Significant growth and interest in the field of rehabilitation medicine has been fueled in part by advances in rehabilitation science within an interdisciplinary research model (DeLisa, 2004). More importantly, research in rehabilitation has witnessed the application of the scientific method to specific functional problems such as the recovery of walking in neurologic populations (Barbeau and Fung, 2001) and the recovery of upper extremity (UE) use after stroke-hemiparesis (Taub and Uswatte, 2003). Recently, this translational research has spawned various protocol-based treatments, for example, to enhance walking in individuals with spinal cord injury (Field-Fote, 2001) and chronic stroke (Sullivan et al., 2002), and to enable use of the hemiparetic UE in adults with sub-acute stroke (Winstein et al., 2003). However, if rehabilitation medicine is to join the ranks of other evidence-based medical and pharmaceutical practices, objective treatment protocols will become a necessary component of valid efficacy and effectiveness research (Whyte and Hart, 2003). The development of specific and objective rehabilitation treatment protocols will be a clear signal of progress in the field of rehabilitation medicine. At present, the majority of published protocols in neurologic rehabilitation lack an explicit scientific rationale for the intensity, duration, and content (e.g., task-specific versus muscle-specific) of training used within the rehabilitation treatments. Without an explicit rationale (or even hypothesis), the precise parameters of training for a given rehabilitation treatment can take on a mythical quality with hidden meaning at worst, and lead to "blind" following at best (Dromerick, 2003). This process undermines scientific enquiry and in some cases tends to hinder the development of alternative and innovative approaches. For example, Why is the signature constraint-induced therapy (CIT) protocol of 6h/day (60 h total) with one-on-one supervised training for no less than a 2-week period (10 days) "optimal" for achieving an effect (Taub and Uswatte, 2003)?1 How important is the "constraint" within a CIT training protocol? Why is a typical bout of step training with body weight support during treadmill walking 20 min in duration, 3 times/week for 4 weeks (Sullivan et al., 2002)? These rhetorical questions suggest that the field of rehabilitation medicine is at a critical cross-road in its development. On one hand, defining rehabilitation treatments is necessary for this field to advance, but on the other hand, its practitioners must heed the temptation to simply adopt these protocols without questioning their rationale, refining patient selection criteria, revising the parameters of training to fit patient characteristics and rehabilitation goals, and developing reliable prognostic indicators of outcome (Dobkin, 2004; Whitall, 2004).
Stroke is the leading cause of disability among American adults. Nearly 3 million of Americans are stroke affected; each year, approximately 700,000 people suffer a stroke and the estimated economic
1 It is perhaps no accident that most behavior modification programs that are based on traditional operant-conditioning methods are 2 weeks in duration.
burden from stroke-related disability is 35 billion dollars annually in direct costs (American Heart Association, 2005). More effective acute management of stroke has resulted in declining mortality while the number of stroke survivors who need long-term care or rehabilitation is expected to greatly increase, imposing an enormous economic burden on individuals and society (Rundek et al., 2000; Chapter 36 of Volume II). Residual burden of care is significant with 44% of community-based individuals post-stroke in a National Survey reporting difficulty with at least five to six activities of daily life (Chan et al., 2002). Surprisingly, despite these impressive statistics, there has been little principled and systematic research to determine the most effective and efficient parameters of training or conditions of task practice for the rehabilitation of the motor skills that constitute a significant portion of daily life.
In cases where movement deficits result from a stroke, intense task practice, defined as repeated attempts to produce motor behaviors beyond present capabilities, is considered the most crucial component for recovery (Butefisch et al., 1995; Kwakkel et al., 1999; Wolf et al., 2002). Previous work that has invoked performance improvements and/or experience-dependent neuroplasticity shows that large amounts of practice (consisting of 1000s sometimes 10,000s of trials) are needed (Pavlides et al., 1993; Karni, 1995; Nudo et al., 1996; Doyon et al., 1997). See Chapters 8 and 14 in Volume I for details about cortical re-organization and learning-dependent changes associated with task practice. These large amounts of practice are a dramatic contrast to the limited time that patients post-stroke spend in therapeutic activities: on average between 30 and 40min/day (Keith and Cowell, 1987; Lincoln et al., 1996). Further, patients typically spend 70% of the day in activities largely unrelated to physical outcome and less than 20% of the day in activities that could potentially contribute to their recovery (Mackey et al., 1996). In sum, current medical "practice" models in stroke rehabilitation are not designed to enhance recovery and maximize functional outcomes. Thus, a critical goal of rehabilitation science is to understand the parameters of training and conditions of task practice that will optimize functional outcomes from rehabilitation programs (Whitall, 2004; Weinrich et al., 2005).
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