Revisiting constraint-induced movement therapy: are we too smitten with the mitten? Is all nonuse "learned"? and other quandaries.(III STEP Series)

In the past decade, several critical reviews of poststroke rehabilitation (1-4) have indicated that task-oriented interventions can induce more substantial functional improvements than neuromuscular reeducation approaches for which weighting of supportive evidence is sparse. One such approach is called "constraint-induced movement therapy" (CIMT), also called "CI therapy."

A Brief Historical Primer

Constraint-induced movement therapy originates from seminal studies by Taub (5) of monkeys that had undergone deafferentation. Taub demonstrated that animals forced to use the insensate upper extremity through immobilization of the intact limb for short periods could soon learn to use the insensate limb even when the use of both limbs was possible. Training of the monkeys that had undergone deafferentation during the forced-use period was achieved through successive approximations as the basis for shaping intended movement. The animals would be rewarded as they progressively reached toward and subsequently grasped objects. Taub proposed that the animals had undergone "learned nonuse" of the affected limb and, given the appropriate behavioral training, could relearn to use it indefinitely. Although the duration of the effect of deafferentation was never assessed, Taub proposed that this approach be used for patients with hemiparesis and presumed that the diaschisis after stroke led to a learned suppression of movement comparable to the suppression of the spontaneous limb use in monkeys that had undergone cervical deafferentation.

At about the same time at which Taub was undertaking a series of elegant subhuman primate studies (6-8) from which the learned nonuse theory was formulated, Basmajian was initiating studies on electromyographic biofeedback applications to patients with stroke. (9-11) This approach consisted of monitoring individual limb muscles, usually with surface electrodes, and providing patients with visual and auditory cues about muscle activity. Electromyographic responses could be conditioned through the use of threshold detectors, and signal amplification settings could be controlled by clinicians to modify the presentation of auditory or visual cues to patients on the basis of whether responses were being "down-trained" (as in the case of hyperactive muscles) or "up-trained" (weakened antagonists).

These studies led to a series of subsequent investigations (12,13) that indicated that the primary predictor of the independent use of the hemiparetic upper extremity in patients with chronic stroke was the ability to initiate elbow, wrist, and finger extension. (14,15) This capability became the primary inclusion criterion for what was initially described as "forced use." (16,17) Forced use is defined as the process through which a patient is made to use the hemiparetic upper extremity through immobilization of the better limb in a sling or while wearing a mitt during most waking hours. During such time, the patient undertakes activities determined collaboratively with the clinician but performed in the home environment. Over a 2-week time interval, the patient is free to contact the therapist for alterations in tasks or questions regarding compliance. Many studies (18-21) continue to use this forced-use approach for patients after stroke.

Constraint-induced movement therapy includes forced use but also includes one-on-one training for as much as 6 hours per day over several weeks as well as repetitive task practice and adaptive task practice (also called "shaping"). Repetitive task practice refers to continuous efforts to execute movements that usually are repeated, for example, eating, grooming, or brushing teeth. During such efforts, the kinematics of the movements can be varied (made more challenging) on the basis of considerations of a patient's reacquisition of movement control. Therefore, the only interruptions that occur are those used to make the execution of the tasks easier or more difficult.

Adaptive task practice is a form of operant or instrumental conditioning (associating a reward with a correct response as a basis for reinforcing the correct response) characterized by repetitions of a defined movement, such as picking up blocks and moving them toward a pall, in a series of trials. Each trial has a defined duration, and often a participant is asked either to increase the successful numbers of repetitions or to reduce the time to complete the task demands successfully with one effort. During these efforts, the patient is coached or encouraged by the therapist. The patient then is shown a performance record over a number of trials and should be motivated to perform even more optimally on the basis of progressive improvement over trials. With respect to CIMT, this training procedure was developed by Taub and his group at the University of Alabama at Birmingham and contains the intense treatment approach and additional home work assigned along with a mutually agreed-on behavior contract as its signature piece (see Taub and Uswatte (22) for a comprehensive review of the basis for CIMT).