Use of lumbar point for the estimation of potential and kinetic mechanical power in running

Abstract

International audienceThe purpose of this study is to estimate the difference between potential and kinetic mechanical powers in running (Pke, Ppe) calculated from the centre of mass and one anatomic point of the body located on the lower part of the runner's back (the "lumbar point").Six runners carried out a treadmill run at constant velocity and are filmed individually with a video camera (25Hz). The 3D motion analysis system, ANIMAN3D, uses a numerical manikin (MAN3D) which compares a voluminal subject (the sportsman) directly to the manikin that possesses the same voluminal properties. This analysis system allows the trajectories of the centre of mass and the lumbar point to be calculated. Then, from these trajectories, potential and kinetic mechanical powers in running are calculated.The results show that the utilisation of the lumbar point rather than the centre of mass of the runner leads to a significant overestimation of Pke (p < 0.05) and a significant underestimation of Ppe (p < 0.05). However, in spite of these differences, the both methods of calculus of Pke and Ppe are well correlated (respectively r = 0.92; p ≤ 0.01 and r = 0.68; p ≤ 0.05).Taking into account that the trajectory of an anatomic point is experimentally easier to access than that of the centre of mass, this kind of point could be used to estimate the evolution of kinetic or potential energy variation in different cases. However, when the lumbar point rather than the centre of mass is used for the estimation of the mechanical energy produced in running, Pke could appear as a discriminating parameter, while it is not