The first goal of this Master's Thesis is to analyze the kinematics between the vertical position of the barbell (or the Applewatch) and the vertical position of the body center of mass. Our hypothesis is Eq. 5, which could expresses the link between these two quantities. The second goal is to determine the rest position of the ”spring” system, and find a method that works for different data sets (different athletes). The rest position is defined, where linearity between the ground reaction force and vertical displacement begins. The third goal is to include vertical ”viscosity”. We could adopt an energetic approach, and check whether viscosity plays a relevant role in the motion or not. The last goal is to calculate the rotational ”dissipation” energy, which could serve as an estimator of technique quality.