Reactive Turning Behavior in Older Adults: Age-Related Decrease is Evident under Increased Task Demand.

A sudden turn initiated at an unpredictable moment is referred to as reactive turning. This study was designed to seek an age-related decrease in reactive turning when the task demand for turning was increased using a task-switching paradigm. Twenty healthy older adults and 14 younger adults were instructed to walk and execute a 90-degree turn under two conditions. In the "reactive turning condition," participants were asked to turn abruptly when the initially presented travel direction (e.g. right) switched to the opposite direction (e.g. left) while walking. This switch occurred in only one-fifth of 40 trials. In the "pre-planned turning condition," participants were informed of the direction beforehand. The onset of the center of mass (COM) shift in older participants failed to reach significance compared to younger participants. However, correlation analyses showed impaired turning performance in older participants, as those with delayed COM shift exhibited larger pelvic rotations over a short period during reactive turning. This suggests that, owing to increased task demand, older adults had difficulty quickly responding and sufficiently rotating their bodies in the new direction. We conclude that reactive turning with increased task demand, using a task-switching paradigm, is a key factor in detecting age-related performance decline.