INTRODUCTION AND PURPOSE
Physical therapy plays a critical role in managing the sequelae of cerebral palsy (CP).1 More than 40% of 3- to 17-year-old children with CP experience challenges crawling, walking, running, or playing.2 For many, the resulting limitations in physical activity negatively impact musculoskeletal and cardiovascular function, and increase risk for secondary medical conditions.3 Feasible and effective interventions are needed to improve the mobility and cardiorespiratory fitness of children with CP.
Principles drawn from the neuroscience literature emphasize the merit of having individuals with neurologic injury engage in high-intensity repetition of gait-like movements to promote behavioral and neurologic recovery of walking, yet this approach is often impractical in real-world settings.4,5 For example, body-weight-supported (BWS) treadmill training has been used to address walking and fitness goals of children with CP6; however, routine use in smaller clinics, schools, and home settings is often infeasible, given physical labor requirements associated with helping a child with notable weakness, spasticity, or endurance challenges sustain stepping. Robot-assisted stepping devices (eg, Lokomat) reduce labor demands; yet, expense limits widespread implementation beyond metropolitan areas.7
The motor-assisted elliptical intervention (Intelligently Controlled Assistive Rehabilitation Elliptical [ICARE]) is used in a variety of settings to address walking and fitness goals of individuals with physical disabilities and chronic conditions.8–13 Traditional ellipticals incorporate varying levels of flywheel resistance to challenge users while training. The ICARE not only includes the resisted modes but also incorporates a motor-drive system that assists with pedal advancement, enabling individuals with limited endurance and/or weakness to cycle in a gait-like movement pattern at speeds up to 65 cycles per minute (CPM).8–11,13–16 As capacity improves, the device's speed, amount of motor assistance, external BWS, and step length can be modified to promote continued challenge. While the ICARE was initially developed for adults and older (taller) children, a prototype version of the device has been created to address gait and cardiorespiratory training needs of children as young as 3 years.15,17 Among other features, the prototype enables step lengths as short as 20 cm (vs the traditional 43-74 cm) and integrates height-adjustable pedals such that children can see and interact with the control console.
Despite growing clinical use, there are only limited published data to guide ICARE use, particularly for children. For example, following a 24-session ICARE intervention, an adult with progressive supranuclear palsy reportedly walked farther (ie, 6-minute walk test) and more efficiently (ie, lower oxygen cost during treadmill walking).8 Published abstracts provide insights into gait improvements following ICARE intervention, but fail to adequately describe the underlying rationale for intervention progression, nor the actual treatment delivered and session-by-session responses.10,11,13
Previous research in adults without known disability identified that ICARE training at faster compared with slower speeds increased demand in key lower extremity muscles essential for stability and forward progression during walking.18 When children developing typically overrode the ICARE motor's assistance, select lower extremity muscles had increased activation (electromyographic activity) compared with exercising with the motor's assistance.15 Given greater skeletal muscle activation at faster speeds and when overriding the motor's assistance, it is conceivable that cardiac load (eg, heart rate) also increased,19 but heart rate data were not reported.
The purpose of this case study was to investigate the effect of a semistructured 24-session primarily moderate- and vigorous-intensity ICARE training program on walking and fitness of a child with CP. Based on prior studies involving adults with neurologic conditions,8,13 we hypothesized that our proposed intervention would enhance the child's walking and fitness. We describe the proposed and actual ICARE protocol progression and highlight suggestions for future research.
DESCRIPTION OF CASE
Prior to participating in the study, parental informed consent and child assent were secured using a protocol approved by the Institutional Review Board at Madonna Rehabilitation Hospitals. Physician clearance was also obtained, confirming the child's capacity to participate.
Child Description and History
A 12-year-old boy diagnosed with spastic diplegic CP participated. The child did not receive other therapy during the study. His medical history included hydrocephalus (ventriculoperitoneal shunting at 17 months old), bilateral hamstring tendon lengthening (at age 5 years), repeated pneumonia, and asthma (managed with 5 mg of Singulair and Advair inhaler, once daily). Preintervention, his motor function was classified as Gross Motor Function Classification System (GMFCS) II20 and he engaged in an intermediate level of physical activity based on his overall rating of 3.2 in the physical activity domain of the Children's Assessment of Participation and Enjoyment questionnaire21 (1- to 7-point scale; 7 represents greatest time engaged in physical activities). Observationally, the child's standing posture was crouched bilaterally and he maintained this posture without external support for 30 seconds prior to the examiner initiating the next assessment. Sit-to-stand transfers were accomplished without use of hands. The child had ankle-foot orthoses that were not consistently used at home, in the community, or during training sessions. Pre- and postintervention evaluations were performed without ankle-foot orthoses. He did not require physical assistance or assistive devices to walk on level surfaces but used a handrail to negotiate stairs and a wheelchair for longer distances. The parent reported the child fell approximately 1 time per week, but none necessitated hospitalization.
During baseline assessment, his blood pressure (BP, 125/73) heart rate (HR, 92), and oxygen saturation (SpO2%, 98) were within normal limits for his age. The child denied joint or muscle pain. Passive range of motion was limited bilaterally. Right and left popliteal angles lacked 71° and 75° of full knee extension, respectively (measured in the supine position with hips flexed 90°). Right and left ankle dorsiflexion were limited to 3° and 7°, respectively (measured with knee extended). Manual muscle testing graded his bilateral hip extensors good (4/5), knee extensors normal (5/5), and ankle plantar flexors poor minus (2−/5). His body mass index (19.7) was between the 50th and 75th percentiles for boys developing typically22 based on his measured height (138 cm) and weight (37.5 kg). Assessment of tone in major lower extremity muscle groups identified an increase in the right hip adductors (scored 1 on the 0- to 4-point Modified Ashworth scale), and the remainder of muscle groups assessed (bilateral knee extensors, ankle plantar flexors, hamstrings, and left hip adductors) were graded as 1+. The child was alert and oriented to person, place, and time. He communicated verbally without apparent difficulty.
DESCRIPTION OF INTERVENTION AND OUTCOME ASSESSMENT
The intervention was performed on an E872MA ICARE (SportsArt, Mukilteo, Washington) motor-assisted elliptical that was modified to enable children as young as 3 years to cycle in a gait-like movement pattern at speeds up to 65 CPM (Figure 1).15 Step length could be adjusted from 20 to 71 cm in the horizontal direction, and the pedals could be elevated up to 38 cm from the original height to enable children of smaller stature to interact with the console. The device included an integrated BWS system.
Prior to starting the intervention, the child was familiarized with select ICARE features (eg, “stop” buttons and speed controls) and baseline training parameters were identified. Specifically, step length was gradually increased until the child, parent, and researcher agreed the length was comfortable and allowed for a late stance trailing limb posture (thigh observationally extended). The child trained with motor assistance for approximately 5 minutes, as speed was progressively increased until the child's HR approximated 70% of estimated HR maximum (HR max) according to the predictive equation: 0.7 × [208 − (0.7 × age)].23
The child attended the first of 24 training sessions, which were planned to occur 3 times per week over the course of 8 weeks. During 24 sessions, a series of systematic manipulations to training parameters (eg, total exercise time, speed, and time overriding motor's assistance) was planned to promote greater cardiorespiratory fitness while also encouraging more step-like movement cycles each session. Consistent with recommendations for building physical activity in children with GMFCS II, initial training sessions were intentionally shorter and less vigorous to allow for acclimation to exercise and reduce the risk of injury.24–26 Later sessions integrated a greater duration of moderate- (50%-70% of predicted HR max) and vigorous-intensity exercise (70%-85% HR max) to promote cardiorespiratory fitness.27 The protocol's conceptual framework emerged, in part, from the exercise sciences, which emphasizes the value of systematic progression.26 Training duration was scheduled to increase by approximately 5% every session and training speed by approximately 5% every 4 sessions. In addition, brief bursts (1-minute bouts) of higher-intensity (>70% HR max) training were scheduled to initiate during the third session by having the child override the device's motor at predetermined intervals. Every 2 sessions, an additional 1-minute bout of higher-intensity training was added (if tolerated). HR and BP were recorded at rest and immediately following each bout of exercise using procedures previously described. The BWS system was used in case of a loss of balance, but external support was not provided. Within and across sessions, intervention customization (eg, adjusting the speed) was allowed to address the child's feedback (eg, perceptions of fatigue) and to fine-tune exercise intensity based on measured cardiorespiratory responses.
Prior to initiating the familiarization and training sessions, seated resting HRs were recorded using the Masimo Rad-5v Signal Extraction pulse oximeter (Masimo Corp, Irvine, California) and procedures described by the manufacturer. During training, exercise HRs were recorded continuously using a Polar H1 Heart Rate Pro Sensor (Polar Electro Oy, Kempele, Finland) and a laboratory-based data logger. Resting BPs were measured with the child seated and arm elevated to heart level using a factory-calibrated (±3 mm Hg or 2% of reading) Omron 7300IT automatic blood pressure monitor (Omron Healthcare Inc, Bannockburn, Illinois) and appropriately fit standard adult cuff aligned over the brachial artery according to the manufacturer's specifications. Exercise BPs were measured immediately following each exercise bout using the same equipment and procedure.
Pre- and Postintervention Mobility and Endurance Assessments
A GAITRite Platinum electronic mat (CIR Systems Inc, Clifton, New Jersey) recorded and quantified gait characteristics (ie, velocity, cadence, and stride length, single-limb support time) as the child completed 3, 10-m walk tests (10MWT) at a self-selected comfortable speed following by 3, 10MWTs at a self-selected fast pace.28 The 2-minute walk test (2MWT), a valid measure of walking endurance,29 was completed by having the child continuously traverse a 38.4-m unobstructed corridor for 2 minutes at a self-selected comfortable speed. Mobility was further assessed by having the child complete 3 Timed Up and Go (TUG) tests, which were modified by using an 80 × 35-cm bench adjusted to position the child in 90° of hip and knee flexion, with feet comfortably on the ground at test initiation. The child was asked to stand up, walk around a cone (placed 3 m away), and return to the bench. Instructions were repeated during test performance. To ensure natural performance, no qualitative instructions were provided (eg, “walk as fast as you can”). The test started as the child's buttocks elevated from the seat and stopped as the child's buttocks again touched the seat at the trial's end. The modified TUG has well-established reliability for assessing children's and adolescents' mobility, including those with CP.30,31 The same measures of mobility and endurance were recorded pre- and postintervention.
Postintervention Feedback on ICARE Intervention. Following the intervention, the child and parent were individually asked to provide a yes/no response to the question “If this piece of equipment was available for you [your child] to use in your home/school/therapy setting would you [your child] use it?” Following each dichotomous response, an open-ended response to “Why?” was sought. The mother manually entered her yes/no reply and response to the open-ended question into the laboratory's Select Survey.net v5.0 software application (ClassApps, Kansas City, Missouri). Given the child's typing skills, the child's responses were recorded verbatim to the Select Survey software application by a member of the research team.
Data from the 3 comfortable 10MWT trials were averaged to calculate the mean speed (m/s), cadence (steps/min), stride length (cm), and single-limb support (% gait cycle) pre- and postintervention. The same approach was applied to the self-selected fast 10MWT trials. Walking endurance was evaluated as the maximum distance (m) traversed during the 2MWT. The best (fastest) of 3 modified TUG tests was used for comparison of dynamic stability and mobility during gait. Minimal clinically important difference (MCID) values were reported for the 10MWT,32 2MWT,33 and modified TUG31,34 and served as a reference for considering the significance of change. Qualitative comments from the child and parent following completion of the intervention were reported verbatim.
DESCRIPTION OF OUTCOMES
Although our a priori goal had been for the child to exercise 3 days per week for 8 weeks, scheduling conflicts (eg, participation in art camp) resulted in the child training an average of only 2.8 times per week. As a result, 9.4 weeks (66 days) were required for the completion of the 24 training sessions. The child and his family confirmed that he did not engage in other therapy throughout the intervention.
ICARE Training Capacity Changes Across Sessions
During the first session, the child trained for 23 minutes with the motor's assistance at an average speed of 39 CPM, allowing for a total of 890 strides at an average step length of 38.6 cm (Figure 2). The average exercise HR across the first session's exercise bouts was 135 beats per minute (bpm). During the first week, the child achieved 70 minutes of moderate-intensity exercise. During the second week, the child completed more than 75 minutes of ICARE exercise, a small portion of which was performed at a vigorous intensity. By session 13, total training time increased to 39 minutes (of which 6 minutes were performed while overriding the motor's assistance) and speed was faster (average of 45 CPM), thus allowing for a nearly 2-fold increase in total strides (1660) compared with baseline. Step length was longer (43.9 cm). This increase in activity was performed at a lower average exercise HR across 13 exercise bouts (104 bpm). The child's HR while overriding the motor's assistance was 144 bpm. During the final training week, the child completed 148 minutes of moderate- to vigorous-intensity (or greater) exercise. By the final session, training was performed for 50 minutes (11 minutes performed while overriding the motor's assistance) at a faster speed (average of 55 CPM). Total strides (2626) increased nearly 3-fold compared with baseline. Step length (41.8 cm) was intermediate. Although average exercise HR (151 bpm) was higher than during previous sessions, the child's HR while overriding the motor's assistance (162 bpm) was not the greatest value recorded.
Pre- to Postintervention Improvements in Gait and Mobility
During comfortable walking, the child's 10MWT speed improved from pre- (0.67 m/s) to postintervention (1.10 m/s), exceeding the MCID of 0.1 m/s for children with CP (Table).32 Increases in both cadence (∼27% faster) and stride length (∼27% longer), both exceeding MCIDs of 14.7 steps/min and 7 cm, respectively,32 contributed to the faster speed postintervention. The proportion of time each lower extremity spent in single-limb support lengthened by postintervention, suggesting greater stability.35 The child's self-selected fast walking speed also improved from pre (1.10 m/s) to postintervention (1.59 m/s), arising from an approximately 21% increase in cadence and approximately 19% longer stride length. Similar to findings during the comfortable paced 10MWT, the proportion of time each lower extremity spent in single-limb support was longer postintervention.
Gait and Mobility Measures Before and After Intervention
|10-m walk test (comfortable speed)
|Stride length, cm
|Left single-limb support time, % gait cycle
|Right single-limb support time, % gait cycle
|10-m walk test (fast speed)
|Stride length, cm
|Left single-limb support time, % gait cycle
|Right single-limb support time, % gait cycle
|2-min walk test, m
|Modified Timed Up and Go test, s
aAchieved minimal clinically important difference.
Compared with preintervention, the increased distance traversed during the postintervention 2MWT (98.8 vs 137.5 m) surpassed the MCID of 16.6 m for children with disabilities who walk independently.33 By postintervention, the modified TUG test quickened from 7.6 to 7.2 seconds, thus allowing for completion 57% faster than the average 16.6 seconds previously documented for children with CP and GMFCS II36 while also exceeding the MCID of 0.36 seconds for similarly aged children with CP and GMFCS II.31,34
Qualitative Feedback From the Child and Parent
Following completion of the 24 sessions, the child noted the intervention “improved how far I can go!” Similarly, his parent conveyed that his “endurance has gotten better.”
Both the child and parent responded affirmatively to the question, “If this piece of equipment was available for you [your child] to use in your home/school/therapy setting, would you [your child] use it?” While the child provided no explanation in response to “Why?” the parent wrote, “He loved the workouts and I believe it helped his flexibility. He is having tendon lengthening surgery in September. Wish he could do it couple of times a week to keep those muscles strong.”
The gait of children with spastic diplegia is often characterized as slow and inefficient,37 leading to difficulties keeping pace with family, friends, and peers and an overall decrease in physical activity. To alleviate these challenges, it is critical that physical therapy interventions address underlying walking deficits as well as the need for improved cardiovascular reserve. This case study provides insights into walking and endurance improvements arising in a child with spastic diplegic CP following participation in a semistructured exercise protocol involving primarily moderate- and vigorous-intensity exercise using ICARE, a rehabilitation device designed to address walking and fitness goals simultaneously. The intervention allowed for mass repetition of a gait-like movement pattern (∼2600 strides/session during later sessions) while the child safely engaged in up to 50 minutes of exercise, closely approximating temporal recommendations stipulated by the US Department of Health and Human Services for health-related benefits for children,38 and exceeding the usual time children with disabilities spend in moderate- to vigorous-intensity physical activities (∼17 minutes).39
As hypothesized, the child experienced increases in walking ability following the 24-session interventions and, while not measured, these improvements may have impacted function beyond the laboratory. Remarkable was the finding that his self-selected comfortable 10MWT speed postintervention was equivalent to his preintervention fast speed (1.10 m/s). At 79% of normative values for similarly aged children developing typically,40 his postintervention comfortable speed exceeded teachers' perceptions of the slowest acceptable walking speed for sixth-grade students with mobility problems (0.88 m/s).41 If sustainable, his postintervention fast walking speed (1.59 m/s) also would have surpassed sixth-grade-line leaders' reported mean speed (1.43 m/s) when guiding classmates approximately 15 m through school hallways.41 Collectively, these data suggest that the child may have been better able to keep up with peers at school, but this was not assessed.
Velocity improvements arose from increases in both stride length and cadence. Subtle gait changes (eg, improved terminal stance heel-off and thigh extension and/or terminal swing knee extension and/or pelvic rotation) likely contributed, in part, to the improved stride length postintervention and point to the need for future research to include formal kinematic (motion) and electromyography (muscle demand) analyses to quantify changes in gait arising from participation in the intervention. Likewise, discerning factors (eg, enhanced calf strength) that might underpin the improved single-limb support time/stability would be beneficial for refining future training guidelines, particularly as they relate to encouraging progressively longer ICARE step lengths across sessions.
Beyond focusing on task-specific training for gait enhancement, this intervention simultaneously integrated an impairment-specific emphasis to build cardiorespiratory fitness. Given preintervention findings, this training emphasis was warranted. For example, during the preintervention 2MWT assessment of ambulatory endurance, the child traversed only 98.8 m, representing approximately 66% of the distance reported for 6- to 12-year-olds developing typically and 77% of that reported for children with CP and other disabilities.33 Across training sessions, the child's HR and BP remained within acceptable training levels.42 Consistent with our initial hypothesis, the child's fitness improved over the course of the intervention as evidenced by his enhanced ICARE training tolerance and improved walking endurance. As summarized in Figure 2, by the later training sessions the child exercised more than twice as long while sustaining a faster average training speed and overriding the motor's assistance for greater than 20% of each session compared with the initial sessions. The child's resting HR was 12.3% lower during the final 5 sessions compared with the initial 5 sessions, indicative of the improved cardiorespiratory fitness. Beyond changes recorded while training, the child's performance on the 2MWT, an NIH Toolbox measure of submaximal cardiovascular endurance, improved 39% from pre- to postintervention, exceeding the MCID for children with disabilities.33 In future work, the addition of formal metabolic assessments (eg, peak volume of oxygen consumed and oxygen cost of walking) pre- and postintervention as well as at a 3-month follow-up would provide greater insights into the effect of the intervention on endurance and the persistence of such improvements.
Although gait technology has traditionally been used to enhance walking in children with disabilities, addressing cardiovascular and cardiorespiratory fitness should also become a major focus of future interventions43 since secondary complications to these systems can further hinder children's functional independence. Additional studies are required to determine the effect of our protocol on walking and cardiorespiratory fitness of children with varied GMFCS levels. Other populations that might benefit from a similar protocol include children who experience strokes, brain injuries, or chromosomal anomalies. In addition, comparison of our ICARE protocol to other locomotor interventions (eg, BWS treadmill training and robotic) will provide understanding of the potential benefits and limitations of each intervention not only to walking function and fitness, and quality of life and capacity to engage in social activities, such that clinical resources can be directed accordingly. Since affordability of this therapeutic device allows for use beyond the research environment, we expect that the exercise protocol implemented in this case report could be adapted in different environments and used with larger sample sizes and other children with disabilities to promote enhanced walking capabilities and cardiorespiratory fitness.
Gait improvements were achieved by a 12-year-old child with CP and GMFCS level II after participation in our ICARE intervention protocol. Moreover, the child was able to exercise at moderate- to vigorous-intensity levels for sustained periods, affirming the device's capacity to address this child's walking and fitness goals simultaneously. Further investigations with larger sample sizes and children with different GMFCS and fitness levels are needed to examine the full therapeutic effect of our protocol.
WHAT THIS CASE ADDS TO THE EVIDENCE-BASED PRACTICE
Beyond difficulties with gait, children with CP often experience challenges engaging in exercise at a sufficient intensity to sustain cardiorespiratory fitness. Integration of moderate- to vigorous-intensity motor-assisted elliptical training can promote simultaneous gains in both walking function and fitness.
The authors would like to acknowledge Alexander Garbin, PT, DPT, for his assistance with data collection.
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