High intensity interval training (HIIT) is becoming increasingly popular as it has been shown to improve both aerobic and anaerobic fitness as well as significantly enhancing insulin sensitivity, blood glucose regulation and the body’s ability to burn fat, compared to much longer periods of steady state cardiovascular activity.
The benefits of HIIT are the result of a greatly amplified ‘excess post-exercise oxygen consumption’ (EPOC), which gets the body back to its natural state and includes elevated fuel consumption (including fat metabolism) in an attempt to restore depleted nutrient stores within the body. In other words, while you might feel like death during your HIIT routine, the benefits don’t actually come until you’ve stopped and your body works hard to get things back to normal – the after burn effect.
Many Bodyscan clients wanting to lose fat say they include HIIT in their routine but only a minority get the great results that can be achieved. The main reason for poor results is that most people simply aren’t working hard enough.
Perhaps HIIT should be renamed VHIIT, because the sweaty bits of a HIIT workout should achieve a VERY high heart rate - about 90% of your maximum (HRmax).
That’s why the work periods of a proper HIIT session should not be more than a minute and the entire session should not last more than 20 minutes because it would be impossible to maintain such a high exercise intensity beyond those limits. If you're exceeding those limits then you're not going to get the benefits.
Whatever your fitness level you need to work with MAXIMUM effort to get the required physiological response. If you’re unfit you’ll reach your 90% HRmax quickly (say, after 30 seconds of work) and need a longer rest period (maybe two minutes) to be able to repeat the process at high output again. As your fitness increases you’ll need shorter rest periods and be able to repeat more cycles but the 60-second and 20-minute limits will apply even for an athlete.
Indeed, research has shown that just ten minutes of work in a 20-minute HIIT session (60-second sprints at 90% HRmax followed by 60-second rests, repeated ten times) has the same effect on 24-hour energy expenditure as performing 50 minutes of steady-state endurance cardio at 70% HRmax.
You can do any type of activity for the working periods, it doesn’t have to be the traditional sprinting or rowing. Pull-ups, push-ups, squats, burpees or anything that gets the heart rate elevated high enough will do.
So if HIIT isn’t working for you, try VHIIT instead. Work shorter but harder.
Written by James Rutherford, Consultant, Bodyscan City. James has a BSc in Sport and Exercise Science and is completing his MSc in Sport and Exercise Nutrition.