Heart Rate Vs Swim, Bike, Run (Simplified Definitive Guide)

Any form of exercise puts a strain on your heart. Understanding the heart rate (HR) zones will help you to take better care of your body.

When I first started running, I knew nothing about this. I’d just go all out. It was after running a half marathon in under 2 hours that my friends noticed that my heart rate had been in zone 5 the entire time. 

My doctor told me afterward that I could have given myself a heart attack if I’d kept going. That got my attention, so I learned all about heart rates, and I now know what HRs to use for what exercises. I’m excited to pass that knowledge on.

So what’s a reasonable heart rate for swimming, biking, and running? I’m going to get into the heart rate zones and which ones are the best for training, competing, and recovering.

What Are the 5 HR Zones?

HR zones are calculated as a percentage of a person’s heart rate. There are many ways to calculate them, from lab-based stress tests to mathematical formulas. Each zone offers a different benefit for athletes; some should be used more than others, and some should be avoided as much as possible.

This table displays each of the five zones. The percentage of your heart rate they begin and end at, what they feel like, and their benefit or use. (Source)

Zone% of Reserve HR (HRR)Feels likeUse
150–60%Very easy, fast walking, barely joggingMoving without stressing the body
260–70%Easy jogging, maintaining a conversationRecovery runs, building endurance, fat burning
370–80%Challenging, but sustainable for a raceBuilding aerobic fitness
480–90%Uncomfortable, anaerobic activityTempo runs, building fitness, short events
590–100%All out effort, not sustainable for long periodsIncreasing speed, perfecting stride

How Do You Calculate Each HR Zone?

The best way is to do a ‘stress test’ at a sports center or physio. Getting access to or being able to afford this test isn’t an option for many people. That’s why there are mathematical formulas to use to get a decent idea. They’re constantly being updated, but the following is one of the most recent. (Source)

First, calculate your maximum heart rate (MaxHR). Use these formulas:

  • Maximum Heart Rate for Males = 208.609 – (0.716 x age) 
  • Maximum Heart Rate for Females = 209.273 – (0.804 x age)

Take me as an example (55 yo male), 208.609 – (0.716 x 55 = 39.38) = 169.23

This result is almost spot-on as I use 170 as my MaxHR.

Next, calculate your reserve heart rate (HRR). Use your resting pulse (RP) for this. That’s your pulse as soon as you wake up. Mine is 59, so we’ll use that.

MaxHR – RP = HRR

169 – 59 = 110

The HRR is what you use to calculate your HR zone minimum and maximum. The formula is your HRR multiplied by the percentage and then added to your resting pulse again. 

Let’s calculate my Zone 3. That’s a minimum of 70% and a maximum of 80%

HRR x 0.70 + RP = Zone 3 Min

HRR x 0.80 + RP = Zone 3 Max

110 x 0.7 + 59 = 136 

110 x 0.8 + 59 = 147

My zone 3 falls between 136–147 bpm. 

For those of you with a sports watch, pop in your MaxHR and RP, and it will do the calculations for you.

Heart Rate Per Activity

For each activity in a triathlon, the best zone to use when training is pretty much the same for each portion, and that’s zone 3. And that would be correct, 70–80% of your heart rate. You’re not over-exerting yourself, but you are training where you need to.  As you get closer to the event, and especially if you’re working on improving your times, you can then move into zone 4, 80–90% of your maximum heart rate.


A typical heart rate zone for running training is zone 3, which is considered the aerobic zone.

In this zone, your body is working at a moderate intensity that is challenging enough to improve your cardiovascular fitness, pace, and muscular endurance but still sustainable for more extended periods. This zone is often referred to as the “fat-burning” zone, as the body primarily uses stored fat for fuel during this level of exertion.

For more advanced runners or those training for a race, the higher heart rate zone 4 — the threshold zone —  may also be utilized to improve speed, power, and anaerobic endurance.


Similar to running, the best heart rate zone for cycling is also zone 3.

It’s sometimes referred to as the “tempo” zone, as it’s often used for longer, sustained efforts such as climbing or time trials.


Like running and cycling, the best heart rate zone for swimming is also zone 3.

Also referred to as the “aerobic” zone, it improves your ability to take in and use oxygen efficiently.

Race Day

The best heart rate zone for a triathlon will depend on the specific event, distance, and fitness level. However, a standard heart rate zone for triathlon training is a combination of zones 2 and 3, which fall between 60% to 80% of your maximum heart rate.

During the swim portion of the triathlon, heart rate monitoring may not be as relevant due to the difficulty in measuring heart rate accurately while swimming. However, for the bike and run portions, monitoring your heart rate can be an effective way to manage your effort level and ensure a consistent pace throughout the race.

During the bike portion of the triathlon, a heart rate zone of 2 or 3 may be utilized, depending on the distance and terrain of the course. For shorter-distance races, you may use a higher heart rate zone to maintain a faster pace, while longer-distance races may require a lower heart rate zone to conserve energy for the run portion.

During the run portion of the triathlon, a heart rate zone of 3 is best, but for shorter-distance races, you can use a higher heart rate zone of 4 to maintain a faster pace.

Ultimately, the best heart rate zone for a triathlon will depend on your fitness level, training plan, and race goals. It’s essential to work with a coach or training plan specific to you and practice race-day nutrition and pacing strategies to optimize your performance.

Recovery Day

It’s important to note that recovery running is not the same as taking a rest day, as it still requires you to engage in some level of physical activity. However, it should feel comfortable and not overly strenuous.

The best heart rate zone for recovery running is typically zone 1, which is the lowest intensity zone. This zone is often referred to as the “active recovery” zone, and it typically falls between 50% to 60% of your maximum heart rate.

In this zone, your body can efficiently recover from previous training sessions and build aerobic fitness without placing significant stress on your body. 

The goal of recovery running is to maintain a low heart rate, which allows your body to focus on repairing and rebuilding your muscles, improving circulation, and reducing inflammation.

Heart Rate Zone 5 – The Danger Zone

As my doctor explained to me, exercising in heart rate zone 5, which is the highest intensity zone, can be very demanding on the body and pose several dangers. Here are some of them: (Source)


Exercising at such a high intensity can push your body beyond its limits and lead to overexertion, which can result in muscle fatigue, dizziness, and even fainting.


High-intensity exercise can increase the risk of injury, especially if you’re not properly warmed up or aren’t using the correct form.

Heart Problems

Exercising at such a high intensity can significantly strain the cardiovascular system, increasing the risk of heart attack or stroke. This is even more true for individuals who already have heart conditions.


High-intensity exercise can cause you to sweat excessively, leading to dehydration if you do not drink enough fluids to replace the lost sweat.

Heat Exhaustion

Exercising in a hot and humid environment while in heart rate zone 5 can lead to heat exhaustion, which can cause symptoms such as dizziness, fatigue, and nausea.

It’s essential to consult with a healthcare provider before engaging in high-intensity exercise and to gradually work up to this level of intensity over time to reduce the risks associated with this type of exercise. You don’t need to avoid zone 5 altogether, but you should keep it to a minimum.

As always, before starting any new exercise routine, it’s essential to consult with a healthcare provider, especially if you’re new to the sport or have any underlying health conditions. Additionally, incorporating a variety of heart rate zones into your training program can help prevent injury and improve overall fitness.

Stephen Christopher

began running at the age of 50 and 2 years later ran his first marathon in just over 5 hours. He continues to join events all over Thailand and South East Asia with Berlin and London on the list for the future.

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