Figure 1. Temporal sequence of forces and torques.

A, position of the stimulus surface. The surface was oriented parallel to the flat portion of skin on the fingertip and was positioned just above the skin surface. The rotational axis of the torque load (a) was aligned with the centre point of the flat portion of the fingertip's volar surface termed the initial contact point (b). At the beginning of each trial the stimulus was advanced, normal to the skin, compressing the fingertip until the target normal force level was reached. Torques of different magnitudes were then applied. B, force and torque profiles showing the various phases; torques were applied in clockwise (continuous line) and anticlockwise (dashed line) directions.