For the STA protocol group, there was no significant difference (P = 0.25) between posttest and 3-week FU mean GMFM group scores. For the PIP group no significant difference was found between posttest and 3-week FU. The second hypothesis that the NDT-based STA protocol group would maintain motor gains at the 3-week FU session was supported.
The between-group difference of the mean GMFM change group scores, pretest to 3-week FU, was not significant (P = 0.11). The GMFM mean group scores in both groups demonstrated high within-group variance during this 3-week postintervention period. This high variance was likely responsible for the nonsignificant differences between groups, pretest to 3-week FU.
The study sample size estimate (n = 20 per group) was calculated a priori to provide 80% power at the 0.05 alpha level based on an unpaired two-group comparison of pre-to-postintervention change scores with a one-tailed hypothesis. The power calculations were based on the minimally important effect size index being “large” by Cohen’s conventions for unpaired comparisons. 22 (Table C.2, p.720) This means that the study would have had an 80% chance of obtaining P ≤ 0.05 on the comparison of score changes if the true difference of the mean changes had been 0.8 times as large as the within-group variability of the changes (ie, the pooled within-group standard deviation).
Because of attrition and local policies, the analyzed sample size was 5 per group. Statistical power for this study based on the actual sample sizes of n = 5 per group, and using the a priori estimations (ie, effect size index 0.8, P < 0.05, one-tailed hypothesis) would have been approximately 31% if the estimations had been accurate. Although the sample size was smaller than originally planned, it turned out that the observed effect size was considerably larger than the original estimate. The nonparametric Mann-Whitney U statistic did reflect a significant group difference, P = 0.048, given the observed 8.2 mean group change difference (GMFM points), with an observed effect size index of 1.12. Post hoc power was 49% when computed using the observed values and actual sample sizes in the study groups. We recognize that the small sample size in this study is necessarily linked to imprecision in the point estimate of the treatment effect. Therefore, the results of this study will need replication in a future trial with a larger sample size.
Clinically Important Change.
Infants in the NDT-based STA protocol group made a mean change on the GMFM of 13.3 and the PIP group made a mean change on the GMFM of 5.1 at the end of intervention. These numerical scores used for the statistical analyses of the study do not describe the clinically important change in function that is often more relevant to parents and therapists.
Russell et al19 calculated the relationship of the actual change in GMFM scores to parental and therapist judgment of the magnitude and importance of change in gross motor function. Russell et al19 determined a “large positive change” in gross motor function as judged by parents and therapists was reflected by an actual GMFM change of 11.4 and 24.6, respectively; a “medium positive change” was reflected by an actual change of 5.2 and 7.0, respectively; and a “small positive change” was reflected by an actual change of 2.7 and 3.8, respectively. For example, the mother of an infant in this study with a 13 GMFM change score reported, “he is able to sit up now longer and not fall over. He has even been able to sit up by himself a few times. He can use his left hand now to pick up toys and it is staying open more of the time. And he is starting to try to stand up in his crib.” The mother of an infant with a 7.7 GMFM change score, pretest to posttest, reported, “he can now hold his head up when I hold him and look around. He is now rolling over from his back to stomach and trying to sit up. He is much more alert.” An infant whose GMFM change score was 0.72 after the intervention was reported by his mother to “look attentively around and laugh and smile.”
According to the findings of Russell et al,19 the STA group mean change on the GMFM of 13.3 would be described by the parents as a “large positive” change. Therapists would describe the same change as a “medium” to “large” change. The PIP group made a mean change on the GMFM at the end of intervention of 5.1. This score would be described as a “medium positive” change by the parents and a “small” to “medium” positive change by therapists.
Improvement in gross motor skills may be achieved with therapeutic intervention of high frequency and short duration for a defined population of infants using an operationally defined intervention protocol and delivered by therapists with advanced, specialized training. The investigators in this study provide evidence for infants with posture and movement dysfunction when interventions are focused on facilitation of dynamic co-activation of trunk flexors and extensors that supports the demands of a specific functional activity. The results have policy implications with regard to (1) generalized play approach delivered by early interventionists or direct intervention from licensed professionals, (2) specific protocols of intervention, and (3) quantity of therapeutic intervention.
Improvement in Motor Function
The NDT approach when applied according the published principles and assessment guidelines with intervention structured according to the sequenced trunk activation protocol seems to produce improved motor performance when provided to infants with posture and movement dysfunction characterized by impairments in head and trunk orienting responses. The specific targeting of dynamic co-activation of trunk musculature in the STA protocol produced better performance than the nonfocused activation of trunk musculature that was inherently present in the play activities used in the PIP protocol group. Even with a small sample size and short intervention duration, the researchers of this study provide statistical evidence that an operationally defined NDT-based trunk protocol may be an effective method of improving independent functional movement for infants with posture and movement dysfunction during the first year after birth.
Future research on the psychosocial ramifications of improved motor gains should include outcome variables for evaluating the relationship between improved function and other enablement dimensions, eg, family functioning and social participation. Harris,23 Ketelaar et al,24 and Jansen et al25 hypothesized that improvement in motor performance may increase family functioning and societal participation.
As described previously, one common methodological problem in infant studies of the effects of pediatric therapy6-13 has been the failure to use a homogenous group of participants. In all five infant studies,6-13 participants were selected with “high risk” medical diagnoses but without documented developmental impairments. The confounding variable of heterogeneity of participants may have contributed to nonsignificant results because the researchers may have been testing the efficacy of pediatric therapy on samples containing a majority of typically developing infants. The current study included only infants identified with homogenous postural and movement impairments and gross motor functional activity limitations.
The NDT approach hypothesizes that functional activity limitations can be linked to specific system impairments that are targeted during intervention.16 Infants in this study demonstrated gross motor delay with posture and movement dysfunction that was specifically characterized by impairments in orienting responses of the head and trunk.
Operationally Defined Protocol
The operationally defined NDT-based STA protocol used in this study specifically addressed the role of dynamic co-activation of trunk musculature in orienting responses as they relate to functional skills in infants. The use of an operationally defined protocol that is linked to a specific impairment common to a group of infants with posture and movement dysfunction can be used to examine the validity of one assumption of the NDT approach: “effective and ineffective posture and movement serve as a link between the individual’s functions and the system impairments.”16 (p.98)
The researchers who conducted the current study illustrated that a specifically defined NDT-based STA protocol can be taught to multiple professionals within the context of a continuing education environment. In addition, we believe this operationally defined protocol will reduce variability and allow replication of the study, important for continuing investigation of the NDT approach for infants.
The PIP protocol was used to control for attention, maturation, and environment. Although it inherently included motor activities, the PIP protocol was not designed to be equivalent to the STA protocol with respect to individualized trunk activities. Future research to evaluate the effects of a generalized play intervention including trunk focused play activities delivered by early interventionists and compared to an individualized trunk activation intervention delivered by NDT infant-trained therapists could address other aspects of EI service models.
Frequency of Intervention
The authors suggest that a short-duration, high-frequency NDT-based STA protocol intervention may produce clinically important changes for infants of ages 4 to 12 months with posture and movement dysfunction. Piper’s 1990 review of the literature26 indicated that physical therapy was more effective in promoting motor milestone development if administered at least twice weekly. Results of improved motor function with higher frequency NDT intervention for children with CP are corroborated by other researchers, eg, Mayo,27 Bower and McLellan,28 Bower et al,29,30 Mahoney et al,31 Trahan and Malouin,32 and Tsorlakis et al.33 Continued research examining the optimal intervention frequency and duration for infants with posture and movement dysfunction is recommended.
Routine Therapeutic Intervention
Throughout the duration of the study, the infants in both groups continued to receive ongoing EI therapeutic services. Both groups improved their GMFM mean group scores after the study intervention of 10 hours over a 15-day period. The STA protocol group gained more with the study intervention than the PIP group, given identical parameters of attention, maturation, and environment. The investigators in this study suggest that increased frequency of intervention over frequencies commonly present in current EI programs may better facilitate maximal progress and realization of potential for infants with posture and movement dysfunction. The observed statistically significant increase in GMFM scores after implementation of the dynamic co-activation of trunk musculature protocol in the STA intervention group cautiously suggests a maximized return on investment of resources for the infants, therapists, and funding agencies. With return to routine EI therapeutic services and withdrawal of the study interventions during the 3-week postintervention period, both groups demonstrated a slight negative trend indicating the possible inability of routine ongoing EI therapeutic services to maintain or improve recent gains in gross motor skills. Implications from this study point to the need for continued research examining both the frequency and type of intervention critical for infants with posture and movement dysfunction, eg, comparisons between direct therapy and consultative service delivery models and intervention frequency.
Retention of Gains
The within-group mean GMFM scores from posttest to 3-week FU provide evidence that gains made from a short, intensive NDT-based STA protocol can be maintained for the short term. Although skills are maintained, continued specific sequential trunk activation intervention is likely needed to promote further progress.
The wide variance in both groups of GMFM change scores posttest to 3-week FU generates questions regarding the infants’ underlying body system impairments and subsequent functional gross motor limitations. Participants whose scores declined in the postintervention to 3-week FU period seemed to have motor limitations strongly influenced by sensory processing dysfunction. Although sensory testing was not conducted, numerous sensory defensive behaviors were observed during intervention. Future research should include discriminatory measures to differentiate infants with and without sensory processing dysfunction. Such identification of infants with sensory processing dysfunction may help clarify which infants will better retain gains made with the NDT-based STA protocol intervention.
In future research, the retention of gains should be assessed over a longer FU period than in the current study. Varying periods of intervention or no intervention is recommended to discover which schedule(s) yield maximal gains and retention effects for specific disabilities and impairments.
Instrument and Rater Reliability
The evaluative tool used in this study was validated for infants with posture and movement dysfunction (ie, CP) to measure change over time as a result of intervention. Studies reported earlier, ie, Goodman et al,6,9 Piper et al,7,8 Weindling et al,11 and Salokorpi et al12,13 used outcome measures that were standardized on typically developing populations. The use of appropriate outcome instruments with reported reliability and validity for specific populations and interrater reliability of examiners masked to group assignment and study intent are critical for addressing the question of intervention efficacy in specialized populations with posture and movement dysfunction.
Possible challenges to EI policy related to service delivery models and frequency of intervention are generated by this study. Scrutiny must be given to the national trend of using a generalized play approach delivered by early interventionists with therapist consultation for motor intervention services to infants with posture and movement dysfunction. The researchers of this study suggest that focused intervention specifically matched to identified impairments and delivered by a NDT-infant-trained therapist can produce a significantly higher level of motor skill improvement compared with nonfocused intervention delivered by a more generally trained interventionist when provided at the same increased frequency. A generalized play approach may have benefits in other areas, ie, cognition, social; however, this may not be true for motor skills.
The balance between using generalized interventionists and licensed professionals with subspecialty training in infant development and movement science within the EI service delivery model is in need of further evaluation. Continued research is essential to define the quantity of intervention, the specific intervention protocol, and the skills of the provider for optimal and cost-effective outcomes for infants with posture and movement dysfunction.
Four primary features of the study limiting the generalizability of results are (1) small sample size, low power, and purposive convenience sampling, (2) rater masked to group assignment but not to study intent, (3) outside routine EI therapeutic services tracked but not controlled, and (4) infant cognition not tested. The small sample size in this study was a result of the referral policies of the specific locale (eg, economics; Health Insurance Portability and Accountability Act) and the 44% to 50% attrition rate. The primary reason for attrition in the PIP group was that parents were interested in participating in the study only if their infants were in the STA treatment group. No measure directly assessed the infants’ cognitive level, although it is clinically assumed to influence the infants’ motivation and ability to learn. Future development of a motor-free cognitive tool for infants’ ages 4 to 12 months is needed. Infant cognitive abilities may then be used to more equitably stratify groups before randomization.
A short-duration, high-frequency NDT-based infant protocol focused on dynamic co-activation of trunk flexors and extensors and specifically sequenced trunk movements significantly improved gross motor function in infants with posture and movement dysfunction compared to a nonindividualized Parent-Infant-Play protocol that only indirectly addressed the trunk. These motor gains were maintained for 3 weeks. Providing attention through guided, enriched play activities and interaction with social support did not significantly improve infant motor performance during the same time period. The infants with posture and movement dysfunction made gains that seemed to be the result of the short-duration, high-frequency, sequential trunk activation interventions provided by pediatric therapists specializing in the NDT approach for infants.
The authors are grateful to Barry Chapman, MS, PT, for his role in testing infants, and to Mitzi Wiggin, MS, PT, for specific support recruiting families, providing the research site, and testing the infants. Special acknowledgment is given to Kristy Loper, BA, Child Life Specialist, for her coordination of the parent-infant play group. Dr. Ed Gracely, Dr. John Pezzullo, and Dr. Steve Allison generously assisted in the sample size write-up. The authors also wish to thank the infants and parents who participated in this study.
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NDT-Based Infant Sequenced Trunk Activation Treatment Protocol Within the NDT Problem-Solving Assessment and Intervention Planning
The STA treatment protocol used in the study was taught to NDT-trained pediatric therapists in a 3-week advanced specialization course for NDT-based infant treatment. Study intervention sessions occurred during treatment practicums, in the second and third weeks of the course. The course faculty supervised the course participant-therapists during the 10 one-hour treatment practicum sessions. The course curriculum consisted of didactic, practical, experiential, and problem solving activities totaling 103.75 contact hours.
Each individualized intervention plan was developed to meet the functional goals collaboratively established by the parents, course participant-therapists, and course faculty from infant and parent needs and concerns. The functional goals addressed transitional mobility skills (eg, rolling, prone to sitting, sitting to quadruped to sitting, quadruped to standing) within a variety of positions, as well as interaction skills with environment and caregiver. The functional goals were analyzed to identify the following essential posture and movement components†:
- Head orientation toward vertical
- Eyes horizontal
- Appropriate base of support for functional activity
- Trunk alignment over appropriate base of support
- Neutral pelvis
- Actively balanced trunk musculature with weight shift
- Trunk elongation on the weight-bearing side
Appropriate orienting of head and body parts to the support surface for maximal contact and proprioceptive sensory input.
The essential posture and movement components that were missing, delayed, or atypical for the identified functional goal were targeted. Dynamic control by the infant of the targeted posture and movement components was then facilitated, repeated, and embedded in the context of meaningful appropriate play activities.
When intervening with the infant during a transitional activity identified in the functional goal(s) and addressing the targeted missing, delayed, or atypical posture and movement components, the course participant-therapist followed a fluid sequence:
- Systems Review: Review both positive and negative effects of relevant systems on the specifically selected functional activity and adapt the intervention plan to capitalize or adjust for system impairment. Systems to be considered are: the auditory, visual, respiratory, cardiovascular, gastrointestinal, integumentary, nervous (state control, arousal), sensory, musculoskeletal, and neuromuscular systems.
- Engage: Build trust. Wait for the infant to actively participate in reciprocal interactions before touching the infant. The infant may actively participate by giving eye contact, vocalizing, or physically touching the therapist.
- Prepare: Address range of motion, level of alertness and arousal, and sufficient postural tone needed for the infant to activate the targeted posture and movement components.
- Align: Make physical and environmental adjustments to align body joints and body mass over an appropriate base of support for the targeted posture and movement components.
- Activate: With clear intention, elicit dynamic co-activation of flexors and extensors of the head and trunk musculature and facilitate weight shifts into the base of support. Weight shifts for dynamic trunk activation are facilitated in a specific sequence of planes of trunk movement: sagittal first, frontal second, and transverse last.
- Repetition: Provide multiple opportunities, within each intervention session, for repetitions of posture and movement components of selected functional goals within the context of an appropriate play or daily life activity. Physical assistance must be graded to allow infant to gradually achieve independent motor skills.
- Home repetition: Integrate selected, targeted posture and movement components into function at home. Use activities of daily living, such as, carrying, picking up, putting down, and diapering for multiple opportunities to strengthen, integrate, and generalize posture and movement components into functional activities in home environment.
The STA protocol intervention was applied specifically to the “activate” portion of each activity sequence. The STA protocol intervention is focused on facilitated dynamic co-activation of trunk flexors and extensors and specifically sequenced trunk movements during transition activities and consists of the following: (1) facilitation of dynamic co-activation of trunk flexors and extensors in the sagittal plane that is adequate to the demands of a specific functional activity, (2) facilitation of active weight shifts in the frontal plane to produce “elongation on the weight-bearing side,” while maintaining the appropriate dynamic co-activation of trunk flexors and extensors,16 and (3) facilitation of active functional trunk rotation, while maintaining dynamic co-activation of trunk flexors and extensors and active trunk elongation of the weight-bearing side, ie, transverse plane. Functional trunk rotation is integral to the development of equilibrium behaviors for variability in motor responses20 and higher level balance.16 (p.41) Functional trunk rotation is facilitated as appropriate for the age of the infant and the specific functional skill within the chosen activity.
Each step in the STA protocol creates the base needed for the next step in the sequence. Intervention that incorporates the STA protocol produces dynamic trunk co-activation in sequenced trunk movements adequate for the demands of transitional activities. In an infant-led session, the individualized application of the protocol may seem different for each infant and within a session depending on the functional activity of interest to the infant.‡
Parent-Infant Playgroup Protocol
A licensed Child Life Specialists coordinated the PIP group that met for 10 one-hour sessions over a period of 15 days. A graduate psychology student, who was a mother of a child with CP, and an aerobics instructor who specialized in postpartum exercises, assisted the Child Life Specialist in the intervention activities for the parents and infants.
The parents delivered the enriched play activities, with guidance from the Child Life Specialist for 30 minutes at each of the 10 intervention sessions (Table 3). The play activities, selected from Gymboree, A Parent’s Guide to Baby Play,21 targeted various areas of development, such as: visual, tactile, auditory, social, cognitive, emotional, and communication.
The psychology graduate student planned and led the discussion sessions. The topics she included during the six 30-minute blocks were (1) importance of self care; (2) ways to feel empowered; (3) Elizabeth Kubeler-Ross’s stages of grieving, particularly in relation to their infant’s disability; (4) coping skills for managing an infant with a disability; and (5) sharing their “stories.”
The postpartum aerobic instructor led the parents in a comfortably paced, general body fitness routine that included their infants. Each session involved continuous activity for 30 minutes, during four of the 10 group sessions. The instructor demonstrated ways to pick-up and put down the infants with appropriate body mechanics to reduce the risk of back injury and to tone the abdominal muscles of the adult. She demonstrated ways to push the infant in the stroller to perform gentle body muscle stretching and strengthening activities. The instructor incorporated holding, lifting, and moving the infant for adult upper and lower body strengthening activities during play times.
*NDT-based STA protocol with clinical example is available by request to the first author.
†The category of effective and ineffective posture and movement function components is depicted in “The NDT Enablement Classification of Health and Disability,” Table 2.1, page 82, found in Neuro-Developmental Treatment Approach: Theoretical Foundations and Principles of Clinical Practice by Howle (2002).16
‡NDT-based STA protocol with clinical example is available by request to the first author.
Keywords:© 2008 Lippincott Williams & Wilkins, Inc.
developmental disabilities; human movement system; infant; infant development; motor skills; physical therapy; postural equilibrium