The effect of handhold orientation, size, and wearing gloves on hand-handhold breakaway strength.

Objective: The aim of this study was to quantify the effect of handhold orientation, size (diameter), and wearing a glove on the maximum breakaway strength between a hand and handhold.

Background: Manual breakaway strength is known to be greatly reduced for vertical compared with horizontal handholds, but oblique orientations have yet to be studied.

Method: For this study, 12 young adults (6 female) attempted to hold on to fixed overhead cylindrical handholds with one hand in low-speed simulated falls as forces on the handhold were recorded in two experimental designs. Breakaway strength was measured for (a) three different-sized cylinders in four orientations while the participants were using the dominant hand and (b) a single-sized cylinder in four orientations while the participants were bare-handed or wearing a glove on the nondominant hand.

Results: Handhold orientation (p < .001), handhold diameter (p < .001), and wearing gloves (p < .001) significantly affected breakaway strength. Breakaway strength increased 75% to 94% as the orientation of the handhold was moved from vertical to horizontal. Breakaway strength decreased 8% to 13% for large-diameter (51-mm) handholds as compared with smaller diameters (22 mm to 32 mm), depending on orientation. Gloves may increase or decrease the ability to hang on depending on interface friction; greater friction increased breakaway force.

Conclusion: Handles oriented perpendicular to the pull direction and high-friction gloves provide the greatest breakaway strength. Smaller handhold diameters than predicted by grip strength afford greater capability in these orientations.

Application: These insights can be used to design handholds that increase the ability to support one's body weight and reduce the effort needed to pull or lift heavy items.