Nathan Dortmann is a CORE Coach and amateur triathlete. He raced the 2022 Ironman World Championship in 8:53:38, good for 10^th in his age group and 20^th overall amateur. Here, he writes about his experience training and racing with CORE.

As we know, Kona is a rough race on the body. With an average temperature of 30 and around 80% humidity, if you don’t like to be challenged, it isn’t for you. The general lack of cloud cover and racing on a black asphalt surface make the race even more challenging. Living in Brisbane, the lead up to Kona is during the winter season so getting used to racing in the heat is a “must do” if you want to have a successful race.

A month of heat acclimatisation

I started using the CORE sensor daily a month before the race. The aim was to get enough heat exposure every day to induce acclimatisation and plasma production. The goal was between 60 to 90 minutes of heat exposure, body temp above 38.5° C (101.3° F) every day, between training and a sauna protocol. I did no fan/fan to regulate body temp during training and 30 to 60 minutes in the sauna straight out of training (to keep body temp high). 

Once in Kona, it was time for some race pace tuning. The goal was to identify the best power output for a manageable body temp in race conditions. Over the first few days it was easy to notice the effect of the heat by comparing body temp/power/hr from back home. During the first few sessions in Kona, I saw around a 20 to 15% drop in performance. After a few days of more heat exposure, we could see that delta reducing and coming back to a more normal level. 

The slow cook strategy

During race day, it was important to use a “slow cook” strategy. Body temp was undeniably increasing with heart rate throughout the day and I had to manage it. I had identified an upper heart rate limit on the bike of 140/145 bpm to keep body temp under control and be able to bring it back down to an acceptable level. Too much time in this zone made it a lot slower for the body temp to come back down and power output would suffer. 

To help keep body temp under control, using the ice cold water at each aid station was a must. But I also used it strategically during low air-flow areas. Plus, opening up the suit was really useful.

The run strategy was very similar. I used ice-cold water down the suit and brought my heart rate down by walking at each aid station. This kept my body temp as low as possible to maintain a maximum performance output. My highest body temp recorded was around the Energy Lab, almost reaching 40° C (104° F) due to a very exposed area with very little air flow and the long hill. 

It was extremely useful to have the CORE sensor throughout the training process. It enabled us to identify the best race pace range for a very specific race such as Kona. Body temp is a metric to keep in mind when racing in the heat if you don’t want to blow up before the end. It allowed me to have a solid race and understand better the different cooling strategies.