From the Heart and Stroke Foundation

By Matt Mayer, MSc.

It can be hard to find time for physical activity. That's why a lot of people are talking about intervals - specifically, High intensity interval training (HIIT). Research shows that HIIT, if done correctly, can pack a lot of cardiovascular benefits into a workout as short as 15 minutes.

But is this training method for you?

HIIT is a punishing regime in which you push yourself to 100% of your physical capacity for 30 seconds - say, sprinting around a track at top speed. This is followed by 30 to 60 seconds of active rest - walking, for example, while recovering your breath. You repeat these cycles 10 to 20 times.

Sounds exhausting? It is.

The good news is, new research is suggesting that you actually don't need to exercise at 100%. In Modified HIIT, you work at 90% of your maximum but make the intervals longer - 60 seconds instead of 30. (Don't worry, I'll explain how to figure out what 90% means.)

So what is the skinny on Modified HIIT?

  • You train for a total of 20-30 minutes per session.
  • Intervals are 60 seconds long and rotate between high intensity and active rest.
  • High intensity here means about 90% of your maximum heart rate.

What is your maximum heart rate? Subtract your age from 220. Then multiply this number by 0.9 to calculate 90%. For example, Mark is a 54-year-old man. His 90% mark would be a heart rate around 150 beats per minute. ((220-54) × 0.9 = 150)

Thoughtful tips for all interval training:

  • HIIT, either full or modified, is not for everyone. For some, it's a good once-a-week challenge among other activities.
  • You'll be tempted to cheat - stretching out early intervals when you feel fresh, and cutting short the later ones when you're exhausted. Don't - you'll lose the benefits of the exercise.
  • A personal trainer can help you find the right intensity and hold you to strict times.
  • A stopwatch or a workout partner - or both - can also help you stick to your intervals.
  • Monitor your heart rate with a heart rate monitor or listen to your body.
  • If you find that you can't complete a full minute you are likely pushing too hard. The high intensity intervals will get more difficult with time but should never be impossible.
  • During active rest intervals, your heart rate should come down after 30 seconds. If it does not, you are likely working too hard and need to scale back.
  • Running, swimming and cycling are excellent activities to try HIIT.
  • Before attempting any workout that is high intensity, seek medical clearance.

So if you feel like trying either full or modified HIIT, pick an activity and go - especially if you are looking for a little extra pump in your routine.

Before starting any physical activity routine, please check with your healthcare provider.

Matt Mayer is an exercise physiologist.

Posted: April 2012

Heart and Stroke Foundation


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