Using CORE during a Zwift Session

The end of summer means a return to indoor riding for many cyclists. Zwift remains a popular virtual platform that makes the indoors fun and competitive. But a major challenge with indoor cycling is overheating. Without the cooling wind associated with outdoor riding, the indoor air quickly becomes hot, humid, and unable to cool you. When your core body temperature goes up, your performance goes down. This is because your body diverts blood away from muscles toward the skin, where it can be cooled.

Using CORE is a great way to help keep you cool and to boost your performance. We’ll cover the basics of it here.

Connect CORE to your bike computer

If you’re brand new to CORE, getting started will take a brief setup – easy-to-follow instructions are here. CORE uses ANT+ and Bluetooth and can connect to leading sports watches and computers. Instructions for pairing with Garmin, COROS, Wahoo and others are found here. Once you’ve made the initial CORE pairing with your bike computer and heart rate monitor, CORE will automatically reconnect for each workout. Just shake the CORE sensor a few times to wake it, and you’re ready to go.

Remember to start wearing the sensor at least 5 minutes before the start of your session – this gives the sensor time to accurately dial in your core temp.

Monitoring and cooling

During you Zwift session, CORE will provide you continual readings of your core temp. You’ll know when you’re approaching a core temp that causes performance loss, allowing you to take cooling measures so you don’t lose watts.

How do you know what core temperature results in power loss? The easiest way is to do a heat ramp test. During this test, you’ll learn at which core temp your power starts to decline.

CORE will also help you identify which cooling measures work best for you. For most indoor cyclists, some combination of cooling the room, adding fans, hydration, dousing with water, and shedding clothes work well. You can systematically evaluate each of the by using your CORE data – try each one and, while maintaining steady power, watch how your core temp reacts over the next 10– 15 minutes.

Be aware that some combinations may work better in some situations than others…humidity and air flow have a big influence on cooling measures. The article Cooling and Hydration Strategies for Top Athletes gives a good overview of these measures.

Tracking performance throughout the season

A great way to improve your indoor cycling is by training hot and racing cool. Our indoor training and racing guide shows you how. It involves heat training, meaning you’ll intentionally do some training with your core temp elevated into your personal heat training zone (which is identified with the heat ramp test).

Heat training builds blood plasma and allows your body to more efficiently cool itself. This means your core temp will rise more slowly, and you’ll lose fewer watts as it does rise. You’ll notice this during your indoor races – you’ll be able to maintain power at higher core temps.

The CORE app allows you to systematically track your heat training. For example, it shows you how much thermal load you’ve accumulated each day, week and month. This tells you if you’re doing enough to maintain your blood plasma gains.

By repeating a heat ramp test every 4–6 weeks, you can monitor your heat adaption. A heat ramp test done after a heat training block should result in a higher heat training zone than previously – this shows that your body can withstand a higher core temp without losing power.