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Heart Rate Zone calculator

Heart rate zones are a fundamental metric to get familiar with if you’re interested in endurance training, especially for disciplines like triathlon. During this article, you’ll learn much more about the different zones, and you’ll be able to calculate your heart rate zone specifically for triathlon.

Fundamentally heart rate zones show you how hard your heart is working and what energy source you’re utilizing. Whether it be carbohydrates or fat. Professional triathletes use heart rate zones in training to optimize their workouts’ value and conserve energy for longer races such as the Ironman

You can use the triathlon heart rate zone calculator below to indicate what your heart rate is in the different zones. However, this formula doesn’t account for genetics and gender or other factors like altitude and hydration.

Heart rate zone benefits for triathlon

For longer races, such as the Ironman or half ironman distances, you should stay in the aerobic zones throughout the race.

Zone% of max HRExertion LevelFitness goalEnergy used
5100-90%Very hardAnaerobic fitness: Boost sprint speed by developing fast-twitch muscle fibersCHO
490-80%HardAnaerobic fitness: Increase effort for shorter bursts. CHO
380-70%ModerateAerobic fitness: Improve enduranceMostly CHO + fat
270-60%LightAerobic fitness: Improve basic endurance. Sustainable for long periods. Fat burning zone.CHO + fat
160-50%Very lightWarm op zoneMostly fat
0>50%No significant fitness results will be gained
Description of heart rate zone benefits for triathletes. CHO = Carbohydrates

You should use a heart rate monitor to get an accurate and real-time estimation of your heart rate zones. We recommend Fenix 5 with the Garmin Triathlon Heart Rate Monitor. This will allow you to monitor your heart rate zones while swimming, cycling, and running.

What is maximum heart rate (MHR)

Your heart beats a certain number of times in a minute. When your body is relaxed, your heart rate is a state called your Resting Hear Rate (RHR). This is the number of times your heart beats when resting is as low as it’s going to get.

When you work out, your heart rate goes up. The higher the intensity, the higher the heart rate. At a certain point, you’ll reach the maximum number of times your heart can beat a minute. This is what we call the maximum heart rate (MHR). When you reach your MHR during high-intensity workouts, you’re struggling, and your body cant’ continue for very long. Imagine yourself in an all-out sprint. Everything burns, and you can hardly breathe from poor exhaustion – you know you’ve reached your maximum heart rate!

When we’re using heart rate zones, it’s always a percentage of your maximum heart rate. In other words, it’s a measurement of how much demand you put on your heart. And that’s a very effective tool to improve your overall fitness and cardiovascular system!

How to find your Maximum heart rate

The simplest way to find your maximum heart rate is to subtract your age from 220. For example, a 50-year-old woman has an MHR of 170. If she wanted to hit zone 3, she needed to hit 80-70% of 170. Amounting to a heart rate of 136 – 119 beats per minute. 

As mentioned before, the formula doesn’t account for several important factors such as gender, genetics, weather conditions, hydration, and altitude. 

Calculate your maximum heart rate with the Gulati method (Women only)

More complex formulas exist, such as the Gulati method for women only. This formula subtracts 206 with 0.88*age. The formula with our 50-year-old woman would look like this: 206-(0.88*50) = 162. To hit zone 3 in her triathlon training would amount to 129 – 113 beats per minute. 

Calculate your maximum heart rate with the Takana method

Another way to measure maximum heart rate is by the takana method. In their studies, they proposed the following formula: (209 – 0.7 x age). In our case with the 50-year-old-woman, it would look like this: 209 – 0.7*50 = 174. Using the takana method her heart rate should be between 139 and 121 to hit zone 3.

Why do we burn carbohydrates in the aerobic zone?

Our body breaks down macronutrients such as carbohydrates into smaller parts to produce energy. Carbohydrates in these processes are excellent energy sources. 

The carbohydrates will be broken down into glucose. Glucose is needed to produce our body’s fuel: ATP (adenosine triphosphate). When we exercise in the aerobic zone and allow our body to breathe correctly, we can produce energy while oxygen is present. This is called aerobic metabolism. 

Because oxygen is available in the process, our body produces much more energy per glucose molecule if oxygen weren’t present. 

In contrast, of course, we have anaerobic metabolism, which is when oxygen isn’t available. Here the process of converting glucose into ATP is much less efficient.

Learn more: Carbohydrate intakes for triathlon athletes

Best heart rate zones for fat loss

When our body produces energy, it typically uses glucose stored in glycogen. However, it can also use fat by tapping into the lower ends of the heart rate zones. 

The body does burn fat during lower-intensity workouts. But due to the lower intensity of the activities, the body uses much less energy (calorie

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