title: Analysis of the force-sharing problem using an optimization model.
abstract: In biomechanics, one frequently used approach for finding a unique set of muscle forces in the 'force-sharing problem' is to formulate and solve a non-linear optimization problem of the form: min phi(f)= summation operator (f(i)/omega(i))(alpha) subject to Af = b and f > or = 0. Solutions to this problem have typically been obtained numerically for complex models, or analytically for specific musculoskeletal geometries. Here, we present simple geometrical methods for analyzing the solution to this family of optimization problems for a general n-degrees-of-freedom musculoskeletal system. For example, it is shown that the moment-arm vectors of active (f(i) > 0) and passive (f(i) = 0) muscles are separated by a hyperplane through the origin of the moment-arm vector space. For the special case of a system with two degrees-of-freedom, solutions can be readily represented in graphical form. This allows for powerful interpretations of force-sharing calculated using optimization.
authors.affiliation: Faculty of Kinesiology, Human Performance Laboratory, The University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4.
authors.forename: R
authors.initials: R
authors.lastname: Ait-Haddou
authors.forename: A
authors.initials: A
authors.lastname: Jinha
authors.forename: W
authors.initials: W
authors.lastname: Herzog
authors.forename: P
authors.initials: P
authors.lastname: Binding
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000379:methods*; D006801:Humans; D008954:Models, Biological; D009142:Musculoskeletal Physiological Phenomena