Preliminary biomechanical study of triple Lutz

In artistic roller skating, there are no quantitative biomechanical studies analysing the Lutz. Therefore, the aim of this research was to analyse the kinematic of the Triple Lutz in world-class athletes. Five subjects were analysed. A motion analysis system was used to reconstruct the position of apposite markers placed on the athlete’s body and on the skate. Relevant biomechanical indices representing linear and angular displacements, angular velocities were analysed in different phases of the considered movement. The pelvis centre raised on average of 25.4 cm at the take-off (range: 19.5 – 34.8 cm). The mean height of the flight trajectory was of 50.5 cm (range: 42.2 – 57.8 cm). The absolute distance between the pelvis centre and the right foot centre at the toe assist was 50.1 cm, whereas at the take-off it was 13.5 cm, i.e. definitely lower, with very wide oscillations between the minimum (2.6 cm) and the maximum (23.6 cm) value. The left knee and the ankle, at the toe assist, were clearly flexed (knee: 62° and ankle: 24° of dorsiflexion). Then, the knee showed the maximum extension in correspondence with the take-off of the left skate (12°). In the same instant, the left ankle showed a moderate plantarflexion of 19°. At the take-off of the right foot, the left knee showed a slight flexion (24°), whereas the ankle showed a little flexion (21°). The inclination of the trunk was more pronounced at the toe assist (37°), and less marked in the following phases (end of the gliding: 32°, and take-off: 28°). The peak velocity varied from 4.72 m/s (recorded before the toe assist) to 4.18 m/s. Then, the velocity further reduced at the take-off of the gliding skate (2.71 m/s), and at the take-off of the jump it is 2.69 m/s. Therefore, the horizontal speed at the end of the gliding was almost equal to that at the take-off. It is possible to explain what described about the pelvis motion by analysing the lower limbs kinematics. The toe assisting leg joints showed a loading action just after the toe assist, that was very little for the hip, moderate for the knee (6°), more pronounced for the ankle (21°). The loading time was the shortest for the knee (0.027 s) and the longest for the ankle (0.09 s). Considering the falling time of the pelvis (0.04 s), it can be concluded that the fall is related to the loading of all the three joints of the toe assisting leg. The gliding leg, at the toe assist, was in the neutral position on the frontal plane, whereas it was markedly flexed such as the knee and the ankle. Then, the three joints made an extension movement, continuing up to the end of the gliding phase. The latero-lateral movements (adduction – abduction) of the hips were less evident in the initial phase for the gliding. Concerning the trunk movements, the subjects showed different strategies about the hip and shoulder movements in the toe assist and take-off points. The upper limbs movements in the toe assist and take-off phases were very different amongst the examined subjects. Therefore, it is not possible to individuate a reference model that can provide useful for a general analysis. In the future, a qualitative analysis of the arms movements will be carried out to understand the different strategies adopted by the various athletes.