Department of Industrial and Manufacturing Engineering, University of Wisconsin-Milwaukee, 3200 North Cramer Street, Milwaukee, WI 53211, USA.
J Biomech. 2011 May 17;44(8):1447-53. doi: 10.1016/j.jbiomech.2011.03.020. Epub 2011 Apr 14.
This study examined the effect of friction between the hand and grip surface on a person's grip strategy and force generation capacity. Twelve young healthy adults performed power grip exertions on an instrumented vertical cylinder with the maximum and 50% of maximum efforts (far above the grip force required to hold the cylinder), while normal and shear forces at each phalanx of all five fingers in the direction orthogonal to the gravity were recorded. The cylinder surface was varied for high-friction rubber and low-friction paper coverings. An increase in surface friction by replacing the paper covering with the rubber covering resulted in 4% greater mean phalanx normal force (perpendicular to the cylinder surface) and 22% greater mean phalanx shear force in either the proximal or distal direction of the digits (p<0.05; for both 50% and maximum grip efforts). Consequently, increased friction with the rubber surface compared to the paper surface was associated with a 20% increase in the angular deviation of the phalanx force from the direction normal to the cylinder surface (p<0.05). This study demonstrates that people significantly changed the magnitude and direction of phalanx forces depending on the surface they gripped. Such change in the grip strategy appears to help increase grip force generation capacity. This finding suggests that a seemingly simple power grip exertion involves sensory feedback-based motor control, and that people's power grip capacity may be reduced in cases of numbness, glove use, or injuries resulting in reduced sensation.
本研究考察了手与握持表面之间的摩擦力对个体握持策略和力量产生能力的影响。12 名年轻健康成年人在装有仪器的垂直圆柱体上进行全力和 50%最大力量（远高于握持圆柱体所需的力量）的紧握力测试，同时记录每个手指的所有五个指节在垂直于重力方向的正交方向上的正压力和剪切力。圆柱体表面分别用高摩擦橡胶和低摩擦纸张覆盖。用橡胶覆盖物代替纸张覆盖物会增加表面摩擦力，从而导致指节正压力（垂直于圆柱体表面）平均增加 4%，手指近端或远端方向的指节剪切力平均增加 22%（p<0.05；对于 50%和最大握力）。因此，与纸张表面相比，橡胶表面的摩擦力增加与指节力与垂直于圆柱体表面的方向之间的角度偏差增加 20%相关（p<0.05）。本研究表明，人们根据握持的表面显著改变了指节力的大小和方向。这种握持策略的变化似乎有助于提高握力产生能力。这一发现表明，看似简单的紧握力测试涉及基于感觉反馈的运动控制，而在感觉麻木、使用手套或因感觉减退而受伤的情况下，人们的紧握力可能会降低。
