Knowing your heart rate when exercising can give you vital information about the intensity of your workout (how hard it is on the body), how your body will adapt to the training and the number of calories you’ve burned. As a general rule: the harder you’re working, the higher your heart rate will be. However, depending on what type of workout you’re doing (fat burning, aerobic base or high-intensity interval training (HIIT training)) you might want to keep your heart rate at a certain level, so a heart rate monitor can help track that. A simple wrist-based heart rate monitor, chest strap heart rate monitor or even stopping to check your pulse with your fingers can help you get the best results from your workout.
Why heart rate responds to exercise
The heart is part of the cardiovascular system. The cardiovascular system is responsible for pumping oxygen-rich blood from the lungs to the muscles and organs of the body via red blood cells in arteries. Muscles and organs use oxygen to power activities that produce energy for the body’s metabolic processes to work. This allows for the kidneys to filter, the stomach to digest food, and for muscles to contract. These processes use up much of the oxygen carried by the red blood cells. Oxygen-depleted blood moves then leaves the organs that use the oxygen and travel back to the lungs to be reoxygenated.
As the intensity of exercise and the demands on your muscles increase you will notice that you breathe harder and your heart beats faster and stronger. This is the body’s natural response to the muscles working harder. Because the muscles are working harder and need more energy, they need the heart to deliver more oxygen-rich blood so that more energy can be produced. It’s a bit of a snowball effect: you start exercising, your muscles need more energy, you breathe deeper and your heart pumps harder, so your muscles get more energy and then can work even harder!
There is a linear relationship between the intensity of your exercise and your heart rate. As you work harder, your heart rate increases.
Is using a heart rate monitor during exercise necessary?
Using a heart rate monitor is not absolutely necessary when exercising. Plenty of people exercise each day without even thinking about what their heart rate is. I know that my grandma doesn’t use a heart rate monitor when she goes for her daily walks around town, but she’s also exercising strictly for the joy of it. If your main goals when exercising are to breathe hard and work up a bit of a sweat, or even just to go out and enjoy nature you definitely do not need to track your heart rate when exercising.
Using a heart rate monitor becomes more necessary as you begin to target certain training outcomes from your exercise routine. If you think of the best marathon runners or Tour de France riders, it makes sense that they would use a heart rate monitor to always know how hard they are working. But even if you’re not trying to win the Boston Marathon, tracking your heart rate during workouts can be a great thing. It can help make sure you’re not overtraining (or undertraining!), ensure that you’re working in the right heart rate zones (more on that below) and even act as a motivator.
If you are looking to add more aerobic training to your workouts, you may want to add cycling to your routine. I wrote a comparison between spin bikes and indoor trainers. In the article, I discuss the difference between the two and which one to pick depending on your cycling background, among other factors.
Benefits of using a heart rate monitor during exercise
Heart rate monitors can provide a ton of benefits to everyone from weekend warriors to the best athletes in the world.
Monitoring intensity
First and foremost, a heart rate monitor is a tool that can tell you how intense your workout is. Most heart rate monitors will provide you with information on your maximum heart rate during the session and the average heart rate during the workout. This information can be very important when it comes to what “type” of training you’re trying to do (i.e. fat loss, aerobic base development, lactic threshold training).
It is so important that the virtual cycling/running app Zwift makes HR one of the key metrics on its display. GPS cycling computers also will give you up to the second HR recordings too – to make sure your training is actually matching your goals.
Click here to learn about what Zwift is and how it works.
Pacing
This information can also help you with pacing your workouts too. After a few workouts, you’ll start to get a good idea of what a sustainable pace is during your exercise based on your heart rate. Let’s say you’re on your third session of a 30-minute bike ride workout at a continuous pace and in your previous 30-minute bike workouts you averaged a heart rate of 140 beats per minute and a maximum of 155 beats per minute. If you look down at your heart rate monitor and it says your heart rate is 163 beats per minute and it has averaged 154 beats per minute, that’s a pretty good sign you should probably slow down. In that regard, you can use your heart rate monitor and a bit of common sense to coach yourself.
Monitoring gains
You can also use your heart rate to measure improvements in fitness. If you have a favourite high-intensity interval workout, you can use your heart rate information to determine improvements in your cardio. Once you finish your workout, you can time how long it takes your body to decrease your heart rate by 50 beats per minute. This gives a really good indication of your fitness and your body’s ability to recover. So it would be great to write that time down every time you do a certain workout. Here is a great article on how your heart rate recovers after exercise.
Average heart rate during exercise can also help monitor gains. If you have a favourite 5-k running route, you could compare your average heart rate from each time you run the course to see if you’re in better shape. Sure, you could use your time to finish the run to compare, but using your average heart rate and your time gives a more holistic view of how your body is changing in response to the training. Your time could be the same but if your average heart rate is lower, you are gaining fitness
Calories Burned
Finally, heart rate monitors give a fairly accurate measure of the number of calories that you burned during your workout. This can be very helpful for those that are looking to lose weight, maintain or even gain weight.
For instance, if you are looking to maintain your weight and you know that you burned 600 calories during your workout, you should probably aim to eat an additional 600 calories over the course of the day to even things out. If you’re trying to lose weight, the more calories you burn in workouts the more likely you are to see weight loss.
Determining your heart rate training zones
When people talk about their heart rates during their workouts, they often talk about zones that they spent time in rather than a certain average heart rate number. This can help contextualize the intensity of the workout and allows for better comparisons between people. For instance, if I work out at an average heart rate of 150 beats per minute that might be the equivalent of my dad averaging 132 beats per minute. We could have worked as hard as each other, but if you simply looked at the numbers it looks like I worked much harder than my dad.
That’s one way that heart rate zones can help you during your workouts. The zones are based on percentages of your heart rate max and can help you plan your workout and compare your efforts to other people. Additionally, training in different heart rate zones can change the way your body adapts to the training and lead to different gains in fitness.
| HR Training Zone | Intensity of the Exercise | Heart Rate (% of Max) | Duration You Can Work in the Zone |
| 1 | Very Light | 50-60% | 1-6 hours |
| 2 | Light | 60-70% | 1-3 hours |
| 3 | Moderate | 70-80% | 50-90 minutes |
| 4 | Hard | 80-90% | 15-45 minutes |
| 5 | Maximum | 90-100% | Less than 15 minutes |
How to estimate your heart rate max
Before looking into your heart rate training zones or your ideal heart rate when exercising, it is important to figure out your heart rate maximum because the zones are based off this. The quick and easy way to estimate your heart rate max is based on your age. This method isn’t as accurate as doing a maximal effort laboratory test, but it provides a very good guideline and approximation of what your heart rate max is and can help you in determining your heart rate training zones.
What heart rate to train at
Now you’re probably wondering what the right heart rate is to be training at. I’ll use the classic scientific answer to that question: it depends. But really, it does depend on a few things but most importantly the right heart rate to workout at depends on what your goals of the session are. Below are descriptions of the zones and what their impact will be on the body:
To determine your heart rate max:
HRmax = 220 – age in years
Training Zone 1 (50-60% HR max):
In this zone, you will feel like you can exercise forever (think of a leisurely walk around downtown). This zone is focused on recovery work and having a workout focused on zone 1 will help you prepare for your next workout.
Training Zone 2 (60-70% HR max):
This exercise is still fairly light. You should still be able to freely hold a conversation with those around you. This zone will help increase your general aerobic base by increasing the number of blood vessels in your muscles so they can get more oxygen and produce more energy. Also, Heart Rate Zone 2 is considered the fat burning zone because your body gets better at oxidizing fats (using fat for fuel) when you spend time exercising in this zone.
Training Zone 3 (70-80% HR max):
Zone 3 is when exercise starts to get a bit tougher. In this zone, you will start breathing deeper and faster, and you will feel your heartbeat pick up. Also, your body will start producing lactic acid when you’re in this zone. You’ll still be able to talk to people around you, but it will be a bit more difficult than in zone 2. Working in heart rate zone 3 will improve your body’s ability to circulate blood and will help make difficult workouts easier down the line.
Training Zone 4 (80-90% HR max):
Heart rate zone 4 is when your body can no longer provide enough oxygen to the working muscles to supply energy needs, so it uses more and more of other sources of energy (mostly carbohydrates). Once you’ve reached this point, it is considered your anaerobic threshold. You also start accumulating lactic acid in your muscles because it’s being produced faster than your body can get rid of it, which makes your muscles feel heavy and burn. Working in this zone helps teach your body to buffer the lactic acid and allows you to push your anaerobic threshold higher – leading to a greater ability to hold high-intensity exercise for longer time periods.
Training Zone 5 (90+% HR max):
Zone 5 is maximum effort work. You’re pushing yourself (almost) as hard as you can, and your heart and lungs respond by reaching their max workload too. Depending on your fitness level you may be able to hold your heart rate in zone 5 for anywhere from a minute to 15 minutes (for top conditioned athletes). This zone is great to work into interval work, where you work at max effort for a short period of time, then have a longer period of lower intensity work before repeating the max effort interval again. This can help you understand your limits and help you overcome the mental difficulty of working maximally.
Now that we know why your heart rate matters when working out, it is time to get after it! If you are working out hard, you may experience muscle soreness in the days after working out. If you do experience delayed-onset muscle soreness and want to learn more about why it happens, check out my article here.