title: Toward isometric force capabilities evaluation by using a musculoskeletal model: Comparison with direct force measurement.
abstract: Developing formalisms to determine force capabilities of human limbs by using musculoskeletal models could be useful for biomechanical and ergonomic applications. In this framework, the purpose of this study was to compare measured maximal isometric force capabilities at the hand in a set of Cartesian directions with forces computed from a musculoskeletal model of the upper-limb. The results were represented under the form of a measured force polytope (MFP) and a musculoskeletal force polytope (MSFP). Both of them were obtained from the convex hull of measured and simulated force vectors endpoints. Nine subjects participated to the experiment. For one posture recorded with an optoelectronic system, maximum isometric forces exerted at the hand were recorded in twenty six directions of the Cartesian space with a triaxial force sensor. Results showed significant differences between the polytopes global shapes. The MSFP was more elongated than the MFP. Concerning the polytopes volumes, no significant difference was found. Mean maximal isometric forces provided by MFP and MSFP were 509.6 (118.4)N and 627.9 (73.3)N respectively. Moreover, the angle between the main axes of the two polytopes was 5.5 (2.3)° on average. Finally, RMS error values between MFP and MSFP were lower than 100N in 88% of the considered directions. The proposed MSFP based on a musculoskeletal model gave interesting information on optimal force orientation parameters. The possible applications in the frame of ergonomics, rehabilitation and biomechanics are proposed and discussed.
authors.affiliation: HandiBio-EA 4322-Université de Toulon, Toulon-Var, 83957 La Garde Cedex, France. Electronic address: vincent.hernandez@univ-tln.fr.
authors.forename: Vincent
authors.initials: V
authors.lastname: Hernandez
authors.affiliation: HandiBio-EA 4322-Université de Toulon, Toulon-Var, 83957 La Garde Cedex, France.
authors.forename: Nasser
authors.initials: N
authors.lastname: Rezzoug
authors.affiliation: HandiBio-EA 4322-Université de Toulon, Toulon-Var, 83957 La Garde Cedex, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Gorce
mesh_terms: D000328:Adult; D001132:Arm / Q000502:physiology*; D001696:Biomechanical Phenomena; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008954:Models, Biological; D053580:Muscle Strength; D055815:Young Adult
keywords: Force polytope; Isometric force; Musculoskeletal model; Upper limb