Apparatus and Method for Lower Body Power Output Estimation

Abstract: One of the Swedish sports federation RF’s ongoing goals is to find new and better methods oftesting athletes. Therefore a project, with the goal of investigating which method to use formeasuring lower body muscle power output during free barbell exercises, in order to givetraining recommendations, was undertaken. This had already been done in a study done byCormie et al 2007 [9]. In this study, the muscle power output is estimated using methods relyingon knowledge of the position of the barbell and the athlete’s reaction forces acting on the floor.The goals of this thesis was to make a test apparatus capable of repeating the test methods usedin Cormie et al 2007 [9], but also explore the possibility of finding other methods of musclepower estimation and to implement these.In order to reach these goals, first a literature study was carried out, looking at other previousstudies, technologies and commercial systems. Then models of the mechanics and the test setupwere developed. Lastly, the test apparatus was developed, using linear position transducers fordetermining the position of the barbell, along with a force plate for measuring reaction forces.The data was then collected and analyzed using a PC-system developed in LabVIEW. As a finalstep, a limited trial was conducted in order to compare results with Cormie et al 2007 [9].The resulting apparatus determines the position of the barbell’s center of mass and its orientationin space, measuring the position of two points on the barbell using a total of five linear positiontransducers, three on one side and two on the other. The reaction forces are measured using aforce plate position under the athlete. All of this, in 3D.One new method of estimating muscle power output is also presented in this thesis. This methodaccounts for the lifter and the barbell as two separate bodies, able to move independently,whereas the previous method of choice only accounts for them as one stiff body.The trial showed good coherence with Cormie et al 2007 [9], comparing the same methods. Alsothe new method gave results that seem reasonable in comparison with the old methods’ results.The conclusion and recommendation of this report is to, in the future, use this new method. Thisnew method should, in theory, be able to capture more of the reality of free barbell exercises thanthe old method. The conclusion of this report is therefore that this method should be used.