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You’ve probably heard of HIIT, or high-intensity interval training. It’s the workout craze that’s sweeping the world, and chances are, you’re doing some form of it.
Also called sprint interval training, HIIT involves quick, intense bouts of butt-busting cardio alternating with shor t recovery periods. It is physically demanding and thought to be more effective at fat burning than moderate-intensity exercise because it repeatedly pushes the body to the limit.
Examples of HIIT workouts are Tabata, which includes a couple of minutes of high-intensity moves like squats, burpees, lunges, crunches and jumping jacks, alternated with about 20 seconds of rest or low-intensity exercises, and Cross Fit, which focuses on specifi c movements executed at high intensity.
HIIT can also be worked into regular cardiovascular activities, like cycling and running. It is an anaerobic activity, meaning that it creates an oxygen defi cit. When your body’s demand for oxygen exceeds the supply available, it has to rely on energy sources stored in the muscles. This is why HIIT is said to be good for muscle strengthening.
IT HELPS YOUR HEART
Besides optimal fat burning, HIIT offers a number of health advantages, says Dr Lim Ing Haan, consultant interventional cardiologist at Mount Elizabeth Medical Centre.
“HIIT pushes the body into the anaerobic threshold, which helps improve exercise tolerance and fitness levels. With enough training, you can build your cardiovascular fitness to the point where you will be able to run or cycle up to twice as long as you used to.
“Besides building a stronger heart, HIIT increases your metabolism and burns calories while preserving your muscles at the same time,” Dr Lim adds.
BUT IT COULD ALSO HURT YOU
Like any other activity that pushes your body to the extreme, HIIT can be dangerous. When you are exercising at the upper end of your maximum heart rate zone, you not only increase your risk of muscle strain and injury; you also overwork your ticker, raising your chances of a heart attack or stroke.
And, if you are not used to vigorous exercise, you may be especially prone to overexertion. But even if you’re already trained and fit, you still run the risk of pushing your heart and body beyond what they can do.
Dr Lim says you should set realistic goals with your exercise programme. Do you want to maintain your fitness, lose weight, build muscle, or just achieve a sense of well-being?
If you do decide to try a high-intensity workout and you are over 35, go for a basic health screening first. This tests for diabetes, as well as your blood pressure and cholesterol levels.
If you are a smoker or have a family history of heart problems, Dr Lim recommends a basic electrocardiogram (ECG) – a test that records the electrical activity of the heart – or a treadmill test before embarking on your HIIT programme.
“As HIIT is physically demanding, you should at least be able to exercise for 20 to 30 minutes at an 85 per cent maximum heart rate without any problems,” she points out. “And always allow five minutes of warm-up and cool-down exercises.”
Also, look out for signs that tell you you’re overdoing it:
• Chest pains
• Difficulty breathing
• Giddy spells
If you experience these symptoms, stop all exercise and cool down by walking around a little before stopping completely. If your symptoms continue, seek medical help immediately.
Another way to tell that you may be overdoing it: “If your hear t rate does not slow down during the resting interval of the workout, then you need to decrease the intensity,” Dr Lim adds. “It may mean that HIIT is not right for you at your current fi tness level.”
If you are new to HIIT, Dr Lim suggests timing your sessions for 10 to 15 minutes, and working out for no longer than 30 minutes.
Less is still more, so avoid doing these high-intensity exercises daily because your body needs time to rest and recover – most of these programmes recommend no more than thrice-weekly workouts.