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Intensity Versus Task-Specificity After Stroke: How Important Is Intensity?

Page, Stephen J. PhD

American Journal of Physical Medicine & Rehabilitation: September 2003 - Volume 82 - Issue 9 - p 730-732
doi: 10.1097/01.PHM.0000078226.36000.A5
Commentary: Intensity Versus Task-Specificity
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Page SJ: Intensity versus task-specificity after stroke: How important is intensity? Am J Phys Med Rehabil 2003;82:730–732.

Recent evidence suggests that intense training regimens can increase the use and function of the more affected limbs of stroke patients. The efficacy of these intense regimens has led some to conclude that intense training regimens should be more widely applied clinically and has caused some physicians to attempt implementation of more intense training regimens with stroke patients. However, intense protocols may not be needed to produce positive motor changes in some patients and may not be plausible in some environments or with some patients. In this commentary, we review the evidence supporting the efficacy of less intense, task-specific training regimens emphasizing the use of the more affected limb. We submit that intensity does not need to be altered to induce substantial clinical improvements, as some have suggested. Rather, the results of the studies suggest that the nature of stroke motor therapy itself can be altered to be more task-specific while remaining within the typical contact time parameters (i.e., 30–45 min/session), yet can be more efficacious than more traditional motor rehabilitative approaches.

From the Department of Physical Medicine and Rehabilitation, University of Cincinnati College of Medicine, Cincinnati, Ohio.

All correspondence and requests for reprints should be addressed to Stephen J. Page, PhD, Department of Physical Medicine and Rehabilitation, University of Cincinnati College of Medicine, 202 Goodman Drive, Suite 275, Cincinnati, OH 45267.

Increased use and function are reported in stroke (cerebrovascular accident, CVA) patients’ more affected upper limbs after participating in an intense protocol called constraint-induced movement therapy (CIT). 1–3 CIT is considered intense (intensity has been operationally defined in terms of number of hours of consecutive therapy) 4 in that repetitive arm movements are performed for 6 hr/day on ten consecutive weekdays. CIT participants also wear restrictive devices on their less affected limbs during most waking hours of the same period, which would also be considered intense by the above-mentioned criterion. Because of the intensity and widely reported efficacy of the CIT practice schedule, traditional CVA motor therapy has been criticized for its lack of intensity, and it has been suggested that CVA motor therapy should be delivered with greater intensity. For example, Taub 5 recently argued that “it is not so much the nature of the (rehabilitation) techniques that require revision…but rather the intensity with which they are delivered.”p vii Many clinicians have also been urged to develop clinical CIT programs. Is simple modulation of practice intensity all that is needed to make CVA motor rehabilitation more effective? Or, given diminishing lengths of stay and diminishing resources, can the nature of CVA therapy be altered while keeping therapy contact variables similar to those that are currently provided?

Butefisch et al. 6 recently criticized traditional CVA therapy approaches (e.g., Bobath), noting that “none of the commonly used traditional physiotherapeutic strategies emphasizes specifically the voluntary activation of the distal arm and hand musculature. Innervation is, rather, stimulated by cutaneous and proprioceptive as well as central facilitation techniques.”p 59 They also posited that nominal provision of task-specific training using the areas in which motor improvement are desired is a primary reason for the low efficacy of CVA motor rehabilitation. This contention seems plausible. Indeed, it is well established that task-specific practice is needed for motor learning to occur. 7 However, CVA patients are typically engaged in therapeutic activities that are nonspecific to either outcome or recovery. 8 Furthermore, it is now generally acknowledged that topography of cortical maps is dynamic and can be remodeled by behaviorally relevant experiences, including structured practice. As such, whereas traditional CVA motor rehabilitation strategies have yielded negligible motor changes, 9,10 task-specific training regimens have induced lasting, cortical reorganization in the representations corresponding to anatomic regions used during practice, as measured by focal transcranial magnetic stimulation and functional magnetic resonance imaging. 11 For example, using functional magnetic resonance imaging, Karni et al. 12 reported a gradual enlargement in the primary motor cortices of healthy participants engaging in daily practice of several motor tasks. The cortices enlarged with practice regardless of the practice strategy used, and this enlargement suggested a slowly evolving, long-term, experience-dependent reorganization of the adult M1 sec. Using transcranial magnetic stimulation, Classen et al. 11 similarly showed that even simple thumb movements, repeated over a short period of time (either 15 or 30 min), are effective in inducing lasting cortical representational changes in healthy participants and that they enlarge as a practice effect begins to shape behavior. Butefisch et al. 6 also demonstrated that short, repetitive, task-specific training (15 min/day, 2 times/day) is sufficient to improve more affected hand strength and function in CVA patients.

Results of the above studies support the contention that task-specific training promotes lasting cortical and functional changes. They also support the explanation of Butefisch et al. 6 of why traditional CVA rehabilitative approaches have been less successful. However, a compelling element of the above-mentioned studies, and several other studies, has been the low treatment intensity at which a treatment effect has been observed when task-specific training has been provided. Indeed, despite support for increased intensity, task-specific training protocols of various intensities have induced lasting cortical and functional changes. For example, as mentioned previously, participation in task-specific training sessions as brief as 15–30 min has produced modulations in the cortical maps of the areas being used, as measured by transcranial magnetic stimulation. 11 Task-specific regimens featuring low intensities more comparable with outpatient therapy (≈30–45 min) have also produced enduring functional effects in CVA patients. For example, considerable evidence supports the efficacy of modified constraint-induced therapy, a less intense version of CIT in which patients participate in 30-min functional training sessions. 13 Furthermore, a task-specific, 30-min, 2-wk reaching program by Dean and Shepherd 14 significantly improved CVA patients’ reaching distance and time required to perform reaching tasks, and it improved muscle activation, load through the more affected leg, and ability to transfer between sitting and standing positions. Galea et al. 15 also reported that a 3-wk program featuring 45-min, task-specific, upper limb training improved motor function, dexterity, and use of CVA patients’ more affected upper limbs. Other, task-specific, low-intensity regimens employing various modalities have also reported significant success in increasing use and function of the more affected limbs of CVA patients. 16–18

The advent of CIT has caused many to attempt provision of more intense training to eligible CVA patients exhibiting learned nonuse in their more affected limbs. However, Taub et al. 19 recently suggested that “any technique that induces a patient to use an affected limb…should be considered therapeutically efficacious. This factor is likely to produce the use-dependent cortical reorganization. …”p 241 Consistent with this, although some CVA patients could benefit from more intense protocols, like CIT, prescription of more therapy time may not be needed to induce meaningful improvements. Rather, the above-reviewed evidence suggests that less intense (e.g., 30–45 min), task-specific training regimens with the more affected limb can produce cortical reorganization and correlative, meaningful functional improvements. This is important information for physicians who prescribe therapy and for therapists who provide therapy.

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Keywords:

Stroke; Intensity; Task-Specificity; Motor Tasks

© 2003 Lippincott Williams & Wilkins, Inc.