@article{ref1,
title="Hand-Handhold Coupling: Effect of Handle Shape, Orientation, and Friction on Breakaway Strength",
journal="Human factors",
year="2009",
author="Young, J. G. and Woolley, C. and Armstrong, T. J. and Ashton-Miller, J. A.",
volume="51",
number="5",
pages="705-717",
abstract="Objective: The aim was to determine the maximum force that can be exerted on an object before it is pulled or slips from the grasp of the hand (&quot;breakaway strength&quot;) for fixed overhead handholds of varying orientation, shape, and friction.  Background: Many studies have quantified hand strength by having participants squeeze, pull on, or create torque on an object or handle, but few studies have measured breakaway strength directly. Method: In two experiments, hand strength was measured as both overhead breakaway strength for handholds typical of fixed industrial ladders and as maximum isometric grip strength measured using a common Jamar grip dynamometer. Results: Breakaway strength was greatest for a fixed horizontal cylinder (&quot;high friction&quot;; 668 ± 40 N and 691 ± 132 N for Experiments 1 and 2, respectively), then for a horizontal cylinder that simulated low surface friction (&quot;low friction&quot;; 552 ± 104 N), then for a vertical cylinder (435 ± 27 N), and finally, for a vertical rectangular-shaped rail (337 ± 24 N). Participants are capable of supporting only their own body weight with one hand when grasping the fixed horizontal cylinder. Breakaway strength for both the high- and low-friction horizontal cylinders was significantly greater than isometric grip strength (1.58 ± 0.25 and 1.26 ± 0.19 times, respectively). Conclusion: Results support the hypothesis that hand-handhold coupling is composed of active (isometric or eccentric finger flexion) and passive (frictional) components. Traditional isometric grip strength alone does not predict the strength of a couple between a hand and a handhold well. Application: This research shows that handhold shape, orientation, and friction are important in the safe design of grab rails or ladders.<p />",
language="",
issn="0018-7208",
doi="10.1177/0018720809355969",
url="http://dx.doi.org/10.1177/0018720809355969"
}