Abstract
Background It is debatable whether adaptive riding (AR) in children with cerebral palsy (CP) improves postural control and gross motor development.
Objective The study aim was to explore the feasibility of an extensive assessment protocol for a randomized controlled trial of therapist-designed adaptive riding (TDAR) in children with CP, with the goals of assessing the effect on child outcomes and evaluating working mechanisms of sitting postural control.
Design A pretest-posttest group design with 2 baseline measurements was used.
Methods Six children (1 girl, 5 boys; age range=6–12 years, median age=8 years 9 months) with bilateral spastic CP (Gross Motor Function Classification System level III) participated. Outcomes were evaluated 3 times (T0, T1, and T2) at 6-week intervals. T0 and T1 were baseline measurements; between T1 and T2, a TDAR intervention including an integrated program of postural challenge exercises (2 times per week for 1 hour) was applied. The complex protocol included the 88-item Gross Motor Function Measure (GMFM-88) and electromyographic (EMG) recording of postural muscle activity during reaching while sitting (EMG recording at T1 and T2 only).
Results The protocol was feasible. Median GMFM-88 scores changed from 64.4 at T0 to 66.7 at T1 and from 66.7 at T1 to 73.2 at T2. The change scores for all children exceeded the minimal clinically important difference of the GMFM-88. Five of 6 children showed a decrease in stereotyped top-down recruitment between T1 and T2.
Limitations Study limitations included the lack of a control group, small sample size, and potential assessor bias for all but the EMG parameters.
Conclusions The feasibility of the complex protocol was established. The data suggested that a 6-week TDAR intervention may improve gross motor function and may reduce stereotyped postural adjustments in children with CP. The limited results warrant replication in a well-powered randomized controlled trial.
Equine-assisted activities and therapies are frequently used in children with cerebral palsy (CP).1,2 However, it is debatable whether equine-assisted activities and therapies are effective in reducing bodily impairments, such as spasticity and impaired posture and balance, and in lessening limitations in activities and limitations in participation in nonequine contexts.2,3
The limited evidence on effectiveness may be partially explained by the heterogeneity in the therapies applied. The heterogeneity is reflected in past and present terminology. In the past, therapies were labeled “hippotherapy,” “therapeutic riding,” or “horseback riding therapy.”1,2 However, these terms were confusing because the services delivered in the different approaches overlapped partially. The American Hippotherapy Association1 recently suggested standard terminology to describe the 2 basic forms of equine-assisted activities and therapies: (1) hippotherapy, implying that a therapist (physical therapist, occupational therapist, or speech therapist) uses the movement or the environment of the horse (or both) to reach specific therapy goals, and (2) adaptive riding (AR), implying recreational horseback riding lessons adapted for people with disabilities.1 Hippotherapy sessions are one-to-one sessions of a therapist and a patient, whereas AR is provided to groups.1 A systematic review and meta-analyses of the 2 forms of equine-assisted activities and therapies revealed that hippotherapy has been better investigated than AR.3 Short-term hippotherapy was found to be associated with a significant reduction in asymmetrical activity of the hip adductor muscle.3,4 The meta-analyses3 indicated that neither hippotherapy nor AR was associated with a statistically significant improvement in gross motor function, as measured with the Gross Motor Function Measure (GMFM),5 or with an improvement in stride length.
Equine-assisted activities and therapies are assumed to improve the postural control of children with CP and therewith to improve gross motor function and eventually function in daily life.1,2,4,6,7 Dysfunctional postural control is a major limitation in children with CP. The postural dysfunction directly influences daily activity performance, the extent depending on the degree of disability.8 In the organization of postural control, 2 functional levels can be distinguished. The first level consists of direction specificity, meaning that when the body sways forward, such as during reaching, primarily dorsal muscles are activated, whereas backward body sway results primarily in ventral muscle recruitment.9 The second level of control is involved with fine-tuning of the direction-specific adjustments in a particular situation, for instance, by changing the order of recruitment of the direction-specific muscles.10 Children with CP generally have direction-specific adjustments.8,10 However, children with CP virtually always show dysfunction at the second level of control. For instance, during reaching in the sitting position, they show stereotyped top-down recruitment instead of the variable recruitment of peers developing typically.10 Children developing typically exhibit a mixture of top-down, bottom-up, and more variable patterns of recruitment order.8,10
Recent literature indicates that therapy based on the principles of motor learning,11,12 including trial-and-error learning, is more effective in improving the motor abilities of children with CP than therapy that involves handling and assisting the child (hands-on therapy).13,14 Therefore, we opted to study the effect of an AR intervention supervised by a pediatric physical therapist. The therapist-designed AR (TDAR) intervention involved minimal hands-on guidance and maximal self-practice of the child and included an integrated program of varied postural challenge exercises.
The primary aim of this preliminary study was to explore the feasibility of an extensive assessment protocol for a randomized controlled trial (RCT) of the effect of TDAR in children with spastic CP, with the goals of assessing effectiveness across all levels of the International Classification of Functioning, Disability and Health: Children and Youth Version—(ICF-CY)15 and evaluating working mechanisms underlying a potentially beneficial effect of TDAR. A pretest-posttest group design with 2 baseline measurements was used. The secondary aim of this preliminary study was to assess the effect of the intervention. The primary outcome parameter was gross motor function, measured with the 88-item Gross Motor Function Measure (GMFM-88),5 with dimension D (standing) and dimension E (walking, running, and jumping) serving as goal areas.5 We hypothesized that 6 weeks of TDAR would result in change scores in dimensions D and E that would exceed the minimal clinically important differences (MCIDs).16 Secondary outcome parameters were spasticity, function in daily life, quality of life, and self-esteem. An important tool for assessing one of the working mechanisms was the evaluation of postural control by means of surface electromyographic (EMG) recording during reaching while sitting.10,17
Method
Participants
Six participants (5 boys, 1 girl; age range=6–12 years, median age=8 years 9 months) were recruited through the outpatient clinic at Rehabilitation Center Revalidatie Friesland, Beetsterzwaag, in the northern part of the Netherlands. The pediatric physiatrist (M.M.) and pediatric physical therapist (B.V.) had prescribed TDAR with the aim of improving the children's gross motor function. Children older than 8 years and all parents signed an informed consent form for participation; this form was approved by the Medical Ethical Committee of the University Medical Center Groningen. All participants met the following 4 inclusion criteria: diagnosis of spastic CP,18 Gross Motor Function Classification System (GMFCS)19 level II or III, age of 6 to 12 years, and ability to cooperate and follow verbal instructions. Children were excluded if they had a predominantly dyskinetic movement disorder (because their postural problems might differ from those of children with spastic CP), severe behavioral problems, unstable epilepsy (≥2 seizures per week), or a known allergy to or fear of horses or if they had received treatment with botulinum toxin during the preceding 6 months or orthopedic or neurologic surgery during the preceding year.
All 6 participants were diagnosed with bilateral spastic CP (GMFCS level III). They needed walking aids and orthoses in daily life. Four children had no AR experience; the 2 oldest children had 6 to 8 months of AR experience (in the preceding year). All participants received their regular therapy at the same frequency throughout the baseline and intervention periods of the study.
Design of the Study
A pretest-posttest group design with 2 baseline measurements was used. Outcomes were evaluated with an extensive assessment protocol 3 times (T0, T1, and T2) at 6-week intervals (Fig. 1). T0 and T1 were baseline measurements; between T1 and T2, a TDAR intervention (2 times per week for 1 hour) was applied. Two sessions were video recorded to improve understanding of the contents of the TDAR program.
Schematic presentation of the study design, including the outcome measures. Moments of evaluation: T0=6 weeks before the start of the therapist-designed adaptive riding (AR) intervention, T1=start of the intervention, T2=end of the intervention. V1 and V2 represent the moments of video recording of the intervention during the second and eleventh sessions, respectively. In addition to the measurements shown, the child's appreciation of each intervention session was assessed with a 5-point “smiley scale.” The therapist-designed AR program was delivered with minimal hands-on guidance and maximal self-practice (1-hour group class, twice weekly). GMFM-88=88-item Gross Motor Function Measure, EMG=surface electromyography, PEDI=Dutch version of the Pediatric Evaluation of Disability Inventory.
TDAR
The TDAR intervention was conducted in the indoor arena of the Riding Center Onder de Linde, which collaborates with Rehabilitation Center Revalidatie Friesland. All children participated in the same 1-hour group class, which met twice weekly. It started at T1 and lasted until T2; that is, 12 TDAR sessions were provided over 6 weeks. Before the study began, the pediatric physical therapist (B.V.) discussed the individual goals and challenges of each child with the certified therapeutic riding instructor, and together they designed the contents of the TDAR intervention for each child and each session. Next, the riding instructor selected 6 trained horses, all of which fit the riding needs of each participant. Our TDAR intervention deliberately opts for varied experience with horses because variation in practice and across contexts is associated with better skill development.13,20 In addition, the instructor selected for each child a saddle pad, a helmet, an experienced horse handler, and a trained side walker (one or none).
The therapeutic riding instructor directed the class with the 6 pairs of children and horses. The instructor herself was coached by the pediatric physical therapist (B.V.), who attended each riding class session. Coaching is one of the novel and promising strategies used in pediatric physical therapy and pediatric rehabilitation.21,22 The riding instructor coached and responded to the group of children as a whole. We opted for a group approach for 2 reasons. First, our program emphasizes the need for self-practice and minimization of hands-on guidance—also a strategy in line with novel approaches in pediatric physical therapy.13,20 Second, group practice fosters a child's social skills and is, in general, associated with increased pleasure. The horse handler led the horse according to the instructor's directions. The side walker walked alongside the horse, coached the child during riding, and ensured safety on the basis of the instructions from the riding instructor. To avoid a horse-specific effect on the children's performance and to increase variation in experience, we rotated horse use: each week, each child used a different horse, so that at the end of the intervention, each child had been riding for 1 week on 1 of the 6 horses.13,20
The TDAR protocol included an integrated program of postural challenge exercises in various riding situations (eAppendix). The protocol also focused on riding skills, as mastery of riding skills is a major motivator for activity based on equine movement performance. The program became increasingly difficult during the course of 12 sessions, challenging the child's postural control. Examples of exercises included raising the arms high up, giving a high five to a side walker, rewarding the horse by tapping the horse's neck (involving forward leaning), or leaning backward to touch the back of the horse when the horse stood still. Five types of saddles were used: sheepskin, 2 different modifications of sheepskin, and 2 typical saddles (Western and English saddles) (eAppendix). The sheepskin modification saddles may be regarded as the “golden mean” between the sheepskin and the typical saddles because—on the one hand—they are less broad and less firm than a typical saddle and do not include stirrups, but—on the other hand—they are more preformed and more firm than a sheepskin saddle. The use of the saddles was varied across children, horses, and sessions.13,20 Note that backward leaning exercises could be performed only when a sheepskin saddle or a sheepskin modification saddle was used. To adapt the contents of the TDAR sessions to individual capacities, the therapeutic riding instructor recorded the children's riding performances in activity logs. The pediatric physical therapist (B.V.) used the activity logs in her coaching of the riding instructor to adjust the contents of the next riding session for the children's needs and challenges.
Outcome Measures
We used an extensive assessment protocol. The same assessment battery was used at each evaluation, with 1 exception: At T0, no EMG recordings were obtained. Electromyographic recordings and GMFM-88 and Tardieu Scale assessments for each child were completed within 1 day at Rehabilitation Center Revalidatie Friesland. All children were tested within 1 week, with T1 occurring in the week before the start of the TDAR intervention and T2 occurring in the week after the last TDAR session. The parents completed questionnaires within 3 days after the assessment date. The complex assessment protocol was administered by experienced pediatric physical therapists (B.V. and M.A.), who were not masked with regard to assessment time (T0, T1, or T2).
The GMFM-88 was the primary outcome measure; dimension D (standing) and dimension E (walking, running, and jumping) were the goal areas, as the participants were school-aged children who were able to walk with walking aids.5 The reliability, validity, and responsiveness of GMFM scores in children with CP are highly acceptable.5,23–26 It is important to understand the MCID, which is a new approach for detecting meaningful change in clinical and research settings.16,26 Recently, the MCID of the total GMFM-88 was studied in children who were 2 to 7 years of age.26 In addition, the MCIDs of goal dimensions D and E were established in children and adolescents who were 4 to 18 years of age.16 For children functioning at GMFCS level III, the minimum change scores needed for MCIDs of medium (0.5) and large (0.8) effect sizes for dimension D were 1.5 and 2.4, respectively; those for dimension E were 1.8 and 3.0, respectively.16
The spasticity of the hip adductor, hamstring, gastrocnemius, and biceps brachii muscles was measured with the modified Tardieu Scale.27 This scale27 takes into account the velocity dependence of spasticity for describing the quality of muscle reaction from grades 0 to 4 and defines the moment of the “catch,” seen in the passive range of motion at a particular joint angle at a fast passive stretch. The difference between the 2 angles (R2 [passive range of motion following slow velocity stretch] μR1 [angle of catch following fast velocity stretch] range) represents the level of dynamic restriction in the joint.27 The reliability and validity of the scale are sufficient.28
The Dutch version of the Pediatric Evaluation of Disability Inventory (PEDI)29 was used to measure function in daily life. The PEDI assesses function in 3 domains: self-care, mobility, and social function. The interrater and intrarater reliabilities of the PEDI are good (intraclass correlation coefficients=.95–.99).30 The PEDI has been validated as a responsive tool, allowing the detection of change over a 6-month period in children with CP.31 In addition, MCIDs for the PEDI mobility domain were recently established by Ko.26 The range of MCIDs (0.3 SD, 0.5 SD, and 0.8 SD at baseline) for the PEDI mobility domain for children functioning at GMFCS level III ranged from 2.61 to 6.96.26
The parents completed 3 questionnaires: the Behavioral Rating Scale of Presented Self-Esteem,32 the generic KIDSCREEN-52,33 and the CP module of the disease-specific DISABKIDS.34 We included these questionnaires on the basis of anecdotal reports of parents stating that their child's self-esteem and overall pleasure in life improved during TDAR. The Behavioral Rating Scale of Presented Self-Esteem has 15 items assessing children's behavioral manifestations of self-esteem (eg, self-confidence, independence, and initiative) and children's social-emotional expression. Items are rated on a 4-point Likert scale. The scale has good validity and internal consistency.32 The KIDSCREEN-5233 and the DISABKIDS34 are tools for measuring health-related quality of life (eg, independence, physical limitations and well-being, self-perception, and peer and social support). Both tools are suitable for a large age range and have acceptable test-retest reliability, internal consistency, and validity; the tested domains cover a substantial part of the ICF-CY domains.33–35 Data on the sensitivity to change, including MCIDs, of the 3 questionnaires are lacking. The children's appreciation of TDAR was evaluated with a 5-point “smiley scale” after each session.
Assessment of Postural Control
Procedures.
At T1 and T2, postural control during sitting while reaching was measured with surface EMG. The children sat on a table without back or foot support. The children reached with their dominant arm to a small toy presented in the midline at arm-length distance. Muscle activity was recorded continuously with bipolar surface electrodes (interelectrode distance: 14 mm). Electrodes were applied to the reaching side of the body on 5 postural muscles (sternocleidomastoid, neck extensor, rectus abdominis, thoracic extensor, and lumbar extensor) and 4 arm muscles (deltoid, pectoralis major, biceps, and triceps brachii). The sessions were recorded in frontal-lateral and lateral views by 2 video cameras. The EMG signal was recorded at a sampling rate of 500 Hz with the Portilab software program (Twente Medical Systems International, Enschede, the Netherlands).17
EMG analysis.
Electromyographic analysis was performed by a medical master's degree student (A.A.) who had not been involved in data collection and who was masked for the timing of the assessment (before or after intervention). The analysis was carried out with the PedEMG program (Division of Developmental Neurology, Department of Paediatrics, University Medical Center Groningen, Groningen, the Netherlands).17 The author who performed the EMG analysis was trained to use PedEMG, which allows for a synchronous analysis of EMG and video data. In brief, the PedEMG program integrates video analysis and EMG analysis to allow for continuous monitoring of the results. The program uses the dynamic threshold statistical algorithm of Staude and Wolf36 to determine onsets of phasic EMG activity. Before onsets were determined, the signal was filtered for 50-Hz noise with a fifth-order Chebyshev stop-band filter. Signal artifacts and cardiac activity were identified when appropriate. Clear signal artifacts were identified manually. Cardiac activity (QRS complexes) was identified by use of a pattern recognition algorithm based on a linear derivative approximation of the signal with a combination of the repeating pattern and specific shapes of the QRS complexes.17
The activity of the postural muscles was considered to be related to the arm movement if increased muscle activity was found within a time window consisting of 100 milliseconds before activation of the “prime mover,” that is, the arm muscle that was activated first, and the duration (the first 1,000 milliseconds) of the reaching movement. For each postural evaluation session, 2 parameters were calculated. The first parameter was the percentage of direction-specific trials at the neck or trunk level (or both); direction specificity meant that the “direction-specific” (ie, dorsal) muscle was recruited before the antagonistic ventral muscle or without antagonistic activation. The second parameter was the order of recruitment of the direction-specific muscles in the direction-specific trials, resulting in the percentage of trials with top-down, bottom-up, simultaneous, or mixed order of recruitment. Recruitment order could be determined only when at least 2 direction-specific muscles showed significant phasic activity. We also determined the preferred recruitment order, defined as the order that was used most frequently.17
Video Recording of TDAR Sessions
The second and eleventh sessions (V1 and V2, respectively; Fig. 1) were video recorded by 6 master's degree students, each filming one child-horse pair. The TDAR contents were analyzed with The Observer (version XT 9.0, Noldus, Wageningen, the Netherlands), which was designed for behavioral observation (see Dirks et al22). The Observer allows for the quantification of behavioral data in terms of duration, frequency, and serial order of defined actions. Using theory and practice, we designed a protocol for evaluating the TDAR sessions (eAppendix). Next, the observation protocol was translated into a coding scheme for The Observer. In this step, we focused on the frequency of specific TDAR components that challenged postural control. The observer (A.A.) was trained in the application of The Observer and the protocol. During video analysis, she was unaware of the timing of the video (V1 or V2). The interrater reliability of the assessment of postural challenges, performed by 2 authors (A.A. and B.V.), was good (ICC [2,1]=.96, range=.86–.98).
Data Analysis
Data analysis started with a graphic presentation of the developmental trajectories of the individual participants. Next, we applied the Wilcoxon signed rank test (IBM SPSS version 20, IBM Corp, Armonk, New York) to analyze changes over time in the group data for GMFM-88 and all of the other outcome parameters. Probability values of less than .05 were considered statistically significant. Probability values were not adjusted for multiple comparisons because of the preliminary nature of the study.
Role of the Funding Source
The Stichting Beatrixoord Noord-Nederland and Stichting Groningen-Almelo funded the study.
Results
All participants completed the 12 sessions of TDAR and all assessments. No adverse effect of the intervention was reported. Moreover, the smiley scales revealed that all children rated the TDAR sessions as 5, that is, as very pleasant. About 70% of the riding time was spent on riding a walking horse. The time spent on exercises challenging postural control increased from 3.3% at V1 to 14.5% at V2 (Wilcoxon signed rank test, P=.046; for details on the number of challenges, see Tab. 1). At V1, 4 children were accompanied by a side walker, but the 2 oldest children (11 and 12 years of age), who were also the 2 children with past AR experience, were not. At V2, only 2 children (6 and 7 years of age) needed a side walker. For 5 children, the side walkers did not touch the children; for 1 child, the side walker occasionally supported the child at the level of the hips. The therapeutic riding instructor, the pediatric physical therapist (B.V.), and the horse handlers were present at all 12 sessions.
Frequencies of Posture and Balance Challenges During TDAR Sessionsa
Figure 2 shows the changes in the total scores and the scores on dimensions D and E of the GMFM-88 for the group and for the individual participants. During the baseline period (between T0 and T1), the total GMFM-88 scores for 2 children (participants 2 and 3) increased considerably, whereas those for the others did not; during the intervention (between T1 and T2), the scores for all 6 children increased. A more or less similar picture was present for GMFM-88 dimensions D and E: during the baseline period, 3 children improved, and during TDAR, all 6 obtained better scores. During the baseline period, the scores of 2 children exceeded in dimension D the MCID of a large effect size (2.4), whereas in none of the children did the changes in dimension E exceed the threshold of the MCID of a large effect size (3.0) (Tab. 2). In contrast, during the intervention, the changes in dimensions D and E largely exceeded in all children the MCIDs of a large effect size in children functioning at GMFCS level III (Tab. 2). Group analyses indicated that the total GMFM-88 scores did not change significantly between T0 and T1, but they did change significantly between T1 and T2 (Fig. 2). None of the secondary outcome measures showed statistically significant changes over time (Tab. 2).
Development of 88-item Gross Motor Function Measure (GMFM-88) scores. (A) Box plots of total GMFM-88 scores for the group data 6 weeks before the start of the therapist-designed adaptive riding (AR) intervention (T0), at the start of the intervention (T1), and at the end of the intervention (T2). Horizontal lines indicate median values, boxes indicate interquartile ranges, and vertical lines indicate the full range. Wilcoxon signed rank test: P=.075 for T1 versus T0 and P=.028* for T2 versus T1 (asterisk represents significant difference). (B–D) Individual developmental trajectories of the percentage scores for the total GMFM-88 (B) and the goal areas (GMFM-88 dimension D [standing] [C] and GMFM-88 dimension E [walking, running, and jumping] [D]) during the baseline (T0 to T1) and during the therapist-designed AR intervention (T1 to T2). Participants 4 and 5 had previous AR intervention experience; the other children did not. For clarity, the GMFM-88 scales (y-axes) in panels C and D differ from those in panels A and B.
Group Comparisons of Outcome Measures at Each Assessmenta
The EMG analysis revealed that 75% of reaches during both measurements (median value, range=27%–100%) were accompanied by direction-specific activity in the neck and trunk muscles. The frequency of top-down recruitment of the direction-specific muscles decreased in 5 of 6 children between T1 and T2 (Figs. 3 and 4). The child (participant 2) who did not show a decrease in top-down recruitment was the only child who, during the EMG assessments, was characterized as showing inattentive and fidgeting behavior. Group analyses indicated that top-down recruitment decreased from 41% to 16% (Wilcoxon signed rank test, P=.17).
Examples of electromyographic (EMG) recordings of postural muscle activity during reaching while sitting. (A) Trial for participant 1 before the therapist-designed adaptive riding (TDAR) intervention. (B) Trial for participant 1 at the end of the TDAR intervention. The vertical dashed lines represent the presence of the reaching movement; the left line represents the moment at which the video indicated the start of the reaching movement, and the right line represents the end of the reaching movement, as observed in a video. The short, bold vertical lines denote the onset of significant EMG bursts, as defined by the computer algorithm. The biceps brachii muscle was the prime mover in both trials; that is, it was the arm muscle initiating the reaching movement. The vertical dotted line indicates the onset of the reaching movement by the prime mover. Both trials showed direction specificity at the neck and trunk levels. In both trials, the neck extensor muscle was activated before the neck flexor muscle. At the trunk level, direction specificity was expressed in 2 different ways: In panel A, thoracic extensor and lumbar extensor muscles were activated but the rectus abdominis muscle was not recruited; in panel B, the thoracic and lumbar extensor muscles were recruited before the rectus abdominis muscle. Panel A illustrates top-down recruitment, during which the neck extensor muscle was recruited before the thoracic and lumbar extensor muscles. Panel B illustrates a mixed order of recruitment of the dorsal muscles.
Changes in top-down recruitment order from T1 (before the intervention) to T2 (after the intervention). (A) Box plots of the group data for the various types of recruitment order at T1 (white boxes) and T2 (gray boxes). The horizontal bars indicate the median values, the boxes indicate the interquartile ranges, the vertical lines indicate the full range, and the circle is an outlier. In group analyses of the effect of the therapist-designed adaptive riding intervention on top-down recruitment order, the P value was .173 (Wilcoxon signed rank test). (B) Individual data on frequency of top-down recruitment order at T1 (white bars) and T2 (black bars). The frequency in participant 5 at T2 was 0%.
Discussion
This preliminary study indicated that it is feasible to conduct a TDAR intervention study with a complex assessment protocol in children with spastic CP. The results suggested that a TDAR intervention of 6 weeks, with an intensity of 1 hour, twice per week, was associated with a significant improvement in GMFM-88 scores.
All children were enthusiastic about TDAR. In addition, the assessment protocol was feasible, notwithstanding its complexity. We hypothesized that TDAR would affect, in particular, gross motor function, especially dimensions D and E of the GMFM-88—and that was the case. However, we also wanted to know whether TDAR would affect the ICF-CY domain participation (PEDI), the children's personal factor self-esteem, the overall measure quality of life, and the underlying working mechanisms (postural control and spasticity). The limited data of the feasibility study (Tab. 2) suggest that a large RCT study would be needed to determine if there are any changes in the participation measures.
The assessment of postural control seems to be a promising way to improve insight into the mechanisms underlying changes in gross motor function. Ideally, postural control also should be assessed during an intervention; future studies may embark on this endeavor. Muscle tone is considered to be another potential mechanism underlying changes in motor performance in children with CP.37 The Tardieu Scale is the best clinical tool available, but it is not a perfect tool.28 To assess muscle tone more reliably, future studies should include the evaluation of muscle tone by EMG recordings, similar to the evaluation in the study of McGibbon et al,4 who reported a significant improvement in hip adductor symmetry after hippotherapy.
Our secondary aim was to assess the effect of TDAR. Therapist-designed AR was associated with improvements in GMFM-88 dimensions D and E that exceeded the MCIDs. The latter finding suggested that the changes were clinically meaningful.16 The data indicated that some children showed larger changes than others, both during the baseline and during the intervention. The children with the largest changes (participants 2 and 3) were relatively young (6–7 years of age) and, therefore, had the largest potential to improve GMFM-88 scores. Our secondary outcome measures assessed functions at other levels of the ICF-CY; the data did not suggest an effect of TDAR. These data correspond to the findings of Davis et al,38 who studied the effect of AR (once per week) in a relatively large RCT. Three factors may explain the absence of an effect of TDAR on our secondary outcomes: the small group size, the short duration of the TDAR intervention, and insufficient sensitivity of the tools used to evaluate the effect of TDAR (eg, the parent questionnaires on quality of life).33–35
A significant improvement in GMFM-88 scores in a small study group needs to be interpreted with caution. It may be a chance finding, as the review of Tseng et al3 indicated that equine-assisted activities and therapies were not associated with significant improvements in GMFM scores. However, the review did indicate that hippotherapy may be associated with improved postural control; a similar effect of AR (without an integrated program of postural exercises) was less clear. Interestingly, in studies (2 on hippotherapy7,39 and 2 on AR40,41) in which the intervention was applied twice per week—as in the present study—a significant improvement in GMFM scores was reported. These data suggested that the intensity of therapy may be a significant factor in determining outcome, similar to what has been reported for other types of physical therapy in children with CP.42 Three other elements that may have contributed to the improvement in GMFM-88 scores were the hands-off approach, favoring self-practice; the variation in experience resulting from the use of 6 different horses per child; and the use of an integrated program of varied postural challenge exercises in our TDAR program. The postural EMG data suggested that the improvement in GMFM-88 scores during TDAR may have been associated with an improved fine-tuning of postural activity because, after the intervention, the recruitment order closely resembled the typical pattern of varied recruitment order. The video recordings of TDAR showed that at the end of the intervention, fewer children were accompanied by a side walker; this result may suggest that their riding skills improved and that they were able to perform more challenging postural exercises. The latter observation supports the suggestion that postural control improved with increasing intervention time.
The limitations of the present study are related to its design as a feasibility study with a small sample of children who had CP and functioned at GMFCS level III—a design that did not allow for generalization to all children with CP. In addition, the use of only one postintervention assessment precluded conclusions about long-term effects. Another limitation was that the assessors were not masked with regard to the intervention; this limitation posed the risk of detection bias.43 The exception to this rule was the masked assessor of the EMG data; she did not know whether the EMG recordings that she analyzed were obtained before or after the intervention.
We suggest that future studies of TDAR use an RCT design to compare the outcome of an intervention and the outcome for nonriding controls with similar assessment tools, such as a battery evaluating outcome across the levels of the ICF-CY,15,20 and—if possible—an assessment of working mechanisms. Relatively large numbers of participants are needed because CP is characterized by heterogeneity.18 We recommend block randomization for the severity of CP (GMFCS levels I–III versus GMFCS levels IV and V). In addition, we suggest that TDAR last for 3 months (1 hour, 2 times per week) and that evaluation (carried out by masked assessors) include follow-up at least 3 months after the intervention. We encourage practitioners to describe their intervention protocols and to evaluate the protocols with video analysis to determine which aspects of the intervention are beneficial and have an impact on a child's life.20
The present study suggests that it is feasible to perform an RCT of TDAR with our complex protocol. The data from this feasibility study suggest that TDAR may enhance gross motor function and postural adjustments in children who have CP and function at GMFCS level III.
Footnotes
Mrs Angsupaisal, Dr Maathuis, Dr Reinders-Messelink, and Dr Hadders-Algra provided concept/idea/research design. Mrs Angsupaisal, Mrs Visser, Dr Reinders-Messelink, and Dr Hadders-Algra provided writing and project management. Mrs Angsupaisal and Mrs Visser provided data collection. Mrs Angsupaisal, Mrs Visser, Ms Alkema, and Dr Hadders-Algra provided data analysis. Dr Hadders-Algra and Dr Reinders-Messelink provided fund procurement. Dr Meinsma-van der Tuin provided participants and facilities/equipment. Dr Meinsma-van der Tuin and Dr Hadders-Algra provided institutional liaisons. Mrs Angsupaisal provided administrative support. Mrs Angsupaisal, Dr Meinsma-van der Tuin, and Dr Maathuis provided consultation (including review of manuscript before submission).
The authors acknowledge the skillful collaboration of the team at the Riding Center Onder de Linde; the support of Tineke Dirks, PT, in the development of the video protocol for the classification of activities and assistance during equine movement; the assistance of the students who filmed the therapist-assisted adaptive riding sessions; and the encouragement and support of Stichting ZorgPKs, Federatie Paardrijden Gehandicapten, and the parent organization, BOSK.
This study was approved by the Medical Ethical Committee of the University Medical Center Groningen.
The Stichting Beatrixoord Noord-Nederland and Stichting Groningen-Almelo funded the study.
- Received April 4, 2014.
- Accepted April 13, 2015.
- © 2015 American Physical Therapy Association
References
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