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

86

2 authors: Some of the authors of this publication are also working on these related projects: Swimming View project RobCat View project Philippe Vaslin Université Clermont Auvergne

146 PUBLICATIONS 439 CITATIONS

SEE PROFILE

Patrick Lacouture French National Centre for Scientific Research

178 PUBLICATIONS 949 CITATIONS

SEE PROFILE

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

Thematic Days of the French Society of Biomechanics : "The human machine with regard to the sport performance" SP2MI – Boulevard Marie & Pierre Curie – Futuroscope (May, 14th - 15th 2009).

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 (SP2MI - Futuroscope - May, 14th - 15th 2009) 2

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) 3

• 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). Introduction

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 4

• 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. Introduction

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 5

• 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). Introduction

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 6

• 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

• ften 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].

Material & Method

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 7

• Quantitative kinematic analysis allows measuring

and computing :

• The trajectories of the athlete's segments and center
• f 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. Material & Method

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 8

• 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 ».

Material & Method

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 9

• 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].

Material & Method

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 10

« 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.

Material & Method

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 11

Theory of reference : Mechanics of multi-body systems Sport Performance Mechanical Parameters

• f the Performance

Mechanical Model Relevant Parameters

• f the Performance

Experimental Protocol (in situ measurements) Measurement Results Simulation Program Theoretical Performance

?

Figure 2 : Method of the mechanical analysis of sport performance.

Material & Method

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 12

• 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. Material & Method

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 13

• 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.

Material & Method

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 14

• 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 :

Material & Method



Fext=∑

i

mi aG i/Rt 

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 15

• 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.

Material & Method

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 16

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) 17

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) 18

Application 1 : Sprint ergometer.

Figure 5 : Results provided by the sprint start ergometer and a video camera.

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 19

Application 2 : Striking ergometer.

Figure 6 : Front and side views of the striking ergometer.

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 20

Application 2 : Striking ergometer.

Figure 7 : French Boxer delivering a straight punch on the striking ergometer.

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 21

Application 2 : Striking ergometer.

Figure 8 : Components of the force measured by the striking ergometer.

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 22

Application 2 : Striking ergometer.

Figure 9 : 3D unit vectors of the upper limb segments of a French Boxer.

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 23

Application 2 : Striking ergometer.

Figure 10 : Maximal wrist force components without wrist strapping.

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 24

Application 2 : Striking ergometer.

Figure 11 : Maximal wrist force components with wrist strapping.

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 25

• The measure and analysis of sport performance

must be done within a theoretical frame, which is continuously growing;

• These theoretical improvements associated with

sophisticated sensors should be applied to the concrete needs of trainers, without compromise :

• This is currently done in some scientific and technical
• rganisations (e.g. LMS, CAIPS, CRITT Sports-Loisirs);
• This may lead to the design of new sport ergometers.
• The results of this Theory-Practice synergy should

be transferred to their main users : sportsmen. Conclusion

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 26

« And nothing could be taught to us of which we already have in mind the idea that is like the material from which this thought is built ».

« Et rien ne saurait nous être appris dont nous n'ayons déjà dans l'esprit l'idée, qui est comme la matière dont cette pensée se forme ». [Gottfried Wilhelm LEIBNIZ (1686) : Discours de

métaphysique, Paris : Gallimard [Folio Essais], 2004, 562 p.]

Conclusion

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 27

Conclusion

The mechanical analysis provides the material from which is built the understanding of the sport gesture, of which the athletes and the trainers, but also the biomechanists, have their own idea or representation. In order to build this common knowledge, it is necessary that biomechanists understand the empirical descriptions currently used by sportsmen, and conversely, that these latter acquire a few mechanical concepts so that all of them could explain the same phenomena with the same words.

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 28

Conclusion

The way opened by Nicolas Copernicus and his successors is not a dead end, neither a one way road forbidden to sportsmen, as could be suggested by this panel placed at the entrance of sympathetic road of Berlin (Germany).

Thematic Days of the French Society of Biomechanics (SP2MI - Futuroscope - May, 14th - 15th 2009) 29

Thanks for your attention.