Handwriting: Hand–pen contact force synergies in circle drawing tasks

Shim, Jae Kun; Hooke, Alexander W.; Kim, You-Sin; Park, Jaebum; Karol, Sohit; Kim, Yoon Hyuk

doi:10.1016/j.jbiomech.2010.04.033

« Previous Next »Journal of Biomechanics
Volume 43, Issue 12 , Pages 2249-2253, 26 August 2010

Handwriting: Hand–pen contact force synergies in circle drawing tasks

Jae Kun Shim
- Department of Kinesiology, University of Maryland, College Park, MD 20742, USA
- Neuroscience and Cognitive Science Graduate Program, University of Maryland, College Park, MD 20742, USA
- Fischell Department of Bioengineering, University of Maryland, College Park, MD, USA
- Department of Mechanical Engineering, Kyung Hee University, Global Campus, Yongin 446-701, Republic of Korea
- Corresponding author at: Department of Kinesiology; Fischell Department of Bioengineering; Neuroscience and Cognitive Science Program, University of Maryland, College Park, MD 20742, USA. Tel.: +13014059240; fax: +13014055578.
Alexander W. Hooke
- Department of Kinesiology, University of Maryland, College Park, MD 20742, USA
You-Sin Kim
- Department of Kinesiology, University of Maryland, College Park, MD 20742, USA
Jaebum Park
- Department of Kinesiology, University of Maryland, College Park, MD 20742, USA
Sohit Karol
- Department of Kinesiology, University of Maryland, College Park, MD 20742, USA
Yoon Hyuk Kim
- Department of Mechanical Engineering, Kyung Hee University, Global Campus, Yongin 446-701, Republic of Korea

Accepted 16 April 2010. published online 20 May 2010.

Abstract

This study investigated synergistic actions of hand–pen contact forces during circle drawing tasks in three-dimensional (3D) space. Twenty-four right-handed participants drew thirty concentric circles in the counterclockwise (CCW) and clockwise (CW) directions. Three-dimensional forces acting on an instrumented pen as well as 3D linear and angular positions of the pen were recorded. These contact forces were then transformed into the 3D radial, tangential, and normal force components specific to circle drawing. Uncontrolled manifold (UCM) analysis was employed to calculate the magnitude of the hand–pen contact force synergy. Three hypotheses were tested. First, hand–pen contact force synergies during circle drawing are dependent on the angular position of the pen tip. Second, hand–pen contact force synergies are dependent on force components in circle drawing. Third, hand–pen contact force synergies are greater in CCW direction than CW direction. The results showed that the strength of the hand–pen contact force synergy increased during the initial phase of circle drawing and decreased during the final phase. The synergy strength was greater for the radial and tangential components as compared to the normal component. Also, the circle drawing in CW direction was associated with greater hand–pen contact force synergy than the CCW direction. The results of this study suggest that the central nervous system (CNS) prioritizes hand–pen contact force synergies for the force components (i.e., radial and tangential) that are critical for circle drawing. The CNS modulates hand–pen contact force synergies for preparation and conclusion of circle drawing, respectively.

Keywords: Handwriting, Kinetics, Force, Three-dimensions, Motor redundancy