Motion capture has been adopted for the production of highly realistic movements, as well as for the clinical analysis of pathological motion. In both cases, a skeleton model has to be identified to derive the joint motion. The optical technology has gained popularity due to the high precision of its marker position measurements. However, when it comes to building the skeleton frames out of the 3D marker positions, significant local skin deformations may penalize the quality of the model reconstruction. We exploit a local fitting tool to visualize the influence of skin deformation on marker movements. Such a knowledge can in turn improve the layout of optical markers. We illustrate our viewpoint on motions of the upper-torso.