The effects of instruction and hand dominance on grip-to-load force coordination in manipulation tasks

• Published in: Neuroscience letters Vol. 504; no. 3; pp. 330 - 335
• Main Authors: Jin, Xin, Uygur, Mehmet, Getchell, Nancy, Hall, Susan J., Jaric, Slobodan
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 31.10.2011
• Subjects: Adult; Biomechanical Phenomena; Control; Coordination; Coupling; Feed-forward; Feedback; Feedback, Physiological; Female; Friction; Functional Laterality - physiology; Gravitation; Hand - physiology; Hand Strength - physiology; Humans; Male; Models, Biological; Motor Skills - physiology; Neural; Scaling; Weight-Bearing - physiology; Young Adult; Scaling; Control; Coupling; Feedback; Feed-forward; Neural
• ISSN: 0304-3940; 1872-7972; 1872-7972
• DOI: 10.1016/j.neulet.2011.09.059

► Even when simultaneously performing mechanically identical task, two hands can exhibit different grip force patterns due to different instructions. ► Instruction “to pull” lead to higher indices of grip force coordination than the instruction “to hold”. ► The non-dominant hand grip force shows a moderate lagging behind both the dominant hand grip and the pulling force. The force applied upon a vertically oriented hand-held object could be decomposed into two orthogonal and highly coordinated components: the grip force (GF; the component perpendicular to the hand–object contact area that provides friction) and the load force (LF; the parallel component that can move the object or support the body). The aim of this study was to investigate the underexplored effects of task instruction and hand dominance on GF–LF coordination. Sixteen right-handed subjects performed bimanual manipulation against a horizontally oriented instrumented device under different sets of instructions. The tasks involved exertion of ramp-and-hold or oscillation patterns of LF performed symmetrically with two hands, while the instructions regarding individual actions were either similar (pull with both hands) or dissimilar (pull with one hand and hold with another). The results revealed that the instruction “to pull” leads to higher indices of GF–LF coordination than the instruction “to hold”, as evidenced by a lower GF–LF ratio, higher GF–LF coupling, and higher GF modulation. The only effect of hand dominance was a moderate time lag of GF relative to LF changes observed in the non-dominant hand. We conclude that the instructions could play an important role in GF–LF coordination and, therefore, they should be taken into account when exploring or routinely testing hand function. Additionally, the results suggest that the neural control of GF of the non-dominant hand could involve some feedback mechanisms.