Equifinal Throwing Movements – Computational Approach, Mechanical Implementation, and Learning Intervention

Whenever high target accuracy is a limiting factor of motor performance, as in goal-oriented throwing tasks, equifinal movement techniques can be used to reduce the influence of inherent biological variability on the task result. In throwing movements, for instance, these techniques are characterized by a specific spatio-temporal organization of the movement trajectory that allows several moments of release that lead to a target hit. Throwing experts (e.g. darts or boule players) with the experience of several ten thousand practice trials show equifinal movements, but also throwing novices can learn to use equifinality after at least 1000 trials of practice. Here, we present a study that aims to scrutinize how the acquisition of equifinal throwing movements can be improved and accelerated. Mechanical guidance was used as intervention method. Determination and mechanical implementation of an equifinal technique in a virtual goal-oriented throwing task as well as results of a four-day intervention experiment are presented. Results confirm that the approaches to compute an equifinal movement trajectory and to implement mechanical guidance are appropriate to support acquisition of error tolerant movement strategies.