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<p>III STEP SeriesEffects of Intensity of Treadmill Training on Developmental Outcomes and Stepping in Infants With Down Syndrome: A Randomized TrialDale A Ulrich, Meghann C Lloyd, Chad W Tiernan, Julia E Looper, Rosa M Angulo-BarrosoDA Ulrich, PhD, is Professor, Department of Kinesiology, and Director, Center for Motor Behavior and Pediatric Disabilities, University of Michigan, 401 Washtenaw Ave, Ann Arbor, MI 48109-2214 (USA). Address all correspondence to Dr Ulrich at: ulrichd@umich. edu. MC Lloyd, MA, CW Tiernan, MS, and JE Looper, PT, MSPT, are doctoral candidates in the Department of Kinesiology, University of Michigan, and are associated with the Center for Motor Behavior and Pediatric Disabilities. RM Angulo-Barroso, PhD, is Associate Professor, Department of Kinesiology, University of Michigan, and is associated with the Center for Motor Behavior and Pediatric Disabilities. [Ulrich DA, Lloyd MC, Tiernan CW, et al. Effects of intensity of treadmill training on developmental outcomes and stepping in infants with Down syndrome: a randomized trial. Phys Ther. 2008;88:114 122.] 2008 American Physical Therapy Association</p> <p>Background and PurposeInfants with Down syndrome (DS) are consistently late walkers. The purpose of this investigation was to test the effects of individualized, progressively more intense treadmill training on developmental outcomes in infants with DS.</p> <p>SubjectsThirty infants born with DS were randomly assigned to receive lower-intensity, generalized treadmill training or higher-intensity, individualized training implemented by their parents in their homes.</p> <p>MethodsResearch staff members monitored implementation of training, physical growth, and onset of motor milestones of all infants on a monthly basis.</p> <p>ResultsInfants in the higher-intensity, individualized training group increased their stepping more dramatically over the course of training. Infants in the higher-intensity training group attained most of the motor milestones at an earlier mean age.</p> <p>Discussion and ConclusionTreadmill training of infants with DS is an excellent supplement to regularly scheduled physical therapy intervention for the purpose of reducing the delay in the onset of walking. View a video clip related to this article at www.ptjournal.org</p> <p>114</p> <p>f</p> <p>Physical Therapy</p> <p>Volume 88</p> <p>Number 1</p> <p>January 2008</p> <p>Treadmill Training in Infants With Down Syndrome</p> <p>D</p> <p>own syndrome (DS) is one of the few disabilities that carries with it the certainty of delays in all of the developmental domains.1 In the United States, DS occurs approximately 1.36 times in every 1,000 live births.2 Down syndrome is a common cause of cognitive decits in childhood3 and results in signicant delays in the onset of motor skills, including qualitative differences in movement patterns, compared with the typical development in children without DS.4,5 Considerable variability exists among infants and children with DS with regard to the degree of disability and the specic features affected. Greater joint range of motion, presumably attributable to ligamentous laxity,6 delayed development of postural reactions and myelination,7 low muscle tone,8 and congenital heart defects9 all contribute to delayed motor skills. For example, children with DS tend to sit without support by 11 months, pull up to a standing position at about 17 months, and walk 3 independent steps at an average age of 24 to 26 months.10 Palisano and colleagues11 found that 73% of the children with DS whom they observed longitudinally were able to stand by 24 months of age and that 40% could walk by 24 months. In contrast, the average ages of onset of standing alone and onset of walking in infants with typical development are 11 and 12 months, respectively.12 Locomotor experience represents a critical life transition for young children and promotes the advancement of perception, spatial cognition, and social and motor skills.13 Researchers have demonstrated that, in infants with typical development, experience with locomotion contributes to the onset of a broad array of psychological skills, such as wariness of heights, recognizing that objects hidden from view may still exist, shiftJanuary 2008</p> <p>Figure 1.Example of an infant with Down syndrome being trained on a small motorized treadmill by her mother. (For a video clip, visit this article online at www.ptjournal.org)</p> <p>ing from self-centered to landmarkbased spatial coding strategies, distance perception, and acquiring aspects of social referencing.13,14 These results suggested that infants learn more about the world around them as they become able to locomote independently and can actively explore their environment rather than passively observing it. On the basis of motor theory15 and principles of neurophysiology,16 we propose that functionally relevant practice should accelerate progress in the acquisition of specic motor skills. Hallett stated that intensive, focused physical therapy should help restore motor function, and evidence shows that the earlier and more intensive the therapy, the better the outcome.17(p xix) The target population for that statement was patients with stroke, but on the basis of the principles of neuroplasticity, this argument also applies equally to pediatric habilitation. An important goal of early motor therapy is to facilitate continual exploration and se-</p> <p>lection of the movement patterns needed for functional movement behavior,16,18 and the earlier this process begins, the better.19 Priority should be placed on functionally signicant tasks, such as locomotion. The major challenge for pediatric therapists and parents is nding innovative ways to promote exploration and practice of locomotor skills, such as crawling and walking, before the skills actually begin to emerge. Ulrich et al20 demonstrated that, by 11 months of age, infants with DS can produce coordinated alternating steps when supported under their arms on a small motorized treadmill (Fig. 1), and stepping increases over developmental time.21 With these systematic observations, they hypothesized that the treadmill holds promise as a potential early intervention. In a 4-year randomized clinical trial, regularly scheduled pediatric physical therapy intervention was supplemented with treadmill training implemented by parents in their homes.5 The results demonstratedNumber 1 Physical Therapy f 115</p> <p>Volume 88</p> <p>Treadmill Training in Infants With Down Syndrome that the structured treadmill training facilitated a signicantly earlier onset of independent walking than did regularly scheduled physical therapy intervention only. The infants who received the supplemental treadmill training walked, on average, at a corrected age of 20.0 months (SD 2.9 months); for the infants in the control group, the corresponding value was 24.3 months (SD 6.6 months). The treadmill training conditions used by the parents were considered to be low-intensity training (8 minutes per day for 5 days per week). In a review of the early intervention literature, Ramey and Ramey22 concluded that greater positive outcomes occur as a result of higherintensity interventions. However, most early interventions are implemented at a relatively low intensity.23 At the conclusion of the original treadmill training study,5 Ulrich and colleagues hypothesized that infants with DS were capable of gradually participating in a progressively higher intensity of training and that the goal of increased intensity should be to provide infants with maximum opportunities for stepping and active exploration of their leg movements in an upright posture. The publication of treadmill training studies carried out with a variety of populations has increased over the last decade.24 26 Belt speeds have ranged from 0.15 m/s to 0.26 m/s for infants and from 0.23 m/s to 0.34 m/s for children. The best results appear to be associated with individualizing belt speeds on the basis of the stepping performance of a child.25,26 Duration was individualized in studies involving older children, and the result was increased performance.26 Individualizing training protocols appears to be a strategy worth testing in infants with DS. Given that the randomized intervention study of Ulrich et al5 was the116 f Physical Therapy Volume 88</p> <p>rst of its type, the optimal level of intensity of treadmill training for infants with DS is not known. Our goal in this study was to test the effects of more intense, individualized training. Specically, we wanted to determine the effects of this protocol on step frequency over time and the onset of functional locomotor skill development and to compare this protocol with the low-intensity, generalized training used in the earlier research.5</p> <p>MethodParticipants Thirty-six infants with DS were recruited to participate in the study via parent support groups located in lower Michigan. Neither race nor sex precluded infants from being enrolled in the study. Exclusion criteria were the presence of a seizure disorder, noncorrectable vision problems, and any other medical conditions that would severely limit a childs participation in the treadmill intervention. All parents signed informed consent forms and provided supplemental information about their child and family background. The criterion for starting the treadmill intervention was the ability to take a minimum of 6 supported steps in a given minute on the treadmill. For most infants, the intervention began at 10 months of age. Infants were randomly assigned to the higher-intensity, individualized treadmill training (HI) group or the lower-intensity, generalized treadmill training (LG) group. Our nal sample included 30 infants (16 in the HI group and 14 in the LG group). Data for 6 infants who were initially recruited were excluded from the analyses because their parents routinely did not adhere to the protocol (1 infant in the LG group and 3 infants in the HI group) or because of emerging medical conditions (2 infants). Table 1 provides a summary of data on participant characteristics prior to the intervention. There were no signicant group differences in the characteristics of the participants.</p> <p>Procedure After each family agreed to participate in the study by signing a consent form, an infant-sized treadmill* was provided to each family for the duration of the training. During the initial visit, each family was trained on how to hold the infant on the treadmill. Treadmill training continued for all infants until they could walk 3 independent steps over ground, at which time the treadmill was removed from the home. Two staff members visited all families every other week to monitor adherence to the treadmill training protocols, to answer questions from the caregivers, to videotape ve 1-minute trials of the infants stepping while supported on the treadmill, and to measure body weight and height and shank length and circumference. A small gauge on the side of each treadmill recorded the amount of treadmill use in minutes. Staff members recorded the gauge value during each visit. The treadmill training protocol for the LG group included 8 minutes per day for 5 days per week at a belt speed of 0.15 m/s throughout the intervention. In the HI group, as infants progressed in their stepping performance, we added ankle weights, increased belt speed, and increased daily duration in an effort to maximize the stepping response. We viewed the legs, during the swing phase, as pendulums and predicted that the addition of weights to the ankles once the infants were stepping would have a positive effect by increasing the forward motion of the leg at toe-off.27 We also expected that the addition of weights would increase afferent sensory feedback and facilitate the development of the neuromuscular system, a critical subsystem needed for stepping.</p> <p>* Carlins Creations, 27366 Oak St, Sturgis, MI 49091.</p> <p>Number 1</p> <p>January 2008</p> <p>Treadmill Training in Infants With Down Syndrome Table 1.Participant Characteristics at Study Entry and Prior to InterventionaCharacteristic No. of boys/no. of girls Race/ethnicity (no. of participants) Karyotype (no. of participants) Mean no. of siblings Congenital heart defects (no. of participants) Mean household income Mothers education (average) Fathers education (average) Corrected age at entry, mo, X (SD) BSID-II motor performance raw score (SD) Height (m) Weight (kg) Head circumference (m) Shank length (m) Shank circumference (m)a</p> <p>HI Group 12/4 1 African American, 13 white, and 2 biracial 15 with trisomy 21 and 1 with mosaicism 1.2 8 $60,000$80,000 College College 9.65 (1.61) 40.87 (6.56) 0.69 (0.02) 8.49 (1.05) 0.44 (0.01) 0.12 (0.01) 0.18 (0.01)</p> <p>LG Group 6/8 1 African American and 13 white 13 with trisomy 21 and 1 with mosaicism 1.9 6 $60,000$80,000 College College 10.40 (2.14) 41.5 (4.81) 0.69 (0.03) 8.45 (1.22) 0.43 (0.01) 0.12 (0.09) 0.18 (0.01)</p> <p>P</p> <p>.30 .77 .67 .95 .41 .16 .36</p> <p>HI higher-intensity, individualized treadmill training; LG lower-intensity, generalized treadmill training; BSID-II Bayley Scales of Infant Development.</p> <p>As a result of observing the infants in our earlier treadmill training study over developmental time,5 we concluded that the infants were capable of more than 8 minutes of training per day and at a gradually increasing belt speed. These conditions were initiated once the infants displayed the ability to take 10 steps per minute and increased when the infants were able to take 20, 30, and 40 steps per minute. The decision on when to increase the training conditions was based on the videotaped performances during the biweekly follow-up sessions conducted by our research team (Tab. 2). The amount of ankle weight added was individualized as a percentage (50%, 75%, 100%, and 125%) of a childs calf mass.27 If a childs performance regressed below the required stepping frequency (ie, 10, 20, 30, or 40 steps per minute) once the training conditions were increased, then we delayed a change in the protocol untilJanuary 2008</p> <p>the stepping frequency was maintained at the minimum frequency required.</p> <p>At study entry, motor performance was assessed with the Bayley Scales of Infant Development28 to deter-</p> <p>Table 2.Intended Intervention ProtocolsaGroup Steps/min Belt Speed (m/s) 0.15 0.20 0.25 0.30 0.30 0.15 0.15 0.15 0.15 0.15 Ankle Weights (% of Calf Mass) 0 50 75 100 125 0 0 0 0 0 Training Duration (min/d) 8 8 10 12 12 8 8 8 8 8</p> <p>HI</p> <p>10 1019 2029 3039 40</p> <p>LG</p> <p>10 1019 2029 3039 40</p> <p>a HI higher-intensity, individualized treadmill training; LG lower-intensity, generalized treadmill training.</p> <p>Volume 88</p> <p>Number 1</p> <p>Physical Therapy f</p> <p>117</p> <p>Treadmill Training in Infants With Down Syndrome mine whether the groups differed in motor development. We also tracked a series of locomotion-related developmental milestones throughout the study by using the motor subscale of the Bayley Scales of Infant Development. Items were selected because they were...</p>