Using a Treadmill Intervention to Promote the Onset of Independent Walking in Infants With or at Risk for Neuromotor Delay

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.