Activity, Activity, Activity: Rethinking Our Physical Therapy Approach to Cerebral Palsy
- Diane L Damiano
Abstract
This perspective outlines the theoretical basis for the presentation with the same name as the second part of this title, which was given at the III STEP conference in July 2005. It elaborates on the take-home message from that talk, which was to promote activity in children and adults with cerebral palsy and other central nervous system disorders. The author proposes that the paradigm for physical therapist management of cerebral palsy needs to shift from traditional or “packaged” approaches to a more focused and proactive approach of promoting activity through more intense active training protocols, lifestyle modifications, and mobility-enhancing devices. Increased motor activity has been shown to lead to better physical and mental health and to augment other aspects of functioning such as cognitive performance, and more recently has been shown to promote neural and functional recovery in people with damaged nervous systems. Although the benefits of fairly intense physical exercise programs such as strength training are becoming increasingly well recognized, few studies on the positive effects of generalized activity programs have been conducted in individuals with cerebral palsy. More research is needed and is currently under way to design and test the efficacy of activity-based strategies in cerebral palsy.
The familiar mantra of “practice, practice, practice” was frequently evoked by speakers and attendees at the III STEP conference in July 2005. Although practice is clearly important for the development and improvement of motor skills, a perhaps more appropriate and timely mantra for physical therapy rehabilitation will be suggested here and used as a basis for this perspective: “activity, activity, activity.” From a personal point of view, the phrase “practice, practice, practice” connotes a deliberate and structured session where one focuses on a specific motor task, such as my own fairly unpleasant childhood memories of trying to master the piano (unsuccessfully). It may be perhaps that “practice” is more relevant to upper-extremity rehabilitation strategies, whereas the term “activity” may be better suited to lower-extremity rehabilitation due to the fundamental differences between typical functioning of the upper versus lower extremities. The upper extremities are used primarily for a wide variety of skilled and discrete fine motor tasks, many of which may be performed unilaterally, with or without assistance from the contralateral limb.
Task-related or other intense upper-limb training paradigms, such as constraint-induced movement therapy, have been shown to be effective in the management of cerebral palsy (CP) and other central nervous system (CNS) disorders,1–4 and the common aspects of successful approaches are functional relevance, cognitive engagement, and massed practice. In contrast, the most common functions of the lower extremities tend to be gross motor activities that involve repetitive, reciprocal, coordinated motions of both extremities in order to move through space and that often require little conscious effort once under way. Effective lower-extremity training paradigms, while intensity may be similar to that in the upper extremities, would more likely involve activity-based strategies that include repetition of various cyclical motions such as walking on a treadmill or cycling, which take advantage of “motor programs” to the extent that these exist and are available or accessible in a given patient.
Echoing the triplicate use of the word “activity,” 3 of the major potential outcomes from an activity-based approach will be discussed in this article. These are: (1) preventing secondary musculoskeletal impairments and maximizing physical functioning, (2) fostering the cognitive, social, and emotional development of the child, and (3) developing, maintaining, and perhaps restoring neural structures and pathways.
The first potential outcome of those listed above has the greatest clinical and scientific support by far compared with the other 2 potential outcomes. It is common knowledge that regular and fairly intense levels of activity throughout the lifespan are important components of optimal health and functioning for all individuals. In fact, helping people become or remain as active as possible is one of the fundamental missions of the physical therapy profession. The “Introduction” to the Guide to Physical Therapist Practice,5 which was published by the American Physical Therapy Association in 1997, stated that physical therapists help people5(p1171):
- alleviate pain
- prevent the onset and progression of impairment, functional limitation, disability, or changes in physical function and health status resulting from injury, disease, or other causes
- restore, maintain, and promote overall fitness, health, and optimal quality of life.
It further stated: “Progression to pathology—or from pathology to impairment to disability—does not have to be inevitable”5(p1174) and that physical therapists can “prevent” or “buffer” this process. Accepting that better physical conditioning leads to better health and prevention or reduction of secondary impairments, a logical corollary to this is that not moving enough or correctly can produce devastating physical or physiological consequences to the muscles, bones, and cardiorespiratory system. These secondary changes contribute to a vicious cycle whereby a disability leads to deconditioning that, in turn, worsens the level of disability.6 Muscles need to be stretched to their limits in CP on a regular basis to maintain length,7 and they need to be loaded adequately and frequently to maintain strength (force-generating capacity).8 Similarly, in people with CP as in all people, bones need compressive loads to stay strong, and the heart and lungs need to be exercised at moderately intense levels on a regular basis to maintain endurance and fitness. People with CP are already at a disadvantage with respect to achieving adequate levels of physical functioning because muscles, bones, and the cardiorespiratory system are not fully developed before the brain injury occurs and, therefore, are likely to have a lower starting point as well as slowed progress in developing these structures. Furthermore, the aging process for everyone involves a gradual decline in muscle strength, elasticity, and bone density,9 which can be particularly devastating for people with motor disabilities who are already compromised in many of these areas and have little reserve to counterbalance these negative effects. Consequently, a startling number of individuals with CP lose the ability to ambulate in early adulthood and experience a loss of independence much sooner than their age-matched peers without CP.10
The second potential outcome emphasizes the inherent importance of activity in a child's overall development. Activity, like the often-heard quip about voting, should probably be done “early and often” while the nervous system and the musculoskeletal system are the most adaptable. While this seems intuitively obvious, strong scientific support is lacking to support this assumption, and in fact, some studies on physical therapy intervention in infants who were at high risk for developing CP have generally failed to demonstrate the effectiveness of early physical therapy intervention alone or in comparison with other alternatives.11–13One notable exception was a randomized trial by Girolami and Campbell14 that used traditional methods as well as postural strengthening techniques, which did show a significantly positive effect on motor (trunk) control in the treatment group.
It is fundamentally known that motor activity is necessary for interaction with the physical world such as speaking, eating, dressing, or traversing through space. Any motor disability or injury will compromise and limit the ability to move or at least to move in an efficient and effective manner. For people who have a developmental disorder such as CP, movement difficulties also may have profound negative effects on cognitive, emotional, and social development; however, these potential consequences have not been adequately investigated. Clinical dogma, unsubstantiated by research, once held that movement quality be emphasized over movement quantity or functionality for a better long-term outcome. In contrast, current thinking is shifting toward a view that children need to be as mobile as possible, regardless to some extent of the manner chosen by them or for them (eg, through the prescription of a mobility device). Although providing an “external” means of mobility is certainly not the same as promoting more voluntary activity, a recent review on powered mobility does emphasize the personal and social effects of offering children, in this case those with more severe motor disabilities, increased mobility options, stating that it “has revolutionized the life experiences of many disabled persons, enabling independence, social interaction, and even facilitation of socio-psychological development”15(p164) and, contrary to conventional wisdom, does not limit future self-mobility and may even stimulate it.16,17
This newer perspective has led to increasing use of mobility devices or motorized wheelchairs for children with moderate to severe involvement. It also has been shown that children who are given more opportunities to be mobile tend to be less likely to develop a passive, “help me” personality and are more likely to be independent and have an “I can do it” attitude.18 The use of self-propelled mobility devices or other methods of accelerating the achievement of motor milestones in children with varying levels of motor disabilities is assumed to have similarly positive effects; however, more data are needed to support this assumption. Investigators only now are beginning to explore the outcomes of early intense training programs in children with CP and other disabilities on multiple aspects of development (DA Ulrich, personal communication, December 2005). Exercise has been shown to have a beneficial effect on depression19 and to reduce the rate of cognitive decline in elderly people.20 Animal studies suggest that activity may enhance learning and memory throughout the lifespan,21 presumably through an increase in brain growth factors.22
The third potential outcome is related to the increasing recognition of the role of activity in the normal development and maintenance of the CNS and its proposed role in promoting neural recovery in damaged nervous systems.23–25 Authors of a review article titled the “Neurobiology of Exercise” made the following comment that is very apropos to this discussion: “Although the general physiology of exercise has been a very active area of research during the past 40 years, the neurobiology of exercise has been virtually absent from public health discourse.”22(p345) The authors then went on to state that: “this is surprising because emerging evidence suggests that physical activity may confer health protective benefits for several neurological diseases.”22(p345) Recent advances in neuroscience have highlighted the importance of motor activity for the establishment and reinforcement of neural pathways, with the converse occurring when activity is reduced. The degradation of neural structures is most dramatically apparent in the case of amputation or a complete spinal cord injury where major cortical reorganization occurs such that areas of the brain that were involved in the control of now-missing or no-longer-innervated body parts become infiltrated and replaced by pathways that control other body areas that are still operational.26
In contrast to spinal cord injury and adult stroke, where the patients did have an intact and normally functioning nervous system prior to injury, CP is a developmental disability, and the injury occurs before the nervous system has matured. This differentiating factor has both positive and negative effects on the potential for neural plasticity in people with CP. On the positive side, dramatic evidence of the great potential for neural plasticity has been reported in pediatric patients. Some investigators27,28 have reported on children with intractable seizures who underwent complete hemispherectomy, with very young patients typically showing surprisingly minor cognitive and motor deficits and extensive brain reorganization. Investigators who have studied these patients have gone on to suggest that identifying how different cortical areas respond and reorganize after these induced lesions might serve as “a basis for specific training promoting the optimal reorganization of cortical networks to enhance motor control”27(p64) in people with other cortical lesions. While the prognosis for a more complete recovery after a hemispherectomy is clearly better for younger children, a recent report detailing the marked improvement over time in a 14-year-old girl who had this procedure concluded that “the critical age beyond which functional reorganization takes place after a unilateral injury in childhood is not known.”28(p967)
If the capacity for reorganization and recovery is so great in children, why is CP so prevalent and often so devastating? Does the damage occur too soon before the cortical structures have developed sufficiently to allow for the capacity to recover, as seen in very young kittens that are blindfolded soon after birth and can never regain their sight?29 One stimulus for recovery in patients with one intact hemisphere is believed to be the presence of bilateral projections to the intact hemisphere in addition to normal or near-normal motor and sensory input from the residual hemisphere. Perhaps this is one explanation for why children with unilateral CP (ie, hemiplegia) tend to be more functional than their counterparts with bilateral injuries,30 where both sides experience similar types of damage and thus cannot “help” each other recover.
On the negative side, while the developing brain is more malleable and may be able to respond to interventions that could redirect this process, an aggressive developmental pruning process occurs in infancy by which unused or less-used pathways are eliminated and more frequently used motor pathways are reinforced. The earliest movements of many children with CP are clearly different and distinguishable from those who do not have CP.31 If these movements persist and are reinforced, this sets the stage for neural adaptations that may restrict future movement options and negatively affect motor prognosis. Although these changes are not necessarily immutable, they may be very difficult to reverse once they are well established.26 This forms the rationale for why early intervention has such potential for establishing or reinforcing functional motor pathways early in development before they are “lost.” Prevention of damage, whether neural or physical, is always preferable to, and likely to be more successful than, trying to repair it after it has already occurred. As the state of knowledge evolves, the physical therapy profession should be well positioned to assume a major role in harnessing the inherent plasticity of the brain and directing changes in neural structures that will produce improved functional performance. The key to these changes is likely to be through prolonged and intense activity that can be accomplished by focused therapy programs, alone or in combination with the use of medication or other novel strategies, as well as by making recommendations for promoting a more active lifestyle outside of the clinical setting.
Evidence for Traditional and Emerging Physical Therapist Practices for Cerebral Palsy
The hallmark of CP is disordered motor control as a result of a developmental brain lesion. Cerebral palsy is, in reality, a collection of disorders with varying etiologies and presentations and is often associated with other sensory or cognitive disabilities that may limit participation as much as or perhaps more than the motor limitations.32 No cures are available or imminent for the majority of the disorders that have been categorized as CP, and potential positive effects of most interventions on most individuals with CP tend to be modest at best.
Physical therapy, along with orthopedic surgery, has been the mainstay of the rehabilitation management of CP for decades. Pediatric therapy has a clear and important role in helping children and their families cope more effectively with the disability through education, advocacy, functional training, and recommendations for adjunctive devices or therapies to optimize function. What is less clear is the extent to which physical therapy can alter the motor prognosis or make a clinically significant change in the level of disability or degree of participation for any given child. Traditional therapy approaches have been shown for the most part to be marginally beneficial33 and demand serious reconsideration by those who still advocate them. In recent years, those who seek or provide care for CP have witnessed the burgeoning of several new therapeutic approaches with varying degrees of scientific support, including conductive education and Adeli suit programs among others. Pediatric neurorehabilitation in contrast to adult neurorehabilitation seems to be more “susceptible” to packaged approaches that incorporate many different types of exercises, making it more difficult to decipher the active ingredients that may be producing any positive treatment effects that are seen. The physiological or neurophysiological mechanisms that may underlie a multifaceted treatment approach may be more difficult to decipher and therefore more difficult to evaluate from a scientific standpoint. Studies that evaluate a specific well-defined treatment or those that use large rigorously obtained databases with sophisticated statistical analyses, such as the efforts by Horn and colleagues to get inside the “black box of rehabilitation,”33 are very much needed in this field so that we can start to identify what specific treatments, components of treatments, or “doses” of treatments work and to ultimately be able to prioritize treatment options based on relative efficacy in specific patient groups.
An example of a specific type of exercise with a clear physiological basis that has been the focus of multiple studies in CP as well as in many other disorders is strength or resistance training. Although the rationale for strengthening people who have weakness as a result of an orthopedic injury is straightforward, the use of strengthening for those who have reduced muscle strength as a direct or indirect result of a brain lesion has been far more controversial and was considered contraindicated until just recently. The main reason for this emerged from neurodevelopmental therapy approaches, which espoused for many years that one should “never strengthen spasticity” because this would only serve to worsen spasticity and make patients stiffer. Based on research evidence to the contrary, the incorporation of strength training into physical therapy regimens for people with CP and other CNS disorders has become increasingly prevalent over the past decade. A systematic review published in 2002 listed 10 studies that showed consistent and significant gains in strength as a result of varied short-term programs in both the upper- and lower-extremity muscles in individuals with CP.8 Evidence negating the claim that spasticity may worsen as a consequence of strengthening has also been reported.34,35 Resultant changes in motor functioning, such as increased gait speed, and the level of activity were generally more modest, and participation outcomes were not addressed.
A more recent summary of systematic reviews on strengthening across multiple health conditions suggested that the duration may need to be longer than typically studied for substantial gains in body structures and functions, activity, and participation to be realized.36 Achieving and maintaining an adequate level of physical conditioning requires a long-term commitment to exercise for all individuals, and those with disabilities are no exception. The marked physical and functional improvements reported in patients with other chronic disabilities as a result of intense and prolonged physical conditioning programs after the same patients had reached a plateau after more traditional approaches suggested that previous treatment protocols may not have been sufficiently intense.37,38 That is, patients were probably “under-rehabilitated” and failed to achieve the recovery they were capable of achieving.
Since the 2002 review8 was published, other research studies have been published evaluating strength training or similar intense programs that included strengthening as a component in CP, and the results have been similarly encouraging.34,39,40 In the review published in 2005 in Physical Therapy that discussed the evidence on the effectiveness of strength training programs across all areas of physical therapist practice,36 the results across disorders were markedly similar to those reported for CP. Besides the short duration of programs, failing to use a sufficiently intense training load was noted in several studies that not surprisingly showed minimal or no effectiveness, and this factor should be considered carefully in the design and evaluation of clinical programs or research studies. The physiological principle underlying strength training is that the load should be close to, but not more than, maximum to safely and effectively induce changes in the muscle.41
Only recently has the use of treadmills in CP been reported, with very encouraging results42–44 that mirror the positive results from the far more extensive work done with patients with spinal cord injury,45,46 stroke,47 and Down syndrome.48 This evolution makes sense because strengthening is only one aspect of physical function; therefore, training programs that focus only on that aspect are limited in their effect on function. Activity-based programs such as treadmill training or cycling that can be designed to address other aspects of motor performance such as endurance and coordination in addition to strength are likely to produce even greater outcomes. Strengthening, because of its intensity and the need for the muscles to rest and recover, is not meant to be performed for long durations at frequent intervals. In contrast, activity is best if done more frequently and with varying intensities and types of programs so that secondary consequences of motor disorders can be better avoided or remediated. The type of activity that is needed to facilitate neural reorganization and recovery is just beginning to be understood. Greater intensity (in the level of muscle activation or numbers of repetitions), greater challenge (eg, trying to solve a motor or cognitive problem), or the use of specific sensory modalities such as electrical stimulation all have been shown thus far to augment neural plasticity.26,49,50
Summary and Conclusions
As evident at the III STEP conference, this is an incredibly exciting time for those working in the field of neurorehabilitation, particularly for physical therapists who are likely to play a pivotal role in the development and implementation of motor strategies to facilitate optimal restoration of function. As movement scientists, therapists who treat people with CP need to optimize their limited therapy time by eliminating those approaches or treatment components that have only marginal positive effects and replace them with evidence-based exercise protocols shown to be more effective in improving current, and potentially future, functioning. In addition, we need to identify more ways to help their patients incorporate “activity, activity, activity” into their lifestyles. The promotion of activity is not in conflict with ecological approaches, because activity can and should occur in natural, everyday settings whenever possible. However, for people with greater physical challenges or for more intense conditioning or training, exercise equipment or computerized devices may need to be utilized.
It becomes increasingly difficult over time for elite athletes to break individual sports records as human limits are approached. In contrast, the state-of-the-science in neurorehabilitation suggests that we are not even close to approaching the human limits for physical and neural recovery in many disorders. A growing body of scientific data, much of which was published in the last few years since the turn of the millennium, strongly suggests that activity-based strategies, which are within the purview of physical therapy, are one of the keys to unlocking the now far brighter potential for functional recovery.
Footnotes
- Dr Damiano thanks the National Institutes of Health and the United Cerebral Palsy Research and Education Foundation, which have provided the major funding for her research efforts. She also thanks the III STEP conference for inviting her to participate.This article is based on a presentation at the III STEP Symposium on Translating Evidence Into Practice: Linking Movement Science and Intervention; July 15–21, 2005; Salt Lake City, Utah.
- Received December 20, 2005.
- Accepted June 7, 2006.
- Physical Therapy
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