With the support of the Fédération Française de Natation, the TechnoSport of Aix-Marseille University is developing three new tools for measuring the performance of swimmers. They will be used, among other things, during the training of the French swimming team as part of the preparation for the 2024 Olympics.
In high-level sport, and in particular timed sports, the contribution of data is becoming increasingly important to help athletes push the limits of their performance. Swimming is no exception, except that this sport faces a major difficulty. As much on land, it is possible to recover physiological, technical and biomechanical data from athletes relatively easily, in a swimming pool, much less. The main reason: water is an obstacle to the transmission of information. To overcome this difficulty, the TechnoSport of Aix-Marseille University is developing three new technologies for measuring the performance of swimmers. This work is carried out in partnership with the French Swimming Federation (FFN), with the 2024 Olympics in sight.
The first tool is a submerged platform whose function is to measure the propulsive force that swimmers must exert when they press their feet once morest the wall of the pool to make their turn, in order to start back in the other direction. A delicate passage where hundredths of a second can be gained or lost. An instrument already exists, except that it costs around 250,000 euros and does not adapt to all swimming pools.
“We diverted sensors used in the food industry and fixed them on a carbon plate, in order to manufacture a new lighter tool, which is easily transportable, says Arnaud Hays, Research Engineer at Aix-Marseille University. We have also designed a system so that it attaches to the edge of the pools without making a hole. As for the problem related to safety, it was solved with the help of a low voltage power supply. For the exploitation of the data, there are very few studies in the scientific literature, and we were faced with the fact that few high-level athletes perform statistical processing. Nevertheless, we managed to exploit them. »
Calculate the speed of the swimmers, following the turn
After several conclusive tests, a first prototype will be made available to the Cercle des Nageurs de Marseille (CNM), an emblematic local club and reference in French swimming. And thanks to the help of the FFN, it will be duplicated in three or four copies so that the French teams train in the other major training centers. But this new instrument will not be sufficient to assess the performance of swimmers during their turn, because it is still necessary to be able to calculate their speed over the first meters following this passage. The hand-held stopwatch is not accurate enough, while the use of a water camera is not a suitable tool for live use when training athletes.
A timed door was therefore developed in collaboration with the LP3 laboratory (Lasers, Plasmas and Photonic Processes). The tool, located at the bottom of the pool, is capable of producing a laser beam and measuring the passage time of the swimmers once the laser line has been crossed. “Light in water propagates much less well than in air and we had to find the right wavelength for the device to work.says Arnaud Hays. We also had to address safety issues, and for now swimmers must wear polarized goggles to protect their eyes from the laser. But in the final version, there will no longer be a need for this protection and we expect to achieve precision to a thousandth of a second. »
Measure heart rate, live, in water
After having demonstrated the concept of this device, a prototype must be tested at the end of January. While the submerged force measurement platform will only be intended for high-level sport, the timed door should be able to serve a wider audience, according to Arnaud Hays: “It is not expensive to manufacture, and there may be a real market for children in particular, during playful exercises in swimming pools, for example to measure their passage time at 10 meters. »
The third and last technology developed is a heart rate monitor. Again, this type of equipment already exists, except that swimmers must get out of the water to use the data. “To do quality training, it is essential to be able to read the heart rate of swimmers live”, assures the expert from Aix-Marseille University. To achieve this, the scientists instrumented a water line, which is usually used to delimit the lanes of each swimmer, by installing sensors there. Their role is to retrieve data from a conventional heart rate belt placed on swimmers. These sensors then transmit their data through the air using Wi-Fi to a reading device. This month, a new prototype will be tested and if the results are conclusive, mass production of an instrumented water line will be launched. “This equipment also makes it possible to geolocate the person in the swimming pool and therefore to calculate their average speed, and the times of passageadds Arnaud Hays. Admittedly, the measurement is a little less precise than the laser, of the order of a tenth of a second, but for daily training, it is quite practical. » Beyond its use for high-level athletes, this tool should also have a medical interest, in the context of functional rehabilitation exercises with patients, in order to monitor their heart rate live.
These three devices should be operational in March or April 2023. Coaches will be able to use them for a little over a year to improve the performance of the swimmers of the French team before the 2024 Olympics.