Simultaneous measurement of the grip/load force and the finger EMG: effects of the object weight

Human has efficient grasping strategies, such as the anticipatory force programming, using the somatic sensation of the various properties of the object. However, it is not clear how the object´s weight and grasping condition affect the motor outputs during the grasping motion. In this paper, the grip/load force and the surface electromyography (EMG) of abductor pollicis brevis muscle (AbPB) and adductor pollicis muscle (AdP) are measured simultaneously to investigate the relation between the objects weight and the motor outputs. The experimental results show that the changes of the object´s weight affect the initial peak grip force and the AbPB EMG activities. These results suggest that (1) the initial peak grip form and the AbPB EMG activities reflect the forces that should be exerted on the object and (2) the object that is previously grasped affects the anticipatory force programming.