France SPRinT Running MeCHaniCS new TeCHnOlOgy , new COnCePTS , new

Be it a direct (e.g. track and field events) or an indirect determinant of athletic performance (e.g. soccer, rugby, bobsleigh), sprint running is a key ability in many sports. For this reason, it is both the focus of specific training programmes and exercises, as well as a major cause of injuries. Further understanding of the mechanics of sprinting will surely help to design better training exercises to improve injury prevention and/ or manage rehabilitation and return to sport strategies. The field of sport biomechanics, like other fields of sport science, is dependent on advances in the technology available to explore human locomotion. This is particularly important when studying sprinting i.e. an all-out ballistic activity that makes the human body move at speeds ranging 30 to 40 km/hour, making any direct biomechanical measurement rather challenging. A new device, the motorised instrumented sprint treadmill (IST), was first developed at the University of St-Etienne, France. This article will present the device, the new concepts and some of the results and new perspectives it has opened up in the fields of sport performance science, injury prevention and rehabilitation. NEW TECHNOLOGY: THE INSTRUMENTED SPRINT TREADMILL One step further Parallel to the widely-used cycle ergometers, sprint treadmills were developed in the late 1980s and 1990s to measure propulsive power1. This had the obvious advantage of being more realistic in assessing the physical capacities i.e. the athletic performance and muscular function of athletes. The main drawbacks of hitherto existing technologies were: 1. Force and velocity mechanical output was not measured at the same location (along the tether system by force transducers and at the foot, respectively). 2. The force along the tether which attached subjects to a fixed point behind them did not correspond exactly to the one produced at the foot (i.e. where velocity is measured). 3. The sampling rate was relatively low (one value each 0.25 seconds at best i.e. a sampling rate of 4 Hz), which may have interfered with the accurate determination of instantaneous maximal power. 4. Although various instrumented treadmills (i.e. Peter Weyand et al2-4) allow the achievement of top speeds similar to those reached over ground, record both ground reaction forces (GRF) and belt velocity at high sampling rates, only the vertical, but not the horizontal, component of the GRF signal can be computed. 5. Furthermore, these treadmills only allow subjects to use ‘flying starts’ when dropping onto the rolling treadmill and not typical sprint accelerations from null velocity. In light of these limitations, we proposed a method based on an existing 3D-force dynamometer treadmill modified to enable sprint use and accurate force, velocity and propulsive power measurements. This was aimed at enabling an accurate assessment of the physical characteristics and performance of sprinters5. The IST (ADAL3DWR, Medical Developpement, AndrézieuxBouthéon, France) is a highly rigid metal frame treadmill fixed to the ground through four piezoelectric force transducers (KI 9077b, Kistler, Winterthur, Switzerland) and installed on a specially engineered concrete – Written by Jean-Benoit Morin, France SPRinT Running MeCHaniCS new TeCHnOlOgy, new COnCePTS, new PeRSPeCTiveS SPORTS SCIENCE