Child development is grounded in the ability to move, explore, and interact with the world.1–3 Infants simultaneously learn to move, and move to learn.4 Children's perceptual-motor experiences gained through self-directed mobility are important for overall development, including advancements in cognition, social, and language skills, and emotional development.1–3 Self-directed mobility is defined as mobility that is controlled by an individual and may include (a) ambulation, such as walking, (b) use of nonpowered technology, such as gait trainers and standers, or (c) use of powered technology, including motorized wheelchairs, battery-operated ride-on toy cars, or other similar devices. In this article, we continue the investigation of the effect of modified ride-on car use on infant behavior and development.5–9
Self-directed mobility is a fundamentally different experience compared with passive mobility.1,10,11 In both animal and human models, self-directed mobility has been shown to impact typical development of visual perception and social cognition.2,3,10–12 Lobo et al3 suggest cognition is grounded in perceptual-motor experiences based on research showing that object interaction, sitting, and locomotion promote exploration and global development of young children.
Children who experience significant delays in mobility often cannot engage in self-directed mobility, and may use a powered mobility device (PMD) as a means to do so. A PMD is defined as “any device that requires a battery or other electrical power source for activation that an individual uses to move from one place to another.”5(p100) The use of PMDs by young children (2 years and younger) is well established, with demonstrated gains in self-directed mobility, exploration of the environment, social and language skills, and cognitive development, including understanding of cause-and-effect relationships.12–16 However, access to traditional PMDs, such as motorized wheelchairs, remains a significant challenge due to several factors, including high cost, device size and subsequent transportation challenges, and the perception of PMDs as a “last resort.”17 Modified battery-operated, off-the-shelf ride-on cars are an emerging PMD option with several benefits supported by a growing body of literature.5–9
Ride-on cars provide a low-cost (<$500) option, and are readily modified by families, clinicians, and community members for use by young children. See previously published technical reports for modification suggestions.18,19 Four reports have demonstrated the potential benefits of modified ride-on car use for an infant with Down syndrome,6 a toddler with cerebral palsy,7 3 young children with complex medical needs,5 and 1 preschooler with a physical disability.9 Most recently, Huang and Chen8 published the first group study showing positive effects for hospital-based modified ride-on car use, with the results suggesting that certain intervention characteristics, such as social environment, may be key for optimal gains. None of the children in these reports were traditional candidates for PMDs because of their young age, diagnosis, or ability to independently walk with support; however, results found that modified ride-on cars are a feasible option for self-directed mobility, exploration, socialization, enjoyment, and play.
The purpose of the current study is to evaluate a modified ride-on car intervention in the home setting. The current study extends the previous literature in 2 key ways. First, it facilitates a picture of ride-on car effectiveness in diverse populations, including 2 of the 3 children with different disabilities than previously reported. Replication is an important part of determining intervention effectiveness. Given small sample sizes of previous research, it is important to determine whether modified ride-on car interventions can be effective for other children. Continued supporting evidence may contribute to the willingness of clinicians to adopt early powered mobility in the form of modified ride-on cars. Second, it adds to the growing body of participation-based modified ride-on car research in home and community environments, to complement recent ride-on car research in a hospital environment.
There were 3 specific aims: (1) to determine the effect of the intervention on mobility; (2) to examine the association between visual attention to the activation switch and switch contacts; and (3) to explore characteristics of daily modified ride-on car use throughout the intervention such as enjoyment, training time, location of driving, and general activities. We hypothesized that each child would learn to independently use the modified ride-on car and demonstrate increased mobility skills following 3 months of daily use of a modified ride-on car. We did not develop an a priori hypothesis for visual attention to the activation switch and switch contacts based on mixed results from previous research.6,7 We hypothesized that families would demonstrate various adherence rates and children would enjoy use of the modified ride-on car in a variety of locations while engaged in different types of activities.
The study was a prospective, nonrandomized AB single-subject case series research design. The design followed the guidelines for rigor and quality established for an evidence level V.20 This study incorporated “heterogeneous” participants with “low-incidence” conditions and participants who may “demonstrate variability from day to day.” This 24-week report included 2 periods: baseline (12 weeks) and intervention (12 weeks).
Three children with disabilities participated in this study. The following information was observed and reported by the parents of each child at the start of the study.
Child A. This was a 29-month-old Caucasian male child with a diagnosis of spastic quadriplegic cerebral palsy. Child A had previously undergone surgery to correct strabismus. He could roll to side-lying and prone, and commando crawl, but he was unable to sit up or walk. He was classified as level III on the Gross Motor Function Classification System. He received the following clinical services throughout the duration of the study: (1) physical therapy 1 to 2 times per week for an average of 30 to 45 minutes per session; (2) occupational therapy once per week for an average of 30 to 45 minutes per session; (3) speech-language therapy 1 to 2 sessions per week for an average of 30 to 60 minutes per session; and (4) early intervention once per week for an average of 30 to 45 minutes.
Child B. This was a 12-month-old Caucasian female child with a diagnosis of 16p 11.2 microdeletion and cortical vision impairment. She was able to sit with assistance and could roll, but otherwise was unable to engage in self-directed mobility. She received the following clinical services throughout the duration of the study: (1) physical therapy twice per week for an average of 60 minutes per session; and (2) occupational therapy once per week for an average of 60 minutes per session.
Child C. This was a 21-month-old African American female child with a diagnosis of microcephaly, strabismus, and limited extraocular movements. She could roll but otherwise was unable to engage in self-directed mobility. The family did not provide clinical service information.
Informed parental consent for all children was obtained prior to the start of the study. The university's Institutional Review Board approved all the procedures.
Modified Ride-On Cars
The research team and family selected a ride-on car model for each child based on the child's body size and hand reach. Common modifications for all 3 ride-on cars included installation of a Velcro pelvic belt for safety, a headrest constructed of polyvinyl chloride (PVC) pipe, and a child-size kickboard attached to the PVC for additional head support. A large activation switch with light-touch pressure sensitivity was installed and placed on the steering wheel (AbleNet 5″, Big Red Twist Switch, $59). All of these materials were used due to their low cost and availability at local hardware and department stores, or online. Child A and child C used a modified 6-V, Fisher Price Power Wheels “Lightning McQueen” ride-on car. Child B used a modified 6-V, Fisher Price Power Wheels “Mater” ride-on car. Both models travel at a speed of 2 mph and can only move in the forward direction. The cost of ride-on car models varies but typically ranges between $100 and $200. Note: Modification to off-the-shelf ride-on cars is an unlabeled use of a commercial product.
Description of Study Periods
Baseline (12 Weeks). The baseline period included 6 home visits that occurred once per 2 weeks, for a total of 12 weeks. During the first home visit, a researcher and the child's parents determined the areas that were safe for use of a modified ride-on car. Researchers and parents completed a Home Assessment Agreement form. Each potential location of ride-on car use was inspected to ensure a safe environment such as an even surface, no descending stairs, and objects/furniture were subjected to a bump test. Safe locations were mutually agreed upon and documented. Next, the research team and parents determined which ride-on car and modifications met the child's current and anticipated needs based on body size, physical skills, and level of functioning. Data were not collected during the first home visit. During the remaining 5 baseline visits, a researcher brought the modified ride-on car to and from each visit to supervise safe fitting and lead the car-play session. The child was provided with 10 minutes to explore and drive to a specific target (eg, a toy or family member). The session was video recorded to determine baseline values of mobility and visual attention. The goal for the baseline period was to familiarize the children with the modified ride-on car and to encourage children to learn how to activate the switch. If children were successful in activating the switch, then only open exploration was provided. During baseline, the child only had access to the ride-on car when a researcher brought it to home visits.
Intervention (12 Weeks). The intervention period included 12 home visits that occurred once per week, for a total of 12 weeks. The ride-on car was left with the family throughout the intervention. The intervention included 2 major components: education and training.
Education. During the first home visit of the intervention, the family was provided with an educational booklet and in-person training on safe modified ride-on car use. The booklet included instructions for battery and switch operation, proper positioning of the child, and initial ride-on car activity suggestions that included basic tasks (activating the switch) to more complex tasks (goal-directed exploration).
Training. During the intervention, the families were encouraged to provide their child with 20 to 30 minutes, 5-days per week of modified ride-on car use that included time for exploration, goal-oriented driving, and play-based activities. A weekly visit by the researcher included time to discuss the driving experiences and to work together to create new and interesting activities, as well as video record a 10-minute, researcher-led car-play session. Daily car-play sessions were parent-led and the duration, along with a parent report of the child's enjoyment, was recorded in an activity log.
Video Recordings. Video recordings of the 10-minute car-play sessions were coded independently by 2 researchers for the dependent measures of mobility, visual attention to the switch, and switch contacts. Researchers were blinded to whether the video recordings were of the baseline or interventions sessions. Initial training on coding procedures occurred with practice video recordings. This allowed for discussion of disagreements and clarification of key behaviors. Interrater and intrarater observer agreement (IOA >90%) was established using the ratio of agreements/(agreements + disagreements) × 100 to establish a percentage of agreement.5–7,9,21 IOA was established prior to formal data coding, halfway through coding, and after all coding occurred. At each time point, IOA was greater than 90% for all variables. Table 1 includes descriptions of mobility, visual attention to switch, and switch contacts.
Standardized Measure. The Pediatric Evaluation of Disability Inventory (PEDI) is a set of tests designed to measure a child's performance of basic skills and the level of assistance or adaptation required, including self-care, mobility, and social function skills.22 For the purpose of this study, only mobility skills are reported. Mobility skills include basic transfer skills and body transport activities such as floor mobility, locomotion with and without object manipulation, and negotiation of outdoor surfaces and ramps. The PEDI includes 2 subscales of mobility skills: functional skills and caregiver-assisted skills. Functional skills (59 items) are scored dichotomously (unable/capable) and intended to assess children's capabilities. Caregiver-assisted skills (7 items) are scored on a 6-point scale based on the amount of assistance provided to a child during each task and intended to assess children's independence. Caregiver-assisted skills are included because the modified ride-on car may afford opportunities for more independence of mobility skills that may not be present given each child's mobility. The PEDI has established content validity,22 construct validity, concurrent validity (r = 0.70-0.80), and internal consistency (Cronbach α coefficients range 0.95-0.99).23 The PEDI was administered by a clinical physical therapist at baseline (0 month), preintervention (3 months), and postintervention (6 months) to quantify change in key categories of behaviors. Scaled scores were calculated and provide a performance score relative to the maximum possible PEDI score that allows for comparison of each child across his or her own baseline and postintervention scores.
Daily Activity Log. The daily activity log included parent reports of the days and minutes of driving time, a “Fun Index” score, location, and general activities such as open exploration or playing with a sibling.6,7 An adherence rate was calculated based on the number of days children drove for at least 20 minutes across 60 days, based on the 5 day per week recommended use during the 12-week intervention. The Fun Index was an ordinal scale that captured the family's perception of the child's enjoyment during daily driving sessions. Parents scored each session from 1 to 10, with a 10 indicating the highest level of fun.
Planned Analysis. The nonoverlap of all pairs (NAP) was calculated for independent mobility and driving time (minutes) between the baseline and intervention periods. NAP is a single-case research analysis method that summarizes data overlap between each baseline data point and each intervention data point.24 NAP values equal “... the number of comparison pairs showing no overlap, divided by the total number of comparisons.”24(p358) A large NAP value suggests a positive change of a dependent measure during the intervention period compared with the baseline period. It is a preferred effect size measure over traditional single-case research overlap-based effect sizes.24 Confidence intervals (CI) were set at 90% based on a previous nonpowered, self-initiated mobility study with a similar number of baseline and intervention data points.25
Visual analysis was used to describe the patterns of visual attention and switch contacts. We did not calculate NAP values for these behaviors because there was not a clear rationale to expect directional differences of either variable between the baseline and intervention periods.6,7
Analysis of the PEDI at baseline (0 month), preintervention (3 months), and postintervention (6 months) was used to determine whether changes occurred for each child, using the reported minimal clinically important difference of 11 points on the scaled score across all subscales, and ± 2 standard error calculation between test occasions.26
Description of Outcomes
Mobility. Data were analyzed from the 10-minute video recordings collected by researchers during biweekly visits throughout the study. NAP effect sizes are interpreted as weak (0-0.65), medium (0.66-0.92), and large (0.93-1).24 Weak to large NAP effect sizes were found for percent of time spent in independent mobility: child A (NAP = 0.5; weak effect; P = 1.0; 90% CI = −0.52 to 0.52), child B (NAP = 0.7; medium effect; P = .21; 90% CI = −0.12 to 0.92), and child C (NAP = 0.93; large effect; P = .007; 90% CI = −0.33 to 1). No to medium NAP effect sizes were found for driving duration (minutes): child A (NAP = 0; no effect; P = .002; 90% CI = −1 to 0.48), child B (NAP = 0.87; medium effect; P = .02; 90% CI = 0.21 to 1), and child C (NAP = 0.88; medium effect; P = .02; 90% CI = 0.23 to 1) (Figure 1).
Visual Attention and Switch Contacts. Child A and child C demonstrated a trend of coupling visual attention to the switch with switch contacts; as one increased or decreased, the other variable did as well (Figure 2).
Pediatric Evaluation of Disability Inventory.
Scaled Scores. In the Functional Skills domain, child A and child B demonstrated an increase of 13 and 15, respectively, in mobility skills from preintervention to postintervention. Child C did not demonstrate a clinically significant change. For the Caregiver Assisted Skills domain, child A and child B demonstrated an increase of 11.6 and 27.3, respectively, in mobility skills from preintervention to postintervention. Child C did not demonstrate a clinically significant change (Table 2).
Daily Activity Log. Please note the following results do not include the days and minutes children drove during researcher-led driving sessions throughout the study.
Child A. The duration of driving sessions varied from 0 to 60 minutes per day. Child A drove 5 days per week on average (range: 5-6 days). The mean driving time was 34.5 minutes (standard deviation, 5.7 minutes) on days that the modified ride-on car was used. Total driving time was 2210 minutes over 64 days (all at least 20 minutes) across 12 weeks of the intervention (adherence rate, 100%). The primary driving location was the kitchen and living room (55 days), while other driving occurred in the driveway. The primary driving activity was open exploration. Parents reported that child A vocalized and laughed a lot, and often chased the dog while using the modified ride-on car. Child A began to steer independently toward the end of the intervention. The parent-rated fun index suggests that child A consistently enjoyed driving his modified ride-on car (fun index: mean, 8.6; standard deviation, 0.8).
Child B. The duration of driving sessions varied from 0 to 60 minutes per day. Child B drove 4 days per week on average (range, 1-5 days). The mean driving time was 26.6 minutes (standard deviation, 8.9 minutes) on days that the modified ride-on car was used. Total driving time was 1225 minutes over 46 days (40 days of at least 20 minutes) across 12 weeks of the intervention (adherence rate, 67%). The driving location was always outside the home, in the driveway. The primary driving activity was open exploration. Parents reported that child B demonstrated an ability to stop-and-go, and engage in goal-directed driving early on during the intervention. Child B often played with her sister while using the modified ride-on car. Child B would use sign language to signal “help” when she was stuck, such as against a wall. Child B attempted to steer toward the end of the intervention. The parent-rated fun index suggests that child B consistently enjoyed driving her modified ride-on car (fun index: mean, 7.1; standard deviation, 1.1).
Child C. The duration of driving sessions varied from 0 to 20 minutes per day. Child C drove 6 days over the first 2 weeks of the intervention, but no driving was reported for weeks 3 to 12. The mean driving time was 20 minutes (standard deviation, 0 minutes) on days that the modified ride-on car was used. Total driving time was 120 minutes over 6 days (all at least 20 minutes) across 12 weeks of the intervention (adherence rate, 10%). The driving location was always in the living room. No activities were reported. Parents reported that child C learned how to press the activation switch very quickly during the beginning of the intervention. The parent-rated fun index suggests that child C enjoyed driving her modified ride-on car (fun index: mean, 10; standard deviation, 0).
The purpose of this study was to evaluate a modified ride-on car intervention in the home setting. Our hypothesis that all children would learn to independently use the modified ride-on car was upheld based on behavioral coding of video recordings for mobility, consistent with previous research.5–9 These results suggest further evidence that children with disabilities under 2 years old can learn how to use a modified ride-on car, as one type of PMD, even with varying exposure to driving opportunities, as indicated by the large variation in adherence rates among children. This is important because it strengthens the evidence that, despite dosage variance, children younger than 2 years are ready and able to independently operate a ride-on car, or other PMDs, earlier than is conventionally prescribed in clinical settings.27,28 Even PMD clinical readiness assessments, such as the Pediatric Powered Wheelchair Screening Test, or Butler et al's wheelchair skills checklist, have been developed and used with children in the 20 to 39 month age range or older, which may not adequately capture the abilities or skills of very young children to learn independent driving.29–31 Considering that children without disabilities are moving independently at the same age without need for a readiness assessment, these results also speak to the current level of gatekeeping by adults that may interfere with a child with a disability's opportunity to explore through self-directed mobility.
Our hypothesis that each child would show increased mobility skills was partially upheld. Child A and child B demonstrated clinically significant gains in scaled scores of mobility skills at postintervention. These findings are consistent with previous modified ride-on car research that administered the PEDI.7,8 While child C did not demonstrate increases in scaled scores across domains, the family report of 6 total driving days fell below the requested amount of driving across the intervention period. This may have impacted the results. This is interesting given that the parents rated the child's fun at the maximum level possible for the 6 driving sessions. There are likely several barriers to adherence of daily driving recommendations that may change from family to family. This may include a lack of adequate driving space and not enough time during a typical day to incorporate driving sessions to the routine of daily life. We are currently exploring how caregivers' attitudes toward disability and mobility may influence the opportunities they provide to their child to use PMDs, including modified ride-on cars.
Two previous case reports on use of modified ride-on cars reported children's visual attention to the switch. One report found a trend of increased visual attention to the switch during the intervention,6 while the other found a trend of decreased visual attention.7 Neither of the previous studies reported switch contacts. In the current study, trends varied for visual attention to the switch. Child A and child C demonstrated a co-occurrence trend; if either visual attention to the switch or switch contacts increased, the other variable did as well. This may indicate a strategy of using visual attention to learn how to press the activation switch. Child B rarely demonstrated visual attention to the switch. Child B was diagnosed with cortical vision impairment and likely relied less on her vision and more on tactile experiences to learn how to activate the switch. However, an anecdote of child B's use of the modified ride-on car reveals more information about her vision. Child B's vision acuity was unknown, but during the intervention her mom reported that child B saw an unfamiliar cat in the driveway from a distance of approximately 20 ft. Unexpectedly, child B pointed at the cat and used the modified ride-on car to travel to the cat to play with it. Her mom reported this as a surprising behavior because it was not clear that child B could see at that distance. This finding, although anecdotal, is encouraging given previously reported research on visual perception and mobility, and offers another avenue to systematically investigate how modified ride-on car use may impact visual development.10
In working toward our broader goal of a multisite modified ride-on car trial with a large number of participants, this continued early evidence for the feasibility and developmental benefits of self-directed mobility shows promise in multiple domains. First, all children in this case series, who were not previously considered candidates for a PMD, learned to drive independently and expressed enjoyment in doing so, and demonstrated varying levels of adherence to the suggested number of driving days during the intervention. Second, 2 children who logged at or above 65% of the drive time goal also showed significant improvements in mobility skills. These results suggest that, even though activities with a high “fun” rating may not be incorporated into the flow of everyday family life as researchers and clinicians hope, positive changes in self-directed mobility can still be facilitated, even with varied practice. This finding also motivates us to work more closely with families to identify facilitators and barriers of modified ride-on car use. Finally, the 3 children who participated in this research had quite diverse medical diagnoses, impairments, and mobility histories; however, each of them successfully used a modified ride-on car to enhance their self-directed mobility, at a time when their peers developing typically are independently walking. Perhaps these successes may help reframe the current standard of PMD provision and encourage researchers, clinicians, and families to rethink the target recipients of PMDs, or how and when PMDs may be used.
As with any study, several limitations are recognized in this work. One limitation is the use of an AB research design. This does not allow insight into whether or not the mobility skills gained would be retained after a period of withdrawal. We are unable to conclude that changes observed were due to the intervention, or some other factor. Results of this single-subject case series cannot be generalized to a broader population of children with disabilities. While recognizing and appreciating the heterogeneity of the participants is key in advancing PMD provision paradigms, it also presents a research challenge in the level of evidence that may be applied to this study. The varying levels of adherence in completing the suggested drive times was a limitation; however, it also offers the opportunity to broaden the conversation about dosage in rehabilitation interventions and the realistic flow of daily family life.
CONCLUSIONS AND FUTURE RESEARCH
Three children with diverse disabilities independently operated modified ride-on cars. Two of the 3 children showed gains in the PEDI mobility domain of Functional Skills and Caregiver Assisted Skills. In light of the growing popularity of modified ride-on cars, it is essential that research continue to investigate the effectiveness of these devices across several domains, including dosage parameters, functional outcomes for children, psychosocial outcomes for children and families, facilitators and barriers to PMD use, and social attitudes/professional roles/gatekeeping surrounding PMD provision and design. Additional single-subject research studies involving modified ride-on cars can use more powerful designs, such as ABAB, that would allow stronger conclusions. It is also important to undertake larger-scale studies that attempt to control for situated heterogeneity as best as possible. For example, even within diagnostically specific matched groups of children with disabilities, it would be beneficial to involve a control group, and to use randomization and blinding techniques as much as is feasible and ethical to produce more generalizable results with a larger cohort.
1. Foreman N, Foreman D. Locomotion, active choice, and spatial memory in children. J Gen Psychol. 1990;117:215.
2. Campos JJ, Anderson DI, Barbu-Roth MA, Hubbard EM, Hertenstein MJ, Witherington D. Travel broadens the mind. Infancy. 2000;1:149–219.
3. Lobo MA, Harbourne RT, Dusing SC, McCoy SW. Grounding early intervention: physical therapy cannot just be about motor skills anymore. Phys Ther. 2013;93:94–103. doi:10.2522/ptj.20120158.
4. Adolph KE, Robinson SR. Motor development. In: Lerner RM, Liben LS, Mueller U, eds. Handbook of Child Psychology and Developmental Science. Vol 2. 7th ed. Hoboken, NJ: John Wiley & Sons, Inc; 2015. doi:10.1002/9781118963418.childpsy204.
5. Logan SW, Feldner HA, Galloway JC, Huang H-H. Modified ride-on car use by children with complex medical needs. Pediatr Phys Ther. 2016;28:100–107. doi:10.1097/PEP.0000000000000210.
6. Logan SW, Huang H-H, Stahlin K, Galloway JC. Modified ride-on car for mobility
and socialization: single-case study of an infant with Down syndrome. Pediatr Phys Ther. 2014;26:418–426. doi:10.1097/PEP.0000000000000070.
7. Huang H, Ragonesi CB, Stoner T, Peffley T, Galloway JC. Modified toy cars for mobility
and socialization: case report of a child with cerebral palsy. Pediatr Phys Ther. 2014;26:76–84. doi:10.1097/PEP.0000000000000001.
8. Huang H-H, Chen C-L. The use of modified ride-on cars to maximize mobility
and improve socialization-a group design. Res Dev Disabil. 2017;61:172–180. doi:10.1016/j.ridd.2017.01.002.
9. Logan SW, Lobo MA, Feldner HA, et al Power-up: exploration
and play in a novel modified ride-on car for standing. Pediatr Phys Ther. 2017;29:30–37.
10. Held R, Hein A. Movement-produced stimulation in the development of visually guided behavior. J Comp Physiol Psychol. 1963;56:872.
11. Libertus K, Needham A. Teach to reach: the effects of active vs. passive reaching experiences on action and perception. Vision Res. 2010;50:2750–2757. doi:10.1016/j.visres.2010.09.001.
12. Livingstone R, Field D. Systematic review of power mobility
outcomes for infants, children and adolescents with mobility
limitations. Clin Rehabil. 2014:28(10):954–964.
13. Butler C. Effects of powered mobility
on self-initiated behaviors of very young children with locomotor disability. Dev Med Child Neurol. 1986;28:325–332.
14. Chiulli C, Corradi-Scalise D, Donatelli-Schultheiss L. Powered mobility
vehicles as aids in independent locomotion for young children. Phys Ther. 1988;68:997–999.
15. Guerette P, Furumasu J, Tefft D. The positive effects of early powered mobility
on children's psychosocial and play skills. Assist Technol. 2013;25:39–48. doi:10.1080/10400435.2012.685824.
16. Rosenbaum P. Effects of powered mobility
on self-initiated behaviours of very young children with locomotor disability (1986). Dev Med Child Neurol. 2008;50(9):644.
17. Feldner HA, Logan SW, Galloway JC. Why the time is right for a radical paradigm shift in early powered mobility
: The role of powered mobility
technology devices, policy and stakeholders [published online ahead of print September 4, 2015]. Disabil Rehabil Assist Technol. doi:10.3109/17483107.2015.1079651.
18. Huang H, Galloway JC. Modified ride-on toy cars for early power mobility
: a technical report. Pediatr Phys Ther. 2012;24:149–154. doi:10.1097/PEP.0b013e31824d73f9.
19. Logan SW, Feldner HA, Bogart KR, et al Toy-based technologies for disabled children simultaneously supporting self-directed mobility
, participation and function: a tech report[published online ahead of print March 2, 2017]. Front Robot AI. doi:10.3389/frobt.2017.00007.
20. Romeiser Logan L, Hickman RR, Harris SR, Heriza CB. Single-subject research design: recommendations for levels of evidence and quality rating. Dev Med Child Neurol. 2008;50:99–103. doi:10.1111/j.1469-8749.2007.02005.x.
21. Harris FC, Lahey BB. A method for combining occurrence and nonoccurrence interobserver agreement scores. J Appl Behav Anal. 1978;11:523–527.
22. Haley SM, Coster W, Ludlow LH, Haltiwagner JT, Andrellos PJ. Pediatric Evaluation of Disability Inventory: Development, Standardization, and Administration Manual. Boston, MA: Trustees of Boston University; 1992.
23. Feldman AB, Haley SM, Coryell J. Concurrent and construct validity of the Pediatric Evaluation of Disability Inventory. Phys Ther. 1990;70:602–610.
24. Parker RI, Vannest K. An improved effect size for single-case research: nonoverlap of all pairs. Behav Ther. 2009;40:357–367. doi:10.1016/j.beth.2008.10.006.
25. Bastable K, Dada S, Uys CJE. The effect of a non-powered, self-initiated mobility
program on the engagement of young children with severe mobility
limitations in the South African context. Phys Occup Ther Pediatr. 2016;36:272–291. doi:10.3109/01942638.2015.1126879.
26. Iyer LV, Haley SM, Watkins MP, Dumas HM. Establishing minimal clinically important differences for scores on the Pediatric Evaluation of Disability Inventory for inpatient rehabilitation. Phys Ther. 2003;83:888.
27. Livingstone R, Paleg G. Practice considerations for the introduction and use of power mobility
for children. Dev Med Child Neurol. 2014;56:210–221. doi:10.1111/dmcn.12245.
28. Lynch A, Ryu J-C, Agrawal S, Galloway JC. Power mobility
training for a 7-month-old infant with spina bifida. Pediatr Phys Ther. 2009;21:362–368. doi:10.1097/PEP.0b013e3181bfae4c.
29. Butler C, Okamoto GA, McKay TM. Motorized wheelchair driving by disabled children. Arch Phys Med Rehabil. 1984;65:95–97.
30. Jones MA, McEwen IR, Neas BR. Effects of power wheelchairs on the development and function of young children with severe motor impairments. Pediatr Phys Ther Off Publ Sect Pediatr Am Phys Ther Assoc. 2012;24:131–140; discussion 140. doi:10.1097/PEP.0b013e31824c5fdc.
31. Furumasu J, Guerette P, Tefft D. Relevance of the Pediatric Powered Wheelchair Screening Test for children with cerebral palsy. Dev Med Child Neurol. 2004;46:468–474.