Abstract
Dosing of pediatric rehabilitation services for children with cerebral palsy (CP) has been identified as a national priority. Establishing dosing parameters for pediatric physical therapy interventions is critical for informing clinical decision making, health policy, and guidelines for reimbursement. The purpose of this perspective article is to describe a path model for evaluating dosing parameters of interventions for children with CP. The model is intended for dose-related and effectiveness studies of pediatric physical therapy interventions. The premise of the model is: Intervention type (focus on body structures, activity, or the environment) acts on a child first through the family, then through the dose (frequency, intensity, time), to yield structural and behavioral changes. As a result, these changes are linked to improvements in functional independence. Community factors affect dose as well as functional independence (performance and capacity), influencing the relationships between type of intervention and intervention responses. The constructs of family characteristics; child characteristics (eg, age, level of severity, comorbidities, readiness to change, preferences); plastic changes in bone, muscle, and brain; motor skill acquisition; and community access warrant consideration from researchers who are designing intervention studies. Multiple knowledge gaps are identified, and a framework is provided for conceptualizing dosing parameters for children with CP.
The purpose of this perspective article is to describe a path model for evaluating the dosing of interventions for children with cerebral palsy (CP) that may inform clinical effectiveness research. First, we describe the immediate need for clinical effectiveness or dosing-related research, particularly in pediatric physical therapy, and clarify dosing terminology. We highlight the variability in published dosing parameters of interventions with known efficacy, including stretching, strengthening, skeletal loading, treadmill training, and upper extremity training. Second, we synthesize evidence on the interrelationships between structural and behavioral changes for specific interventions in children with CP. This evidence is particularly important because dosing related outcomes occur across multiple domains of the International Classification of Functioning, Health and Disability1 (ICF) model. We use published study results to highlight differential intervention effects across the ICF domains. Third, we introduce a path model as a framework for researchers to systematically study the complex interactions of dosing pediatric physical therapy for children with CP. Our path model accounts for contextual and individual variation, allowing researchers to study dosing and advance the field toward establishing guidelines for clinically effective pediatric physical therapist practice. We conclude by discussing the implications and use of the path model.
CP and Dosing
Cerebral palsy is the most common motor disorder in childhood and results in abnormal tone and movement.2 Clinical effectiveness research identifies which interventions work for which patients and under what circumstances and involves both clinical- and patient-relevant outcomes.3 Establishing a clinically effective dose of pediatric physical therapy for children with CP would ideally yield positive changes perceptible both clinically and to the children. Dosing is a key component of clinical effectiveness in the field of physical therapy. Dosing of pediatric physical therapy and other rehabilitation services for children with CP and other developmental disabilities has been identified as a national priority.3
Pediatric physical therapy services, which promote motor development and independent function, can play an important role in mitigating the effects of lifelong chronic disability as a result of CP on the individual, the family, and society.4 The lifetime cost of care for children with CP is approximately $1 million per person.5 Understanding how to effectively dose pediatric physical therapy interventions has the potential to result in improvements in the health, motor, and independent skill development of children with CP. Yet, in most cases, we are unable to accurately prescribe an optimal dose of physical therapy interventions for a child with CP.
Improvements in outcomes following interventions designed to improve bone health,6 muscle strength,7 and functional performance8 of children with CP suggest that dosing may need to reach a specific threshold to create change. Research over the past 20 years also has demonstrated the powerful influence of family,9 environment,10 and comorbidities11 on outcomes. Given the multiple influences (eg, variation in age, level of severity, environment, other characteristics) on the outcomes, hypothesis-driven research about dosing is a necessary next step for pediatric physical therapy.
Dosing, in this article, is operationally defined within the context of its parameters, which include: (1) frequency, or the number of sessions a week and number of weeks; (2) intensity, or how strenuous the exercise is each session; (3) time, or the amount of time per session; and (4) type, or the type of exercise that is performed.12 Parameters can be varied to individualize an exercise program for a patient's needs and preferences. For example, aerobic exercise for heart conditioning of a lower intensity for a longer time can produce the same benefit of a higher intensity for a shorter time.13 A similar concept is true with exercise that targets muscle and bone.13,14
CP and the ICF Model
The ultimate goal of physical therapy for children with CP is functional independence to the best possible extent. Functional independence includes aspects of activity, the execution of tasks, and participation or involvement in life situations.15 Functional independence also includes aspects of performance, that is, what a person actually does in everyday life.15 To maximize functional independence, physical therapy interventions usually target 1 or more of the 3 domains of the ICF (Fig. 1): body structures and function (eg, musculoskeletal or central nervous system), activity (eg, walking), and participation (eg, ability to play community sports). Physical therapy interventions also target changes in capacity (ie, a person's inherent abilities).15
Pediatric physical therapy interventions framed by the International Classification of Functioning, Disability and Health. Interventions are targeted at body structures and function, activity, and participation. Adapted and reproduced with permission of the World Health Organization from: Toward a Common Language for Functioning, Health, and Disability: The International Classification of Functioning, Disability and Health. Geneva, Switzerland: World Health Organization; 2002:9.
Improvements in 1 domain of the ICF may have a “ripple effect” and can be associated with improvements in other domains. For example, interventions aimed at improving muscle length are expected to affect gait, and improved gait has implications for wellness, muscle mass, bone mass,6 and cardiorespiratory fitness.16 Similarly, increased levels of activity are associated with increased levels of participation.17 Satisfaction with participation is associated with increased quality of life, promotes self-concept and physical health, and is an important patient-centered outcome.17–20 Yet, how interventions influence the relationships among these levels, such as muscle length, and gait or physical function remains unclear.21
The interrelationships among ICF domains are not linear, which complicates delineating optimal dosing parameters. For example, an improvement in quadriceps muscle strength does not always result in improved knee biomechanics during gait22 or improvements in community ambulation.21 Franki et al23 described 20 strengthening intervention studies that demonstrated improvements in the body structures and function and to a lesser extent in activity and participation. It is plausible that the effect of interventions may not directly and uniformly affect outcomes across all levels of the ICF as a result of mediating and moderating factors. Mediating factors are the intervening variables through which the intervention indirectly affects outcomes.24 Moderating variables are those factors that may modify the form, strength, or direction of the relationship.24 Hence, dosing thresholds for changes at the different levels of the ICF and for different children may be variable. As such, studying optimal dosing requires capturing more information about mediating and moderating factors.
Dosing studies need to establish dosing parameters for pediatric physical therapy interventions aimed at 1 domain of the ICF that can be “dosed” to effect meaningful, sustainable changes in other domains. For example, how much dosing and for whom can reducing spasticity improve activity and participation? To increase understanding of complex interrelationships among the factors that influence optimal dosing of physical therapy interventions, we have designed a multivariate model to conceptualize dosing parameters of interventions for children with CP. This model is intended to expand the types of inquiry for clinical effectiveness studies that may be useful for increasing knowledge about what interventions work for whom, and when.
Path Model of Dosing
The path model is intended to frame questions and guide designs for pediatric physical therapy effectiveness studies. Our model was developed through: (1) synthesis of the literature of efficacious interventions in children with CP, (2) discussion among the authors, and (3) discussion with basic science and pediatric physical therapy researchers (Kolobe and colleagues, unpublished research). The model is intended to inform research design and analysis and lends itself to statistical modeling techniques, such as structural equation modeling, that are well suited for the complex dosing parameters discussed previously. Ultimately, this model is intended as a framework to advance knowledge on mediating and moderating factors that shape dose-response relationships.
Any investigation of dosing parameters and the effectiveness of pediatric physical therapy interventions must take into account the amount and type of gains made by the child, as well as outcomes in body structures and function, activity, and participation. Using the ICF as a framework, with functional independence as the desired outcome, the proposed path model includes potential mediating and moderating factors of the dose-response relationship.
The path model for examining dosing parameters is presented in Figure 2. The premise of the model is that, for the pediatric population, how a type of intervention (focused on body structures, activity, or environment) imparts its influence on a child is mediated through the family, and its impact is moderated by the dose (frequency, intensity, time), to yield plastic structural and behavioral changes and improve functional independence. Family characteristics may mediate both the intervention type and dosing levels. Plastic structural changes in brain, muscle, and bone and behavioral changes in motor skill capacity may both be moderated by the child's characteristics. Community effects are exerted on the dosing parameters, family, and functional independence and, therefore, may mediate the relationship among type of intervention, dosing, and child outcome. Functional independence is what the person does with the newly acquired structural and behavioral (activity and participation) changes.15
Path model for evaluating dosing parameters for children with cerebral palsy. Dashed boxes represent characteristics of the constructs that warrant consideration.
In the following paragraphs, we present selected findings that support and inform the constructs of the path model. Our discussion will follow the model presented in Figure 2. We begin with different types of interventions, family, dosing parameters, community, and child characteristics that mediate or moderate the treatment responses in structures and function, capacity, and functional independence. In Figure 2, dashed boxes represent features of each construct that warrant consideration in studies designed to identify specific dosing parameters. We also underscore the importance of each construct in assisting physical therapy researchers and clinicians in identifying effective dosing parameters given variability in individual, family, and community characteristics.
Type of Intervention
The path model begins with the type of intervention (Fig. 2). Most interventions (strengthening, gait training, or learning to use a power chair) have a primary focus on changing body structures and function, activity, or participation outcomes. The “ripple effect” of positive outcomes, most often not uniform in magnitude of change or gain, can occur in other domains. Hence, an intervention must demonstrate that it is effective at least on 1 level of the ICF before studies about optimal dosing are undertaken. Another attribute of type of intervention is the mechanism by which change occurs. For example, did the strength training (body structures and function) include open-chain or loaded functional exercise? In this section, we will discuss the findings of various types of interventions that target the domains of body structures and function, activity, participation and that may be effective in producing change in 1 or more domains of the ICF.
Interventions focused on changes in body structures and function.
Stretching has demonstrated improvements in at least 1 domain of the ICF in children with CP, and multiple methods are used to apply stretch. In 7 studies on the effectiveness of passive stretching on range motion or spasticity25–31 in children with CP of varying levels of motor ability, only 1 study25 reported outcomes in the activity domain (gait speed). Passive stretching demonstrated improvements in spasticity and gait speed, but not passive range of motion.32,33 However, a combination of passive and active stretching demonstrated changes in passive range of motion, strength, selective motor control, spasticity, balance, and gait speed in ambulatory children with CP.34 Despite the benefits demonstrated among these studies, the stretching interventions were delivered in various ways—either passively or actively, with electrical stimulation, or with the assistance of a robot, splints, or a positioning device—making dosing comparisons across studies difficult. Passive stretching alone has not conclusively demonstrated effectiveness at any level of the ICF.35 Whether using robotics or positioning devices, stretching that combines active task-directed movement and passive range of motion shows promise.36
A variety of methods, including free weights, isometric, open- and closed-chain isotonic, body weight, weighted backpacks, pulley systems, isokinetic,7,37,38 and electrical stimulation,38 have been used to increase muscle force production. Systematic reviews of strengthening interventions with children with CP suggest that muscle force production can be improved,7,37 although a meta-analysis demonstrated a negligible effect.38 Nonetheless, the impact of strengthening interventions on the domains of activity and participation is inconclusive. Clinically meaningful effects on gait speed,38 gait kinematics,22 or gross motor function ability38 in ambulatory children with CP have not been consistently demonstrated. There are limited reports of the positive impact of strengthening on self-concept or quality of life.38,39
Skeletal loading interventions have produced inconsistent results in improving bone mineral density of children with CP.6,40,41 Type of skeletal loading may be an important factor. Types include static activities, vibrating platforms, use of static or dynamic standers, and a combination of weight-bearing and strengthening activities. These interventions may or may not be given in conjunction with growth hormone treatment, calcium and vitamin D supplementation, or bisphosphonates. Observed treatment effects are often greater in children who are ambulatory compared with children who are nonambulatory,6,40,41 suggesting that this characteristic of the child moderates the impact. For the prevention of osteoporosis and hip and spine deformity later in adulthood,42,43 it is not clear which type of skeletal loading is most effective for children who are ambulatory compared with those who are nonambulatory. Most reports on skeletal loading interventions have not reported changes at the level of activity or participation.6,40,41
Interventions focused on changes in activity.
Activity-based interventions such as treadmill training23 and upper extremity training8 in children with CP have demonstrated improvements in the domain of activity, and to a lesser extent participation and body structures and function. In general, treadmill training can affect endurance, gait speed, and community ambulation.23 Upper extremity training has demonstrated positive, but not always simultaneous, effects on all 3 domains of the ICF—changes in body structures and function,44 activity level,45 and participation.46 Yet, great variability exists in the way the interventions are applied. Treadmill training protocols utilize a self-selected pace, preset pace, or fast pace and include varying amounts of body-weight support.23 Variability in upper extremity training includes utilizing bimanual activities or constraining the use of the affected arm by putting the unaffected arm in a cast or mitten during constraint-induced movement therapy (CIMT).8
Interventions aimed at changing participation.
There is emerging evidence to support that participation-based interventions can affect body structures and function47 or activity.48 Examples of participation-based interventions with a positive impact on other domains of the ICF include powered mobility cars for infants,47 community-based fitness programs,49 and “context-focused” interventions.50 A randomized controlled trial compared outcomes of child-focused interventions (activities to improve range of motion and joint alignment and to promote normal movement patterns) compared with context-focused interventions (activities that modified the task or the environment).48 The results were inconclusive; gains in activity and participation in both groups were significant and equivalent. Law et al48 asserted that more information is needed about the dosing thresholds for improving outcomes across all 3 domains of the ICF for different types of interventions.
Family Characteristics
Family characteristics mediate the type of intervention and dose (Fig. 2), as all interventions are filtered in some way through the family to the child. Families serve as vehicles for many professional-mediated interventions, and their roles are not only a critical dosing parameter but also are all-encompassing. The family environment reflects each caregiver's emotional and behavioral responses to a child's condition as well as the physical environment of the family home. Follow-through by families on interventions aimed at strengthening, stretching, skeletal loading, and task-specific training is an example of how families mediate dosing.
Some known family characteristics that may influence dosing parameters and treatment effectiveness are parental physical, psychosocial, and socio-economic status.9,51–53 Attributes such as the quality of caregiver-child interactions are dynamic in nature and modify how the parent conveys and adapts various types of intervention to match the child's temperament and level of engagement. Therefore, these interactions may result in explicit or implicit changes in dosing levels and have major implications for long-term outcomes for child health and behavioral outcomes.9
Another mechanism that may explain familial influence is epigenetics. Epigenetics is defined as a functional modification of the deoxyribonucleic acid (DNA) that does not involve alteration of the sequence but rather changes in the chromatin environment or the histone proteins that regulate the operation of the genome.10 Transcription of the genome is regulated through signals or transcription factors that bind to specific DNA sites.10 Transcription factors are responsive to environmental stimuli.54 Throughout the life span, adaptation to both intrinsic and environmental stimuli may create a disposition for disease55 or influence rehabilitation outcomes,9,56 suggesting that epigenetics may be embedded in familial characteristics and, therefore, interact with dosing.
Community Characteristics
The community can mediate dosing parameters and functional independence outcomes (Fig. 2). Social support; respite; accessible transportation, buildings, and after-school activities; and access to health care and information can act as additional mediators of functional independence. Funding sources for health services (private, public, or both), number of health and rehabilitation services a child receives, and population density of the child's community may directly influence the frequency and duration of pediatric physical therapy services. Positive intervention approaches that promote community involvement and family-centered care can enhance overall parental satisfaction, empowerment, and mental health,4 which, in turn, can positively influence child outcomes. Community supports, such as accessible recreational programs, are positively related to participation outcomes57,58 (Fig. 2).
Dose
The dose attributes of frequency, intensity, and time are modifiable components of the model and are moderators of outcomes at the different levels of the ICF. Variability in frequency, intensity, and time is pervasive among intervention studies of all types and is a major limiting factor in developing guidelines for dosing parameters. Thresholds for frequency, intensity, and time for specific types of interventions to create sustainable changes have not been established. Guidelines exist for frequency, intensity, and time of specific types of interventions to increase muscle length,59 strength,60 and skeletal structure61 for children with typical development. These guidelines should be considered when developing parameters for frequency, intensity, and time for individual children with CP.
The American College of Sports Medicine recommends 60 minutes of daily physical activity, including stretching and strengthening activities 2 to 3 times a week, for children who are developing typically.60 Frequencies of 4 times a week of passive stretching for 9 months have demonstrated effective results in increasing hamstring muscle length in children with typical development.59 Results from 3 systematic reviews of interventions with children with CP with varying levels of severity23,35,62 and 5 additional studies28,34,63–65 demonstrated the frequency of passive or active stretching interventions, ranging from a one-time session, 3 to 5 times per week for 4 to 10 weeks, or 1 or 2 times per week for 9 months, with intensity and time spent stretching varying given the type of stretching performed. Reported strengthening interventions7,23,37,38 with children with CP who are ambulatory are generally 3 times a week for 6 weeks, although some are for 2, 4, 8, or 10 weeks, with variability among studies in intensity and time per session.
Similarly, variability in frequency per week, number of weeks, and intensity was a limiting factor in studies of skeletal loading for children with CP.40,41 Frequencies of reported skeletal loading interventions include 30 minutes 5 times a week for 2 months to twice a day for 30 minutes for 6 months,6,40,41 with no studies reporting the approximate amount of ground reaction force produced by the intervention. Frequency, intensity, and time (3 times a week, 8 times body weight, 8 months)61 of skeletal loading are important factors in producing sustainable treatment effects in skeletal structure in children who are developing typically. Longer-duration and higher-frequency interventions may be needed for children with CP who cannot tolerate similar ground reaction forces.14
Time spent practicing and practice in everyday life also may be critical factors in the link between capacity and performance. For example, in a randomized control trial comparing 10 days of 60 hours or more of either CIMT or bimanual training, similar gains were observed in the domain of activity for both interventions, and barriers to participation were reduced in both groups.46 Gordon et al66 reported similar improvements in capacity with similar treatment times of CIMT and bimanual training, with the bimanual training producing greater improvements in performance. Practicing activities at home with caregiver guidance67 is a way to increase practice time. Synthesis of evidence68 suggests more practice was better (eg, 90 hours over 15 days resulted in better improvement than 60 hours over 10 days). Time spent practicing also may be a factor in effectiveness of treadmill training. A 30-minute session, either twice a day for 2 weeks69 or twice a week for 6 weeks or more,16,70 improved endurance and gait speed. Frequency and time in treatment appeared to be critical to the success of either child- or context-based interventions.48 Thresholds for time to produce changes in performance given variation in age, level of severity, and intensity of work in a session warrant further investigation.
Child Characteristics
Identifying the optimal dosing parameters of any type of intervention also is dependent on each child's personal characteristics. The child's characteristics can moderate dose-related responses. Age, level of severity, comorbidities, preferences, and “readiness to change” can be important moderators of the dose-response relationship (Fig. 2). Higher levels of severity may be associated with decreased parental well-being51,71 and poor child health.11 Children with more severe involvement or comorbidities may have more motor abilities to gain in order to be even with their peers without CP or other health comorbidities compared with children with milder involvement.16,72,73
Children with CP who have severe cognitive or motor deficits have barriers to practicing and learning tasks and have poorer social and health outcomes.11 Treatment outcomes for children who are more severely involved may or may not include improvements in activity, such as improved gait speed or transfers,72 but may include improvement in other domains, such as bone density6 or quality of life.23 Conversely, a greater treatment effect may or may not be observed in children with more moderate motor deficits compared with children with mild deficits.46 Children with moderate involvement have the potential to improve more than children with mild deficits. Level of severity may be a key determinant of treatment outcomes and effectiveness, and the relationship may be curvilinear, not linear. Dosing based on level of severity should be a focus for upcoming investigations.
The interaction of level of severity and age has important implications for the timing of interventions to promote changes in motor skills. Established developmental skill acquisition trajectories for children with CP of varying Gross Motor Functional Classification System (GMFCS)74 levels can be used to identify critical ages for skill development or prognosis and expected benefit of interventions given the child's age at the time of treatment.
Age of the child and level of severity also have major implications for moderating the impact of treatments targeting the musculoskeletal system as a result of critical periods for plasticity of the system, the impact of brain injury on the development of the musculoskeletal system, and the ability of the child to tolerate interventions of high intensity and long duration. Two systematic reviews of interventions for increasing bone density in children with CP40,41 concluded that the heterogeneity in age, level of severity of CP, and the intensity of skeletal loading masked treatment effectiveness. Optimizing dosing of skeletal interventions must carefully consider how to modify frequency given differences in age, level of severity, and the ability of the child to tolerate different levels of loading.
A child's readiness to change—the combined effect of temperament, motivation, internal drive, willingness to please, and ability to follow directions and carry over/learn50,75—has important implications for timing of interventions and may moderate outcomes. The Canadian Occupational Measure (COPM) has been used to assist with goal setting and designing interventions to maximize “readiness to change.”48 The COPM enables parents and children to determine activities that are personally important and that may maximize motivation and internal drive. No matter the level of motivation and internal drive, children with a difficult temperament can affect parental behavioral and emotional responses,51 which may confound delineating treatment effectiveness.
When evaluating the dose-response relationship in the domain of performance, preferences for and satisfaction with activities76 may moderate treatment effects. Participation in daily life is highly variable given differences in children, families, and environments.53 Individual preferences for participation may be a reason interventions that target body structures and function or activity differentially affect participation. Satisfaction with level of participation also is critical for interpreting the impact of an intervention.53,58
Structural Changes
For children with CP, pediatric physical therapy interventions that target body structures and function primarily focus on changes in the nervous, muscular, or skeletal systems (Fig. 2). Pediatric physical therapy interventions capitalize on the plasticity of these systems and the critical periods for growth, development, and repair. Intervention studies of stretching, strengthening, and skeletal loading should consider critical periods for development of the musculoskeletal system and known parameters for positive plastic responses into dosing parameters.60,77,78 Critical periods of development for refinement of neural circuits79–81 and differentiation of the corticospinal tract82 offer potential for motor skill development. Interventions to combat disuse atrophy of systems from mobility restrictions during the life span should be considered.83
Changes in Capacity and Functional Independence
Motor skill changes, such as the ability to stand and cruise along furniture or sit upright independently, result in changes in capacity (Fig. 2). Changes in capacity can lead to improved performance and improved activity and participation,15 or increased functional independence. A disconnect between capacity and performance often is observed when a child with CP may be able to perform a skill in the clinic at the request of a therapist but fail to do so in real life. Thus, gains observed in the clinic as a result of an intervention may not be realized in everyday life. Explanations for this phenomenon include thresholds for motor learning, or the processes associated with practice or experience that lead to relatively permanent changes in the capability for movement,84 as well as contextual factors.85
Dose-related investigations and decisions about dosing parameters must reconcile the disconnect between changes in capacity and performance. Investigations of activity-based interventions such as treadmill training and upper extremity training demonstrate inconsistencies among studies in evaluating changes in both activity and participation or inconsistent treatment responses.
Implications for Research
The proposed model to evaluate dosing parameters highlights at least 2 important considerations for researchers interested in effectiveness research: (1) operationalizing the variables of interest for each component in the model and (2) obtaining a large enough sample size to ensure statistical power. The constructs in the path model should be operationalized and measured using valid tools. Because the potential exists for the number of measures to be high and cumbersome, consensus needs to be developed among researchers, clinicians, and families about which measures provide the most meaningful information.3 Measures also should be comparable across studies and should minimize the burden of data collection for research teams and participants.86
Observational studies that track characteristics deemed important in the proposed model will require large heterogeneous samples and most likely will require multicenter involvement. Study designs should include stratification by level of severity and age, either in sampling or in analysis, to account for the effects of severity and age. A minimum sample size of 200 participants is recommended for structural equation modeling24; however, given the large number of variables and the need for stratification, much larger sample sizes (eg, more than 400 participants) may be needed. Large-scale practical clinical trials87 that document child, family, environmental, and intervention characteristics may be more cost-effective compared with randomized controlled trials for delineating dosing parameters for each distinct intervention type.
Implications for Clinicians
Clinicians may find the path model a useful framework for clinical decision making about dosing parameters. Clinicians can use the path model as a framework to consider characteristics of the intervention, family, child, and community in conjunction with what is known about current intervention responses to guide decision making. Because path models are intended to guide scientific inquiry, at this time not enough evidence exists about the magnitude of the relationships proposed in the model to guide prioritization of dosing decisions. Structural equation modeling is well suited for evaluating the relationships among the constructs of the path model, and until such time that data are available, clinicians can use the model during assessment, interpretation of the assessment findings, and program planning to ensure that recommended interventions are likely to address the goals of individual families and children in meaningful and effective ways.
Conclusion
A multivariate model is proposed to expand the knowledge base about parameters for dosing interventions for children with CP, all of whom have their own unique set of individual, family, and environmental characteristics. The path model is ecological. It examines the child's response to interventions in a biopsychosocial framework and accounts for important factors that influence outcomes either directly or indirectly.
Studies designed to evaluate dosing need to consider components of the model to effectively move knowledge forward. Studies should focus on outcomes across all 3 domains of the ICF for impairment-focused, activity-based, or context-focused interventions while accounting for contextual and individual variation. More information about mediating and moderating factors of the dose-response relationship and the link among changes in body structures and function, activity, and participation on functional independence is foundational knowledge for developing effective practice guidelines. Multiple gaps in knowledge have been described, and a framework for conceptualizing dosing thresholds for individual children with CP has been proposed.
Footnotes
All authors provided concept/idea/project design, writing, and fund procurement.
A preconference course on this work was presented at the Combined Sections Meeting of the American Physical Therapy Association; January 21–24, 2013; San Diego, California.
This study was supported by a Research Summit III Conference Grant from the Section on Pediatrics of the American Physical Therapy Association, the National Institutes of Health (grant R13HD070615 to Dr Kolobe), the Eunice Kennedy Shriver National Institute of Child Health & Human Development, and the National Institute of Neurologic Disorders and Stroke.
- Received January 28, 2013.
- Accepted November 8, 2013.
- © 2014 American Physical Therapy Association
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