July 26, 2024
All photos courtesy of Jim Mahaney
Even though the invention of swimming likely dates back millions of years to soon after humans first evolved, the science behind what actually are the best techniques for competitive swimming has lagged far behind that of much “younger” sports. A new collaboration between the Departments of Computer Science, Mathematics, and Exercise and Sport Science and USA Swimming seeks to tackle fundamental questions on swimmer performance and leverage those answers in time for the 2028 Summer Olympics in Los Angeles.
The original idea for this project came from a chance meeting of Professors Richard McLaughlin and Claudio Battaglini, both of whom are avid swimmers. McLaughlin runs the Joint Fluids Lab in Applied and Computational Mathematics, and his years of experience working in the field of fluid dynamics paired perfectly with Battaglini’s background in exercise science. Battaglini is also a world-renowned swim coach and is currently a sprint coach for the U.S. National Junior Team. To round out the group, Jim Mahaney from Computer Science was added to handle the research engineering needs of the team.
Understanding the mechanics of a person swimming is a difficult and complicated task, so the first step was to look for ways to optimize individual body parts. The hand was the obvious place to begin, and a system was designed by Mahaney which could measure the forces on a model hand suspended in a recirculating tank. The system uses strain gauges mounted at 6 different axes to record the force that the water exerts on the submerged model hand as it flows past. The water itself is flowing at a speed that matches that of an Olympic swimmer, so the forces observed are analogous to what one would see in the pool.
With this system in place, the group moved to create a more realistic hand model. Mahaney and undergraduate computer science and mathematics double-major Steven Tio visited the UNC Swimming and Diving Team and measured the left hand of each swimmer, then used that data to produce a 3D model of the average hand size of a UNC swimmer. The model was then split into three parts, allowing for easy replacement of the fingers or thumb when testing different hand positions. The resulting model was then printed using a resin-based printer to create a solid hand with a smooth surface that is impervious to water.
In parallel to creating a realistic hand model, the team has also been working with a technique known as Particle Image Velocimetry, or PIV. This method provides a way to visualize and track the flow of fluid around an object. In practice, a laser sheet is shone into a fluid, bisecting the object of interest. Tiny glass spheres are added to the fluid, and as they flow through the laser sheet, the reflected laser light can be tracked by a camera system. By combining the tracks of many spheres, it is possible to visualize the flow of the fluid, calculate its speed, and more.
Once the optimal hand positions have been determined, the next step will be to train swimmers to master these new techniques. In order to achieve this, coaches will need to know the precise positions of each athlete’s thumbs and fingers while they are swimming. To that end, work has already begun to create a lightweight glove that will log these positions in real time. Computer science major Harper Callahan has designed a prototype system which uses flex sensors at each finger joint to track their orientation. Further work by information and library science major Lilly Nekervis has taken Callahan’s original design and added it to a flexible wooden hand, so that the accuracy of the sensors can be validated. Once the design is fully tested, the sensors will be integrated into a glove for use by actual swimmers.
USA Swimming is also interested in improving performance in open water swimming. The U.S. has never medaled in men’s or women’s marathon swimming, which has been held since the 2008 Summer Olympics. With the help of the Joint Fluids Lab’s 120-foot-long wave tank, offshore conditions can be simulated in a controlled environment, allowing research into the effects of waves, currents, and even wind on swimmers.
With mere milliseconds making the difference between a gold or silver medal, the goal is to give the U.S. Olympic swimmers a competitive edge that is backed by hard science. Battaglini says that current advances in swimming are based on stopwatch comparisons without experimental evidence to support them. This research aims to not only unlock the science behind swimming, but also to serve as a springboard for opening up new fields of research in the tracking of human movement, both in and out of the pool.