On the Relation of Skin Stretch and Finger Joint Angle Evolution in Human Hand Grasping Tasks

In the human body, skin stretch is intrinsically related to motion execution, providing important proprioceptive cues for movement perception and control, as is the case of human hands and fingers. However, as of today, a quantification of the amount of skin stretch across multiple hand joints notably lacks. In this study, we aim at bridging this research gap, quantifying skin stretch on the dorsal part of hand fingers, and more specifically across Proximal InterPhalangeal (PIP) and MetaCarpal (MCP) joints. We correlated the estimated skin stretch with human hand kinematics, in grasping tasks with several items. Twelve able-bodied participants were required to grasp twenty objects. We used an RGB-D camera for reconstructing hand kinematics (more specifically PIP and MCP values), while optical markers were placed on the hand dorsum to estimate skin displacement across joints. We characterized the relationship between joint angles and the corresponding skin stretch estimation over time using a linear regression analysis, with no statistically significant differences between participants and objects. The experimental data we collected are publicly available at this link [1]. This research sheds light on the intricate interplay between skin stretch and hand/finger movements. These outcomes can pave the path to the design of non-invasive skin stretch-based feedback devices for accurately conveying hand proprioceptive cues, with interesting implications for rehabilitation and advanced human-machine interaction.