Development and application of a multi-axis dynamometer for measuring grip force

Abstract

Objective This article describes the development and application of a novel multi-axis hand dynamometer for quantifying two-dimensional grip force magnitude and direction in the flexion-extension plane of the fingers. Methods A three-beam reconfigurable form dynamometer, containing two active beams for measuring orthogonal forces and moments regardless of point of force application, was designed, fabricated and tested. Maximum grip exertions were evaluated for sixteen subjects gripping cylindrical handles varying in diameter. Results Mean grip force magnitudes were 231 N (SD=67.7 N), 236 N (72.9 N), 208 N (72.5 N), and 158 N (45.7 N) for 3.81 cm, 5.08 cm, 6.35 cm and 7.62 cm diameter handles, respectively. Grip force direction rotated clockwise and the centre of pressure moved upward along the handle as handle diameter increased. Conclusions Given that the multi-axis dynamometer simultaneously measures planar grip force magnitude and direction, and centre of pressure along the handle, this novel sensor design provides more grip force characteristics than current sensor designs that would improve evaluation of grip characteristics and model-driven calculations of musculoskeletal forces from dynamometer data.

Wearable Monitoring Devices for Biomechanical Risk Assessment at Work: Current Status and Future Challenges—A Systematic Review

“…The measure of the grip force is also provided by instrumented gloves (i.e., equipped by force sensitive resistors) or by force sensor mats applied to handles [ 73 , 121 , 122 , 123 , 124 , 125 , 126 ]. Instrumented gloves remove the need for the handle to be instrumented but disturb grasp interaction [ 127 ]. Furthermore, force sensor mats embedded within gloves acquire only normal forces, require calibration and may shift during measurements.…”

“…Furthermore, force sensor mats embedded within gloves acquire only normal forces, require calibration and may shift during measurements. In order to overcome these limitations multi-dimensional grip dynamometers have been developed to adapt to a wide variety of handle sizes and geometries allowing a continuous measure of fatigue and forces [ 119 , 127 , 128 ]. Recently dynamometers able to measure both angle and force with high levels of sensitivity and inter-examiner reliability have been developed [ 129 , 130 , 131 , 132 ].…”

Multiaxis Grip Characteristics for Varying Handle Diameters and Effort

“…The multiaxis dynamometer described by Irwin et al (2013) was used in the current experiment. It consisted of two instrumented beams for the fingers and a static reference beam for the thumb.…”

“…Regardless of measurement method, independent studies on grip strength in which hand aperture varied report that the amount of grip force people can exert changes as handle diameter changes (e.g., Edgren et al, 2004; Fitzhugh, 1973; Oh & Radwin, 1993; Seo & Armstrong, 2008; Seo, Armstrong, Ashton-Miller, & Chaffin, 2007). Additionally, studies have demonstrated that force direction changes as diameters vary (Edgren et al, 2004; Irwin, Towles, & Radwin, 2013). This finding means the ratio of normal to shear force changes based on hand geometry and is potentially very important to proper hand-handle interface design.…”

“…Some studies indicate finger contributions are similar regardless of effort level and handle size (Amis, 1987; Talsiania & Kozin, 1998) and object weight (Reilmann, Gordon, & Henningsen, 2001), whereas others report varying contributions (Irwin et al, 2013; Radwin et al, 1992). …”