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RIGINAL ARTICLE

hanges in Dynamic Trunk/Head Stability and Functionaleach After Hippotherapy

im L. Shurtleff, OTD, OTR/L, John W. Standeven, PhD, Jack R. Engsberg, PhD

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ABSTRACT. Shurtleff TL, Standeven JW, Engsberg JR.hanges in dynamic trunk/head stability and functional reachfter hippotherapy. Arch Phys Med Rehabil 2009;90:1185-95.

Objectives: To determine if hippotherapy (therapy using aorse) improves head/trunk stability and upper extremity (UE)eaching/targeting in children with spastic diplegia cerebralalsy (SDCP).Design: Pre-postoperative follow-up with a 12-week inter-

ention and 12-week washout period after intervention.Setting: A human performance laboratory with 6 camera

ideo motion capture systems for testing.Participants: Eleven children (age 5–13y, average 8y) with

DCP, 8 children (age 5–13y, average 8y) without disabilities.Intervention: Hippotherapy intervention performed at 3

herapeutic horseback riding centers.Main Outcome Measures: Video motion capture using

urface markers collecting data at 60Hz, a mechanical barrel tohallenge trunk and head stability, and functional reach/target-ng test on static surface.

Results: Significant changes with large effect sizes in head/runk stability and reaching/targeting, elapsed time, and effi-iency (reach/path ratio) after 12 weeks of hippotherapy inter-ention. Changes were retained after a 12-week washouteriod.Conclusions: Hippotherapy improves trunk/head stability

nd UE reaching/targeting. These skills form the foundationor many functional tasks. Changes are maintained after thentervention ceases providing a skill foundation for func-ional tasks that may also enhance occupational performancend participation.

Key Words: Cerebral palsy, diplegic; Equine; Head move-ents; Horse; Occupational therapy; Physical therapy; Posture;ehabilitation; Spastic; Upper extremity.© 2009 by the American Congress of Rehabilitationedicine

N A HIPPOTHERAPY SESSION, a therapist uses a horseand its movement as well as the barn/farm/psychosocial

nvironment to challenge multiple body systems in the client toccomplish specific therapeutic goals determined to be impor-ant during preintervention assessments. Hippos is the Greekord for horse, and hippotherapy is therefore defined as ther-

py using a horse.1,2 Children with SDCP often struggle with

From the Human Performance Laboratory, Program in Occupational Therapy,ashington University School of Medicine, St. Louis, MO (Shurtleff, Standeven,

ngsberg); and Therapeutic Horsemanship, Inc, Wentzville, MO (Shurtleff).Supported by the Horses and Humans Research Foundation (HHRF2006).No commercial party having a direct financial interest in the results of the research

upporting this article has or will confer a benefit on the authors or on any organi-ation with which the authors are associated.

Correspondence to Tim L. Shurtleff, OTD, OTR/L, Washington University Schoolf Medicine, Program in Occupational Therapy, 4444 Forest Park, St. Louis, MO3110, e-mail: [email protected]. Reprints are not available from the author.

0003-9993/09/9007-00663$36.00/0doi:10.1016/j.apmr.2009.01.026

ead/trunk stability, even during reaching and functional tasks3

nd are frequent recipients of hippotherapy.Beliefs about the positive effects of hippotherapy are

trongly held.4,5 Anecdotal evidence and several studiesupport the benefits of hippotherapy for people with CP (eg,mprovements in walking, gross motor improvements and re-uction of motor disability,6 decreased energy expenditure andncreased efficiency while walking,7 improvements in muscleymmetry,8 gross motor and functional performance,9 and gaitpeed and gross motor performance).10 Haehl et al11 showedmprovement in the coordination of the movement of the uppernd lower trunk in the sagittal plane with 2 children with CPfter 12 weeks of hippotherapy. Bertoti12 showed improve-ents in trunk stability, strength, balance, and muscle tone

fter therapeutic horseback riding in 11 subjects. Our pilottudy also found improvements in head and trunk control in 6hildren with CP.13

CP refers to nonprogressive syndromes characterized bympaired voluntary movement or posture and resulting fromrenatal developmental malformations or perinatal or postnatalentral nervous system damage. Syndromes manifest before 5ears of age. CP causes nonprogressive spasticity, ataxia, ornvoluntary movements; it is not a specific disorder or singleyndrome. CP syndromes occur in 0.1% to 0.2% of childrennd affect up to 15% of premature infants.14 In SDCP, theower extremities are more involved than the UEs, and therunk is often also affected. The degree of disability for chil-ren with CP are described by the GMFCS, a 5-level system inhich GMFCS-I indicates minimal impairment and children at

he GMFCS-V level cannot sit upright or ambulate indepen-ently.15

Children with spastic CP also have difficulties in fine-tuningostural muscle contraction to task specific conditions duringeaching and show an excess of antagonistic coactivation andifficulties with subtle modulation of postural activity.16 Thisrunk instability contributes to the instability of the proximaloundation of the UEs of children with CP. This proximalnstability at the shoulder may reduce their distal control,ausing them difficulties with reaching and targeting duringunctional tasks. Clinical options to address UE control mayse a stable seated position to isolate UE motor control andtrength. Although UE control may improve, underlying prox-

List of Abbreviations

C7 cervical vertebrae 7CP cerebral palsyGMFCS Gross Motor Function Classification SystemL5 lumbar vertebrae 5OT occupational therapyPT physical therapyROM range of motionSDCP spastic diplegia cerebral palsyT10 tenth thoracic vertebrae
UE upper extremity
Arch Phys Med Rehabil Vol 90, July 2009

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1186 TRUNK STABILITY/REACHING POST HIPPOTHERAPY, Shurtleff

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mal stability is not targeted and will be only minimally af-ected if not challenged. As an example, a very commonlinical option to address core strength and trunk stability forhildren with CP is to use Swiss ball exercises. Children oftenit on the ball independently and perform exercises or task-elated activities. They may also sit, lie prone, or supine acrosshe ball while being moved by the therapist to build coretrength and postural responses. Although this can be effective,he limitation in this application is that the time and repetitionsypically last only a few minutes or a few sets of repetitions.lthough such activities might address core strength and prox-

mal stability, it would be rare indeed for a child to tolerateeing moved about on a Swiss ball for 45 minutes or for aherapist to be able or willing to move a child rhythmically andonsistently for such a long session in the clinic. In contrast tohis, during a hippotherapy intervention, a mounted client ex-eriences several thousand horse strides (3-dimensional chal-enges to trunk and head stability) in a 45-minute session.17

he child also typically changes positions during the session soifferent motor units can be targeted. During hippotherapy, inddition to this rhythmic movement of the horse’s gaits, theorse also moves less predictably through space (eg, stoppingnd starting, turning circles, weaving cones, or negotiatingerrain). This added vestibular and anticipatory challenge isurther claimed by those who use horse movement for thera-eutic effect to further challenge and train clients to improveotor control and functional ability.5 The motivation and the

fun” of riding a horse may be an even more important con-ideration. It is the addition of this meaningful and motivatingspect of hippotherapy to an intense exercise regimen that mayontribute much of the power of the hippotherapy interven-ion.18

Many sport-related activities are also available to childrenith CP and are also believed to help (eg, adapted skiing,

ledge hockey, martial arts, and so on).19 Literature to date toupport those beliefs is limited. However, it seems that anyntervention that directly addresses postural stability, if effec-ive, may also positively impact many aspects of functionalompetence and occupational performance.

No investigations have objectively quantified changes inoth head/trunk control and in functional reaching/targeting asconsequence of hippotherapy. We believe that such objectiveata can augment the clinical rating scales and measures usedn many of the previous investigations. As a primary researchuestion, we wanted to provide objective evidence to supportr refute efficacy of hippotherapy, an intervention that has beenlaimed for many years to address the basic problem of trunk/ead instability, thus providing a foundation on which manyther functional skills could be improved. The purpose of thisnvestigation is to quantify changes in head/trunk stability andeaching speed/efficiency as a consequence of hippotherapyntervention.

METHODS

articipantsEleven children with SDCP were recruited (table 1). Inclu-

ion criteria included prior diagnosis of SDCP from theirersonal physicians, between 5 and 17 years old, able to sitpright unaided on a static surface, intact receptive communi-ation, ability to follow directions, ability to abduct hips to sitstride a horse and the testing device, and available for up to 26eeks. Participants’ personal physicians approved participa-

ion. The Human Studies Committee (Institutional Reviewoard) of Washington University School of Medicine and the

nstitutional Review Board of St. Louis University approved w

rch Phys Med Rehabil Vol 90, July 2009

he study. All participants and parents signed assent or consentorms.

Excluded were children with any significant history of ridingorses, defined as not having participated in hippotherapy,herapeutic riding or any riding lessons, or having frequently oregularly ridden horses in an informal/nonlesson setting. Weid not exclude children who had taken 1 or 2 pony rides at aark or ridden briefly once or twice (ie, on a relative’s or familyriend’s farm) because we believed that would make it tooifficult to recruit sufficient subjects and we did not anticipatehat such a limited exposure would make a real difference inhe variables we were measuring. As it turned out, none of thehildren had ridden a horse in over a year, and most had neveridden horses. We also excluded other neuromuscular impair-ents; cognitive, attentional, sensory, or psychosocial diag-

oses making them unable to follow direction; uncorrectedisual impairments; and recent injection of botulinium toxin6mo), surgery (1y), or any planned medical or surgical inter-entions to modify effects of CP during the period of the study.ll participants were screened for precautions and contraindi-

ations for therapeutic riding listed by the North Americaniding for the Handicapped Association and judged to be safe

o participate in hippotherapy. Most study participants with CPere previously referred by their physicians for PT or OT and

eceived therapy in other contexts that continued during theeriod of the study. They were recruited for the study and thenpproved by their physicians so hippotherapy could be per-ormed after a new evaluation by a physical therapist or anccupational therapist familiar with hippotherapy.After the subjects with SDCP were recruited, 8 children

Table 1: Participant Recruitment Table

CP Group

Participants Sex Age GMFCS1 M 5 II2 F 5 IV3 M 5 I4 F 6 III5 M 7 I6 M 8 II7 M 8 II8 F 9 III9 M 12 II

10 F 12 III11 F 13 IV

Total in CP group6 boys 8.18 average age5 girls 2.994 SD

WD

Participants12 M 5 WD13 M 5 WD14 F 7 WD15 M 7 WD16 M 7 WD17 M 9 WD18 F 12 WD19 F 13 WD

Total in WD group5 boys 8.13 average age3 girls 2.997 SD

bbreviation: WD, without disability.

ithout disabilities were recruited to match the ages of the

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1187TRUNK STABILITY/REACHING POST HIPPOTHERAPY, Shurtleff

hildren with CP (see table 1). They each completed the testattery once. Their results provided data for typically develop-ng children as a normative comparison with the CP group.hey were compensated for their participation ($25) but re-eived no intervention because they did not have the impair-ent that the intervention was intended to address and an

ntervention would have little meaning.

nterventionThe intervention (45 minutes on a horse, 1 time/wk for 12

eeks) began with an OT/PT evaluation to identify specificmpairments and develop a unique treatment. The interventionas conducted by licensed occupational or physical therapists

xperienced with hippotherapy. Horses were selected for sizend movement characteristics to challenge participants but notverwhelm them. Interventions were performed by physicalherapists, occupational therapists, or certified occupationalherapy assistants at 3 local therapeutic riding centers. All ofhem received training from the American Hippotherapy As-ociation to become registered with the North American Ridingor the Handicapped Association as level II hippotherapy ther-pists. All 3 therapeutic riding centers are Premier Accreditedenters with the North American Riding for the Handicappedssociation. In the local centers in which hippotherapy waserformed, physical therapists and occupational therapists haverained together and have developed a broad overlap in the usef intervention tools for hippotherapy. In this context at theseenters, it is difficult to distinguish a PT from an OT treatment,nd both used tools from either specialty to give these childrenhat they needed, based on their initial evaluation and goal

etting. The common denominator between all of the treatmentlans was 45 minutes mounted on a moving horse in walknd/or trot performing various positions (eg, forward astride,ide sit, tall kneel, reverse astride, quadruped), often withransitions between positions and sometimes while the horseas moving. This was not a riding lesson, and the participantad no control of the horse. Horses were led by an experiencedeader. The therapist and trained side walkers walked alongsidessisting and coaching the child in positions and activities andnsuring safety. UE activities, stretches, cognitive games, andxercises were included. As a few examples, stretches mightnclude reaching forward up the neck to place clips in the maner rings on the horse’s ears. The child might also stretch downo touch his/her feet or back to touch the horse’s tail. Activitiesnd games included catching, throwing, and placing balls,ings, and toys as directed by the therapist. Reaching to graspbjects while sitting or kneeling on a moving horse and thenlacing them onto a stationary surface, or to/from a therapistwho may be using a reacher) further challenges reaching intoll planes while riding. Cognitive games might include mem-ry or recognition games in which the child would identify;earch for and find objects, letters, and/or toys around therena; and remember where they were so he/she could go backo find them. They might change gait or position while movingoward each new object. All of these and many other activitiesere performed while on a moving horse. The horse varied

peed and gait during the activity or perform a school figurecircle, weave cones, and so on) while the child was engaged in

fun and meaningful task. This integrates the effect of thehythmic movement and the vestibular effect of the schoolgures with UE tasks while responding to a cognitive chal-

enge.Hippotherapy is believed by those who do it to integrate

hese basic skills of stability and balance with the more refinedkills (functional and cognitive tasks). This integration is con-
idered by those who do hippotherapy to be one of its strengths.
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herefore, there was no attempt to separate training that tar-eted only stability from the UE tasks that might affect theunctional reaching test because both were considered goals ofhe hippotherapy treatment and were most effectively targetedimultaneously. Even the school figures consisting of straightines, large and small circles, weaving cones, and riding onhallenging terrain were performed with transitions betweenaits and speeds. This further challenged the children to inte-rate their motor abilities with meaningful tasks and fun expe-iences.

utcome Assessment TestingOutcome testing was performed within 2 weeks before be-

inning the hippotherapy intervention, within 2 weeks afterompletion, and 12 to 14 weeks postintervention. During theashout period, the children did not ride horses but continued

ny other ongoing activities or therapies.

ideo Motion Capture Data CollectionBarrel test. A mechanical barrel (fig 1) was used to assess

he control of head and trunk movement.13 The barrel was an8-gal plastic drum covered with 1-inch thick neoprene, a wooladdle blanket, and 2-inch strips of Velcro, giving a finishediameter of 18 inches. Foam blocks were affixed to the Velcrotrips around the hips and thighs to stabilize the pelvis forositioning and safety. The barrel had 1 translational degree ofreedom with an amplitude of 16cm. It moved on wheels in annternal steel track that was supported on inverted T-legs andas powered by a variable speed 0.25 horsepower, DC, vari-

ble speed gear motor. The reciprocating speed was variablerom 0 to 1Hz. A spotter sat on each side of the barrel duringach test to ensure participant safety. The mechanical barrel

ig 1. Child with surface markers sitting on testing barrel withpotters low on side. One (of 6) cameras in the background.


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rovided a precisely replicable testing motion to challenge andest trunk/head stability in a reliable manner.

Nineteen reflective surface markers (4mm) were placedn the head and trunk of each participant (table 2) for videootion capture. Four markers were placed on the barrel to

stablish a barrel frame of reference. Each subject rode thearrel in the astride position for 2 trials at a reciprocatingpeed of 1Hz. A 6-camera video motion capture systemEvaRealTimea V. 5.0.4 using MAC Eagle Digital Cam-rasa) captured the movement of the surface markers during5-second interval trials. The video motion capture softwarereated a stick figure or “tinkertoy” image (fig 2) that coulde rotated in all planes to observe recorded movementuring a testing time series from any viewpoint. To ensureonsistent marker placement on trunk and UEs, markersere placed on bony landmarks or placed proportionatelyetween bony landmarks per our lab protocol. Marker place-ent reliability in our laboratory for a single person apply-

ng the markers during an investigation has been shown toe excellent (r�0.95).20 Test-retest reliability within a sin-le session for the video motion capture barrel test was alsoxcellent (r�0.94).13

During testing, the child was given a ball or small stuffed toynd asked to hold it with both hands in front of the abdomen.his put the arms in adduction with elbows flexed and slightly

nternally rotated. This put all children into a similar armosition, kept them from supporting themselves with UEs, andeduced protective extension when barrel movement started. Itlso avoided random arm movements from blocking reflectivearkers. The child was asked to look at a target (a drawing offace on the wall) or a parent standing directly in front of

im/her. This kept the child facing forward and his/her headelatively stable.

Upper-extremity functional reach test. A simple “reach totarget” task adapted from an investigation of hemiplegic

troke recovery was used to assess UE functional reach.21 The

Table 2: Anatomic Landmarks fo

Vertex R Zygomatic Arch L Zygomatic Ar

C7 Sternum T4L midclavicle L1 L5L greater trochanter Horse RF Horse LF

bbreviations: L, left; LH, left hind; R, right; RH, right hind.

ig 2. Markers as seen in video capture software in computer,howing markers used for analysis.


articipants sat on a wooden box or backless stool. Ninedditional surface markers were placed on each arm and handtable 3). Four markers were placed on the floor to establish aaboratory frame of reference. A target (2.5-cm diameter re-ective marker on a tripod) was set at shoulder height in theidline sagittal plane (fig 3). The initial distance to the targetas set where the child could reach without any trunk move-ent. The child was asked to rest his/her palms on the thighs

nd reach to touch the target with his/her index finger. Afterouching the marker, the child returned the hand to the thigh.he target was then moved to each side for the coronal plane

ests (fig 4). The tests were repeated 3 times for each directionnd with both hands. After completing each “easy reach,” thearget was moved an additional 10cm for the younger children5–9y) and 15cm for the 3 older (12, 13y) children to compen-ate for differences in arm length. This “extended reach” pro-ided an additional challenge to trunk stability requiring thehild to lean his/her trunk off of midline and recover to aesting position with the hand back on the thigh. All of thesehildren had some degree of UE control issues derived fromheir CP, which may have been compounded depending onheir level of trunk control. This measure was intended tossess change in UE targeting and efficiency as a consequencef the trunk control intervention rather than an absolute indexf isolated UE control or of the difference in mechanisms usedn the trunk to improve the reaching/targeting at the 3 testingimes.

ata AnalysisSurface marker data were tracked and edited to produce

-dimensional coordinates as a function of a time series. Ap-roximately 15 cycles were obtained for each trial yieldingbout 30 cycles of data for a test. However, only the last half7.5s) of each trial was used after the barrel had reached aonstant reciprocating speed of 1Hz. Data were imported intospreadsheet for analysis.Dynamic stability in the sagittal plane was defined as the

bility to keep the head and trunk relatively stable while theelvis was in motion. Two sets of sagittal plane variables wereetermined from the tracked data: (1) head angle and (2)nterior posterior translation of the spine and head. Five mark-rs on the head and trunk (see fig 2) and 2 on the barrel weresed for this anterior/posterior head angle and translation anal-sis (Vertex, Cyclops, C7, T10, L5, horse left fore, horse leftind).

d/Trunk Markers for Barrel Test

R Acromion L Acromion Offset R Scapula

T7 T10 R midclavicleR Iliac crest L Iliac crest R greater trochanterHorse RH Horse LH Cyclops eye

able 3: Additional Markers for Upper-Extremity Functional ReachPlaced on Both Right and Left Upper Extremity

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The head angle analysis compared the maximum and mini-um angle of the head relative to the horizontal over a time

eries. Head angle was the angle of the Vertex-C7 line com-ared with a horizontal line represented by a front and backarrel marker (horse left fore and left hind). The maximumngle was the largest angle over several movement cyclesmost vertical head or beyond vertical into extension), and theinimum was the least angle over the same time series (mostexion). The difference was described as the ROM of the headver the 7.5-second time series of the test. The standard devi-tion of all of the angle measurements over the 7.5-second timeeries was also used as a variable itself because it effectivelyescribed the degree of variability of head angle over several7–9) movement cycles.

Translation was quantified by using the markers at the ver-ex, a virtual marker calculated between the eyes (the “Cyclopsye”), and markers at C7, T10, and L5 (top, middle, and bottomf spine) (see fig 2). The average horizontal translation of thesearkers was determined. One barrel marker quantified theovement of the barrel (horse) as the challenge to the subject.ifferences in barrel movement noted are within the precisionf the video motion capture measurement tool (�0.5mm). Thepecific variables were the maximum amplitudes of horizontalranslations of each marker averaged across a 7.5-second

ig 3. Functional reach test: child reaching forward to touch tar-et.

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For the reaching test, every child performed 3 reaches for-ard (see fig 3) and 3 to the side (see fig 4) with each arm at

he “easy reach” distance (no trunk movement required) andhe “extended reach” distance (plus 10 or 15cm). This yielded4 reaching trials at each testing time. In a few cases, trialsere thrown out when data were not clear or the child used aifferent movement than that requested. The elapsed time wasalculated as the time from the beginning of movement fromesting position to first touch. Reach/path ratio was calculateds the sum of the distances moved by the index finger markeretween all observations (60 frames per second) from rest toouch and divided by the straight line distance from the initialesting position to the target. The elapsed time and reach pathatio were averaged for all of the good trials. Those 2 averageumbers aggregated the elapsed time and reach path ratio forhat testing period for each child. These numbers were used fortatistical analysis between pretest, the first postinterventionest immediately after hippotherapy intervention ceased, andhe second postintervention (washout) test 12 weeks after hip-otherapy ceased and were averaged for the groups of subjectsor each testing time for graphics. The group without disabilityas only measured once. A horizontal dashed line was placedn the graphs indicating the without disability result as atypically developing” normative comparison.

ig 4. Functional reach test: child reaching to side to touch tar-et.


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tatistical AnalysisResults were entered into SPSS V16.b A repeated-measures

nalysis of variance was used to compare absolute head angle,ranslation, and functional reach variables at 3 time pointsefore and after hippotherapy for the group with CP with an ariori significance level of ��0.05. The same variables wereetermined for the without-disability participants. The 1-timeithout disability baseline results were compared with pretest,

he first postintervention test immediately after hippotherapyntervention ceased, and the second postintervention (washout)est 12 weeks after hippotherapy intervention ceased for thearticipants with CP by using independent samples t tests.

Effect sizes (Cohen’s d) were calculated by using a pooledtandard deviation to compare the results of the interventionetween test times. The effect size interpreted as d � 0.2 is amall change, d � 0.5 is a moderate change, and d � 0.8 is aarge change and is described as “grossly observable” and cane interpreted to indicate clinical change.22,23 Positive effectizes are movements in the anticipated or positive direction.egative effect sizes indicate regression.

RESULTSEleven children with SDCP completed the intervention and

he pretest and first postintervention test. Ten children withDCP completed the second postintervention (washout) test.ne child failed to return; the family did not respond to several

ontact attempts. His data were kept in the results for there-first postintervention test, but the washout results werealculated without him.

ead AngleThe head angle results showed a significant change in head

ontrol between pre- and posttests that was maintained after theashout period. The significant changes in SD, ROM, andinimum head angle were maintained after the washout period

figs 5–7). There were no significant changes between the firstostintervention test and the second postintervention tests onhese variables. The changes in the average minimum angleetween the pretest and first postintervention test were signif-cant with a large effect size, but they were not significantlyifferent between the first postintervention test and the secondostintervention test. The significant changes in SD and ROMlso showed very large effect sizes (table 4). The first postin-

ig 5. Movement variability (SD) of head angle compared withorizontal indicating that changes from pre-post1 and pre-post2 areignificant (P<.05), and no significant change occurred post1-post2ndicating that changes were maintained. Abbreviations: post1, first
ostintervention test; post2, second postintervention (washout)est.
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ervention/second postintervention differences that were notignificant also showed very small effect sizes.

nterior Posterior TranslationThe results for the translation analysis show a reduction inovement for all participants as the markers moved away from

he barrel and toward the head (fig 8). Thus, L5 only varied amall amount compared with the translation of the barrel be-ause it is so close to the barrel. At T10 and C7 and the markersn the head (Cyclops and Vertex), there was much moreeduction in translation between the pre- and posttests. Therere 2 key results. The first key result is that there was aignificant reduction in horizontal translation at C7, at theyclops eye, and the Vertex in the CP group after the hippo-

herapy intervention. This change was maintained in the secondntervention test after the washout period. The second key

ig 6. Range of motion of head angle comparing pre-post changeso washout period. Pre-post1 and pre-post2 changes are both sig-ificant (P<.05), but post1-post2 is not significant, showing thathanges are maintained. Abbreviations: post1, first postinterven-ion test; post2, second postintervention (washout) test.

ig 7. Minimum head angle in the sagittal plane indicating im-roved ability to hold the head more upright while moving afterippotherapy, it is significant between pre and post (P<.05). Thehange is maintained after washout (post1–post2 not significant).
bbreviations: post1, first postintervention test; post2, secondostintervention (washout) test.

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esult was that the change in the CP group after the interventionrought their results closer to that of the without disabilityroup. The average amplitude at C7, the Cyclops eye, and theertex for the CP group were significantly different from theithout disability group before the intervention. These 3 mark-

rs remained significantly different from the without-disabilityroup after the intervention. There were no significant differ-nces between the first postintervention and the second postint-rvention test on these variables for the CP group.

unctional ReachResults showed that both the reach path ratio (fig 9) and the

lapsed time (fig 10) decreased from the pretest to the posttestnd continued to decrease to the third test. Both variables wereignificant for the children with CP at the second postinterven-ion test measurement after the washout period, but only thelapsed time was significant immediately after the intervention.he reach path ratio was also significantly different between

he first postintervention and second postintervention test. Be-ween the pre- and first postintervention tests, both of theseeasures for the children with CP moved toward results for the

hildren without disabilities. Between the first postinterventionnd second postintervention test, they continued to move towardhe without-disability baseline but remained significantly different.

Table 4: Effect Sizes and Significance of Head

Max Mea

Pre-post1 change 0.38 �0.3Pre-post2 change 0.26 �0.1Post1-post2 change �0.16 0.2

bbreviations: post1, first postintervention test; post2, second postP�.01.P�.05.

ig 8. The average amplitude of the markers on the head and trunkuring the last half of the barrel test after the barrel had reachedonstant speed. The y-axis represents the average amplitude of thearkers at each of 6 points on the horse, trunk, and head (repre-

ented by the x-axis). The lines on the graphs represent the 3 testslus the without-disability (WD) group as specified in the legend. Allhanges between pre and post1 were significant, and significanceas maintained until post2 (P<.05). All comparisons above thearrel (horse) between the CP and WD group were significant andemained so from pre to post1 and post2 (P<.05). There were noignificant differences between post1 and post2 for the CP group.
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DISCUSSIONThe purpose of this investigation was to objectively evaluate

he efficacy of hippotherapy in improving head/trunk stabilitynd functional reaching in children with SDCP. Three pub-ished studies focus attention specifically on trunk stability andippotherapy. Our objective results reinforce Bertoti’s conclu-ions about improvements in trunk control and sitting balancefter hippotherapy, including the ability to right the trunk afterisplacement.12 Haehl et al11 showed improvement in the co-rdination of movement with the horse of the upper and lowerrunk in the sagittal plane with 2 children with CP after 12eeks of hippotherapy. They used kinematic measurementsith 3 markers each on both the child’s and a live horse’s

pine.11 The results of the present investigation support Haehlt al’s conclusions that hippotherapy improved trunk coordi-ation by showing a reduced translation of the upper trunk andead and reduced variability of the head angle in response to anxternal perturbation at the pelvis. However, we have includeddditional subjects and anatomic markers allowing the calcu-ation of translation and rotation variables at several levels.

acPhail et al24 measured kinematic postural responses of 6ithout-disability children and 6 with CP to horse movement in

he coronal plane. They reported differences between childrenith no disabilities, those with diplegic CP, and those withuadriplegic CP. They concluded that kinematic measurementsould be a sensitive and effective means to measure changever time resulting from horseback riding.24 This study re-ponds to their recommendation by applying video motionapture tools to enable kinematic measurement to understandhe effect of a hippotherapy intervention on children with CP.

les and Movement Variability (ROM and SD)

Min ROM SD

1.2* 1.14† 0.93*0.55 0.66* 0.91*0.62 �0.54 �0.10

ention (washout) test.

ig 9. Reach/path ratio comparing results from the CP group over 3est times with the WD group. Changes were significant from pre toost2 and from post1 to post2 tests (P<.05). The dashed line is the WDaseline for comparison. The graph shows movement toward the WDaseline by the CP group after hippotherapy; however, the differenceetween CP and WD remained significant (P<.01) for all 3 test times.

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o do so, we defined improved trunk stability as reducedovement at the top of the spine in response to perturbation at

he pelvis. We believe it is good that translation decreases ase move our measurement up the spine. The results in ourideo motion capture barrel test show this as a good thingecause the children with CP have shown that they can betterbsorb external perturbations with reduced movement distallyupward from pelvis) and have become more like their peersithout disability on this measure.In our pilot study, we recruited 6 children with SDCP and a

ithout-disability comparison group (n�6). Results of the pilottudy showed significant changes between pre- and postresultsn both head angle and head/upper trunk translation, whichoved toward the results of the without-disability group. After12-week hippotherapy intervention, the CP group was no

onger significantly different from the without-disability resultsn the trunk and head translation variables.13 The current groupf 11 children with CP did not achieve the result of no signif-cant difference between the without-disability and CP groupst the top of the spine after the hippotherapy intervention as inur pilot study.13 We explain this because the current grouptarted out more impaired in stability by our measure butmproved about the same absolute amount. Because they hadarther to go, they did not achieve the “no significant differ-nce” result like the pilot CP group did. We think that thisaises the question of dosage and whether more interventionight have taken them to that point or if the hippotherapy

ntervention only goes so far. Maybe it reaches a plateau inesults, and after that point diminishing returns sets in makingne question whether hippotherapy should continue. We be-ieve these questions warrant further study.

For the pilot study, we also developed the video motionapture measurement methods and the mechanical barrel tohallenge and test head/trunk stability and showed the value ofsing objective kinematic measurements in the laboratory tonderstand the results of hippotherapy on motor learning forhildren with CP.13 The motorized testing barrel was used forreasons. The first was the difficulty associated with collectinginematic data of the participant with a 6-camera system withimited portability at the riding arena. Thus, having a piece ofquipment that could be used in the laboratory was very ap-ealing. The second was to establish a reliable method forollecting data. Laboratory testing is likely to reduce testingariability because the mechanical barrel produces preciselyhe same challenge perturbation every movement cycle,

ig 10. Reaching elapsed time. The average elapsed time from resto first touch comparing results from the CP group to the WD groupver 3 test times. Abbreviations: post1, first postintervention test;ost2, second postintervention (washout) test.

hereas it has been reported that kinematics (ie, tempo and m


tride length) of the same horse’s gait vary substantially event the walk.25 To fully use the precision of the 3-dimensionalideo motion capture testing process (�0.5mm at 60Hz), thehallenge to trunk stability to which the subject responds foresting needed to be a constant, not a variable. With real horses,eplication of the same testing movement after 3 and 6 monthslso becomes even more problematic. We believed that itould obscure the measurement of changes in the subjects’

bility to respond to the trunk challenge. Therefore, the advan-age of using such a precise measurement tool would be di-inished. Because our results support previous reports inhich data were collected from participants riding horses,11,12

t would appear that our artificial environment of the mechan-cal challenge barrel in the laboratory did not prevent changesrom being documented. Future work should compare theseethods.The results of this investigation add to the body of knowl-

dge in several ways. This study extends our pilot work with aarger sample of children with CP. It also recruited and testedn age-matched without-disability comparison group anddded a measure of UE distal control. The measure of UEontrol could be affected by the proximal improvements inrunk and head stability. Most importantly, this study added a-month washout period during which subjects did not rideorses. Our results showed that the increased level of controlersisted after the intervention ceased. The results of thisurrent study further support the notion that meaningful dataan be conveniently collected in the laboratory instead of theiding arena.

The reduction in translational movement at the upper trunknd head along with the decreased angle variation of the headlso effectively stabilizes the visual and vestibular systems,oth of which are resident in the head and are 2 primaryensory systems providing input to control posture and func-ional movement.26 This improved stability might also contrib-te to the improvement we measured in gross movement of theE that may enable improved functional competence. Addi-

ional work is needed to isolate, define, and quantify relation-hips between increased stability in these sensory systemsecause of hippotherapy and improvements in functional com-etence.Results indicate that hippotherapy improves the ability of

hildren with CP to control the movement of their trunk andead as a result of learning to respond to rhythmic movement.he prepost changes for the minimum angle, ROM, and SD

see figs 5–7) are all significant. Effect sizes are very largendicating that these changes should be visible to casual obser-ation and are likely indicative of clinical change.22,23 Themall changes between the first postintervention test and theecond postintervention test are not significant, with low effectizes indicating that little change occurred and that preposthanges were maintained for at least 3 months after the inter-ention ceased.“Forced use” has been established as an effective approach

o deal with childhood hemiparesis secondary to CP.27 Theoncept of forced use is also applied to treadmill training forait training for children with CP because a patient must steporward to keep up with the treadmill.28 It is not a long leap topply the same concept to a child’s trunk that has decreasedtrength and motor control mounted on a rhythmically movingorse. Thus, hippotherapy becomes a “forced-use” head/trunkxercise while mounted because the child must respond to theovement of the horse’s back imparted to the pelvis as each

tep of the horse thrusts him/her mostly forward but with some
ovement in other planes/axes as well.

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Furthermore, neuroscientists who study motor learning haveoncluded that both massed practice and variable practice areery effective practice conditions to reinforce new motor learn-ng.29 Changes in speed, gait, and direction and positionhanges during a hippotherapy session create variability whilehe child is experiencing the rhythmic movement. Therefore,he experience of riding a horse can be thought of as a massedut variable practice of 3000 to 5000 repetitions of a forced-useostural challenge and trunk/head righting exercise per 45-inute hippotherapy session.Although we recognize that there are differences between

P and stroke, there are also many parallels, both in etiologyoften caused by ischemia/hypoxia) and in treatment (focus onotor learning, reduction in abnormal and asymmetric tone

nd strengthening). Therefore, some of the literature regardingtroke recovery and treatment may apply here and help toxplain these results. Lang et al30 reported that typical numbersf repetitions for PT and OT sessions for neurorehabilitationfter stroke average from 34 to 39 repetitions with only 12 forurposeful movements and 292 steps for interventions address-ng gait. However, animal models showing motor recoveryfter ischemic lesions included 400 to 600 repetitions beforeesults were conclusive.31,32 In this context, hippotherapy coulde considered as a rhythmic trunk challenge/recovery andore-strengthening exercise. Thus, the extremely large numbersf repetitions per hippotherapy treatment session (ie, 3000–000) exceed typical OT/PT treatments in numbers of repeti-ions by an order of magnitude. They also far exceed animalodels of motor learning.31,32 This intense practice conditionay begin to account for the results we have measured here in

he improvement of dynamic stability.It was interesting to note that the without-disability children

ad more lumbar mobility than the children with CP. This isikely desirable because much of the movement of a horse, theesting barrel, or the forward pelvic movement from walking/unning with one’s own lower extremities represent challengeso trunk stability and balance that are typically absorbed in theumbar spine so as not to be transmitted to the upper spine andead. Thus, lumbar mobility enables reduced movement at theop of the trunk. The initial response to new postural demandsor children with CP is to respond as a much younger typicalhild, to cocontract to improve stability, and as they mature tose more typical patterns as motor learning and strength im-rove.16,33 Our children without disability were likely well pasthis trunk cocontraction stage in which a child with CP might

ove stiffly, like a mast on a ship, either on a horse, on theesting barrel, and even while ambulating. The SDCP children

ay still be stuck in or moving through this early stage oftrengthening/motor learning as they begin to learn to respondo the rhythmic movement of a horse.

The change in the reach path ratio in the reaching test wasot significantly different from preintervention to the firstostintervention test. However, it was significant between thereintervention test and the second postintervention washoutest. This was initially a bit perplexing. The explanation mighte that the improvements that stabilized the trunk also stabi-ized the proximal foundation for the upper extremities. Be-ause proximal stability enables distal control, we hypothesizehat this may have facilitated better functional use of the handsn everyday activities. As the children became more effectivend efficient with daily functional tasks, they might have doneven more with their hands, maybe with more success or lessffort, moving their measured improvement further by the timef the third test. Thus, initial improvements may have initiatedvirtuous cycle that reinforced itself without more interven-

ion. It would be worthwhile to determine if this trend contin- c

es over longer time periods. It would also be worthwhile toetermine if additional intervention would accelerate the im-rovement.Even with only a 12-week intervention, these children with

P appear to have moved closer to a typical range of head,runk, and UE control. The lack of significant change in trunk/ead stability and in these basic UE skills between the firstostintervention and second postintervention test (the final testfter the washout period) indicates that the changes measuredmmediately after a series of therapist-directed hippotherapyessions persisted with these children for at least 3 months afterhe intervention ceased. This is important because it indicateshat this improvement in dynamic trunk stability and functionaleach is not transitory and not limited to the period of activeherapy. This new stability may provide a permanent platformn which these children can continue to develop functional andobility skills to improve their occupational performance and

articipation in other activities of everyday life.Results from this study leave questions unanswered about

he effects of dosage. No studies measured varying levels ofosage objectively as a factor in determining how much im-rovement comes from different levels of intervention overarying periods of time. Knowing this could be a significantactor in providing additional evidence of efficacy for hippo-herapy to the medical and funding communities, and couldrovide valuable information to support treatment planning toherapists who perform hippotherapy.

tudy LimitationsOne limitation of this study was the short time of interven-

ion. The intervention lasted only 12 weeks (amounting to 8ours on a moving horse). Many children with CP experienceuch longer therapy interventions over months and even years.owever, there is no literature addressing the effects of varying

evels of dosage of hippotherapy, either by varying intensity oruration of the therapy.A methodologic limitation of this study was the lack of 2

reintervention baseline assessments. These assessmentsould have quantified any changes in the outcomes that mightave occurred over time and could have assisted in factoringut any effect of maturation and other ongoing therapies.owever, Palisano et al34p981 found that “by middle childhood,

hildren with CP do not make substantial changes in the grossotor abilities measured by the Gross Motor Function Mea-

ure” (which includes measures of trunk stability). Their resultsn�586) showed the improvement curves of children at eachf the 5 GMFCS levels plateauing after approximately 60onths.34 This published evidence suggested that the signifi-

ant prepost improvements, with large effect sizes, found in ourilot study with a group of children who were older than 60onths13 likely represented real change and were not simply a

esult of maturation. Our sample in this investigation alsotarted at 60 months and had an average age of 8 years. Therant supporting this effort also required that we complete thetudy in 1 year. Therefore, we had to make a tradeoff betweenprebaseline and a washout period test. Our choice, therefore,

or this investigation was to investigate persistence of anyhange that might occur after hippotherapy intervention ceasedecause this would become new information.The UE Functional Reach test is not a true functional test

ecause it only involves reaching and touching a target, and noomplete functional task is performed. However, these 2 mea-urements (the ability to move the UEs quickly [elapsed time]nd efficiently [reach/path ratio]) quantify improvement in thebility to get the hands to the task. They measure very basic
omponents that are necessary to perform almost all functional

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asks using the UE. An improvement in these impairment levelomponents should predict improved performance at the tasktself. In other work (UE recovery of function after stroke),hese components of the task (reach path ratio and elapsedime) are considered essential to many functional activities,nd, thus, our results are interpreted in that context.21 Furtherork should include tests that assess changes in the ability to

omplete whole functional tasks as a consequence of hippo-herapy. In addition, further analysis of our data quantifyingny changes in trunk stability that might have occurred duringhe reaching tasks from pre- to postassessment might offerdditional insight regarding the mechanism of reaching im-rovement.

CONCLUSIONSThe purpose of this investigation was to objectively evaluate

he efficacy of hippotherapy in improving head/trunk stabilitynd functional reaching in children with SDCP. We used aotorized barrel and kinematic measurements to quantify mo-

or learning affecting dynamic stability of the head/trunk andhe speed and efficiency of functional reaching that occurred inhildren with CP resulting from a therapist using the rhythmicovement of a horse as a treatment tool. These changes were

ompared with a baseline of the same movement patternseasured in an age-matched group of children without disabil-

ties. Subjects were also tested after an additional 12 weeks toetermine if changes persisted after the intervention ceased.esults indicated that children with SDCP responded to a seriesf weekly experiences with the rhythmic movement of theorse by increasing motor control of their trunk and head. Thismproved control of the trunk stabilized the proximal founda-ion of the UEs and may account for the improvements weeasured in the functional reach test. Changes in trunk/head

tability and in reaching/targeting persisted for at least 3onths after the intervention ceased. These objective improve-ents in dynamic stability suggest that hippotherapy can pro-

ide a valuable therapeutic tool in the practice of OT and PThat may enable improved function in many activities of ev-ryday life for children with CP. It appears that further use ofhis measurement model and further development of additionalystematic and objective data about the results of hippotherapyntervention will further inform physicians, therapists, andhird-party payers about the benefits of hippotherapy as anffective treatment strategy in the context of OT or PT forhildren with CP.

Acknowledgments: We thank Rachel Proffitt, OTD/S, for pro-essing the data, and the participant children, their families, the ther-pists, staff, and volunteers at 3 local therapeutic riding centersTherapeutic Horsemanship, Wentzville, MO, Ride-on St. Louis,immswick, MO, Exceptional Equestrians of the Missouri Valley,ashington, MO) who provided hippotherapy treatment for the

roject.

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Suppliers. EvaRealTime V. 5.0.4 and MAC Eagle Digital Cameras; Motion

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