An investigation of the task specificity of reaching: Implications for re-training

Abstract

An experiment investigating the effects of object and task constraints on the formation of reaching trajectories is reported. Six male and four female subjects over 55 years of age, with normal movement control, participated in an experiment in which they were required to grasp a mug with a handle and a mug without a handle and to perform either a moving or a turning task with the mugs. Reaction times and kinematic movement characteristics were recorded in three dimensions using a computer-based optical tracking system. The results indicate that a greater proportion of movement time was spent in the grasp phase of reaching when grasping the mug with a handle, a smaller proportion was spent in the grasp phase when turning compared to moving, and the maximum aperture size was larger when turning compared to moving. It was concluded that reaching movements are organised differently according to task constraints. The clinical implications of these findings are discussed using re-training of upper limb function following stroke as an example.