The effect of bracing availability on force-exertion capability in one-hand isometric pulling tasks
Authors: Monica L.H. Jones, Matthew P. Reed, Don B. Chaffin.
In activities of daily living and industrial tasks people encounter obstructions in their environment that kinematically limit the postures that they can achieve. These obstructions can also provide an opportunity for additional support such as bracing with the hand, thigh or other body part. The reaction forces acting at hand or body coupling, which are in addition to those acting at the feet and task hand, may support some percentage of body weight, allow modification to postural behavior strategies, or provide the ability to generate oppositional forces relative to the task force. The effects of kinematic constraints and associated bracing opportunities on isometric hand force were quantified in a motion-capture study of 25 men and women with a range of body size. The objective of this work was to quantify the effect of bracing availability on force-exertion capability. Analyses of one-hand maximal pulling tasks demonstrated that the additional force reaction surfaces enable participants to exert more force at the task hand, by 31% on average, but these values were greatly affected by the location and utility of the constraint and the specified force direction.