Pressure Is a Viable Controlled Output of Motor Programming for Object Manipulation Tasks

Abstract

While force output is discussed as the predominant controlled output of the motor program for object manipulation, various studies have demonstrated that local pressure distribution at the fingerpad and coefficient of friction at the finger-object interface are also important for grasp control. We investigated the role of local pressure as a possible controlled output during a lift-hold-replace task. Participants lifted one of two masses with either normal or slippery contact surfaces using one of two grip postures that varied contact area. Grip force data was collected by a force/torque transducer while pressure and contact area data were collected using a Tekscan flexible sensor. Grip force and pressure both increased with increased mass or reduced friction while contact area increased with reduced friction and use of the flat grip posture. Additionally, grip force was significantly affected by a friction-grip posture interaction, whereas pressure was significantly affected by a mass-grip posture interaction.