Everyone loves a good HIIT (High Intensity Interval Training) session, which pushes you and gets you to the end feeling like you’ve had a great workout.  Gyms and PT’s everywhere have morning and evening sessions/classes, body weight, weighted, motivated by great fitness instructors and music.  But what is HIIT? Where did it come from? And how has it evolved? And finally what should HIIT be used for?

As part of this blog I have had the input from two other experts in the fitness field, one been Rickey Lovel of Achieve Physiotherapy who is one of the best physio’s in the country, specialising in biomechanics and movement.  He actively takes part and competes in Cross fit.

The other is Graeme Woodward MSc ASCC; lead Coach Education Tutor for England Athletics and the Fell Runners Association and the Rugby League.

This is to have an unbiased approach to this subject.

Then there is me, a UKA endurance and Coach in Running Fitness, and HIIT trainer, with over 20 years of experience participating and instructing HIIT sessions indoors and out, with the military, police, and amateur and high-level runners.

Firstly, what is HIIT?

The true definition of HIIT is exercise consisting of repeated bouts of high intensity work above lactate threshold (hard or greater), interspersed by periods of low intensity (recovery).  It is an exercise that is unsustainable, and one at which your body would eventually force you to lower your intensity. (This definition is from Laursen and Buchheit). To get fitter these periods of intense effort must be hard enough to stress an identified physical quality in the body and the rest periods enough for the athlete to recover to perform again.

My own experience of HIIT.  I started doing HIIT sessions before I joined the army, and as part of my army training and career, it was a major part of our fitness training to condition you for battle and fighting the enemy, to draw on that last bit of strength when it mattered most.

When I became a fitness instructor after leaving the military, I instructed indoor and outdoor circuits.  These were HIIT based sessions mainly based around RPE (rate of perceived exertion), and I learned all about the different heart rates to target, for specific energy systems, VO2 max, a-lactate, lactate, threshold and high aerobic.  If you do the sessions correctly, it should condition the heart, lungs and energy systems enough so that once you are fully recovered you can perform better.  One issue with HIIT, is that it is misused by PT’s to sell a fitness product because everyone identifies with the word HIIT.  Also, a lot of PT’s don’t fully understand HIIT and don’t structure the sessions correctly to target an energy system or form of HIIT that is suitable for all taking part.  Most PT’s and Coaches simply don’t know the reasons why they prescribe a certain session or what specific physiological benefits it has.

As I became a better runner, I then used HIIT to supplement my running, for 20% of workouts, if I didn’t have time for a structured speed sessions or hill reps, I’d do a shorter HIIT session, that been said, speed and hill sessions are also HIIT.

As a running coach (this is true of any coach) you have to individualise HIIT to the athlete and the ‘event’ they are competing or running in.  HIIT isn’t a one size fits all, it is very much individual, which also makes group sessions harder for the coach, as running set distance repeats could target one energy system for one athlete, and a different energy system for another, for example, 400m could take 50 seconds for one person, and 2 minutes for someone else, and therefore another energy system. Plus the effort put in will also be different.

So, where did HIIT come from?

 It actually came from running.  As early as the 1900’s and was made famous by athletes who used it such as Zatopek and Bannister.  The first form was developed by the Coach Volmer in 1912 and Pihkala and Nuimi is the 1920’/30’s.  They started with high speed running in intervals with recovery.  The running coach Holme then invented Fartlek in the 1930’s.  This means speed play and meant you could pick a distance or time and run fast for that, then pick a different distance for the next interval.  The rest periods also mixed, so in essence you could ‘make’ it up as you ran as long as the efforts were hard enough.  Gerschler then perfected Fartlek in his own way, before Hron started VO2 max training and got his athletes to complete 2 HIITs a day,

The 1960’s then saw Astrand and Lydiard introduce their forms of HIIT, Astrand bringing in long intervals and improving VO2 max training, and Lydiard along with Percy Wells introducing periodisation and the 80/20 rule.

2000 saw coach Bilats bring in anaerobic training.  This is also when Izumi Tabata introduced his form of HIIT.

So how do you do HIIT for running and what does it do? 

HIIT is individual and sport specific.  Believe it or not, one form may not suit you, where another might, and it also depends what you are training for and what sport you do.

HIIT trains the heart and lungs in different ways depending on the energy system targeted, and also neuromuscular systems.  It conditions the heart to pump more blood around the body more efficiently, and in conditioning the lungs, allows more oxygenated blood to be produced.  It can be used for sports to target characteristics such as direction change, or repeat sprint ability.  Again, it is something you should do once a week and for a period of 4-6 weeks to show progression, before changing the form of HIIT, which is where Lydiard’s Periodisation comes in.

A lot of coaches with runner’s complete distance repeats, for example 400m with 60 second recovery, which is a simple form of HIIT.  However what energy system is targeted and what is the goal of the coach with this session?  400m for an elite athlete would be under 60 seconds, so if working hard enough would be working lactate (Glycolytic), however a non-elite may take 2 minutes to complete 400m so would be working high aerobic, and that also depends on the heart rate.  This is why track sessions held by clubs should be split in abilities and rather than been distance specific, be time specific so the individual trains correctly.

This is where Rickey mentions that HIIT also only works well if your biomechanics work well, which is why you must work on technique and form, otherwise you risk injury from overuse at high tempo.

With running, if your event is short track and field, the intervals may be shorter and recovery longer, where as a 10k, half or marathon runner would use longer intervals and potentially shorter recovery periods.

Further to that, you have to look at the demands of your event, in my case fell running and apply all that could occur. Fell running is probably the most physically demanding running sport going, so many forms of HIIT would apply.

How much should you do and for how long? 

As mentioned, HIIT should be done once a week, and for 4-6 weeks depending on training period and conditioning.  Once you decide what energy system you are training, then that decides on the time period you can train at high intensity, and also decides how much recovery you require, then the sport you play, can help decide what format it takes.  Field sports are predominantly high aerobic with spirts of lactate (sprints) so that’s what you should train, but each individual can only tolerate a certain amount per week which is why its individual.  A typical periodisation length is four weeks but could also be 5 or 6 weeks before requiring a recovery week.  So, if HIIT is only part of the 20% of the week, it could only take up 5% of that so what else can you do? Tempo runs at high aerobic heart rate, strength training which Rickey states runners do not do enough of! And run drills, to perfect the movement of running in order to prevent injuries.  You can also use HIIT at the end of a session as a ‘finisher’ which is used quite a lot in CrossFit workouts and gym sessions.  This could be in the classic form of Tabata 20:10 for 4 minutes.

The advantages as Graeme puts it, doing less but getting fitter is better time management and can reduce over training, something that many endurance athletes do but don’t admit.  It has been shown to be so good for athletes that they can reduce the hours spent biking, running, swimming, etc.

To Finish! 

HIIT is good for you…. but has to be specific to the sport you are doing and individual, therefore periodized.  If you enjoy going to many gym classes per week, you need to pick a certain few to work above threshold (hard) and the rest you work easy or high aerobic, otherwise you risk not recovering enough and reducing your immunity.

You must must must make sure you learn to do the movements correctly, so the exercise is effective and the HIIT will then be quality exercise, and you will reduce the chance of injury.  Listen to your body, if it aches and you are tired, ease off and have a recovery day.  Also, recovery is just that, it is off your feet recovery, chilled on the couch, not getting ‘easy’ ’junk’ miles in, you just don’t need them, and the muscles will not repair.

If you have any questions on this subject, please ask.  Email me, message me and I will do my best to reply as soon as I can.

I am not a scientist, I don’t have a degree, but I have experience through practical experience and application.  I have also read and educated with reliable books and by talking to experts on the subject and have asked experts for their own knowledge on this subject from there field of expertise.

Source of reading: - Science and Application of HIIT by Paul Laursen and Martin Buchheit.