Using CORE - High Core Temp during a Cool Race

Do you need a cooling strategy even when racing in a cool outside air temperature? This case study from CORE Coach Erik Åkesson from Toppfysik coaching in Sweden shows a rider’s core temp during both a warm and cool race.  

A one-person case study of the effects of a cooling strategy versus non-cooling strategy in two different MTB XCO races

This one-person case study was performed on a national elite rider in two different SWE-CUPs. The weather forecast was typical for Sweden with over 25°C / 77°F and no clouds on the first race, and about 13-14°C / 56°F and cloudy in the race one week after. There was no rain or big differences in the wind, but the exposure in the sun was significantly higher in the first race.

Race one – hot and sunny

Location: Lugnet, Falun. May 30th.

22.72 km

88 minutes of racing

15.5 km/h average

918 meters of elevation

The mean temperature for the race (according to Garmin) was 25.4 / 77°F degrees, with 30.0°C / 86°F degrees maximum in the sun and low speed. In the figure below we see the core temperature in the gray in the background, the elevation of the race course in green (6 laps), and the skin temperature in blue. As you can see the skin temperature rises in the longest hill every lap (strong sun exposure and low speed, which meant almost no cooling from wind). The skin temp follows the elevation profile pretty well.

The interesting thing about core temperature (which had a maximum of 39.57°C / 103.2°F) is that it isn’t as affected by outside factors as the skin obviously is. Rather, core temp is also strongly affected by mechanisms inside the body. The thing that can help the core temperature to cool down is pouring cold water over critical areas of the body, like the back, thighs, hands and head. In this case the athlete started to pour cold water over himself after three laps (after about 35 minutes). After that he kept cooling himself on the same place every lap.

The skin temperature was almost immediately regulated, with lower peaks and lower downs. But the core temp kept rising about 0,5°C more, before it started to flatten out after about one lap, and started decreasing about 30 minutes after he first started to cool himself. The average core temperature of the race was 38,87°C / 101.9°F and maximum 39,57°C / 103.2°F.

What do we learn from this?

In hot races (25.4 / 77°F is hot for Sweden), you need to cool down from the start. Since the power output decreases with every +1°C the core temp rises it is critical to cool down and to keep the core temperature as low as possible. In this case more frequent coolings and probably ice cubes on the back and/or drinking cold slushies would help even more. One important thing to remember is that it, depending on the race course, is pretty hard to keep up with both drinking and cooling down, since there are limited parts of the course that allow taking hands of the handlebar at all.

But we learn…next time!

Next race – cool and cloudy

Location: Borås, June 12th

18,69 kilometers

74:26 minutes of racing

15.1 km/h average

495 meters of elevation

According to Garmin (the gray line in the figure below) the outside temperature was about 14-15°C / 56°F. The elevation profile is shown by the green line and shows six laps of the course. The core temperature as usual is the gray in the background. This race didn’t have a clear elevation profile, and was up and down almost all the time with many minor climbs.

The athlete started with a core temp that was pretty high, above 38°C / 100.4°F which is not optimal. After the start, his core temperature sank a bit before it skyrocketed. Since the outside temp wasn’t as high as the week before in Falun, the cyclist didn’t have a cooling plan and did not pour water over him since “it felt cold outside”. If you look closely at the core temperature you can see a small plateau between laps 5–6.

With a core body temperature that didn’t stop rising even though the outside temperature was low shows that the body still generates a lot of heat while racing. After the finish the athlete had a maximum temperature at 39.88°C / 103.8°F and average 38.97°C / 102.1°F. Compared to the first, hotter race, both the average and maximum core temps were higher in the second race.

What are the lessons to be learned here?

First always have a cooling strategy, no matter how cool the outside temperature. Second, start to cool down long before you think. Third, you don’t need to be in Kona, Down Under, Spain or South Africa to benefit from heat training.

The outcome for the athlete in both races was pretty similar, finishing in the top 10 in both races. Since the athlete was used to heat training and worked continuously with heat training in his normal training plan, the high rise of the core body temperature didn’t affect him in the same ways it affected many of his competitors who suffered a lot more from fatigue, especially in the first, hot race in Falun.

About the coach

Name: Erik Åkesson

Age: 24

Location: Falun, Sweden


I’m a 24 year old cycling coach from Sweden. I am currently competing myself in the national elite XCO and XCM, as well as the XCM World Series. As a coach I work closely with high school athletes as well as elite and other cycling-enthusiasts. As MTB is my main focus and head discipline as a coach and as a rider, I also coach on the only Track we have in Sweden trying to get the interest in track cycling bigger in the country.