The Feasibility and Efficacy of a Postural Continuous Tracking Task: Exploring the Dosing of Postural Task Practice in Parkinson Disease.

Research Report
Population: Adult

Heather Anne Hayes, DPT, NCS, PhD, Assistant Clinical Professor, University of Utah heather.hayes@hsc.utah.edu

Sydney Schaefer, PhD, Assistant Professor, Utah State University sydney.schaefer@usu.edu

Leland Dibble, PT, PhD, Associate Professor, University of Utah lee.dibble@hsc.utah.edu

Keywords: Plasticity, Motor Learning, Postural Control, Feasibility

BACKGROUND: Parkinson disease (PD) impairs both postural control and motor learning. Motor learning tasks used to document impaired learning have been seated discrete upper extremity tasks that do not necessarily challenge postural dysfunction with PD. Furthermore, recent evidence suggests that exogenous dopamine could further impair motor learning in PD despite improving certain motor signs. PURPOSE: To test the feasibility and efficacy of a standing continuous tracking task (CTT) for measuring postural motor learning. To account for the effects of age, disease, and dopamine replacement medication with this task. HYPOTHESES: 1) The prescribed dose of practice would be feasible for all participants, 2) Control subjects (healthy elderly [HE]; healthy young [HY]) would learn the standing CTT faster compared to individuals with PD randomized to on or off medication (PD On; PD Off), such that the prescribed dose would be less efficacious for learning in participants with PD. SUBJECTS: N=39 (10 PD on; 9 PD Off; 10 HE; 10 HY). METHODS: The CTT required anterior posterior COP movement to track a visual target. The task contained an embedded repeating pattern and error was recorded as the difference between the target and participant’s trajectory (root mean square error [RMSE]). A dose of 120 repetitions of the repeating pattern was provided over 2 days (12 blocks of 10 repetitions). Feasibility was measured as the number of participants who completed the required practice dose without adverse events (fatigue/falls). To measure efficacy, learning rates were estimated by fitting an exponential decay function to the root mean square error (RMSE) data across the 12 blocks of practice for each participant, with growth rate indicating the number of blocks needed to achieve an asymptote in performance (i.e. steady state). The percentage of individuals within each group that achieved this steady state within the prescribed dose of practice describes efficacy.  RESULTS: The prescribed dose of postural task practice was feasible for all participants in all groups (no adverse events). This dose was not, however, efficacious for 100% of participants in any group to achieve a steady state in performance. In light of our hypothesis though, the HY group had more participants (90%) achieve steady state within the dose compared to the other groups (HE=70%, PD On=78%, PD Off=33%). CONCLUSIONS: This postural CTT was a feasible means to assess changes in postural motor performance due to practice in people with and without PD. Furthermore, this dose of practice on the postural CTT was selectively efficacious in promoting postural motor learning, even more so on dopamine replacement medication than off for individuals with PD. CLINICAL RELEVANCE: These results suggest that motor learning deficits reported previously in people with PD may be in part attributed to the motor task, the practice dose, and medication status. Further assessment is warranted to determine the amount of practice (i.e. dose necessary for each group to achieve 100% efficacy).

Citation:
Hayes, Heather Anne, DPT, NCS, PhD; Schaefer, Sydney Y, PhD; Dibble, Leland E, PT, PhD. The Feasibility and Efficacy of a Postural Continuous Tracking Task: Exploring the Dosing of Postural Task Practice in Parkinson Disease.. Poster Presentation. IV STEP Conference, American Physical Therapy Association, Columbus, OH, July 17, 2016. Online. https://u.osu.edu/ivstep/poster/abstracts/040_hayes-et-al/

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