Biomechanics of Front and Back-of-Tablet Pointing with Grasping Hands

Considering the kinematic model of the hand allows for deeper understanding of target selection on the front and on the back of tablets. We found that the position where the thumb and fingers are naturally hovering when the device is held results in shortest target selection times. We broaden our understanding of that ergonomic optimum by analyzing the touch data as well as 3D data. That allows us to model the entire hand pose including finger angles, thumb angles, and orientation. We show how target acquisition with grasping hands is realized through bending the joints of the digits. For targets located very close to the palm of the grasping hand, the digit joints have to be bent till their limit, which is a less ergonomic motion that therefore requires longer selection times than pointing at targets with relaxed digits that are further away.