Constraints on Practice (2007)

For over 40 years, questions about the amount of practice necessary to acquire skill have appeared in the rehabilitation literature. Most recently, practice has been considered a critical force that can drive neuroplastic changes following a neurologic lesion. Lang and colleagues study1 bridges concepts in several important ways. It meshes motor learning principles (promoted by the II-STEP conference in 1990) with neuroplasticity (a III-STEP conference buzzword). It contrasts bench research with the messy world of treating patients who have myriad lesion types and comorbidities. And via a snapshot into the natural world of neurologic outpatient treatment, this paper compares what we say we should do with what is done. Early motor learning research manipulated the quantity and quality of practice to study its effect on simple outcomes such as movement errors or reaction time. This work nudged neurologic practice toward active, functional participation by clients in real world tasks that they wanted and needed to do. It instructed therapists that the ultimate in independent function is the ability to adapt to the variety of environmental challenges proposed by the client's world. Animal research in the 1990s demonstrated quite elegantly that meaningful task repetition could result in cortical reorganization in both the intact and lesioned brain.2 Exciting recent reports on humans demonstrate similar findings.3 Therapists can impact the nervous system by prescribing tasks that are difficult but doable, motivating, and even fun for the patient. The key word is “prescribing”—which tasks should be selected, and how much repetition is optimal? Answering these questions in practical terms is easier said than done. Lang and colleagues nicely illustrate the challenges of translating evidence from animal or even human research into day-to-day practice. Humans execute tasks that are much more complex than those studied in animals—and perform an enormous variety of tasks in a single day. Patients poststroke not only have larger lesions than animal research subjects, but are apt to have other physiological influences on their capacity for plastic changes. Variables such as these are examples of patient-centered constraints on optimal performance. Alternately, therapy providers, and the health care system in which they operate, constrain the type and amount of practice during therapy sessions. Together these challenges suggest that clinical practice could be informed by distinguishing patient-centered from therapist-centered constraints on task practice. Patient motivation, compliance, lesion location and size, cognitive ability, age, pain, fatigue, and other variables likely modify the amount of task practice that can be performed and that is needed to acquire skill. Some of these variables are amenable to change; future research might elucidate which factors should be addressed to optimize quality and quantity of practice and therefore performance. Relationships between these intrinsic factors and practice prescription may be uncovered. For example, Underwood et al recently reported no relationship between pain and fatigue and intensity of constraint induced movement therapy (CIMT), which averaged 4.5 hours/day of functional task practice and guiding/shaping activities.4 This study involved a group of mild to moderately impaired subjects who were 3 to 9 months poststroke. I propose that therapist-centered constraints on amount of task practice are even more amenable to change. The authors consider some factors that may explain the number of repetitions observed during their study. These factors largely represent the fact that what is being practiced influences the number of repetitions that can be performed. The data revealed a large number of activities (mean = 7) per session, therefore the amount of minutes that can be devoted to any one is logically less. Complex tasks—those that typically require skill and guidance—are less likely part of a home exercise program, and more likely practiced in therapy. These may take longer, or may take more of a practitioner's time. Therefore, carefully choosing what is practiced is critical. Based on the evidence, therapeutic activities must be functionally relevant tasks, prioritized to patient goals. Animals that repetitively reached for a food pellet performed differently if they were hungry vs. satiated. Therapists should choose tasks that our patients are “hungry” to perform, in order to optimize patient engagement and the benefits of practice. Also it would be intriguing to correlate the therapist's decision-making processes to the number of repetitions observed. I hypothesize differences in active/purposeful repetitions prescribed by therapists vs. assistants, and this analysis may have been a useful addition to the paper. For example, are repetitions limited in number because of a concern that more practice may cause fatigue or boredom? Besides the individualized plan of care, broader therapist-centered constraints might involve the models currently in popular use for service delivery. Therapists who are impairment-focused may prescribe exercise repetition more than functional task practice. Often several patients are seen at once, limiting the amount of time a therapist can spend guiding one patient's practice. And finally, reimbursement constraints are often cited as a culprit that compromises intensive intervention. How can therapy sessions more accurately reflect what research suggests will optimize neuroplasticity? Address the therapist-centered constraints¡ Following are my own proposals combined with those of the authors: prioritize task practice as a home exercise component, and monitor compliance; empower patients with information about the relationship between practice and plasticity; increase expectations of what patients can tolerate; move away from the notion of “exercise” as the bulk of time with patients. And finally, advocate for a change in service delivery model with patients for whom it is appropriate.