<LEAP> highlights the findings and application of Cochrane reviews and other evidence pertinent to the practice of physical therapy. The Cochrane Library is a respected source of reliable evidence related to health care. Cochrane systematic reviews explore the evidence for and against the effectiveness and appropriateness of interventions—medications, surgery, education, nutrition, exercise—and the evidence for and against the use of diagnostic tests for specific conditions. Cochrane reviews are designed to facilitate the decisions of clinicians, patients, and others in health care by providing a careful review and interpretation of research studies published in the scientific literature.1 Each article in this PTJ series summarizes a Cochrane review or other scientific evidence resource on a single topic and presents clinical scenarios based on real patients to illustrate how the results of the review can be used to directly inform clinical decisions. This article focuses on an infant with Down syndrome. Can a treadmill intervention positively affect the onset of independent walking and overall motor development in a preambulatory infant with Down syndrome?
Delayed attainment of locomotion can have widespread, long-lasting negative effects on motor, social, and cognitive capabilities.2–5 Treadmill training is one intervention often used and studied to promote the development of walking in children with or at risk for neuromotor delay. Although there is evidence to support the use of treadmill training to promote earlier onset of independent walking in infants with Down syndrome,6,7 its effectiveness for other outcomes and for other clinical populations remains unclear.8–10 The treadmill is of specific interest because it provides a way to elicit stepping practice in preambulatory infants. When held supported on a treadmill, infants as young as 1 month will perform coordinated alternating stepping movements that share many kinematic patterns with adult walking. Between 3 and 5 months of age, they demonstrate increasingly stable alternating stepping responses to the treadmill.11 The theoretical justification for treadmill training is that using the treadmill to elicit stepping practice is task-specific for walking and it incorporates many of the principles of neuroplasticity12: it addresses the principles of “use it or lose it” and “use it and improve it,” is specific, is repetitive, can be intense, can be implemented with prelocomotor infants (principles of timing and age), and may affect skill development beyond walking through the principle of transference.
A Cochrane systematic review by Valentin-Gudiol and colleagues13 examined the evidence for treadmill training to promote the onset of independent walking in children under 6 years of age with or at risk for neuromotor delay. They included randomized and quasi-randomized controlled trials if the studies included children younger than 6 years of age who had delays in gait development or the attainment of independent walking (could not walk independently by the age of 18 months). Trials of children at risk for neuromotor delay, a category primarily consisting of children with nonprogressive neurological disorders, also were included. Trials that included children diagnosed with a condition for which physical activity is contraindicated (eg, infants with genetic degenerative diseases such as neuromuscular dystrophy) or with diagnoses that preclude independent walking were excluded.
Trials of treadmill interventions of any type, frequency, or intensity were eligible if they were aimed at: (1) improving gait parameters such as walking speed, endurance, or quality of step (how the foot lands on the floor surface) or (2) facilitating onset of independent walking or walking with assistance. Comparison groups received no treatment or another treatment. Primary outcomes were step frequency (number of alternating treadmill steps per minute, cadence during independent walking), step quality (foot doing toe versus flat contact during treadmill stepping), age of onset of independent walking, age of onset of walking with assistance, gross motor function, falls, and injuries due to falls. The key results of the review are summarized in Table 1.
The review search was conducted in March 2011, and 9 articles reporting the results of 5 trials involving 139 participants were included in the review. Overall, 8 of the 9 articles reported on the results of interventions for preambulatory infants, and 7 articles reported on trials of infants with Down syndrome. Results for all primary outcomes (step frequency, step quality, age of onset of independent walking, age of onset of walking with assistance, gross motor function, falls, and injuries due to falls) are provided in Table 1. Here we focus on 2 main outcomes for which pooled data were presented: onset of independent walking (2 trials) and gross motor function (2 trials).
Three of the 5 trials examined treadmill intervention versus no treadmill intervention. One trial included preambulatory infants at risk for neuromotor disabilities,14 another trial included preambulatory infants with Down syndrome,6 and the third trial included young children (between 3.5 and 6.3 years of age) with cerebral palsy, most of whom were walking with an assistive device prior to the intervention.15 For onset of walking, meta-analyses of 2 trials6,14 support that treadmill intervention was effective in promoting earlier independent walking (effect estimate*=−1.47; 95% confidence interval=−2.97, 0.03). At the individual trial level, this effect was significant only in the trial of infants with Down syndrome (infants in the treadmill group walked at an average chronological age of 19.9 months compared with 23.9 months in the control group)6 and not in the trial of infants at risk for neuromotor disabilities.14 Based on these results, the authors confirmed that treadmill training is an effective intervention for promoting earlier onset of independent walking in infants with Down syndrome but found that there is not sufficient evidence to support treadmill training as an effective intervention for promoting earlier onset of independent walking in children at risk for neuromotor disabilities or with cerebral palsy. For gross motor function, a meta-analysis of 2 trials14,15 showed that treadmill intervention did not improve Gross Motor Function Measure scores compared with no treadmill intervention (effect estimate*=0.88; 95% confidence interval=−4.54, 6.30).
The remaining 2 trials compared different types of treadmill interventions in preambulatory infants with Down syndrome: low-intensity versus high-intensity treadmill intervention7,16–19 or treadmill training with orthotics versus without orthotics.20 There was not a difference in onset of independent walking when comparing low-intensity versus high-intensity treadmill training or treadmill training with orthotics versus without orthotics. Gross Motor Function Measure scores were not assessed when comparing low-intensity versus high-intensity treadmill training, although lower total scores were reported 1 month after completion of treadmill intervention with orthotics, indicating that early use of orthotics might hinder gross motor progress.
Case #18: Applying Evidence to an Infant With Down Syndrome
Can treadmill training help this patient?
“Isabella” was an 11-month-old girl with Down syndrome who was receiving physical therapy at our community-based outpatient center. An interdisciplinary early intervention team first evaluated her at 3 weeks of age, and physical therapy was initiated. The focus of our early sessions was on parent education to promote activities to encourage development of motor skills. We coached her parents on how to help position and play with Isabella throughout her daily routines to promote the development of skills such as rolling, reaching, sitting, and crawling. When Isabella was 9 months old, she was able to sit independently and would bear weight when supported in a standing position. At this time, we educated her parents on the theory and evidence related to treadmill training to promote the onset of independent walking in infants with Down syndrome. We conducted several 5-minute supported stepping trials on the treadmill during our regular physical therapy sessions at the clinic; however, Isabella was not actively stepping on the treadmill. After a discussion with her parents, we decided to not initiate regular treadmill training intervention and agreed to revisit the idea of treadmill training when onset of walking became our primary goal.
At 11 months of age, Isabella was able to independently crawl on hands and knees but was not yet pulling to stand. As Isabella was independently mobile via crawling, and thus experiencing the positive effects of mobility on development, we decided it was appropriate to shift the primary focus of our intervention. Stepping on the treadmill was tried again, and Isabella was able to bear weight and take steps consistently. Her parents became interested in specifically working on treadmill training at this time. She was at high risk for a delay in the onset of independent walking due to her diagnosis of Down syndrome, and independent walking was a very important goal for Isabella's parents. She had no contraindications to participating in a treadmill-based intervention.
Treadmill training intervention
The intervention occurred in our clinic with a physical therapist and in her home with her parents, from 11 months of age until she was walking 10 steps independently at 16 months of age. We used an adult-sized treadmill in the clinic. Her family used a similar adult-sized treadmill to practice stepping in their home. Isabella came to the clinic once per week, and treadmill training was performed at the beginning of the physical therapy session. The therapist or parent sat on a bench that fit across the treadmill, in front of Isabella, and supported her by holding around both sides of her trunk. Isabella did not wear shoes or orthoses during the treadmill training. She was encouraged to step by positive feedback when she produced steps; we also motivated and entertained her using toys, a mirror, and music.
We based our intervention on the high-intensity treadmill training protocol described by Ulrich and colleagues.7 We started with the treadmill speed at 0.5 mph during the first session, as this was the lowest setting on the treadmill and within the range of speeds used in the high-intensity treadmill training trial group (they progressed from 0.33 mph to 0.67 mph).7 We used the speed and duration protocol in the high-intensity group to guide our protocol; however, we did not use ankle weights and had to adjust the speed settings based on the equipment we had available. We started with a goal of 8 minutes per session at 0.5 mph. Approximately each month we progressed the speed or duration as shown in Table 2. By the last session, duration had increased to 12 minutes and speed had increased to 0.7 mph.
We were able to meet our duration goal for time for approximately 95% of the in-clinic intervention session; however, it should be noted that we had to allow several breaks, lasting about 30 seconds each, to achieve this goal. For this infant, her parents were willing and able to provide stepping practice at home, using a setup similar to that in our clinic. Their goal was to practice stepping 4 days per week (in addition to the 1 day of practice in the clinic).
Treadmill training was a part of Isabella's overall physical therapy intervention. We worked on a variety of activities to promote improved control, strength, and coordination with movement. We focused on setting up the environment to encourage upright movement and exploration. We continuously changed the environment to encourage experimentation with many strategies to solve a movement problem. Isabella also practiced using a reverse walker, first in the clinic and then at home, to provide more opportunities to practice stepping and to promote independent exploration of her environment. Outcome measures included attainment of parent-driven goals, which included onset of independent walking (at least 10 steps) and improved independence and participation in family activities. We also used the 88-item Gross Motor Function Measure (GMFM-88) before and after intervention to measure change in gross motor skills. We noted an improvement in overall GMFM-88 score of 18%; the majority of improvement was seen in the standing and walking domains.
How do we apply the results of the Cochrane review to Isabella?
Isabella has a diagnosis (Down syndrome) and a developmental skill range (preambulatory, able to take steps when supported on the treadmill) for which treadmill training has demonstrated effectiveness in promoting an earlier onset of independent walking.7 It is possible that she might have been ready to start the intervention before 11 months, but she was not stepping on the treadmill at 9 months, and we did not try again until 11 months. These aspects of the results of the Cochrane review apply directly to Isabella. Our goals were to encourage the onset of independent walking activity and to increase her overall gross motor function, both of which are consistent with the outcomes assessed in the Cochrane review.
The onset (developmental skill level), frequency (5 days per week), and duration (8–12 minutes per session) of our intervention matched the published protocols, although our intensity did not fully match. We increased the duration and treadmill speed as Isabella progressed, which was done in the high-intensity intervention7 but not in the original randomized controlled trial where the treadmill speed was held constant.6 We did not, however, use ankle weights to create a full “high-intensity” intervention.7 We waited until Isabella was able to walk 10 steps independently to stop the intervention, whereas the trials in this review stopped the intervention for participants with Down syndrome when 3 steps of independent walking was achieved.6,7,20
How well do the outcomes of the intervention provided to Isabella match those suggested by the systematic review?
Isabella achieved her goal of walking 10 steps independently at 16 months of age. This result is earlier than the published results from treadmill training trials, where onset of 3 independent steps occurred, on average, at 19.9 months following the original treadmill training protocol,6 21.3 months after low-intensity treadmill training,7 and 19.2 months after high-intensity treadmill training.7 The standard deviation for the high-intensity treadmill training group was 2.8 months; accordingly, 16.4 months would be 1 standard deviation (68%) from the mean. This finding means Isabella took 10 steps independently somewhere around the time 32% of the population would be expected to take 3 steps independently following the published high-intensity treadmill training protocol.
Isabella's overall gross motor function improved (as measured by the GMFM-88), which is expected as she achieved independent walking. This result is difficult to compare with the Cochrane review, where the comparison in gross motor skill gains was between groups to determine whether one group improved more than the other. Isabella's improvement in overall GMFM-88 score of 18% from 11 to 16 months of age appears to exceed the predicted improvement of about 12% for children with Down syndrome and mild motor impairment in this age range; however, this is a speculative comment based on our estimate of numerical values from published graphs of predicted GMFM scores.21
Finally, Isabella's participation in family life as a toddler increased because she was able to walk independently; however, participation level goals were not included in the trials and thus were not included in the Cochrane review. In general, we feel that Isabella's positive outcomes exceeded those that were significant in the Cochrane review.
Can you apply the results of the systematic review to your own patients?
Of the 139 participants in the trials included in this Cochrane review, by diagnosis there were 41 participants at risk for developmental delay, 8 diagnosed with cerebral palsy, and 90 with Down syndrome. By age, there were 131 preambulatory participants who were less than 22 months chronological age and 8 children with cerebral palsy who were between 42 and 75.6 months of age at trial onset. Applying the results of this Cochrane review to preambulatory infants with Down syndrome is fairly well defined. Treadmill training intervention has been shown to promote earlier onset of independent walking. The optimal intensity may not have been identified yet; however, an effective protocol does exist.
Applying the results of this Cochrane review for promoting earlier onset of independent walking in preambulatory infants with neuromotor delays due to conditions other than Down syndrome is not well defined. The effectiveness has not been demonstrated, although the theoretical rationale is strong and case trials have demonstrated feasibility and possible beneficial outcomes. This Cochrane review does not address treadmill training for children who are greatly delayed in the attainment of walking, as 4 of the 5 trials intervened when participants were less than 2 years of corrected age,6,7,14,20 although the Cherng et al trial15 included children with cerebral palsy between the ages of 3.5 and 6.3 years who were walking with (n=6) or without (n=2) assistive devices prior to intervention. This Cochrane review also does not address whether young children with neuromotor delays who are already independently ambulatory can improve their gross motor function and various gait parameters following a treadmill-based intervention.
What can be advised based on the results of this systematic review?
The available data are insufficient to definitively establish whether or not treadmill training has beneficial effects in promoting the onset of independent walking and improving gait quality and overall gross motor function in infants with or at risk for neuromotor delay. Eight minutes of treadmill training, 5 days per week at 0.2 m/s (0.46 mph), has been shown to be effective at promoting earlier onset of independent walking for preambulatory infants with Down syndrome regardless of whether starting when the infant is able to sit independently for 30 seconds 6 or to take 6 steps on the treadmill.7 Although the benefits have not been established in other populations, treadmill training is feasible, and there is a sound theoretical rationale. Adult-sized treadmills can be used for the intervention, as long as they are capable of a slow enough belt speed and an adequate bench can be designed for the parent or therapist to safely hold the infant. More research is needed to define optimal dosing parameters and to define the effects of different parameters on specific outcomes.
- Received November 28, 2012.
- Accepted June 23, 2013.
- © 2013 American Physical Therapy Association