title: Determination and optimization of joint torques and joint reaction forces in therapeutic exercises with elastic resistance.
abstract: A model has been developed to definitively characterize the resistance properties and the joint loading (i.e., shear and compressive components of the joint reaction force) in single-joint exercises with ideal elastic bands. The model accounts for the relevant geometric and elastic properties of the band, the band pre-stretching, and the relative positioning among the joint center of rotation and the fixation points of the band. All the possible elastic torque profiles of ascending-descending, descending, or ascending type were disclosed in relation to the different ranges of joint angles. From these results the elastic resistance setting that best reproduces the average-user's knee extensor torque in maximal isometric/isokinetic efforts was determined. In this optimized setting, the shear tibiofemoral reaction force corresponding to an anterior (posterior) tibial displacement was 65% smaller than (nearly the same as) that obtained in a cam-equipped leg-extension equipment for equal values of resistance torque peak, whereas the compressive tibiofemoral reaction force was 22% higher. Compared to a weight-stack leg-extension equipment, an elastic resistance optimized setting has the potential to give a more effective quadriceps activation across the range of motion, and greatly reduces the anterior cruciate ligament strain force, which represents the main drawback of existing open kinetic-chain knee-extension exercises.
authors.affiliation: University of Perugia, Department of Surgical, Radiologic and Odontostomatologic Sciences, Medical Physics Section, Via E. dal Pozzo pad. W, 06126 Perugia, Italy. biscarini@fisica.unipg.it
authors.forename: Andrea
authors.initials: A
authors.lastname: Biscarini
mesh_terms: D004548:Elasticity; D005081:Exercise Therapy / Q000379:methods*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008954:Models, Biological; D019415:Torque