In the spring of 2023, I was contacted by Thomas Ogander. A potential scientific collaboration with one of the toughest races in the world held in our backyard, the Stockholm Archipelago!? The energy and passion Thomas emitted were contagious.
– Sounds crazy and very exciting. Count us in! Was my immediate reply.
I’m a researcher in exercise physiology, the strategic leader of the Sport and Exercise Research & Innovation Centre – Stockholm, as well as a part of a center of excellence for research on exercise and brain health, both located at the University GIH in Stockholm, Sweden. Getting the opportunity to study elite athletes during a live extreme race that evokes a multitude of physiological stresses is a unique opportunity for researchers like me and my colleagues.
The ambition early was to measure as many physiological parameters as possible to try to study the factors that limit human capacity and performance. Preferably live monitoring on as many parameters as possible – aim high! Four months to the 2023 race, in a challenging environment to conduct research, to say the least. Accordingly, the goal for 2023, pilot and explore the feasibility.
I thought I was able to mentally grasp the challenge, the distance, and the environment before the race started, but following the teams live from start to finish, seeing their pain, and seeing their courage and determination, was an extraordinary experience. More feelings than I can express in writing.
On a selection of athletes, we were able to monitor the activity level and heart rate using the Oura™ ring. Why not a conventional chest-worn heart rate sensor with a strap? Imagine the discomfort and tear of the skin after +50 hours of continuous wearing with severe humidity. Not an option. The Oura ring enables long-time monitoring combined with algorithms for sleep quality and heart rate variability which also enables pre- to post-race changes in those parameters. Our analysis of a sub-group of athletes showed an energy turnover of approximately 10’000 kcal during the first 16 hours of the race which progressively decreased to about 8’000 kcal per 24 hours toward the end of the race. While most individuals consume between 2’000 to 3’000 kcal per day, one can imagine the challenge of consuming those amounts of food during an active race with almost 50% of time spent in the water!
Speaking about nutrition, we were of course interested in monitoring the athletes’ blood glucose levels, as these levels are critical for brain function and exercise capacity. On a sub-group of athletes, we placed continuous glucose monitors (CGMs) from SuperSapiens™. These CGMs were originally designed for diabetes care but modified by SuperSapiens for use in sports and to enable continuous monitoring of blood glucose levels via Bluetooth. While the CGMs are designed to be worn on the back of the arm, our first concern was if they would stick the entire race or fall off while taking the wet suit on and off. Luckily, we placed a few sensors on the belly as the arm-worn sensors fell off. Trial and error, that is the essence of research. The data we generated showed that these athletes primarily kept their blood glucose levels at a desired level. A result of very focused feeding strategies. Getting full coverage from all athletes will be a major benefit as some athletes, who did not have sensors, clearly struggled with keeping food and maintaining mental focus.
In late August in the Stockholm Archipelago, close to the open sea, water temperatures average around 15°C. Feel for a long swim? Spending long periods of time in the water, in some cases for two to three hours, evokes a major challenge. Of course, the athletes shiver, go numb, and feel pain due to the cold, but does it become critical? Accordingly, we placed Core™ temperature sensors on a few athletes, which enabled real-time monitoring of skin and core temperature. To somewhat of a surprise, all athletes that wore a temperature sensor kept their core temperature at 37°C or above, even though the skin temperature dropped to 26°C combined with massive shivering in some cases. So, seemingly very tough, but not critical. Interestingly, we in hindsight noted that one athlete started with a fever. That athlete later had to withdraw due to illness. This clearly showed the usefulness of these sensors from a medical perspective.
All in all, the 2023 race was a massive learning experience for me as a researcher, both from a practical perspective and a physiological perspective. But! We have merely scratched the surface of what we want to achieve. Now is the time to accelerate.
The clear objective for 2024 is to acquire live tracking of heart rate, blood glucose levels, core temperature, skin temperature, and blood ketone levels from all athletes. This will have a major influence on the scientific outcome, and the viewer’s perspective as well as strengthen race security for the medical team and the race directory.
But we are not satisfied with that. A critical aspect that we could not monitor during the 2023 race was the cognitive status of the athletes. Thus, one key objective, supported by colleagues from the center of excellence for exercise and brain function, is to study the cognitive function of the athletes before the race as well as when they terminate or cross the finish line. We will also draw blood from the athletes before and immediately after the race. This will enable studying e.g., the impact of the immune system, stress factors linked to brain and heart function, and more.
Altogether, generating knowledge of the limits of human capacity!
Text by: Marcus Moberg, researcher in exercise physiology, GIH/Sport and Exercise Research & Innovation Centre – Stockholm