For more than 25 years, the most common physical therapy method used to improve the locomotor capacities of children with spastic cerebral palsy (CP) has been the neurodevelopmental (NDT) approach.1,2 The motor problems of CP arise fundamentally from a central nervous system impairment that interferes with the development of normal postural control, with concurrent changes in muscle tone and activity.1,2 One of the basic tenets of the NDT approach advocates facilitation techniques by the physical therapist to inhibit spasticity and facilitate more normal movement patterns.2 However, the child was a relatively passive recipient of the NDT treatment. Over time, it was realized that atypical motor patterns became established through practice and experience in the “competition of motor patterns,”3 influenced by musculoskeletal components.2 Thus, therapeutic interventions before ineffective movement patterns become dominant expand the range of movement possibilities.4
Through the development of the sciences of motor control and motor learning, the hierarchical reflex model of motor control adopted by the Bobaths has been replaced by a more dynamic approach.4–8 Thus, in the treatment of CP, motor behavior is said to emerge from the dynamic cooperation of all subsystems (central nervous system, biomechanical, psychological, and social-environmental systems) within the context of a specific task (ie, the dynamic systems theory).4–8
Furthermore, motor programs have been hypothesized to develop that do not require feedback to be elicited but can be initiated by central processes within the nervous system to perform practical functional tasks (ie, feed-forward system).2 In this model, the child must be an active participant and be provided opportunities for repetitious, task-specific practice, in order for motor learning to occur. Thus, if walking is the goal of the treatment, then the individual must practice walking.9 The development and clinical use of partial weight-bearing systems employing treadmills has expanded the opportunities for children with neuromuscular disorders to practice walking skills. However, few studies have examined the outcome of these therapeutic activities on ambulation.10
An important link between clinical research and clinical treatment is the development of a clinical treatment methodology based on theoretical frameworks (eg, NDT and dynamic systems theory) that are supported by scientifically validated findings.8,11 Determining the type of therapy and its duration (in weeks or months), frequency (sessions per week), length of time per session, and intensity (time, frequency, and duration) is imperative if the link between clinical research and clinical treatment is to be established. Indeed, the American Academy for Cerebral Palsy and Developmental Medicine recently produced an evidence report concerning the efficacy of various interventions for the management of CP and other developmental disabilities.11 This report was an aggregate of all that has been published about outcomes of different treatments for CP. The authors of the report found it difficult to evaluate the effectiveness of any single therapy approach for a host of reasons. Paramount among these reasons was variation in duration and intensity of treatments. Although most studies demonstrated that therapy programs providing an increased intensity improved outcomes,12–15 one did not.16
In keeping with the NDT and dynamic systems approaches to treatment, a new type of task-specific approach to attainment of locomotor skills in children with CP has been identified, that of partial body weight treadmill training (PBWTT).9,17–19 PBWTT involves a special overhead structure supporting a harness that encircles the trunk of the child, allowing the child's body weight to be partially or fully supported to facilitate a normal gait pattern while stepping on a treadmill. Thus, PBWTT uses the support of body weight, allowing for manual guidance of foot and leg movements in a repetitive, task specific approach to walking on a moving treadmill.
There have been exploratory attempts to gain insight into the feasibility and efficacy of PBWTT and its clinical applicability in improving the functional gait capacity of youth with CP.9,17,19 Richards et al17 studied the effects of PBWTT with a treatment frequency of four times per week for a period of four months. A study by Schindl et al19 involved two to three, 30-minute sessions of treadmill training per week for three months. In a case report, Day and colleagues9 studied the effects of 44 sessions of PBWTT ranging in duration from 11 to 25 minutes. Differences in the quantity and intensity of PBWTT sessions and methods of evaluating outcomes make comparisons among these studies difficult.
A primary concern related to these studies9,17,19 involves the duration of treatments or episodes of care (ie, three to four months). The small improvements reported in the measured outcomes (eg, Gross Motor Function Measure [GMFM], Pediatric Evaluation of Disability Inventory [PEDI]) could have resulted from growth or maturation or from characteristics of the outcome measurements. In addition, the practical problem with extended (three to four month) period of intensive intervention programs involving children with CP is the associated cost. The more-is-better phenomenon has been identified as a theme in studies about service utilization and service integration.20,21 Families are likely to think that increasing the intensity of treatment will increase the likelihood of the therapy being more effective for their child. Thus, therapeutic practices can become controversial when they are described as beneficial without evidence-based guidelines established through clinical research.
Determining the effectiveness of intensive physical therapy that incorporates traditional treatment methods and treadmill training with a length of four to eight weeks (ie, as compared with three to four months) has not been established. However, investigators have reported that intensive treatment programs with lengths of four to eight weeks have produced some improvements in locomotor outcomes.10,15,22 Eagleton and colleagues,22 using a strength training program lasting 40 minutes three times per week for six weeks, demonstrated improvements in gait velocity, step length, and cadence in adolescents with CP. Adams et al10 reported improvements in gait patterns using a one-hour program of NDT-based therapy twice a week for six weeks. Intermittent, intensive NDT was studied by Trahan and colleagues15 of four times per week for four weeks followed by eight weeks without physical therapy given across a six-month period. Results indicated improvements in motor performance in children with CP with severe involvement, (Gross Motor Function Classification System [GMFCS] Level IV, V) that were maintained over the rest periods.15
Therefore, the purpose of this study was to examine the effects of an intensive physical therapy program using traditional treatment methods combined with treadmill training on functional motor capacity and ambulatory skills of five children with CP of different ages and levels of severity.
Participants were chosen from a sample of convenience from children referred for physical therapy at an outpatient clinic. Participants included five children (one girl, four boys), diagnosed with spastic CP (one with quadriplegia and four with diplegia), ages 2.3 to 9.7 years. Parents or guardians of each child signed an informed consent form before initiation of the study. Approval for the study was obtained from the University's institutional review board, and all participants had been cleared by their physician to participate in the therapeutic procedures followed in this study. At baseline, one child was preambulatory, two of the children walked independently, and two walked with assistive mobility devices. Descriptive characteristics, including diagnosis, ambulatory ability, assistive devices, orthotics, GMFCS level and prior outpatient physical therapy of each participant are found in Table 1. During the study, participants 1 and 5 continued with their regularly scheduled occupational therapy.
Measures and Outcomes
Locomotor and gait performance were evaluated at baseline and after the four-week intensive physical therapy program using the GMFM,23 the PEDI,24 Doc-U-Prints pedograph, and the Timed 10-Meter Walk Test. The two physical therapists involved in the treatment of the participants performed the clinical tests; one for participants one, two, and five, and the other for participants three and four.
Instruments and Tests
Gross Motor Function Measure (GMFM).
The GMFM (2nd edition) is a standardized observational instrument that meets the criteria of reliability and validity to measure change in functional gross motor skills in children with CP.23,25,26 The test is administered by the clinician, following the Guidelines for Item Scoring section in the GMFM manual. The test consists of 88 specific gross motor tasks that are divided into the following five dimensions: (1) Lying and Rolling, (2) Sitting, (3) Crawling and Kneeling, (4) Standing, and (5) Walking, Running, and Jumping. Each of the 88 items is scored on a four-point Likert scale. A total score for the items in each dimension is converted into a percentage. Each dimension percent score is weighted equally to determine the total percent score.
Pediatric Evaluation of Disability Inventory (PEDI).
The PEDI was developed to measure functional status in young children.27 The PEDI can be used both for discriminative and evaluation purposes and meets the criteria of reliability and validity.24,27,28 The PEDI may be administered through structured parent interview or by direct observation and testing. The test includes three domains: Self-Care, Mobility, and Social Function. The typical level of perceived caregiver assistance also is measured for the items within each domain.
Doc-U-Prints pedographs (NDT Programs, Inc, Augusta, GA) were used to record changes in spatial gait parameters for each participant. The pedograph method has been established as a valid and reliable method for temporal and linear gait analysis.29,30 This method can also reveal small changes in gait often not detected by using observational gait analysis31 and has been used as an outcome measure when comparing NDT treatment methods in children with CP.10 Doc-U-Prints are a carbon paper pedograph system secured to the floor, creating a walkway for recording footprints as the participant walks independently or with assistive devices. Doc-U-Prints were used in this study to assess the following spatial gait parameters: step length, stride length, base of support, and line of progression. Print density provides information about foot contact (ie, presence of heel strike, foot pronation, toe drag) and areas of relatively high or low pressure during contact. When the entire footprint was not recorded on the pedograph because of the participant walking on his or her toes, a paper template of the participant's (opposite) foot was superimposed over the recorded imprint of the forefoot and toes to mark the anticipated heel strike. This allowed for measurements of stride and step length, and base of support using a consistent landmark, the heel point. Stride and step length and base of support for each Doc-U-Print were recorded as an average of the number of steps measured for each participant. The number of steps recorded varied among participants.
Using permanent markers, a mark was made at the center point of the heel on each recorded step. A line was drawn to connect these points for each foot to show the line of progression. Lines of progression were color coded for clarity, that is, red for right, and blue for left. A perpendicular line was drawn from the center point of each heel to the line of progression of the opposite foot. A metal yardstick was used to measure the distances for stride length, measured along the line of progression between the heel points of two consecutive footfalls of the same foot, and step length, measured as the distance from the heel point of one footfall to the heel point of the next consecutive footfall on the opposite foot. Base of support was measured as the perpendicular distance between the heel points of each footfall to the line of progression of the opposite foot. Base of support was indicated as a negative number if scissoring occurred, that is, the line of progression of each foot was reversed. Measurements were recorded to the nearest quarter of an inch.
Timed 10-Meter Walk Test.
Gait speed was measured utilizing a timed 10-meter walk.32–34 Time, use of adaptive equipment, and level of physical assistance (if necessary) was recorded for all participants. The participant was instructed to walk at a comfortable, normal pace for 10 meters. The middle six meters were timed to eliminate the effects of acceleration and deceleration. A handheld Sportline stopwatch was used to time the 10-meter walk to the nearest one hundredth second.
Treadmill and Unweighting System.
A GaitKeeper™ 1800L treadmill (Mobility Research, Tempe, AZ) was used for PBWTT. Treadmill speeds range from 0.1 to 4.0 mph, adjustable in 0.1-mph increments. Elevation can be adjusted from level to a 15% grade. The Standard WalkAble™ (Mobility Research, Tempe, AZ) was used for partial unweighting over the treadmill. The frame consists of an overhead four-point suspension system, extending from a rigid, vertically adjustable, Y-shaped yoke. The WalkAble unit is appropriate for children weighing up to 75 pounds and measuring up to 4 foot 2 inches tall over the GaitKeeper treadmill or 4 foot 8 inches tall over the ground. The height of the handlebars is fully adjustable. Four adjustable straps connect the yoke to the accompanying pediatric pelvic harness worn by the participant. The bottom of the harness was positioned to cross the participant's greater trochanters. Lower, middle, and upper lateral straps were cinched bilaterally to create a snug fit. A padded groin strap passed between the participant's legs to attach to the bottom of the harness anteriorly and posteriorly. The design of the harness supports the participant in vertical alignment, allowing full hip extension during gait.
Physical Therapy Sessions
Physical therapy sessions were scheduled for two hours per day, four days per week, for four consecutive weeks in four of five participants. Because of parental time constraints, participant four was scheduled for two hours per day, three days per week, for four weeks. Attendance rate was 94% for participant four, 100% for all other participants.
Physical therapy sessions consisted of traditional treatment techniques with PBWTT during each session. Traditional treatment techniques included NDT in a dynamic systems approach (ie, facilitation of active motor learning in attainment of developmental positions and transitions, both in floor mobility and standing and walking activities).10 Therapeutic exercises were used to stimulate muscle lengthening and strengthening using myofascial release, kinesiotape, and therapeutic activities to improve strength and motor coordination. Therapeutic activities, for instance, climbing stairs, ladders, and cargo net, tricycling, and rollerskating, were performed with assistance and adaptations as needed by participant. Activities for postural and motor control included additional perturbations of balance distal to proximal35 in dynamic ball sitting with feet on floor, sitting and standing on static and mobile surfaces and swings to provide vestibular stimulation.
PBWTT allowed for prolonged walking practice by facilitating stepping through assisting hip extension during terminal stance, stretching hip flexors and ankle plantar flexors to initiate the next step. Manual stimulation of gait components during PBWTT allowed for development of intra- and inter-limb coordination through temporal sequencing of joint movements.35
Gait training on level surfaces, inclines, and stairs was a primary focus of treatment, using manual facilitation by the therapist and various assistive devices as indicated (eg, posterior walkers, quad canes, and single point balance poles). Treatment sessions also were augmented by neuromuscular electrical stimulation, applying kinesiotape, and postural control garments (Theratogs), with the latter two continued at home if indicated. Participants continued to wear ankle foot orthotics (AFOs); however, AFO use during therapy sessions was at the therapist's discretion. For example, participants may have participated in PBWTT without AFOs if their age and muscular status allowed them to use active ankle dorsiflexion and forward progression of weight over feet (ie, stimulation of foot rockers)36 with ease in a partially weighted environment. When AFOs were not worn during PBWTT, participants were barefoot or wore minimal foot coverings such as water socks.
PBWTT generally consisted of three to five bouts per session, for a total of 15 to 35 minutes per session. PBWTT was performed using the Standard WalkAble™ on the GaitKeeper treadmill by all participants, with the exception of participant two who performed treadmill training without the supportive harness system. Participants one and two did not wear AFOs during PBWTT, participant five wore AFOs 50% of the time, and participants three and four did wear AFOs during PBWTT.
During PBWTT, the child was secured into the harness and positioned on the Gaitkeeper treadmill in the Standard WalkAble. The child's body weight was supported in an erect posture to allow for full knee extension during midstance phase and full hip extension during terminal stance phase of gait. Treadmill speed was determined based upon the ability of the child to maintain rhythmic stepping with or without assistance. Treadmill training time was progressed based upon the ability to maintain the walking pattern, ending each bout (or PBWTT session) if the gait pattern deteriorated, or the participant or therapist experienced fatigue.
The therapist was positioned behind the child during PBWTT to facilitate the gait pattern by stimulating full range of hip extension and equal stance time on each limb, preventing premature initiation of swing phase, insuring heel strike at initial contact, and preventing knee hyperextension during midstance phase. The prolongation of the stance phase in combination with the backward movement of the treadmill belt resulted in increased hip extension, believed to be an essential component in improving the gait pattern of children with CP. Facilitation was provided from the pelvis, behind the knees, or at the ankles as determined by the gait pattern demonstrated. As the participant developed the ability to sustain the proper gait pattern, facilitation was faded or eliminated and replaced with verbal prompts.
The criteria for initial speed of treadmill and percent body weight support (%BWS) as well as incremental changes (ie, increases in treadmill speed and decreases in %BWS) were determined by gait mechanics of the child. For example, incomplete hip extension usually results when the speed of the belt is too fast. The partial unweighting system used in this study did not allow for direct measurement of percent body weight support. Therefore, the %BWS was set so that the child was able to demonstrate sufficient hip flexion and knee flexion/extension during swing phase to allow foot clearance, and full hip and knee extension during mid-stance phase of the gait cycle.
Means and standard deviations were calculated for measures of all variables. A Wilcoxon paired-sample test was computed to examine whether differences existed between week one and week four for progression of treadmill speed and time for PBWTT, total score for GMFM, Doc-U-Prints pedograph measures, and Timed 10-Meter Walk Test. All calculations were performed using SPSS® 12.0 (SPSS for Windows, Re. 11.0.1, 2002; SPSS Inc., Chicago, IL) and for all analyses statistical significance was set at p < 0.05. Percentage changes were presented for each of the domains (functional skills and caregiver assistance) for the PEDI. Significant changes for each domain of the PEDI were determined according to standards included in the PEDI manual.24
Progression of the PBWTT (ie, week one to week four) in speed and time on treadmill for each participant can be found in Table 2. There were no significant changes in speed or time on treadmill. Results of the GMFM for each of the five dimensions and comparison of the pre- and post-therapy total score (composite of all five dimensions) are found in Table 3. When comparing the group pre- and post-test total score for the GMFM, no significant changes were observed (Table 3). However, when considering the percent changes for each of the five dimensions, some positive changes were noted. Four of five participants demonstrated improvements in their total percent score on the GMFM. Participant one demonstrated the greatest improvement in dimensions A, B, and C, while participant five exhibited the most improvement in dimension D. All five participants progressed in dimension E.
Table 4 illustrates pre-and post-test scaled score results for the functional skills and caregiver assistance domains of the PEDI. Participant one demonstrated improvement in mobility (6.6%) and social functional (5.2%) in the functional skills domain. Participant two showed improvements in mobility functional skills (11.9%). Participant five demonstrated improvements in self care functional skills (9.2%) and caregiver assistance (23.3%).
Results of the pedographs for right and left step length, right and left stride length, pre- and post-test differences between right and left step and stride length, and base of support are found in Table 5. Although improvements were seen in all these parameters, significant differences were only seen in pre- and post-test differences in step length. A significant decrease in step length differentials in right and left limbs of participants one, two, three, and four indicates an improvement in gait symmetry. Base of support increased for participants one, two, and five, but decreased for participants three and four.
Although not significant, all participants demonstrated increased speed of ambulation as measured by the Timed 10-Meter Walk Test (range = 10.6–76.1%). Participant one showed the greatest increase in walking speed by 24.6 seconds, while participant two demonstrated minimal change in walking speed (0.5 seconds).
The development of gait in children with CP is a primary concern of parents and a complex treatment issue for physical therapists. Although various treatments have been shown to be effective,9,15,17,19 no systematic approach has been published that has established a high probability of producing measurable changes in gait. This pilot study was an attempt to validate a treatment approach, namely intensive physical therapy with PBWTT, and identify clinical tests that effectively measure treatment outcomes. Motor learning in an intensive episode of physical therapy requires active assisted, task-specific practice of skills in various therapeutic activities that contain components for strengthening and opportunities for unpredictable perturbations of balance.35 Although the therapeutic activities varied among participants, PBWTT and gait training over ground were conducted during each session in the study. This provided the opportunity for repetitious, task-specific practice of gait parameters.
Results reflect improvements in gait and functional skills as noted in the outcome measures. As with previous studies, improvements were noted in GMFM scores, specifically dimension E, walking, running, and jumping. Similar to Day and colleagues,9 we found the PEDI effectively measured improvements in the mobility functional skills scaled scores in two participants, and in self care functional skills and caregiver assistance in one participant. Pedographs showed increases in step length, and a significant decrease in step length differentials in four of five participants. This reflects an increase in symmetry between right and left step or stride lengths, indicative of an increase in consistency in measured gait parameters. This may also reflect improvements in dynamic postural control during gait. Although group significance was not shown, all participants exhibited increases in speed of walking. When considered together, namely improved gait parameters and inter-limb coordination along with increased walking speed, these results are reflective of improvements in gait pattern efficiency. Notably, participant two experienced a decrease decrease in falling per parent report, while participant four progressed to assisted walking with less support in therapy (ie, from quad canes to balance poles).
By design, this study contains a selection bias, because participants were chosen from a sample of convenience. Variable age of participants of different GMFCS classifications limits comparison between a heterogeneous group. Internal validity of this study was limited by factors such as standardization of time, speed, and number of bouts during PBWTT, protocol for progression of manual and external assistance during PBWTT, administration of pre- and post-tests by nonblind therapists, verbal instructions for walking speed during the Timed 10-Meter Walk Test, and standardization of pedograph length. Generalization of results is limited by the small, highly variable sample of participants.
Strengths of this study include high external validity, as this study was completed in a typical outpatient clinical setting with current therapy clients. Two physical therapists were involved in the study; however, intrarater reliability was strong because the same therapist provided all treatment and testing for a particular participant. Attendance across all participants was high (94–100%). Measurements of outcomes using accepted standardized tests and tools readily available in the clinic setting allow for ease of replication and comparisons between children of similar diagnostic types.
In striving to produce positive changes in functional motor skills and gait in children with CP, a different approach to traditional once-weekly or twice-monthly physical therapy may warrant consideration. Further study is needed to determine optimal treatment intensity (ie, length, frequency, and duration) as well as timing of episodes of intensive physical therapy to produce positive outcomes in motor skills and gait.15 Therapists' identification of sensitive periods of readiness in children that they treat may optimize treatment effects during these episodes.13,37–39 For instance, participant one's improvements in postural control and floor mobility was reflected in GMFM dimensions A, B, and C. In addition, participant one's pedographs also recorded increased base of support and symmetry in stride, with increased speed of walking. This suggests a transition during the intensive treatment episode from preambulation to assisted ambulation.
Additional studies are needed to address the efficacy of intensive treatments during sensitive periods of readiness39 for improvements in motor performance and locomotor skills. Further studies are needed to establish treatment protocols, including traditional methods and PBWTT in children with CP with similar GMFCS classifications. These should include design and progression of treatment, treadmill speeds, degree of body weight support, manual facilitation, and use of assistive devices and footwear. Continued studies of gait parameters through pedographs may measure the effects of bracing and/or assistive devices on gait.
Expanded use of clinical tests such as the GMFM, PEDI, and pedographs can lead to a quantity of data by which to measure treatment outcomes related to motor performance and gait. Information gained could be used in multi-center studies of larger numbers of homogenous groups of children, leading to improved treatment strategies and outcomes in physical therapy treatment of children with CP.
1. Bobath K, Bobath B. The neuro-developmental treatment. In Scrutton D, eds. Management of the Motor Disorders of Children with Cerebral Palsy
. Philadelphia; JB Lippincott; 1984;6–18.
2. Bly L. A historical and current view of the basis of NDT. Pediatr Phys Ther
3. Mayston JJ. The Bobath concept-evolution and application: In: Forsberg H, Hirschfeld H, eds. Movement Disorders in Children
. Basel: Karger; 1992;1–6.
4. Howle J. NDT Approach: Theoretical Foundations and Principles of Clinical Practice
. Laguna Beach, CA: NDTA; 2002.
5. Thelen E. Motor development: a new synthesis. Am Psychol
6. Kamm K, Thelen E, Jensen JL. A dynamic systems approach to motor development. Phys Ther
7. Scholz JP. Dynamic pattern theory: some implications for therapeutics. Phys Ther
8. Kelso JAS. Anticipatory dynamic systems, intrinsic pattern dynamics and skill learning. Human Movement Sci
9. Day JA, Fox EJ, Lowe J, et al. Locomotor training with partial weight body support on a treadmill in a nonambulatory child
with spastic tetraplegic cerebral palsy: a case report. Pediatr Phys Ther
10. Adams MA, Chandler LS, Schuhmann K. Gait
changes in children with cerebral palsy following a neurodevelopmental treatment course. Pediatr Phys Ther
11. Butler C, Darrah J. Effects of neurodevelopmental treatment (NDT) for cerebral palsy. Develop Med Child Neurol
12. Mayo NE. The effect of physical therapy for children with motor delay and cerebral palsy. Am J Physical Med Rehabil
13. Bower E, McLellan DL. Effect of increased exposure to physiotherapy on skill acquisition of children with cerebral palsy. Develop Med Child Neurol
14. Bower E, McLellan DL, Arney J, et al. A randomized controlled trial of different intensities of physiotherapy and different goal-setting procedures in 44 children with cerebral palsy. Develop Med Child Neurol
15. Trahan J, Malouin F. Intermittent intensive physiotherapy in children with cerebral palsy: a pilot study. Develop Med Child Neurol
16. Bower E, Michell D, Burnett M, et al. Randomized controlled trial of physiotherapy in 56 children with cerebral palsy followed for 18 months. Develop Med Child Neurol
17. Richards CL, Malouin F, Dumas F, et al. Early and intensive treadmill locomotive training for young children with cerebral palsy: a feasibility study. Pediatr Phys Ther
18. McNevin NH, Coraci L, Schafer J. Gait
in adolescent cerebral palsy: the effect of partial unweighting. Arch Phys Med Rehabil
19. Schindl MR, Forstner C, Kern H, et al. Treadmill training with partial body weight support in nonambulatory patients with cerebral palsy. Arch Phys Med Rehabil
20. McWilliam RA, Tocci L, Harbin B. Services Are Child-Oriented and Families Like It That Way—But Why
? Early Childhood Research Institute: Service Utilization Findings; 1995;1–5.
21. McWilliam RA, Young HJ, Harville K. Therapy services in early intervention: current status, barriers, and recommendations. Topics Early Childhood Spec Ed
22. Eagleton M, Iams A, McDowell J, et al. The effects of strength training on gait
in adolescents with cerebral palsy. Pediatr Phys Ther
23. Bjornson KF, Graubert CS, Buford VL, et al. Validity of the Gross Motor Function Measure. Pediatr Phys Ther
24. Nichols DS, Case-Smith J. Reliability and validity of the Pediatric Evaluation of Disability Inventory. Pediatr Phys Ther
25. Palisano R, Rosenbaum P, Walter S, et al. Development and reliability of a system to classify gross motor function of children with cerebral palsy. Develop Med Child Neurol
26. Russell DJ, Rosenbaum PL, Avery LM, et al. Gross Motor Function Measure (GMFM-66 and GMFM-88) User's Manual
. London: Mac Keith Press; 2002.
27. Haley SM, Coster WJ, Ludlow LH, et al. Pediatric Evaluation of Disability Inventory: Development, Standardization, and Administration Manual
. Boston, MA: New England Medical Center Inc., and PEDI Research Group; 1992.
28. Fieldman AB, Haley SM, Caryell J. Concurrent and construct validity of the Pediatric Evaluation of Disability Inventory. Phys Ther
29. Gardner GM, Murray MP. A method of measuring the duration of foot-floor constant during walking. Phys Ther
30. Embrey DG. A practical method for evaluating foot placement during gait
. Phys Occup Ther
31. Holden MK, Gill KM, Magliozzi MR, et al. Clinical gait
assessment in the neurological impaired: reliability and meaningfulness. Phys Ther
32. Grieve DW, Gear RJ. The relationship between the length of stride, step frequency, time of swing and speed of walking for children and adults. Ergonomics
33. Winchester P, Kendall K, Peters H, et al. The effect of therapeutic horseback riding on gross motor function and gait
speed in children who are developmentally delayed. Phys Occu Ther Pediatr
34. Blundell SW, Shepherd RB, Dean CM, et al. Functional strength training in cerebral palsy: a pilot study of a group circuit training class for children aged 4–8 years. Clin Rehabil
35. Farmer SE. Key factors in the development of lower limb co-ordination: implications for the acquisition of walking in children with cerebral palsy. Disability Rehab
36. Perry J. Gait Analysis, Normal and Pathological Function
. Thorofare, HJ: Slack, Inc.; 1992.
37. Schreiber J. Increased intensity of physical therapy for a child
with gross motor development delay: a case report. Phys Occup Ther Pediatr
38. Heriza, C. Motor development: Traditional and contemporary theories. In Lister MJ, ed. Contemporary Management of Motor Control Problems: Proceedings of the II STEP Conference
. Alexandria, VA: Foundation for Physical Therapy; 1991;99–126.
39. Campbell SK, Physical Therapy for Children
. 2nd ed. Philadelphia: WB Saunders Co.; 2000.