The men’s Ironman World Championship was held in Kona, Hawaii last weekend. The course on Kona has a legendary reputation and is considered one of the most iconic endurance events out there because of its history, extreme environment and level of competition.
The first Ironman race was held in Hawaii in 1978, where it began as a simple challenge between athletes debating which discipline (swimming, cycling, or running) required the greatest endurance. The race was created by Judy and John Collins, who linked the Waikiki Roughwater Swim, a local Oahu cycling club route, and the Honolulu Marathon courses together to create the ultimate endurance test. "If you do it, I'll do it," John famously said, adding "...whoever finishes first we'll call him the Iron Man."
Kona’s landscape is famously brutal, with intense heat, strong crosswinds, and high humidity. The course includes a 2.4-mile swim in open ocean in the waters of Kailua Bay with the sunrise over Mt. Hualālai as the backdrop. In the 112-mile bike ride, athletes travel from Kailua-Kona to the Hawi turnaround and back on the iconic Queen Ka'ahumanu Highway. The journey requires athletes to compete across hot lava fields with radiant heat while also facing challenging elevation. During the final 26.2-mile run, triathletes navigate a rolling course with intermittent steep stretches and a victorious lap through Kona.
Typically known for high temperatures that can exceed 90°F, this year’s Kona conditions while still hot were a bit more tolerable. At 6:00am the air temperature was 77°F with 84% humidity. By 1:00pm the temperature rose to 84°F. In contrast, the prior year’s world Championship in Nice, France boasted a 73°F start, with 53% humidity. Many athletes and coaches acknowledge the challenging conditions that Kona presents and work to ensure that their athletes arrive early and acclimate to the heat as well as develop a heat training plan. Not adequately preparing for the heat and humidity of Kona can result in cramps, premature depletion, heat stroke and far more.
Kona attracts the top triathletes from across the globe, all of whom are required to qualify for the race by winning or placing highly in other Ironman events. The Kona field included a list of 2,491 athletes. This year 81 athletes that started the race did not finish. Approximately 3.4% of individuals who started the race were not able to cross the finish line despite their training and commitment to the sport. It’s also worth noting that 110 athletes did not start.
At Nix, we receive frequent feedback from users who are astounded by their own personal sweat and electrolyte losses. When they take their unique personal sweat metrics and develop a hydration plan, they’ve confirmed that they feel stronger, have decreased cramping, and have been able to complete their races even in the toughest conditions.
During the month of October, Nix athletes in Kona recorded an average fluid loss rate of 30 oz per hour and 1,450 mg of electrolyte losses per hour. This is 19% higher in fluid losses and 53% higher in electrolyte losses than workouts recorded in Seattle, Washington & Portland, Oregon - which is usually cooler and less humid.
Races in which conditions are similar to the Kona World Championships require additional heat acclimation and training. It’s important to train properly to prepare the body for these intense conditions and avoid heat stroke.
There is a reabsorption function in the sweat gland that attempts to retain critical electrolytes. As the body sweats faster, the reabsorption function can’t keep pace. As a result, a higher concentration of electrolytes escape into the sweat. Therefore, it is common for athletes to see a proportionally higher electrolyte losses when producing more sweat. This was reaffirmed by the data that we studied specifically for workouts in Kona.
Nix users and athletes Fabio Carneiros and Santiago Ascenço, both of Brazil, were spotted wearing Nix during the days leading up to the big race.
Understanding your personal sweat stats and how they change with different environmental conditions is paramount to successfully training and racing in any sport.
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Data for this article was compiled based on location for workouts in the month of October 2024. Only workouts of at least 30 minutes in length are included within the dataset.