HIIT, or High Intensity Interval Training to give it its full name, exploded into popularity a decade ago.  It has made somewhat of a resurgence since.  So is it all its cracked up to be?

Back when the nine-time Olympic gold medal winner Carl Lewis retired in 1997, he claimed one of the reasons he was so fit and so quick was down to HIIT.  As far as I can tell, partly it’s from his influence and that of Dr. Tabata that HIIT started to so widely proliferate as a fitness, and then as a weight loss, tool. 

HIIT involves short bursts of intensive exercise, broken up by pre-determined rest periods.  The concept is that work rate can remain high as the rest allows the person exercising enough recovery to push at the high work rate in subsequent rounds.  So for instance, instead of running 1000m in six minutes, you could run each 100m in twenty seconds, with a ten second rest in between.  The 1000m would be completed in five minutes.  Therefore the training load is higher because the recovery in between has enabled it to remain relatively high.

Tabata is a little more specific.  It involves twenty seconds of maximal activity followed by ten seconds of recovery for a period of four minutes.  That was the amount Dr. Tabata determined was proportionate to an hour of moderate intensity exercise for the aerobic system. 

Subsequently HIIT has become a staple of people trying to lose weight.  There is actually some good science to back that up.  By sending the heart rate to eighty-five percent and above of its max periodically it forces the body to uptake more body fat for recovery.  There are plenty of issues with this, however.  Most people cannot sustain their heart rate at that level of intensity for very long, and struggle to get their heart rate back down during the rest periods.  That leads to an overall fatiguing effect, which means the first few rounds performed at high intensity rapidly give way to subsequent rounds of lower and lower intensity because the recovery required grows increasingly.  What you therefore get is more of a moderate intensity workout, rather than true HIIT.

A lot of what I see labelled as HIIT is actually circuit training.  You can’t really do this.  It’s a modification that changes the training, turning it once more into moderate intensity.  I could pair two exercises together and make both of them relatively short, for instance each one of fifteen to twenty seconds, but beyond that you aren’t really doing HIIT training anymore.  Not to mention that the transition between the two exercises would have to be instantaneous and the first would have to have no muscular fatiguing effects on the second.  It would be far better to do one exercise and plan out the rest periods properly. 

So the key with HIIT is the getting the right intensity and the right rest periods.  Now there is a problem with this.  Lets take something like running.  I can make someone run fast enough that they get to 85% of their maximum heart rate, but they need to have a strong enough running base to really be able to hit that.  Most beginners will not get close before their legs will go and they wont be able to produce anymore effort even though their heart rate remains relatively low.  Equally, they will spend a long time recovering back to a sensible level and even then, because their recovery and cardiovascular systems are inefficient, they wont get up to the levels required in any of the subsequent rounds. 

This is why a base of low and moderate intensity exercise is required before you attempt HIIT.  And that isn’t a bad thing.  After all low and moderate intensity training will increase your fitness if you are untrained, see you lose weight and give you quicker recovery and less chance of injury than HIIT, so why wouldn’t you start there?  Once you have mastered those then HIIT would be a potential progression you could take, should you wish to.

HIIT and its derivatives mostly have a benefit for fitness.  This is what it was designed for.  I have undertaken HIIT swimming sessions and I can tell you it is gruelling, but you get a lot more speed and fitness as a result.  If you are a seasoned runner, swimmer, cyclist or indeed anyone who plays sport regularly then HIIT is something that would benefit you under the right circumstances.  Nevertheless, that doesn’t mean you should only train HIIT exclusively.  There is a time and place for it and it is best programmed into training sparingly. 

As you may be able to tell from the above getting HIIT right is incredibly difficult.  That’s why you see bastardised forms of it everywhere.  People also tend to consider it a panacea, but is it?

HIIT is popular because it is hard.  People think if they maximise their workouts that’s the best thing they can do for themselves.  There is also the awkward fact that a lot of people are motivated to work out because they dislike themselves, and HIIT is an excellent way to punish yourself.  HIIT should be done with individuals as a targeted way to improve fitness in a given period of programming or as a means to intensify fat metabolisation, again for a short term period of programming.  It shouldn’t be something undertaken for long periods of your training programme and shouldn’t be something done as the first step in a weight loss process.  Those ways lead to injury and failure.

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