Quantification of handwriting performance: Development of a force acquisition pen for measuring hand-grip and pen tip forces

Suitable apparatuses for exploring the kinetics of handwriting performance are limited, which hinders a thorough understanding of the control mechanisms between the hand and a pen. This study proposes a force acquisition pen (FAP) that detects the contact forces between digits and the pen barrel, as well as the force between the pen tip and writing surface. Tests of the validity and reliability of the FAP and the variability of the acquired kinetic information of handwriting performance were conducted. Acceptable validity (R² > 0.9986, p < 0.0001) and reliability (intraclass correlation coefficients >0.79) were obtained, indicating the feasibility of the proposed pen. From the force information acquired from the digits and pen tip, kinetic parameters were determined for a detailed investigation of the coordination and control mechanism between the digits and a pen.