VIDEO | How to know if you’re exercising hard enough

Our hearts are pumps. The blood they pump transports oxygen and minerals to the rest of our bodies.

Fit people have lower heart rates than unfit people, because their hearts pump more blood each time they contract. So their heart muscles need to work fewer times in a minute as they are more efficient pumps.

When you exercise your heart rate increases simply because the body, and muscles in particular, need more oxygen.

How do you know if you’re exercising at the right intensity?

There’s a formula you can use, says sport and exercise medicine doctor Jon Patricios.
1. Subtract your age from the number 220

2. Your heart rate needs to be 80% of that number to be exercising intensely

60% to 79% is regarded as “moderate” intensity


You’re 50 years old.

1. 220 – 50 = 170 (this number is your maximum heart rate)

2. 80% of 170 = 136 (this number is 80% of your maximum heart rate)

So, if a 50-year-old person is exercising at the right intensity, their heart rate needs to rise to 136 during a workout.

If you don’t have a heart rate monitor, exercising at 80% of your heart rate is when it becomes hard to speak to someone or when you become out of breath. If you are able to speak comfortably, that is “light exercise”.

It is also useful to look at your resting heart rate. That’s the rate at which your heart beats when you wake up. It gives you an idea of your baseline fitness.

If your resting heart rate decreases, it means you’re getting fitter. If it goes up, you could be sick or overtraining.

What does exercise do for your body?

It keeps your body healthy — you’re less likely to fall ill. A recent study showed that people who did 150 minutes a week of moderate intensity physical activity were 42% less likely to die when they contracted Covid-19.

How often should you exercise to stay healthy?

The sweet spot is between 150 and 300 minutes a week.

If you do 150 minutes, you need to exercise at 80% of your maximum heart rate. If you do 300 minutes, you can exercise at a lower intensity.

How should you exercise to burn fat?

Studies show you’ll burn more fat if you do high intensity interval training. That means you go very hard for a short period, say one to two minutes, followed by a short resting period of say, 30 seconds. You then repeat a few rounds of that (rather than exercise at the same pace for an entire workout).

When should you exercise?

Mornings are generally better than evenings, especially if you’d like to lose weight because it raises your metabolic rate for a more sustained period for the rest of the day. A morning sweat may also lead to better mental health and productivity during the day, as exercise is great for reducing stress.

Jon Patricios is a sports and exercise medicine physician in private practice and a professor in the faculty of health sciences at the University of the Witwatersrand.This story was produced by the Bhekisisa Centre for Health Journalism. Sign up for the newsletter.

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Mia Malan
Mia Malan
Mia Malan is Bhekisisa's editor-in-chief and executive director. Malan has won more than 20 African journalism awards for her work and is a former fellow of the Reuters Institute for the Study of Journalism at Oxford University.

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