Understanding your heart rate to maximise your work out

What’s the connection between heart rate and exercise intensity? We find out how to measure your heart rate plus how to calculate your target heart rate for exercise.

Lucy E. Cousins
November 2018

When it comes to exercise, most of us think of puffing and sweating as indicators of how hard we’re working.

Exercise physiologist Victoria Burton, says we’re on the right path – but your heart rate is a more accurate measure than perceived exertion.

“Understanding your maximum heart rate can help you accurately track how hard you’re working more than just going by how hard you feel like you’re working,” she explains. “Your maximum heart rate (MHR) can also help you classify how intense your workout should be for your fitness levels.”

What does MHR mean?

Your MHR is an estimation of the maximum number of times your heart can safely beat during exercise or activity. When we aren’t working out our heart rate is usually around 60 – 100 beats a minute. It rises when we exert energy.

The more intense the exercise, the harder your heart has to work to pump blood around your body. This is linked to how much resistance your workout includes, as well as your age and fitness levels. When you know your MHR, you can check if you’re doing low, medium or high intensity exercise by tracking your heart rate.

How do you measure your target heart rate zones?

To calculate your MHR, check your resting heart rate before you exercise by counting your pulse for 15 seconds and multiplying that number by 4. Then enter this number in the Heart Foundation’s calculator at Heart Online.

To monitor your heart rate during exercise, you can use a smart watch or heart rate app, but accuracy varies. The latest Apple Watch released in 2018 has improved heart rate monitoring but at the time of writing it’s only available in the US.

What do the different heart rate zones tell you?

With this personalised MHR number, you can work out your target heart rates for different levels of exercise. These heart rate zones help to classify how intense a workout is, and because everyone’s heart rate will be different, the ‘heart rate zones’ are based on a percentage instead.

“There are different heart rate zones that you can train in,” explains Burton. “The percentages change depending on who you ask and what source you’re looking at, but the 2 that are most relevant to exercise are super intense: 85% of your max heart rate and higher and moderate: 50–70% of your max heart rate.”

Does exercise need to be high intensity to be beneficial?

Australia’s Physical Activity & Sedentary Behaviour Guidelines for Adults recommend 150 to 300 minutes of moderate intensity physical activity or 75 to 150 minutes of high intensity physical activity each week. Moderate exercise may include activity like cycling. Interval training is an example of high intensity exercise.

Getting enough exercise can make a huge difference to your health. Benefits include maintaining a healthy weight, building strong muscles and bones and reducing your risk of heart disease, type 2 diabetes and some cancers.

Burton says to not confuse working out effectively with working out at high intensity.

“Working out at high intensity is really taxing on your nervous system,” she explains. “When you’re working out, your cortisol levels rise which means that if you work out at that level every day, your body will be in a flight or fight phase with very high cortisol levels [stress] for a long period of time. This can keep you from building up muscle and you’ll end up actually starting to use your muscle for energy.”

Burton adds that by measuring and monitoring heart rate recovery over a period of time (how
fast it returns to your resting heart rate), you can monitor and increase your fitness level. 

“For example, if you can jog at a steady state for 30 minutes, you can then start to pick up your pace and speed over time,” says Burton. “Consistent and repetitive movement, as well as monitoring your heart rate and your heart rate recovery times” can help you improve your fitness.

But even low intensity exercise like walking can be beneficial for your health, so it’s up to you to choose which type of exercise is best for you and which you are most likely to stick with.