O Springer-Verlag 1988 Programmed and triggered actions to rapid load changes during precision grip

Summary. A test object (grip apparatus) was held at its upper part using a precision grip. Small balls were dropped into a target cup at the bottom ot the apparatus. The grip force, the load force (vertical lifting force) and the vertical movement were mea-sured. Electromyographic activity (e.m.g.) was re-corded from four antagonist pairs of handlarm mus-cles primarily influencing the grip force or the load force. The balls were dropped either by the subject during a bimanual task, or unexpectedly by the experimenter. When the subject dropped the ball, preparatory actions occurred before the rapid increase in the vertical load caused by the impact. These actions appeared ca. 150 ms prior to the impact and involved a grip force increase and a liftin