Mtrologie et expertise de la performance sportive (slides in English) - PDF document

See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/233864099 Métrologie et expertise de la performance sportive (slides in English) Conference Paper · May 2009 CITATIONS READS 0 86 2 authors: Philippe Vaslin Patrick Lacouture Université Clermont Auvergne French National Centre for Scientific Research 146 PUBLICATIONS 439 CITATIONS 178 PUBLICATIONS 949 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: Swimming View project RobCat View project All content following this page was uploaded by Philippe Vaslin on 05 June 2014. The user has requested enhancement of the downloaded file.

Measurement and Analysis of Sport Performance Philippe VASLIN* & Patrick LACOUTURE # * Laboratory of Informatics, Modeling and Systems Optimization (LIMOS – UMR 6158 CNRS) – Blaise Pascal University – Clermont-Ferrand. # Laboratory of Solids Mechanics (LMS – UMR 6610 CNRS) - Poitiers University Thematic Days of the French Society of Biomechanics : "The human machine with regard to the sport performance" SP2MI – Boulevard Marie & Pierre Curie – Futuroscope (May, 14 th - 15 th 2009).

Introduction • Generally, sport performance consists in :  Running as fast as possible ( citius );  Going as far or as high as possible ( altius );  Creating the highest force as possible ( fortius ). Figure 1 : Amsterdam Olympic Stadium (1928 Olympic Games). Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 2

Introduction • On the field, the evaluation of sport performance is resumed to the measurement of :  A time (e.g. running events);  A distance (e.g. jumping and throwing events);  A mass (e.g. weightlifting). •However, these raw measures do not allow the coach or the trainer to know HOW and WHY the athlete achieved that performance. • Moreover, these measures are not convenient to many other sports (e.g. team sports). Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 3

Introduction • The trainer must understand the causes and processes of the athlete's actions in order :  To provide him relevant advice;  To improve his performance. • For studying the processes involved in the performance (in the English sense) and trying to give them a mechanical explanation, they should be evaluated directly on the field. • The mechanical evaluation of sport performance implies to respect theoretical, methodological but also experimental constraints. Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 4

Introduction • For analysing and understanding the performance, it is essential :  To build a theoretical model, as close as possible to the movement reality;  To identify the mechanical parameters involved in the performance;  To measure the relevant parameters with appropriate instruments. • These instruments could be simple or complex and they should be used as near as possible of the actual conditions of practice (e.g. stadium). Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 5

Material & Method • How was achieved the performance ?  The answer to this first question is partly obtained from a descriptive analysis of the movement, usually based on the trainer's visual memory and often on qualitative analysis of video recordings;  « It is a mistake to believe that the facts already contain the explanation. It must be introduced into them... The basis of the experimental method is the invention of the mathematical formulae ». [Suzanne BACHELARD, Logique et philosophie des sciences , Paris : Hachette, 1944]. Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 6

Material & Method • Quantitative kinematic analysis allows measuring and computing :  The trajectories of the athlete's segments and center of mass;  The linear and angular velocities and momenta;  The kinetic and potential energies, etc. • When associated with dynamic measurements, that analysis could answer many of the questions asked by the athlete and his coach about the way the movement was performed. Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 7

Material & Method • Sometimes, this first analysis could invalidate some pseudo-mechanical explanations :  After « pushing » in the starting-block, the sprinter would « progressively » accelerate;  In long jump, the ground reaction force should « pass trough the athlete's center of mass » at takeoff;  In some fighting sports, the maximum impact force should result from the « sum of segments velocities ». Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 8

Material & Method • Why was the performance achieved this way ?  The first difficulties of the mechanical analysis of sport performance appear when we try to answer this question.  For that purpose, an important intellectual process must be followed, which is usually called « modeling » and was brightly described earlier [Bessonnet, G., Modélisation et simulation du mouvement humain, Journées Thématiques de la Société de Biomécanique : La machine humaine au regard de la performance sportive , Futuroscope, 14-15 mai 2009]. Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 9

Material & Method « In front of a given and generally complex situation, the first step is to identify the fundamental parameters or the physical quantities that play a relevant role in the studied phenomenon. These quantities must be then expressed by some mathematical objects (integers, real or complex numbers, vectors, functions...) compelled to verify some relations that allow reducing the studied physical problem to a classical mathematical problem (resolution of an algebraic equation, study of a differential equation, integral computation...) ». [Roger PETIT, DEUG et MATH : Mathématiques indispensables pour la pratique des Sciences Physiques en DEUG. Paris : Masson, 1996, 318 p. Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 10

Material & Method ? Theoretical Sport Performance Performance Theory of reference : Mechanics of multi-body Mechanical Parameters systems of the Performance Mechanical Model Simulation Program Relevant Parameters of the Performance Experimental Protocol Measurement Results ( in situ measurements) Figure 2 : Method of the mechanical analysis of sport performance. Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 11

Material & Method • The first step of the modeling process is to choose the athlete's mechanical model :  Mass-point model : athlete's center of mass;  Multi-body system : the athlete's body is represented by several segments linked by joints and moved by skeletal muscles (movement actuators). • The choice of the athlete's model depends on the complexity of the studied movement, on the up-to- date knowledge on this movement, and on the technical means available for doing the study. Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 12

Material & Method • Whatever the chosen athlete's model, it allows applying the classical mechanical laws :  Fundamental principle of dynamics (Newton's laws);  Theorems of the dynamic resultant and of the dynamic moment;  Theorems of the kinetic resultant and of the angular momentum. • However, these models contain their own limits :  Mass-point model : translational analysis, only;  Multi-body model : segments are assimilated to rigid and homogeneous solids. Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 13

Material & Method • Nevertheless, this latter model allows :  Movement analysis both in translation and in rotation;  Energetic evaluation of the movement;  Computation of joint efforts (inverse dynamics);  Evaluation of the coordination of the movements performed by the athlete;  Contribution of these movements in the force production : F ext = ∑  a G i / R  t  m i  i Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 14

Material & Method • The relevant parameters of sport performance can be identified from the simulations obtained with the model; • They must be measured by convenient sensors, which should :  Have the best measuring features;  Be placed close to the measured parameters;  Not disturb the athlete during his movement;  Be used on the field of the sport practice;  Provide quick and useful results to the trainer. Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 15

Application 1 : Sprint start ergometer. Figure 3 : Kinematic analysis of a sprint start. Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 16

Application 1 : Sprint start ergometer. Figure 4 : Female athlete on the sprint start ergometer. Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 17