a significant increase in GMFM-66 scores was observed in phase B compared with A1 (Fig. 3). This improvement was maintained in the A2 phase. A 2.71 point improvement on the GMFM-66 was observed when the mean baseline score was compared with the score at the end of the 13-week B phase, exceeding the 3.5-month MDC95 of 1.58 points.28 Interrater reliability for the GMFM-66 between the two raters was moderate (ICC1,2 = 0.70).

Improvements in walking endurance were also observed, with an increase of 27.1% in the distance walked in 6 minutes from the mean of the A1 phase [232.94 m (SD = 10.16)] to the end of the B phase (296 m). This child increased her walking speed by 9 m/min and walking distance by 56 m, which exceeds the MDC95 of 47.4 m, suggesting a significant improvement above potential measurement error. In the A2 phase, her speed and distance for the 6MWT progressively decreased over time, returning to baseline values. Data analysis using the 2SD band method confirmed the robustness of these findings, with 8 consecutive points in the B phase at or above the +2SD band (Fig. 4).

A significant decrease in MEEI from baseline to phase B was observed (Fig. 5). A decrease in MEEI suggests changes in the body function component of the ICF and represents a significant improvement in walking efficiency. The mean MEEI was lower in the B phase [3.12 bpm (0.19)], compared with that of A1 [4.04 bpm (0.31)] and A2 phases [3.61 bpm (0.36)], whereas mean walking speed [45.19 m/min (3.06)] was greatest in the B phase. Thus, the participant walked with both maximum efficiency and speed in the B phase. Improved walking efficiency occurred because the child walked at higher speeds, whereas her mean WHR remained constant.

The child’s exercise tolerance increased during phase B. Her treadmill training speed in the pool increased from 24 to 48.3 m/min (Fig. 6). By the end of phase B, the participant was able to exercise in her THR zone 4 times longer (32 minutes) than at the beginning of the intervention (8 minutes; Fig. 7). Total exercise time represents a sum of multiple shorter bouts of exercise. Her ability to sustain exercise also improved with training. She began walking on the pool treadmill at 24.1 m/min for 4 continuous minutes and progressed to 48.3 m/min for 8 continuous minutes, before requiring a rest break.

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In this study, the effects of aquatic aerobic exercise on participation, activity, and body function components of the ICF were evaluated in a 5-year-old girl with spastic diplegia. With the aquatic intervention, improvements in all ICF component indices were observed, supporting the robustness of these findings. Improvements in gross motor skills and endurance were similar to those reported in other aquatic exercise studies.14,15

We observed participation component changes after a 12-week intensive aquatic aerobic exercise program. Improvements in the participation component have been documented for school-age children with CP, engaging in a land-based exercise program including a combination of strength, aerobic, and anaerobic training.40 Participation component changes after aquatic exercise, however, have not been previously documented. We used the COPM to index participation component changes because it provides information about a child’s performance of functional activities in the context of her home and community as perceived by the child’s mother. Participation measures such as the COPM help to identify whether changes seen at body function and activity components of the ICF actually translate to improvements in participation, an important aim of PT intervention. Our intervention did not include specific practice of the activities specified by the mother on the COPM (eg, pulling up pants while standing and playing with toys while standing or walking outdoors with a walker). Components of these activities, however, were evident in our aquatic exercise program. For example, the majority of aquatic activities was performed in a standing position and consisted of standing and walking with minimal arm support or assistance. In addition, aquatic activities focused on increasing walking speed and endurance and walking/running while holding toys, which were directly related to goals her mother identified on the COPM. Thus, although the intervention was not designed to target COPM goals, some overlap is apparent. Given evidence supporting task-specific training, this overlap may have contributed to the robustness of gains in the participation component. The COPM was scored by the mother, who accompanied the child for most exercise and testing sessions. Although the scores of previous administrations of the measure were not disclosed to the parent, her ratings may have been influenced by her knowledge or expectations of the study. Expectation biases are an inherent weakness of repeated administration of self- and parental-report measures without blinding. Significant change in other outcomes in the body function and activity components, however, supports the idea that these changes suggest actual participation improvement for the child. Future studies should consider adding participation measures to those that involve parental report, incorporating ratings by individuals (eg, school PT, teachers) that remain masked to study design.

Significant increases in GMFM-66 scores suggest that the aquatic exercise program, which specifically targeted endurance, also improved this child’s gross motor function. Several possible explanations, both direct and indirect, should be considered. First, the aquatic exercise program included walking and running, which are also evaluated with the GMFM. Indeed, the child showed improved scores on the standing and walking items of the GMFM across the B phase, which suggest a direct translation of upright activities and walking abilities from water to land. Second, the aquatic program likely provided challenges to both muscular strength and endurance,13,26,41 which may contribute indirectly to improvements in gross motor function. Aquatic activities (fast walking, running, and repetitive jumping) were performed at relatively fast speeds to maintain an increased heart rate. An increase in the speed of movement in an aquatic environment provides higher resistance to movement. When speed doubles, resistance increases 4-fold.42 Improvements in muscle strength and endurance may relate to gains on several GMFM items, including those indexing balance. Other studies of aerobic training in persons with disabilities have demonstrated a link between strengthening and improved balance. For example, treadmill training significantly increased knee extensor and flexor strength and also improved balance in adults with Down syndrome.43 In this aquatic study, the child showed marked static balance gains on items 53 and 56 (standing: maintains arms free for 3 seconds and 20 seconds, respectively). At baseline, the child could not stand without support. Postintervention she stood without support for 6 seconds or more (Fig. 8). Static balance is defined as the “ability to maintain a posture.”44 Improved static balance could be related to increased muscle strength and endurance, and improvements in flexibility, motor control, postural control, or proprioception. Muscle strength, flexibility, motor control, and proprioception were not measured in this study. Therefore, the mechanisms underlying improvement in gross motor function remain unclear. In future studies, additional measurement of muscle strength, range of motion, and postural control would allow further exploration of the relations between improvements in land-based gross motor function and aquatic exercise.

The child’s GMFM improvement in phase B seems to be clinically meaningful and beyond that likely with development alone. Based on GMFCS Level III reference curves,45 a mean change of 3.3 percentile points is anticipated over a 1-year period for a 5-year-old child with CP classified at level III.46 Furthermore, there is an 80% probability that GMFM scores for a child at level III will be within 15.9 percentile points over a 1-year period. In this study, the child improved 10 percentile points, from 70th percentile up to the 80th percentile, over just the 13-week intervention phase. This amount of improvement exceeds what would be predicted for her over this short time frame. Her improved performance was partially maintained over the A2 phase, when she decreased to the 75th percentile. The A2 phase decline, however, did not exceed the 3.5-month MDC95 and was not considered significant.

The GMFM-66 was repeated multiple times during the study, introducing a risk of training effects. Relative stability in scores across 6 baseline testing sessions, however, does not support the idea that repeated measurement and training effects confounded the results. Two data points during the intervention phase could be viewed as a weakness of our study design. It is ideal to have 5 or more data points in each phase, however, because of the administration time burden and potential for training effects from repeating the GMFM-66 during the intervention phase, we determined that 2 points during the intervention phase were reasonable. Three data points for the A2 phase were not ideal, but were chosen to limit testing burden for the child and family. In addition, to increase study design rigor, we had another therapist who was not involved in the intervention score, the GMFM-66, from videotapes which were presented in a random sequence. We anticipated that the interrater reliability would be high; however, this analysis revealed a moderate correlation (r = 0.72). Several factors should be considered to explain this moderate correlation: (1) the testing therapist may have been biased given her involvement in the intervention, although she did not have previous test scores available during testing and scoring; (2) the therapist who was masked to test order did not grade some items and had difficulty grading other items due to poor video quality and these items might have been graded incorrectly; and (3) the therapist who was masked to test order was relatively inexperienced in scoring the GMFM-66. In planning future studies, these factors would be altered to improve study rigor.

As anticipated, MEEI decreased with aerobic training. This finding is similar to that of other studies in which walking efficiency for self-selected or fast-paced walking improved after participation in a land-based fitness program that had an aerobic exercise component.47,48 When the intervention was discontinued in the A2 phase, the child’s energy expenditure increased, indicating a decrease in walking efficiency. Taken together, these findings suggest that energy expenditure decreased as a result of the aquatic intervention and that continued vigorous exercise is necessary for this child to maintain training effects.

The improvement in GMFM-66 scores was maintained across a 13-week period of no intervention, whereas increases in speed and distance in the 6MWT were not. Children perform the gross motor skills of walking, getting up from the floor, and standing with and without support while playing. This daily practice may enable a child to maintain gross motor abilities gained during the intervention; however, continued cardiorespiratory and muscular endurance training may be necessary to maintain improvements in walking speed and energy cost. Verschuren et al40 reported similar findings that improvements in aerobic capacity for children and adolescents with CP were not maintained 4 months after the training program ended.

Variability in MEEI scores was observed, and not all data points were significant in phase B. Because workload (distance walked and speed) does not stay constant across times of measurement in a 6MWT as it might on a treadmill protocol, EEI data can be challenging to interpret. A design in which distance and/or speed were held constant would allow for a more direct comparison of energy expenditure across times of measurement and provide clearer results for interpretation. Although overall mean MEEI decreased in phase B, her MEEI across all phases of the study is still much higher than in typically developing children of her age.36 This finding supports previous reports of higher energy costs for walking in children with CP.35,49

During phase B, this child increased the frequency with which she performed moderate to vigorous physical activity as indexed by the physical activity questionnaire (Fig. 9). Even with this increase in physical activity during the intervention phase, she still did not meet the Department of Health and Human Services current Physical Activity Guidelines for Americans. These guidelines recommend that children do 1 hour or more of moderate to vigorous physical activity daily. Without the opportunity to participate in a formal, structured program as in the aquatic exercise program, this child rarely attained the recommended minimal physical activity requirements during A1 and A2 phases.

We found that the effects of training were lost during the withdrawal phase; therefore, continuation of aerobic exercise to maintain training gains is recommended. Adapted aquatic exercise or swim programs and inclusive land- or aquatic-based exercise programs at local health clubs may have assisted this child in maintaining or continuing to improve her level of aerobic fitness, activity, and participation.

Finally, over a 20-week period from baseline to the beginning of phase A2, the participant grew in height and weight, yet her body mass index decreased from 16.5 (81st percentile) to 16.2 (75th percentile). Rate of height gain exceeded weight gain, which may relate to an increase in this child’s energy expenditure during training. Future work should include monitoring height, weight, and body composition to evaluate the relationship between training and anthropometrics.

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An aquatic aerobic exercise program is feasible in a clinical setting with pool access. Evaluation of and intervention for aerobic function in children with CP is a key component of physical therapy management. Physical therapists must consider the potential impact of cardiorespiratory system function on activity and participation for children with CP. Exercise in an aquatic environment introduces children with CP to a medium in which they can perform activities with less joint stress than on land and, hence, attain a higher aerobic training intensity.11 Activities in the water can also be fun and more novel for children, potentially enhancing motivation and interest (Table 2).

Improvements in all three components of the ICF—body function, activity, and participation—were observed for a child with CP after participation in an aquatic aerobic exercise program implemented by a physical therapist. Continued training is required to maintain the gains in all components. Although a single-subject design has limited generalizability, this pilot study can be used to guide design of future, more methodologically rigorous studies. The findings provide preliminary evidence supporting the effectiveness of an aquatic aerobic exercise program in children with spastic CP and support the need for additional research in this area.

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The authors thank the child and her family for participating in this study.

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activities of daily living/classification; cardiovascular physiological phenomena; case study; cerebral palsy/therapy; child; exercise therapy; health promotion; motor activity/physiology; physical endurance/physiology; physical fitness/physiology; respiratory physiological phenomena; walking

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