The Motor Control Consequences of Excessive Physical Therapist Support in Individuals With Stroke

Independent motor task performance is the most highly prioritized outcome of physical therapy for individuals with motor disability. Accordingly, a key priority for physical therapists in multiple practice settings is the advancement of functional motor independence. Therapists must determine when a patient requires assistance (e.g., verbal cues, physical support) to complete a motor task and when a patient is able to execute a motor skill with less assistance. If a therapist does not provide enough support, the patient is at risk for unsuccessful task performance. As such, therapists often default to providing a higher level of assistance.

An individual following stroke, for instance, may demonstrate an increased magnitude of postural sway while completing self-care activities at the sink. A therapist may decide to provide physical support for the patient to decrease sway variability, whether or not the patient requires this support to maintain performance. The motor control consequences of providing this assistance (thus constraining movement variability and providing fewer options for adapting movement) when assistance is actually not needed is unknown. The purpose of this study is to systematically determine the effect of unnecessary assistance during the practice of an upper limb task on functional performance and underlying motor control patterns when learning (or re-learning) motor skills in individuals with stroke. The insights gained from the current project will have the potential to improve the currently available physical therapy interventions for individuals with stroke.

The effects of unnecessary physical therapist support will be examined in terms of upper limb task performance, retention, and transfer, and in terms of the postural control supporting task performance. The study is currently planned for individuals with stroke. Participants will be required to maintain the position of a virtual laser within a target while standing. An experimental group will receive postural support (physical assistance to maintain upright posture) during a practice period in order to specifically determine the effect of postural support on upper limb task performance and postural sway patterns. Participants will also engage in a light finger force production transfer task to ascertain the influence of postural support on a different supra-postural task.

It is hypothesized that providing unnecessary assistance (and thus limiting independence) during practice of a novel motor task will result in (a) faster improvements in task performance but reduced retention and more limited transfer to another, similar task; and (b) reduced task- sensitive postural sway adjustments (measured in terms of both the quantity and temporal structure) during practice, at transfer, and at retention, reflecting reduced adaptability of postural patterns to task demands.