114 Mersul La Copii Cu Sindromul Down

Effects of Intensity of TreadmillTraining on Developmental Outcomesand Stepping in Infants With DownSyndrome: A Randomized TrialDale A Ulrich, Meghann C Lloyd, Chad W Tiernan, Julia E Looper,Rosa M Angulo-Barroso

Background and PurposeInfants with Down syndrome (DS) are consistently late walkers. The purpose of thisinvestigation was to test the effects of individualized, progressively more intensetreadmill training on developmental outcomes in infants with DS.

SubjectsThirty infants born with DS were randomly assigned to receive lower-intensity,generalized treadmill training or higher-intensity, individualized training imple-mented by their parents in their homes.

MethodsResearch staff members monitored implementation of training, physical growth, andonset of motor milestones of all infants on a monthly basis.

ResultsInfants in the higher-intensity, individualized training group increased their steppingmore dramatically over the course of training. Infants in the higher-intensity traininggroup attained most of the motor milestones at an earlier mean age.

Discussion and ConclusionTreadmill training of infants with DS is an excellent supplement to regularly sched-uled physical therapy intervention for the purpose of reducing the delay in the onsetof walking.

View a video clip related to thisarticle at www.ptjournal.org

DA Ulrich, PhD, is Professor, De-partment of Kinesiology, and Di-rector, Center for Motor Behaviorand Pediatric Disabilities, Univer-sity of Michigan, 401 WashtenawAve, Ann Arbor, MI 48109-2214(USA). Address all correspondenceto Dr Ulrich at: [email protected].

MC Lloyd, MA, CW Tiernan, MS,and JE Looper, PT, MSPT, are doc-toral candidates in the Depart-ment of Kinesiology, University ofMichigan, and are associated withthe Center for Motor Behavior andPediatric Disabilities.

RM Angulo-Barroso, PhD, is Asso-ciate Professor, Department of Ki-nesiology, University of Michigan,and is associated with the Centerfor Motor Behavior and PediatricDisabilities.

[Ulrich DA, Lloyd MC, TiernanCW, et al. Effects of intensity oftreadmill training on developmen-tal outcomes and stepping ininfants with Down syndrome: arandomized trial. Phys Ther.2008;88:114–122.]

© 2008 American Physical TherapyAssociation

III STEP Series

114 f Physical Therapy Volume 88 Number 1 January 2008

Down syndrome (DS) is one ofthe few disabilities that car-ries with it the certainty of

delays in all of the developmentaldomains.1 In the United States, DSoccurs approximately 1.36 times inevery 1,000 live births.2 Down syn-drome is a common cause of cogni-tive deficits in childhood3 and resultsin significant delays in the onset ofmotor skills, including qualitative dif-ferences in movement patterns,compared with the typical develop-ment in children without DS.4,5

Considerable variability existsamong infants and children with DSwith regard to the degree of disabil-ity and the specific features affected.Greater joint range of motion, pre-sumably attributable to ligamentouslaxity,6 delayed development of pos-tural reactions and myelination,7 lowmuscle tone,8 and congenital heartdefects9 all contribute to delayedmotor skills. For example, childrenwith DS tend to sit without supportby 11 months, pull up to a standingposition at about 17 months, andwalk 3 independent steps at an aver-age age of 24 to 26 months.10 Pal-isano and colleagues11 found that73% of the children with DS whomthey observed longitudinally wereable to stand by 24 months of ageand that 40% could walk by 24months. In contrast, the average agesof onset of standing alone and onsetof walking in infants with typical de-velopment are 11 and 12 months,respectively.12

Locomotor experience represents acritical life transition for young chil-dren and promotes the advancementof perception, spatial cognition, andsocial and motor skills.13 Researchershave demonstrated that, in infantswith typical development, experi-ence with locomotion contributes tothe onset of a broad array of psycho-logical skills, such as wariness ofheights, recognizing that objects hid-den from view may still exist, shift-

ing from self-centered to landmark-based spatial coding strategies,distance perception, and acquiringaspects of social referencing.13,14

These results suggested that infantslearn more about the world aroundthem as they become able to loco-mote independently and can activelyexplore their environment ratherthan passively observing it.

On the basis of motor theory15 andprinciples of neurophysiology,16 wepropose that functionally relevantpractice should accelerate progressin the acquisition of specific motorskills. Hallett stated that “intensive,focused physical therapy shouldhelp restore motor function, and ev-idence shows that the earlier andmore intensive the therapy, the bet-ter the outcome.”17(p xix) The targetpopulation for that statement waspatients with stroke, but on the basisof the principles of neuroplasticity,this argument also applies equally topediatric habilitation. An importantgoal of early motor therapy is to fa-cilitate continual exploration and se-

lection of the movement patternsneeded for functional movement be-havior,16,18 and the earlier this pro-cess begins, the better.19 Priorityshould be placed on functionally sig-nificant tasks, such as locomotion.The major challenge for pediatrictherapists and parents is finding in-novative ways to promote explora-tion and practice of locomotor skills,such as crawling and walking, beforethe skills actually begin to emerge.

Ulrich et al20 demonstrated that, by11 months of age, infants with DScan produce coordinated alternatingsteps when supported under theirarms on a small motorized treadmill(Fig. 1), and stepping increases overdevelopmental time.21 With thesesystematic observations, they hy-pothesized that the treadmill holdspromise as a potential early interven-tion. In a 4-year randomized clinicaltrial, regularly scheduled pediatricphysical therapy intervention wassupplemented with treadmill train-ing implemented by parents in theirhomes.5 The results demonstrated

Figure 1.Example of an infant with Down syndrome being trained on a small motorized treadmillby her mother. (For a video clip, visit this article online at www.ptjournal.org)

Treadmill Training in Infants With Down Syndrome

January 2008 Volume 88 Number 1 Physical Therapy f 115

that the structured treadmill trainingfacilitated a significantly earlier onsetof independent walking than did reg-ularly scheduled physical therapy in-tervention only. The infants who re-ceived the supplemental treadmilltraining walked, on average, at a cor-rected age of 20.0 months (SD�2.9months); for the infants in the con-trol group, the corresponding valuewas 24.3 months (SD�6.6 months).The treadmill training conditionsused by the parents were consideredto be low-intensity training (8 min-utes per day for 5 days per week).

In a review of the early interventionliterature, Ramey and Ramey22 con-cluded that greater positive out-comes occur as a result of higher-intensity interventions. However,most early interventions are imple-mented at a relatively low intensi-ty.23 At the conclusion of the orig-inal treadmill training study,5 Ulrichand colleagues hypothesized that in-fants with DS were capable of grad-ually participating in a progressivelyhigher intensity of training and thatthe goal of increased intensity shouldbe to provide infants with maximumopportunities for stepping and activeexploration of their leg movementsin an upright posture.

The publication of treadmill trainingstudies carried out with a variety ofpopulations has increased over thelast decade.24–26 Belt speeds haveranged from 0.15 m/s to 0.26 m/s forinfants and from 0.23 m/s to 0.34m/s for children. The best results ap-pear to be associated with individu-alizing belt speeds on the basis of thestepping performance of a child.25,26

Duration was individualized in stud-ies involving older children, and theresult was increased performance.26

Individualizing training protocols ap-pears to be a strategy worth testingin infants with DS.

Given that the randomized interven-tion study of Ulrich et al5 was the

first of its type, the optimal level ofintensity of treadmill training for in-fants with DS is not known. Our goalin this study was to test the effectsof more intense, individualized train-ing. Specifically, we wanted to deter-mine the effects of this protocol onstep frequency over time and theonset of functional locomotor skill de-velopment and to compare this proto-col with the low-intensity, generalizedtraining used in the earlier research.5

MethodParticipantsThirty-six infants with DS were re-cruited to participate in the study viaparent support groups located inlower Michigan. Neither race norsex precluded infants from being en-rolled in the study. Exclusion criteriawere the presence of a seizure dis-order, noncorrectable vision prob-lems, and any other medical condi-tions that would severely limit achild’s participation in the treadmillintervention. All parents signed in-formed consent forms and providedsupplemental information about theirchild and family background. The cri-terion for starting the treadmill inter-vention was the ability to take a mini-mum of 6 supported steps in a givenminute on the treadmill. For most in-fants, the intervention began at 10months of age. Infants were randomlyassigned to the higher-intensity, indi-vidualized treadmill training (HI)group or the lower-intensity, general-ized treadmill training (LG) group. Ourfinal sample included 30 infants (16 inthe HI group and 14 in the LG group).Data for 6 infants who were initiallyrecruited were excluded from theanalyses because their parents rou-tinely did not adhere to the protocol(1 infant in the LG group and 3 infantsin the HI group) or because of emerg-ing medical conditions (2 infants). Ta-ble 1 provides a summary of data onparticipant characteristics prior to theintervention. There were no signifi-cant group differences in the charac-teristics of the participants.

ProcedureAfter each family agreed to partici-pate in the study by signing a con-sent form, an infant-sized treadmill*was provided to each family forthe duration of the training. Duringthe initial visit, each family wastrained on how to hold the infanton the treadmill. Treadmill trainingcontinued for all infants until theycould walk 3 independent steps overground, at which time the tread-mill was removed from the home.Two staff members visited all fami-lies every other week to monitoradherence to the treadmill trainingprotocols, to answer questions fromthe caregivers, to videotape five1-minute trials of the infants step-ping while supported on the tread-mill, and to measure body weightand height and shank length and cir-cumference. A small gauge on theside of each treadmill recorded theamount of treadmill use in minutes.Staff members recorded the gaugevalue during each visit.

The treadmill training protocol forthe LG group included 8 minutesper day for 5 days per week at abelt speed of 0.15 m/s throughoutthe intervention. In the HI group,as infants progressed in their step-ping performance, we added ankleweights, increased belt speed, andincreased daily duration in an effortto maximize the stepping response.We viewed the legs, during theswing phase, as pendulums and pre-dicted that the addition of weights tothe ankles once the infants werestepping would have a positive ef-fect by increasing the forward mo-tion of the leg at toe-off.27 We alsoexpected that the addition of weightswould increase afferent sensory feed-back and facilitate the development ofthe neuromuscular system, a criticalsubsystem needed for stepping.

* Carlin’s Creations, 27366 Oak St, Sturgis, MI49091.



As a result of observing the infants inour earlier treadmill training studyover developmental time,5 we con-cluded that the infants were capableof more than 8 minutes of trainingper day and at a gradually increasingbelt speed. These conditions wereinitiated once the infants displayedthe ability to take 10 steps perminute and increased when the in-fants were able to take 20, 30, and 40steps per minute. The decision onwhen to increase the training condi-tions was based on the videotapedperformances during the biweeklyfollow-up sessions conducted by ourresearch team (Tab. 2). The amountof ankle weight added was individu-alized as a percentage (50%, 75%,100%, and 125%) of a child’s calfmass.27 If a child’s performance re-gressed below the required steppingfrequency (ie, 10, 20, 30, or 40 stepsper minute) once the training condi-tions were increased, then we de-layed a change in the protocol until

the stepping frequency was main-tained at the minimum frequencyrequired.

At study entry, motor performancewas assessed with the Bayley Scalesof Infant Development28 to deter-

Table 1.Participant Characteristics at Study Entry and Prior to Interventiona

Characteristic HI Group LG Group P

No. of boys/no. of girls 12/4 6/8

Race/ethnicity (no. of participants) 1 African American, 13white, and 2 biracial

1 African American and13 white

Karyotype (no. of participants) 15 with trisomy 21 and1 with mosaicism

13 with trisomy 21 and1 with mosaicism

Mean no. of siblings 1.2 1.9

Congenital heart defects (no. ofparticipants)

8 6

Mean household income $60,000–$80,000 $60,000–$80,000

Mother’s education (average) College College

Father’s education (average) College College

Corrected age at entry, mo, X (SD) 9.65 (1.61) 10.40 (2.14) .30

BSID-II motor performance raw score (SD) 40.87 (6.56) 41.5 (4.81) .77

Height (m) 0.69 (0.02) 0.69 (0.03) .67

Weight (kg) 8.49 (1.05) 8.45 (1.22) .95

Head circumference (m) 0.44 (0.01) 0.43 (0.01) .41

Shank length (m) 0.12 (0.01) 0.12 (0.09) .16

Shank circumference (m) 0.18 (0.01) 0.18 (0.01) .36

a HI�higher-intensity, individualized treadmill training; LG�lower-intensity, generalized treadmill training; BSID-II�Bayley Scales of Infant Development.

Table 2.Intended Intervention Protocolsa

Group Steps/min Belt Speed(m/s)

AnkleWeights (%of Calf Mass)

TrainingDuration(min/d)

HI �10 0.15 0 8

10–19 0.20 50 8

20–29 0.25 75 10

30–39 0.30 100 12

�40 0.30 125 12

LG �10 0.15 0 8

10–19 0.15 0 8

20–29 0.15 0 8

30–39 0.15 0 8

�40 0.15 0 8

a HI�higher-intensity, individualized treadmill training; LG�lower-intensity, generalized treadmilltraining.



mine whether the groups differed inmotor development. We also trackeda series of locomotion-related de-velopmental milestones throughoutthe study by using the motor sub-scale of the Bayley Scales of InfantDevelopment. Items were selectedbecause they were important precur-sors or were related to the develop-ment of independent walking. Theyincluded the following: moves for-ward using prewalking methods(item 43), raises self to sitting posi-tion (item 47), raises self to standingposition (item 52), walks sideways/cruises (item 54), walks with help(item 60), stands alone (item 61),walks alone (item 62), and walksalone with good coordination (item63). The items were monitored dur-ing each biweekly follow-up session.In addition, parents were given aform with a description of these mo-tor items and asked to record thedate of their emergence in order toassist in accurately determining theactual onset of these skills. We veri-fied the onset of parent-reportedmilestone achievement during thenext biweekly visit.

Data Reduction and AnalysisVideotapes of infants’ treadmill per-formances during staff member visitswere coded for the frequency of al-ternating steps over the five1-minute trials. Next, the averagenumber of alternating steps perminute was determined. Finally, anaverage number of alternating stepsper minute over a 2-month span wascalculated and used for statisticalanalyses. For a “step” to be counted,the foot had to initiate toe off behindthe trunk and pass the midline of thebody in the sagittal plane. An “alter-nating step” was defined as a step inleg 1 followed by a step in leg 2; theswing phase of leg 2 had to occurduring the stance phase of leg 1.

In order to determine whether theprotocol provided to the HI groupwas more beneficial than the proto-

col provided to the LG group interms of increasing the number ofalternating steps taken over time, weconducted 2 analyses. First, a t testwas performed for the number ofalternating steps taken during thefirst visit to assess whether differ-ences existed between the groups atstudy entry. Second, we used a 2(group) � 5 (time) analysis of vari-ance with repeated measures acrosstime and with frequency of alternat-ing steps as the dependent variable.Given that infants in each groupwalked at different ages, the num-bers of actual data collection pointsfor each infant varied. For this anal-ysis, we used bimonthly average stepfrequencies. A total of 5 time pointswas chosen because that was theminimum number of bimonthly ses-sions common to all participants. Forchildren who walked later and hadmore than 5 bimonthly sessionsthroughout the study, the 5 visitsmost equally spaced over the totaltime from study entry to walking on-set were selected for analysis (ses-sion quintiles), thereby allowing usto capture stepping performancethroughout the entire span of partic-ipation in the study.

To test the hypothesis that the HIgroup would acquire motor mile-stones at a younger age than the LGgroup, we initially conducted a testof homogeneity of variances in theage of onset of each motor mile-stone. All of the variances weresmaller for the HI group, but only 4of the 8 values were statistically sig-nificant. The Mann-Whitney U test29

was used to test for significant groupdifferences in the age of onset ofeach milestone. As a follow-up to thenonparametric procedures, we cal-culated effect size statistics (stan-dardized difference between groupmeans, expressed as standard devia-tions). We also conducted a princi-pal components analysis (PCA), inwhich we treated the group of 8 mo-

tor milestones as a unidimensionallocomotor construct.

ResultsAll parents kept training logsthroughout the study and wereasked to record the following: thedays on which training occurred, thenumber of minutes practiced perday, reasons for days of trainingmissed, and a statement about thechild’s performance while engagedin the treadmill training. From theparents’ logs, we calculated the av-erage protocols that were carried outfor the HI and LG groups (Tab. 3).The results demonstrated that, on av-erage, the HI group gradually in-creased training conditions through-out the study and the LG groupmaintained a constant set of condi-tions, as we planned. However,some variance from the intendedprotocols occurred (Tabs. 2 and 3).Parents’ logs suggested that thisvariance was attributable to a varietyof circumstances, such as family va-cations, child and caregiver illnesses,busy personal schedules, and regres-sion in treadmill stepping frequencyfor some infants when the protocolconditions increased. Unlike the sit-uation in our earlier treadmill train-ing study,5 the parents in the presentstudy were not as successful in theirefforts to make up for days of train-ing missed or unexpected perturba-tions in their daily schedules.

Assessment of TreadmillStepping PerformanceThe t-test results revealed that theHI and LG groups were not differentwith regard to the numbers of al-ternating steps taken at entry intothe study. However, a 2 (group) � 5(time) analysis of variance of thechange in the numbers of alternat-ing steps taken from study entry toonset of independent walking re-vealed significant time (P�.0001)and interaction (P�.05) effects forthe HI group. Figure 2 shows thenumbers of alternating steps taken



over the 5 quintiles during the train-ing interval by group. Infants in bothgroups showed increases over time.However, at training onset, they per-formed and improved similarly; bythe last 2 quintiles, the infants in theHI group were progressing fasterand stepping more than those in theLG group.

Assessment of Effects ofTreatment on the Onset ofMotor MilestonesThe influence of the 2 treadmill train-ing protocols on the onset of motormilestones was a primary questionfor this study. Although Table 4 sug-gests that the infants in the HI groupattained all of the motor milestonesat an earlier mean age and withsmaller standard deviations than theinfants in the LG group, only item 43,moves forward using prewalkingmethods, and item 52, raises self tostanding position, reached statisticalsignificance (P�.01 and P�.05, re-spectively). Statistical power waslow for each of these statistical testsand was influenced by the loss of 6infants during the study. Effect sizestatistics were calculated for eachmilestone (Tab. 4). The federal agen-

cies that funded this research ac-cepted our position of setting a min-imum effect size of 0.50 to representa meaningful treatment effect. An ef-fect size of 0.50 indicates that theaverage child in the HI group ac-quired a motor milestone 0.50 stan-dard deviation earlier than the aver-

age child in the LG group. Theresults indicated that there weremeaningful differences30 for the HIgroup in 6 of the 8 milestones:moves forward using prewalkingmethods, raises self to standing posi-tion, walks sideways/cruises, walks

Table 3.Actual Intervention Protocolsa

Group Steps/min

Belt Speed (m/s) Ankle Weights (% of CalfMass)

Training Duration (min/d)

X SD Range X SD Range X SD Range

HI �10 0.18 0.03 0.15–0.25 14 27.9 0–100 6 2.4 0–11.3

10–19 0.18 0.04 0.15–0.25 43 37.4 0–100 6 3.1 0–11.3

20–29 0.19 0.02 0.15–0.25 74 30.8 0–125 6 2.3 0–11.3

30–39 0.20 0.02 0.15–0.25 88 31.5 0–125 7 2.5 0–11.2

�40 0.22 0.04 0.2–0.35 115 18.1 50–125 9 2.4 3.4–16

LG �10 0.18 0.03 0.15–0.2 0 6 2.5 0–10.1

10–19 0.18 0.02 0.15–0.2 0 6 2.6 0–10.5

20–29 0.18 0.02 0.15–0.2 0 6 2.2 0–12.6

30–39 0.18 0.02 0.15–0.2 0 7 1.8 2.4–10.9

�40 0.18 0.02 0.15–0.2 0 6 1.9 0.8–8.8

a HI�higher-intensity, individualized treadmill training; LG�lower-intensity, generalized treadmill training. Values shown reflect average group values.

Figure 2.Alternating steps taken by infants who received higher-intensity, individualized tread-mill training (high) or lower-intensity, generalized treadmill training (low). Data arereported as mean (SE indicated by error bars).



with help, walks alone, and walksalone with good coordination.

A PCA of the 8 motor milestonestreated as a unidimensional locomotorconstruct also was performed. Datafor children who achieved the 8 motormilestones during their participationin the study (11 in the HI group and 12in the LG group) were included in thePCA. The PCA revealed a significantgroup difference for the HI group(P�.04), suggesting that the infants inthe HI group acquired the locomotorconstruct earlier.

DiscussionFor infants and young children withDS, early interventions are critical topromoting positive developmentaloutcomes in both the motor and thecognitive domains.5,8 Often there islittle or no empirical evidence to in-dicate the level of effectiveness ofinterventions or the intensity atwhich they should be implemented.Treadmill training has been shownto be effective in decreasing the de-lay in the onset of independent walk-

ing in infants with DS.5 The resultsof the present study reinforced theeffectiveness of treadmill training forfacilitating walking onset comparedwith the average age of walking on-set in infants who have DS but whoreceive traditional physical therapyalone.5,11 In the present study, weattempted to improve the effective-ness of the treadmill training pro-tocol for infants with DS by ma-nipulating the training conditions togradually increase intensity.

Our results demonstrated that partic-ipants in both the HI and the LGgroups showed increases in the fre-quency of alternating steps overtime. However, a significant group �time interaction with regard to alter-nating step frequency suggested thatthe patterns of change across thetraining period were different for theHI and LG groups (Fig. 2). The 2groups were similar during the initialtreadmill training primarily becausethe intensities of training were simi-lar. We propose that the addition ofweights to the ankles of participants

in the HI group had an initial effectof depressing alternating step fre-quency until sufficient strength tomanipulate the added mass was ac-quired. This process took longerthan originally conceived. Eventu-ally, infants in the HI group benefitedbecause their increased leg strengthresulted in significantly more step-ping during the last 2 quintiles. Inthe LG group, increases in step fre-quency occurred gradually and con-sistently over the 5 quintiles.

The data from the present study rep-licate and expand on the results ofour earlier treadmill training study5

indicating that the infants who re-ceived the experimental treadmilltraining walked, on average, at a cor-rected age of 20 months. In thepresent study, the infants in the LGgroup walked independently, on av-erage, at 21.3 months—earlier thanthe infants who received physicaltherapy intervention but no tread-mill training in the earlier study andwho walked at an average age of24.3 months.5 In the present study,

Table 4.Motor Milestone Achievements

Item Milestonea Corrected Age, mo, X (SD) P Effect Sizeb Power

HI Group LG Group

43 Moves forward usingprewalking methods

11.61 (1.69) 13.64 (1.91) .01 1.07 .73

47 Raises self to sittingposition

13.07 (1.42) 13.82 (2.78) .41 0.36 .13

52 Raises self to standingposition

13.40 (1.82) 15.18 (2.84) .05 0.76 .13

54 Walks sideways/cruiseswhile holding on tofurniture

15.03 (1.94) 16.42 (3.10) .15 0.55 .49

60 Walks with help 14.33 (2.23) 16.19 (3.72) .10 0.62 .30

61 Stands alone 17.89 (3.87) 18.15 (4.08) .86 0.07 .05

62 Walks alone 19.23 (2.80) 21.36 (4.72) .14 0.56 .31

63 Walks alone with goodcoordination

21.52 (5.23) 24.97 (5.34) .13 0.65 .32

a According to the Bayley Scales of Infant Development.b An effect size of 0.50 was used to represent a meaningful treatment effect and can be interpreted as the average infant receiving higher-intensity,individualized treadmill training (HI) achieving the milestone 0.50 standard deviation earlier than the average infant receiving lower-intensity, generalizedtreadmill training (LG).



the infants in the HI group walkedindependently at an average age of19.2 months—earlier than the infantsin previous reports.5,11 Palisano andcolleagues11 reported that in a sampleof 121 infants who had DS and whowere receiving early intervention ser-vices, only 40% walked independentlyby 2 years of age. In the present study,94% of the children in the HI groupand 71% of those in the LG groupwalked before 2 years of age. The abil-ity to walk independently at least 3 to4 months earlier than would be typi-cally expected is important both clin-ically and functionally in the life of achild with a disability and his or herparents.

In the present early interventionstudy, several infants displayed ade-quate leg strength and postural con-trol needed to walk and were able towalk well with assistance. Unfortu-nately, they refused to let go oftheir parent’s fingertips and walk in-dependently for an additional 3 to 4months. Similar results were ob-served in our earlier treadmill train-ing study.5 It is our hypothesis thatthese infants displayed a higher levelof instability because of ligamentouslaxity around their ankle joints andthat this instability affected their in-dependent walking behavior. Futureresearch is needed to test this hy-pothesis and to design and test mod-ifications to the treadmill trainingprocedures, such as the use of ortho-ses to reduce instability around thefeet and ankles once an infant as-sumes a standing posture.

Several other motor milestones weremonitored throughout the presentstudy (Tab. 4). No statistically signifi-cant differences were found betweenthe HI and the LG groups, with theexception of the following items:moves forward using prewalkingmethods and raises self to standingposition. Given that the milestone ofmoving forward using prewalkingmethods was acquired quite early in

the intervention period, it is not likelythat it was attributable to the HI pro-tocol because at that point, the HI andLG protocols were very similar. Theeffect sizes, however, showed that HIdid make a meaningful contribution tomost of the motor milestones. The re-sults of the PCA, in which the 8 motormilestones were combined into a uni-dimensional locomotor construct, sup-ported this view.

Early intervention theory suggests thathigher-intensity interventions may pro-duce greater positive outcomes19,22;however, there is little empirical evi-dence to support this position. Werecognize that most therapists defineintensity in terms of frequency oftherapy sessions and total minutesper session. Our goals in the presentstudy were to explore gradual in-creases in treadmill training condi-tions in anticipation of significantlyincreasing the amount of treadmillstepping practice occurring before achild began to walk independentlyand to evaluate whether increasedpractice speeds hastened the onset ofmotor milestones. We are currentlytesting whether the HI proceduresprovide other benefits, such as thoserelated to overall physical activity(stamina) or quality of walking gait.

Several factors could have contrib-uted to the limited statistically signif-icant differences in the onset of mo-tor milestones. Table 3 shows thatthe treadmill training protocol forthe HI group was not implementedexactly as intended by some families,although it was gradually more in-tense than the protocol for the LGgroup. Several factors could have in-fluenced the outcomes. Parenting inthe early years of a child’s life is hec-tic and stressful; this situation is mag-nified when a child in the family hasa disability that requires a consider-able amount of attention.31 The timecommitment required for the HI in-tervention appeared not to be overlyburdensome; however, 6 to 8 min-

utes per day for 5 days per week maybe the saturation point for busy par-ents. Finally, it also is possible thattoo many variables were manipu-lated in this exploratory attempt togradually increase the intensity oftreadmill training for infants with DS.Manipulating belt speed, daily dura-tion, and the amount of weight at-tached to the ankles on the basis ofindividual infant performance mightbe too complex. To reduce complex-ity for parents and researchers, weadvise that each condition be manip-ulated separately. Our lack of signif-icant group differences could meanthat the LG protocol was intenseenough to meaningfully increase thefrequency of stepping and push theinfants to achieve motor milestonesearlier than they would have withoutthe treadmill intervention. In consid-ering which procedures to manipu-late in the future in an effort to in-crease intensity, gradually increasingbelt speed as an infant increases thefrequency of stepping should be thefirst condition selected. As an infantbegins to take more steps on thetreadmill, belt speed is associatedwith more stepping, assuming thatthe speed is not too fast.

ConclusionThe results of the present study sup-port the evidence produced in ourearlier treadmill training study in-volving infants with DS.5 Low-intensity treadmill training used as asupplement to regular physical ther-apy intervention for infants with DSresulted in an earlier onset of walk-ing and other locomotor milestonescompared with the findings for in-fants who had DS but who receivedphysical therapy intervention only.Our efforts to explore and test pro-cedures to gradually increase the in-tensity of treadmill training resultedin greater increases in the frequen-cies of alternating steps for partici-pants in the HI group than for thosein the LG group and meaningful dif-ferences in the age of onset of most



locomotor milestones. The HI proce-dures used in the present study ap-peared to be more challenging forparents to implement consistently. Im-portant parts of the treadmill trainingprocedures are providing parents withfeedback on their implementation ofthe intervention and answering theirquestions. Parents of participants inboth the HI and the LG groups consis-tently claimed that they liked the struc-ture provided by the treadmill trainingintervention program because theyknew exactly what to do, how to do it,and for how long each day.

On the basis of the accumulationof evidence supporting the use ofthe treadmill as a supplement tophysical therapy intervention forinfants with DS, we advocate thathospitals and clinics consider pur-chasing appropriate treadmills andbegin to rent them to parents on amonthly basis. Each infant-sizedtreadmill built for the present studycost about $1,200.

Dr Ulrich provided concept/idea/research de-sign, writing, data collection, fund procure-ment, facilities/equipment, and institutional li-aisons. Ms Lloyd, Mr Tiernan, and Ms Looperprovided writing and data collection and anal-ysis. Dr Angulo-Barroso provided concept/idea/research design, data collection and anal-ysis, fund procurement, and facilities/equipment. The authors thank the families andinfants who participated in this research alongwith the Families Exploring Down Syndromeparent organization and the Down SyndromeAssociation of Western Michigan for assistingin the recruitment of infants.

This study was reviewed and approved bythe University of Michigan Health SciencesInstitutional Review Board.

This work was funded by a research grantfrom the US Office of Special Education andRehabilitative Services (H324C010067), a USOffice of Special Education Programs Lead-ership Training Grant (H325D020028), andthe Steelcase Foundation in Michigan.

Preliminary data were presented as a posterdelivered at the III STEP Symposium onTranslating Evidence Into Practice: LinkingMovement Science and Intervention; July15–21, 2005; Salt Lake City, Utah; and as anInvited Keynote Address at the International

Symposium of Adapted Physical Activity; July5–9, 2005; Verona, Italy.

This article was submitted May 8, 2007, andwas accepted July 26, 2007.

DOI: 10.2522/ptj.20070139

References1 Newberger D. Down syndrome: prenatal

risk assessment and diagnosis. Am FamPhysician. 2000;62:825–832.

2 Centers for Disease Control and Prevention(CDC). Improved national prevalence esti-mates for 18 selected major birth defects:United States, 1999–2001. MMWR MorbMortal Wkly Rep. 2006;54:1301–1305.

3 Chapman RS, Hesketh LJ. Behavioral phe-notype of individuals with Down syn-drome. Ment Retard Dev Disabil Res Rev.2000;6:84–95.

4 Kubo M, Ulrich B. Coordination of pelvis-HAT (head, arms and trunk) in anterior-posterior and medio-lateral directions dur-ing treadmill gait in preadolescents with/without Down syndrome. Gait Posture.2006;23:512–518.

5 Ulrich DA, Ulrich BD, Angulo-Kinzler RM,Yun J. Treadmill training of infants withDown syndrome: evidence-based develop-mental outcomes. Pediatrics. 2001;108:84–91.

6 Livingstone B, Hirst P. Orthopedic disor-ders in school children with Down’s syn-drome with special reference to the inci-dence of joint laxity. Clin Orthop RelatRes. 1986;207:74–76.

7 Haley SM. Postural reactions in infantswith Down syndrome: relationship to mo-tor milestone development and age. PhysTher. 1986;66:17–22.

8 Sacks B, Buckley S. Motor Development forIndividuals with Down Syndrome: An Over-view. Portsmouth, United Kingdom: TheDown Syndrome Educational Trust; 2003.

9 Spicer RL. Cardiovascular disease in Downsyndrome. Pediatr Clin North Am.1984;31:1331–1343.

10 Henderson SE. Some aspects of the devel-opment of motor control in Down’s syn-drome. In: Whiting HTA, Wade MG, eds.Themes in Motor Development. Boston,Mass: Martinus Nijhoff; 1986:69–92.

11 Palisano R, Walter S, Russell D, et al. Grossmotor function of children with Downsyndrome: creation of motor growthcurves. Arch Phys Med Rehabil. 2001;82:494–500.

12 Brouwer SI, van Beijsterveldt TC, BartelsM, et al. Influences on achieving motormilestones: a twin-singleton study. TwinRes Hum Genet. 2006;9:424–430.

13 Campos JJ, Anderson DI, Barbu-Roth MA,et al. Travel broadens the mind. Infancy.2000;1:149–219.

14 Bertenthal BI, Campos JJ, Barrett KC. Self-produced locomotion: an organizer ofemotional, cognitive, and social develop-ment in infancy. In: Emde RN, Harmon RJ,eds. Continuities and Discontinuities inDevelopment. New York, NY: PlenumPress; 1984:175–210.

15 Ulrich BD, Ulrich DA. Dynamic systemsapproach to understanding motor delay ininfants with Down syndrome. In: Savels-bergh GJP, ed. Advances in Psychology:The Development of Coordination in In-fancy. Amsterdam, the Netherlands: NorthHolland; 1993:445–459.

16 Edelman GM. The Remembered Present: ABiological Theory of Consciousness. NewYork, NY: Basic Books; 1989.

17 Hallett M. Guest Editorial: Neuroplasticityand rehabilitation. J Rehabil Res Dev.2005;42:xvii–xxi.

18 Hadders-Algra M. Early brain damage andthe development of motor behavior inchildren: clues for therapeutic interven-tion? Neural Plast. 2001;8:31–49.

19 Latash ML. Motor coordination in Downsyndrome: the role of adaptive changes.In: Weeks DJ, Chua R, Elliott D, eds.Perceptual-Motor Behavior in Down Syn-drome. Champaign, Ill: Human Kinetics;2000:199–223.

20 Ulrich BD, Ulrich DA, Collier DH. Alternat-ing stepping patterns: hidden abilities of11-month-old infants with Down syn-drome. Dev Med Child Neurol. 1992;34:233–239.

21 Ulrich BD, Ulrich DA, Collier DH, Cole EL.Developmental shifts in the ability of infantswith Down syndrome to produce treadmillsteps. Phys Ther. 1995;75:14–23.

22 Ramey CT, Ramey SL. Early interventionand early experiences. Am Psychol.1998;53:109–120.

23 Shonkoff JP, Hauser-Cram P, Krauss MW,Upshur CC. Development of infants withdisabilities and their families: implicationsfor theory and service delivery. MonogrSoc Res Child Dev. 1992;57:1–153.

24 Bodkin AW, Baxter RS, Heriza CB. Tread-mill training for an infant born pretermwith grade III intraventricular hemor-rhage. Phys Ther. 2003;83:1107–1118.

25 Richards CL, Malouin F, Dumas F, et al.Early and intensive treadmill locomotortraining for young children with cerebralpalsy: a feasibility study. Pediatr PhysTher. 1997;9:158–165.

26 Schindl MR, Forstner C, Kern H, Hesse S.Treadmill training with partial bodyweight support in nonambulatory patientswith cerebral palsy. Arch Phys Med Reha-bil. 2000;81:301–306.

27 Ulrich BD, Ulrich DA, Angulo-Kinzler RM.The impact of context manipulations onmovement patterns during a transitionalperiod. Hum Mov Sci. 1998;17:327–346.

28 Bayley N. Bayley Scales of Infant Devel-opment. 2nd ed. San Antonio, Tex: ThePsychological Corp; 1993.

29 Green SB, Salkind NJ, Akey TM. UsingSPSS for Windows: Analyzing and Under-standing Data. Upper Saddle River, NJ:Prentice Hall; 2000.

30 Cohen J. Statistical Power Analysis forthe Behavioral Sciences. Rev ed. NewYork, NY: Academic Press; 1977.

31 Roach MA, Orsmond GI, Barratt MS. Moth-ers and fathers of children with Down syn-drome: parental stress and involvement inchildcare. Am J Ment Retard. 1999;104:422–436.



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