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Maximizing Participation During Walking in Children With Disabilities

Is Response to Unpredictability Important?

Gosselin, Dora, PT, DPT, PCS; Wright, Alexis, PT, PhD, DPT, OCS, FAAOMPT; Sole, Gisela, PT, MSc(Med) Exercise Science, PhD; Girolami, Gay, PT, PhD; Taylor, Jeffrey, PT, PhD, DPT, OCS, SCS, CSCS; Baxter, G. David, PT, TD, BSc(Hons), PhD, MBA

doi: 10.1097/PEP.0000000000000575
SPECIAL COMMUNICATION

Walking ability is one of the primary components of human motor function, and interventions aimed at improving walking ability are common in physical therapy, particularly in children. One element encountered in a participatory, or natural, environment is unpredictability, defined as the presence of an unexpected obstacle, stimulus, or alteration of the environmental conditions. Little research has assessed the influence of unpredictability on biomechanical adaptations to walking in children who are developing typically or children with motor disabilities. A variety of impairments may result in an inadequate response to unpredictability, and we propose that there may be a relationship between response to an unpredictable visual cue and mobility-based participation.

We believe that a child's ability to respond to unpredictable circumstances while walking may provide additional information regarding participation limitations that have yet to be captured in existing clinical gait tools.

High Point University (Drs Gosselin, Wright, and Taylor), High Point, North Carolina; University of Otago (Drs Sole and Baxter), Dunedin, New Zealand; University of Illinois at Chicago (Dr Girolami), Chicago, Illinois.

Correspondence: Dora Gosselin, PT, DPT, PCS, High Point University, One University Pkwy, High Point, NC 27268 (dgosseli@highpoint.edu).

Grant Support: This work was supported by a grant from High Point University Research and Sponsored Programs, High Point, North Carolina. Additional support was provided by an APTA Academy of Pediatrics Mentored Grant and a NTDA Mini-Research Grant.

The authors declare no conflicts of interest.

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INTRODUCTION

Participation is an individual's ability to function within society: one's involvement in a real-life situation.1 Despite similar levels of enjoyment in participatory activities,2 , 3 the variety and types of the participatory activities of children and youth with disabilities are less when compared with peers who are developing typically.2 , 4 For example, children with cerebral palsy (CP) participate in a narrowed range of activities, 16.8 out of 49 designated activities, compared with peers who are developing typically who participated in 26.2 out of 49 activities. Children with CP participated at half the frequency of their peers who are developing typically: twice in 4 months compared with once a month, respectively.2 Children with disabilities tend to participate through more passive activity,4 with higher levels of adult involvement,5 and in more informal social activities.6 Participation is a complex and multidimensional concept that represents individual interests and desires. For children with CP in particular, impaired walking performance has negative effects on participation and physical quality of life.7

The ultimate goal of physical therapy intervention is to improve a child's participation in ways that the child and caregivers perceive as meaningful. As such, it is important that physical therapy assessment and intervention target elements that improve a child's participation. To do this, therapists must be aware of the requirements of the environment(s) within which their patients desire to participate, as well as be able to analyze the impairments that result in a child's decreased ability within the specific environment.

Because walking is one of the primary components of human motor function, interventions aimed at improving walking ability are common in physical therapy, particularly in children. For children with disabilities who are walking, an assessment of ability to walk in a participatory or real-life environment requires assessment of a more comprehensive set of elements of gait than what is typically assessed (eg, gait speed and energy expenditure). We believe that a child's ability to respond to unpredictable circumstances while walking may provide additional information regarding participation limitations that have yet to be captured in existing clinical gait tools. We propose that a better understanding of how children respond to unpredictability may foster the development of innovative interventions to improve a child's gait performance in real-life walking environments, potentially resulting in improved levels of participation and quality of life.

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THE RELATIONSHIP BETWEEN MOBILITY AND PARTICIPATION

A number of studies have confirmed the relationship between higher levels of mobility and gross motor functioning and increased participation.2 , 8–11 Pediatric physical therapists should consider participation as they collaborate with children and their families to develop goals and design interventions aimed at maximizing participation.

In an attempt to more accurately describe the environment in which an activity or participation is being executed, the International Classification of Functioning, Disability, and Health (ICF) proposes the qualifiers of capacity and performance. Capacity defines the ability of a person in a standardized environment, while performance defines what a person does in a natural environment.1 Recently, the gap between laboratory and clinic-based gait assessment (capacity) and real-world function (performance) of children with CP has been investigated by a group of researchers looking for mediating effects of activity performance on measures of activity and walking capacity and participation. The group concluded that “the relation between what an ambulatory child with CP is able to perform in a clinical setting and their participation in life is significantly mediated by what they actually do motorically in the day-to-day life.”12

Children with CP who have a Gross Motor Function Classification System of level I have the highest participation in activities with friends and outside the home, suggesting that the ability to walk without restrictions increases participation.11 This finding emphasizes the importance of understanding the demand of gait performance outside the home and when with friends, and warrants consideration and assessment of a more comprehensive set of elements of gait than those that are commonly considered (ie, gait speed and energy expenditure).

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THE GAP IN MEASURING PARTICIPATION

Within the field of pediatric physical therapy, there are very few gait assessment tools that selectively measure participation.13 Two recent systematic reviews identified, evaluated, and reported on variables and psychometric properties of pediatric gait assessment (PGA) tools.14 , 15 The majority of PGA tools included in these reviews measure the body structure/function (6/24) or activity (24/24) components of the ICF.16 , 17 Only 1 tool, the Community Mobility Scale includes a component that assesses ability in the participation domain (Table). For example, the commonly administered 6-minute walk test measures heart rate, blood pressure, and oxygen saturation (body structure/function), and total distance walked (activity). Assessment of the body structure/function and activity domains of the ICF is important for monitoring progress as well as for choosing interventions; however, limiting assessment to these 2 domains may fail to accurately assess the way that a child walks in a participatory environment, arguably the most important from the child/parent point of view. Participatory environments are inherently more demanding than laboratory settings because they take into account other people, changes or shifts in environmental requirements, and higher-level tasks. Existing PGA tools are limited in their ability to capture these more complex components of gait. Of the 24 clinical gait tools included in the reviews, all included a measurement of activity but only 1, the Community Mobility Scale, included a measure related to participation. These findings emphasize the importance for rehabilitation professions to (1) understand the requirements of the participatory environment in which the child desires to function; (2) assess what the child must do to safely and efficiently walk in that environment; and (3) design, implement, and progress focused interventions to improve the child's performance. An assessment of gait performance, not capacity, will yield a more accurate representation of a child's gait ability in a participatory environment.

TABLE

TABLE

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THE CONTEXT OF WALKING

While standardized gait and observational gait assessment are important, a comprehensive understanding and assessment of a child's participatory environment is needed for successful intervention. To provide structure for such assessment, we propose a term, the context of walking (CoW), as a concept that encompasses (1) the environment; (2) the task or the purpose of the movement; and (3) the individual (Figure 1). Every CoW has a net demand, determined by the combined requirements of the task, the environment, and the individual's capacity (Figure 2). An individual's capacity is defined as the walker's ability to respond to the requirements of the task and environment posed in the CoW. The threshold for walking capacity in each CoW demand is not fixed because an individual's capacity varies based on a number of elements, including neuromotor health and cognitive load.18 In addition, participatory environments are constantly changing, moment-to-moment and episode-to-episode, resulting in an ever-changing demand of the CoW. This resultant CoW may eventually surpass an individual's capacity, resulting in gait modifications (posture, movement) to fully and safely complete the task. A healthy individual may easily be able to generate an adequate response to the demand of the CoW (Figure 2a) whereas a person with movement impairments may require a larger, and, potentially, insufficient response to the same demand (Figure 2b). The differences in the requirements of the CoW between the scenarios in Figures 2a and 2b are only influenced by the individual's capacity, which, in Figure 2b, could be the result of a movement impairment.

Fig. 1

Fig. 1

Fig. 2

Fig. 2

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UNPREDICTABILITY

Unpredictability can be defined as the presence of an unexpected obstacle, stimulus, or alteration of the environmental conditions. Because the presence of unpredictability is an unavoidable component of a participatory or real-life walking environment, we propose that a child's ability to respond to unpredictability is one of the less traditional, but critical, elements of gait that must be assessed. The challenge with unpredictability is that it often necessitates an unplanned response, and the frequency, magnitude, and interaction of unpredictable events are infinite.

Unpredictability significantly impacts an individual's environment, directly impacting the net demand of the CoW. Unpredictability runs along a continuum ranging from persons walking ahead of you slowing their gait speed to respond to a door unexpectedly opening, to rapidly having to change speed to avoid contact when an automobile runs a red light. Each circumstance requires having the capacity to respond efficiently and safely in both scenarios. In contrast, an individual with impairment, and a decreased individual capacity, may have decreased efficiency or an inadequate ability to respond (Figure 2b). Influences of unpredictability on the components of the CoW have been explored, demonstrating that unpredictable circumstances impact performance and movement strategy, even in healthy individuals.19–22 Healthy adults use less efficient strategies, including multiple anticipatory postural adjustments, and tethering of the center of mass and the base of support in unpredictable conditions, confirming that unpredictability does increase the net demand of the CoW.19

The consequences of unpredictability are more significant for adults with balance impairment. Schulz and colleagues23 studied the difference in response between balance-impaired and unimpaired women to an anterior or posterior waist pull of unknown magnitude or direction. Participants in the balance-impaired group took additional compensatory steps because their initial step was not sufficient to stop the momentum of the waist pull. We can use the method of this study to consider the influences on the CoW. A balance impairment decreases an individual's capacity to respond and a waist pull of unpredictable direction would increase the complexity of the environment. Our model would suggest that, to maintain a safe CoW in this circumstance, the task or purpose of the movement must be altered to sufficiently neutralize the net demand of the CoW. This alteration could occur in a number of ways (ie, decreasing gait speed or increasing step width).

Little is known about developmental maturation of children's responses to unpredictability while walking. Woollacott and Assaiante22 used magnets to unexpectedly restrain the swing leg as children moved from standing to initiating gait and found that a child's ability to generate compensatory postural adjustments in the magnet condition matured with development, as evidenced by a decrease with age in response variability (stepping with the nonperturbed leg). Children in the oldest age group, (4-5 years), demonstrated the least variability and changes in kinematic and muscle recruitment patterns compared with younger children, confirming a developmental trajectory in response to unpredictability.

The aforementioned studies substantiate the importance of assessing response to unpredictability by demonstrating the existence of compensatory responses in individuals with and without balance impairments, as well as developmental changes in response to unpredictability. The strategies that are exhibited by children as well as individuals who are healthy and balance impaired (ie, increased variability and error and tethering of the body segments) are also observed in immature walkers and in children with CP.

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THE RELATIONSHIP BETWEEN MOBILITY, PARTICIPATION, AND UNPREDICTABILITY

An individual's ability to walk safely and efficiently in an open environment requires that they have mature postural integration and the ability to respond to unpredictability using either a feed-forward mechanism or a successful compensatory response.

Our focus is on children with CP; however, limitations in participation that are related to mobility have been confirmed in children with other motor disabilities (ie, spina bifida and developmental coordination disorder),4 and these groups should be included in future studies.

Research confirms that individuals respond to unpredictability using compensatory strategies. Recently, Malone and colleagues24 looked at the differences between predictable obstacle crossing in children with and without CP, and Dixon and colleagues25 , 26 investigated how children with CP change directions while walking. Both research groups demonstrated differences in the way that children with CP negotiate the increased demand in the CoW (obstacle crossing and turning, respectively), compared with children who are developing typically. Given these findings, it is possible that one reason children with CP have greater difficulty walking in more demanding CoWs is their reduced internal capacity to generate the compensatory strategies necessary when unpredictable circumstances exist in the CoW.

Increased demand of the task and/or environment as well as unpredictability requires walkers to make real-time coordinated adjustments to posture and movement. Children with CP may have impairments in body structure and function elements (ie, increased spasticity, decreased trunk control, and decreased selective voluntary motor control) and functional activities (ie, difficulty with gait speed control and negotiation of uneven surfaces) that have consequences for their ability to efficiently and safely respond. It is possible that a diminished internal capacity response to unpredictability in children with CP may add to the challenge of walking and could negatively influence social interactions and participation when navigation of more demanding environments is required.

No studies to date in pediatrics have specifically evaluated the effect of mid-gait unpredictability on the biomechanical variables of gait in children. We believe there is a need for enhanced knowledge about how children (with and without CP) respond to an unpredictable visual cue while walking and will carry out an innovative protocol that may begin to elucidate differences in responses between children with CP and their developing typically peers. Nearly all pediatric physical therapists (87%-90%) treat children with CP,27 and gait training is a very common intervention,28 which warrants beginning to understand the influences of unpredictability on gait is warranted in this group. In addition to the condition of unpredictable visual cues, our protocol will investigate the biomechanical variables of both groups of children when walking and turning in an environment with fixed visual cues. We hypothesize that the differences between the groups will be more significant as the requirements of the CoW, and subsequently the net demand of the CoW, increases. In addition to the walking conditions in our protocol, subjects will also complete a number of clinical tests, including selective motor control and balance testing, that will allow us to look for relationships that may exist between these ICF body structure/function and activity-level assessments, and gait variables; this may provide more information about potential interventions to improve gait performance when the CoW requires an unpredictable change of direction. Because it is possible that there is a relationship between internal capacity to respond to unpredictability and mobility-based participation, we will use a validated questionnaire29 to investigate this possible link.

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IMPLICATIONS FOR FUTURE RESEARCH

More research to investigate the effect of unpredictability in the CoW is important; however, we also believe that clients may benefit when clinicians have an increased awareness of the importance of assessing their clients' ability to respond to unpredictability. Future studies should investigate children's responses to an unpredictable visual cue while walking; however, there are an infinite number of unpredictable scenarios (ie, auditory, visual distraction, cognitive demand, and object transportation) that should be investigated with the goal of developing a comprehensive assessment of walking performance, and—in turn—a better understanding of interventions that improve the ability to respond to unpredictability.

The current level of PGA does not incorporate an element of the child's ability to respond to unpredictability, and therefore does not adequately capture a child's ability to walk in a participatory environment.

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ACKNOWLEDGMENTS

I gratefully acknowledge Professor Leigh Hale for her support of this idea and her role as an advisor on my PhD Committee.

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REFERENCES

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Keywords:

cerebral palsy; children; gait; participation; variability

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