Development of a Biomechanical Model of Hand/Handhold Coupling

Research Trainee: Justin Young, MSE, PhD Student, Dept. of Industrial and Operations Engineering at the University of Michigan

Faculty Researcher: Thomas J. Armstrong, PhD, Professor of Industrial and Operations Engineering and Biomedical Engineering at the University of Michigan

The aim of this research is to create a model that explains the strength of the coupling between the hand and a handhold. More specifically, this work will be used to develop a biomechanical model that can be used to predict the amount of force needed to break the coupling between the hand and a grasped handhold (“breakaway strength”) given the size, orientation, and surface characteristics between the hand and handhold.

Our proposed biomechanical model and preliminary research show that the breakaway force for handles of a given shape and orientation are significantly different from grip strength measured by squeezing two parallel bars together. Friction at the handle surface is a critical factor in the capability of the hand/handhold couple.

The proposed study will 1) determine how handle size and orientation affect total breakaway strength of the hand/handhold coupling 2) determine how common work gloves affect surface friction and breakaway strength 3) examine the force distribution at the hand/handle interface during external loading and 4) integrate the results of these investigations into a simple model of grasp capability that can be easily implemented by designers to improve the safety and usability of handholds and work objects.
The models developed in this study can be used to establish design criteria for handles and handholds on ladders, fixed equipment, stairwells, tools, and other safety critical items. They also can be used to design handles that minimize force requirements, localized fatigue and the risk of work-related musculoskeletal disorders.


Publications resulting from this project:
Young JG, Woolley CB, Ashton-Miller JA, Armstrong TJ. The effect of handhold orientation, size, and wearing gloves on hand-handhold breakaway strength. Human Factors. 2012;54(3):316-333. doi: 10.1177/0018720811433585.

Young JG, Woolley C, Armstrong TJ, Ashton-Miller JA. Hand-handhold coupling: effect of handle shape, orientation, and friction on breakaway strength. Human Factors. 2009;51(5):705-717. doi: 10.1177/0018720809355969.

Young JG, Sackllah ME, Armstrong TJ. Force distribution at the hand/handle interface for grip and pull tasks. Proceedings of the Human Factors and Ergonomics Society Annual Meeting. 2010;54(15):1159-1163. doi: 10.1177/154193121005401515.


Research trainee’s current position:
Justin Young completed his PhD in January 2011 and is currently an Assistant Professor of Industrial Engineering at Kettering University.