Heart Rate During a Half Ironman Race

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Knowing your heart rate while you train and race is a valuable tool when it comes to half Ironman triathlons. Wearing a monitor during a race helps you determine when to hold back or push it a bit. Working out in a variety of heart rate zones as you train helps you strategically raise your fitness level and get ready for your race.


You’ll use three main heart rate zones as you train and race. The recovery and endurance zone is 60 to 70 percent of your maximum heart rate. The aerobic and tempo zone is 70 to 80 percent of your max. Your anaerobic threshold zone is 80 to 90 percent of max, says John Mora, author of “Triathlon Workout Planner.” To find your maximum heart rate, use the Karvonen formula which takes your age and resting heart rate into account. First take 220 and subtract your age. So if you are 40, your max is 180. Then take that result and subtract your average resting heart rate to get your zone baseline. If it is 55, you end up with 125. To get each percentage use the following formula: zone baseline multiplied by percentage plus resting heart rate. To get 60 percent using the example, that is 125 times 60 percent, or 0.6, for a result of 75. Then add your resting heart rate of 55 for a result of 130.

Base Training

Utilize zone 1 during the base training phase. This is when you are building up to the distances you must complete. Base training helps you build endurance and adapt to the distances in your race. Also stay in zone 1 during your recovery workouts once your base training phase is complete. A recovery workout typically follows either a high-intensity workout or a long workout.

Race Day and Speed Training

Most of the training you do for a half Ironman race will be conducted in heart rate zone 2. Working in this zone helps make your respiratory system more efficient, build your lactic acid threshold and achieve gains in speed as well as endurance. Zone 3 workouts amp up gains in speed and stamina, but should always be followed by workouts in zone 1 the following day. During a race, stay in zone 2 and avoid hitting zone 3. While some triathlon experts like Mora say the heart rate monitor can help you gain a personal best, not everyone advocates wearing a heart rate monitor on race day. “Triathlon Training” author Michael Finch says the adrenaline and excitement on race day may elevate your heart rate over what it would be on a training day. Seeing this reflected on your monitor may cause you to underperform, Finch says.


Use your heart rate to determine whether you are overtraining. Your heart rate will not return to normal once you end a workout as quickly as usual if you are overtraining. In general, you should be back to a normal heart rate after 120 beats, Mora says. Also monitor your resting heart rate each day before you get out of bed, Finch recommends. If your rate is 10 beats higher than normal per minute, you need a break.