Does Practice Beyond Performance Plateau Improve Motor Learning in Healthy Adults?

What is the ideal amount, or dose, of practice needed for a person to learn a motor skill? Studies suggest that "more is better," but the optimal dose of motor practice is unknown. Motor learning is defined as a set of internal processes leading to a relatively permanent change in the capability for a motor skill. Older adults and people with neurological disorders have a critical need to learn and relearn motor skills to remain independent, but standard clinical rehabilitation currently provides practice doses that are insufficient to result in motor learning. Under-dosing of practice results in sub-optimal clinical outcomes, while research studies that are dosed insufficiently to identify between-group differences are prone to misinterpretation. Therefore, it is essential for both clinical care and for research that we determine the practice dose needed to optimize motor learning.

Performance curves (i.e., plots of the average performance of a group or individual for each of a number of practice trials or blocks of trials) demonstrate that performance improves (e.g., error decreases or speed increases) during practice, until a point at which performance improvement begins to plateau. Additional practice provided beyond the point at which an individual reaches a performance plateau will be termed overpractice. Amounts of practice that are insufficient to reach a plateau tend not to demonstrate motor learning, while overpractice typically results in retention of the practiced task.

Pilot Study #1: The first pilot study will include healthy young adults who are randomly assigned to practice a postural stepping task for one day, or for five consecutive days of practice. The investigators will use this data to determine an operational definition (i.e., a mathematical definition) of performance plateau. This definition will be used to differentiate the groups in Pilot Study #2.

Pilot Study #2: The second pilot study will include healthy older adults who will be divided into three groups: a standard of care group (i.e. very low dose), an overpractice group, and a no overpractice group. All groups will practice a postural stepping task. The experimental group will be the overpractice (OVP) group, in which each participant will complete 100% additional practice trials after reaching their performance plateau. In contrast, the two active control groups will be the no overpractice (NoOVP) group (in which each participant will stop practicing immediately after reaching a performance plateau), and the standard of care (SoC) group (in which each participant will perform one block of practice).