Effects of task complexity on reaction time and movement kinematics in elderly people

In clinical practice, occupational therapists identify characteristics or demands of a task and, to improve coordination or problem solving ability, grade it along the complexity dimension. Effects of increased complexity of functional tasks have not been studied to date. The purpose of this study was to continue to examine the characteristics of occupation by testing the effect of task complexity on motor performance in elderly people.

A counterbalanced repeated-measures design was used. Twenty-eight elderly people without motor problems (9 men, 19 women) performed checker game moves ranging from one to four steps. Only the first segment of movement from start position to the first designated place was kinematically analyzed and compared among the four conditions because it has been shown in earlier studies that differences in strategy are apparent from the first segment.

Generally, the more complex moves elicited higher peak velocity (indicating greater force employed, F[3,72] = 3.45, p = .0210) and more movement units (indicating a less smooth and less efficient movement, F[3,72] = 4.71, p = .0047) than a simple move.

The results indicate that in this study, task complexity affects forcefulness and smoothness of motor performance, supporting the practice of activity analysis and gradation along the complexity dimension in occupational therapy. When treating elderly people in clinics, therapists may increase the number of steps within a task to facilitate the force embedded in movement, or decrease the number of steps to facilitate smooth and economical movement.