Upper-Limb Isometric Force Feasible Set: Evaluation of Joint Torque-Based Models

Abstract

A force capacity evaluation for a given posture may provide better understanding of human motor abilities for applications in sport sciences, rehabilitation and ergonomics. From data on posture and maximum isometric joint torques, the upper-limb force feasible set of the hand was predicted by four models called force ellipsoid, scaled force ellipsoid, force polytope and scaled force polytope, which were compared with a measured force polytope. The volume, shape and force prediction errors were assessed. The scaled ellipsoid underestimated the maximal mean force, and the scaled polytope overestimated it. The scaled force ellipsoid underestimated the volume of the measured force distribution, whereas that of the scaled polytope was not significantly different from the measured distribution but exhibited larger variability. All the models characterized well the elongated shape of the measured force distribution. The angles between the main axes of the modelled ellipsoids and polytopes and that of the measured polytope were compared. The values ranged from 7.3° to 14.3°. Over the entire surface of the force ellipsoid, 39.7% of the points had prediction errors less than 50 N; 33.6% had errors between 50 and 100 N; and 26.8% had errors greater than 100 N. For the force polytope, the percentages were 56.2%, 28.3% and 15.4%, respectively.

Comparison of strength profile representations using musculoskeletal models and their applications in robotics

“…Such strategies for human strength estimation predominately rely on empirical measurements of Maximum Voluntary Contractions (MVC), or model-based approximations, to estimate whole-limb strength ( Sasaki et al, 2010 ; Hernandez et al, 2015 ; Rezzoug et al, 2021 ). The main drawback of this approach is the resources and time necessary to acquire good quality data as it requires consideration of factors such as managing body posture and sensor placement and handling fatigue.…”

On-Line Feasible Wrench Polytope Evaluation Based on Human Musculoskeletal Models: An Iterative Convex Hull Method

“…Several capacity metrics have been developed over the years, first by the robotics community [3] [4], and later adapted to the human motion analysis [5][6] [7]. The most well known representatives being wrench, twist and acceleration capacity.…”