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Highly effective or hopeless hype?

Photo by Clem Onojeghuo

  1. What is HIIT?

  2. Intensity

  3. Aerobic vs anaerobic

  4. Endurance vs HIIT

  5. How?

  6. How often?

Unless you have been living under a rock for the past few years, you will doubtless have come across HIIT training be it in the media, at your gym or over a conversation at the water cooler in between Bakeoff/Derry Girls/GameofMarbles-Housety Dragon chitchat.  

HIIT stands for High Intensity Interval Training and it has become the buzz workout of recent times promising to torch fat in record time, attach speed rockets to your metabolism and help create the fat-burning, ripped body you have always dreamed of. Bold claims. So is this hype or does this method of training really work?

I will explain the hows, whats and wherefores forthwith (m’lud).


Photo by Leon Ardho

HIIT comes in different guises: fartlek (blame those comedians, the Swedes), tabata (konichiwa Nippon) or, as we know it, interval training. Although it has existed for centuries, it came to wider attention when the Finnish athlete, Paavo Nurmi, used it to prepare for the 1924 Olympic Games & subsequently went on to win 5 gold medals. In more recent times, Sebastian Coe memorably broke numerous middle distance records in the 1970s using “quality and intensity” in the form of 200m sprint repeats with a mere 30 second recovery to protect his lactate threshold to succeed in consistently out-performing his competitors. As his father and coach commented, “long, slow distance running just creates long, slow runners”1. Variety in pace means you won’t simply default to the one speed.


In essence this method of training comprises short, sharp work intervals followed by brief breaks until you either throw up or pass out. Ok, maybe I’m exaggerating the last bit. That said, a HIIT workout needs to be done correctly to reap the benefits it touts and most people get nowhere near the intensity required. Much like the fact that any weight loss diet will work if you stick to it, a HIIT workout can potentially do the following:

  1. Improve heart health

  2. Increase flow of oxygen & fuel into muscles

  3. Increase fat oxidation

  4. Improve carbohydrate sparing, ie increase in body’s ability to burn fat as fuel instead of carbs

  5. Increased EPOC (Excess Post-Exercise Oxygen Consumption), i.e. oxygen consumption remains elevated post exercise session resulting in ongoing calorie consumption whilst body works to restore homeostasis (return to equilibrium)

In addition to these benefits, HIIT training is also time efficient.  An effective session can be over and done with in a matter of minutes.  Short, sharp efforts with minimal recovery and bingo! Job done! However, the key focus is the intensity level.  You are looking to achieve your maximum effort, short recovery, rinse and repeat. 


Photo by Marinko Krsmanovic

Just as we all have a different perception of pain so we do of intensity. What can feel quite mild to one person, can seem racked up to 11ty-stupid for someone else. The easiest & most effective way of gauging your training intensity level is to use the PRE or Perceived Rate of Exertion method.  On a scale of 1 – 10, if 1 is lying in the couch with a glass of wine & 10 is beetroot-faced reaching for the bucket, you want to be nearer the bucket than the couch when doing HIIT.  Eight, nine or ten are the numbers you are aiming for, i.e., puffing hard & unable to hold a conversation.  It is highly subjective which allows for differing fitness levels. 

If you want a more mathematical and precise way of gauging your exercise intensity, I would suggest using a heart rate monitor. Treadmills, stationary bikes etc have them however, please note that these are usually highly inaccurate (as are the energy expenditure predictions but that’s another conversation). They can however be a guide if you have nothing else. If you have your own monitor then follow this age appropriate formula to estimate your maximum heart rate (MHR):

220 – your age x target intensity range (from 70 – 85%) = MHR

Choose your target intensity range (THR) according to how hard you want to work, e.g. 70-75% for tough, 75-80% for really tough & 80-85% for uber hard. So, if you are 35 years old wishing to train like a demon, here is your formula:

220 – 35 = 185 (MHR) x (80-85%)(THR)

Therefore, your target heart rate range would be 148-157.25 beats per minute

The point of the intensity is that you cannot maintain the pace for long so you work maximally, rest and repeat. Think of a 100m sprint. Explosive power & a short, 10 second effort, give or take.


Photo by 7inchs

Aerobic means “with oxygen” so we apply this to more sustainable, slower, longer exercise sessions such as jogging, hiking and longer distance cycling. We can potentially keep going (until we can’t!). Anaerobic means….you guessed it, “in the absence of oxygen”. This applies to properly performed HIIT and other short bursts of intense effort such as the push to sprint to the top of a hill or the end of a race, the blast of burpees performed to finish a workout. Very quickly the lactate kicks in forcing us to slow down & stop.



At first glance the above table makes both types of training appear similarly beneficial however, if there is one thing we want to avoid it is potential muscle loss.  Couple your sessions with resistance training and you will mitigate any muscle loss. According to a research article carried out at the University of New Mexico, HIIT training performed 3 times a week showed a 10% increase in heart stroke volume compared to a long, slow distance training group.  In addition, VO2 Max (the body’s ability to use maximal oxygen for energy production) improvements were noticeably higher in an 8 week HIIT training program (15%) vs continuous aerobic training (9%).  

Consistent HIIT training has also been shown to improve the efficiency of the body to utilize fat for fuel thus saving carbohydrates and enabling the athlete to train harder for longer.


Photo by cottonbro

So how is it best to introduce some HIIT training into your schedule?  If you enjoy distance running or cycling, adding a couple of HIIT sessions into your week could see you significantly improving your power output, i.e. your ability to power uphill more quickly or find that final push to beat your competitor and reach the finish first.  It can be the perfect, time efficient side dish to your resistance training main course too if you are looking to maintain muscle whilst shredding fat.  

Keep it simple and begin gradually. The beauty of this training is that it can be done in any number of ways be it on a treadmill, running outside, on a bike, a rower, with a skipping rope or doing burpees (yeah, as if). Fire up your imagination and keep mixing it up. A simple initial workout could be:

Minimum, 10 minute warmup (really, really important so that you don’t injure yourself),

30/60 split x 6 = 30 seconds all out effort followed by 60 second recovery to be repeated 6 times

As you progress, change one variable at a time, e.g. reduce the rest periods down to 45 or 30 seconds, or increase the work effort to 45 or 60 seconds or increase the number of intervals to 8 but probably never more than 10.  If you have enough left in the tank after 10 intervals then the intensity wasn’t high enough.  Go back and start again!


Photo by Bich Tran

Once to twice a week is plenty.  Proper recovery between sessions is vital because this is where the body adapts. Remember: intensity is the key, ie quality of the session over quantity.

Once you have been doing these a while, you can try jogging the recovery periods rather than being bent double wheezing into a bucket.   I’m not asking you to enjoy them but I can promise you there is a huge sense of satisfaction at the end plus the wonderful added double bonus of adrenalin and feel good endorphins racing around your body.  Not to mention the nerdy science physiological benefits too.  

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Have you already embraced HIIT training and, if so, how, how often and have you noticed improvements?

We’d love to hear from you so please post your comments and, if you enjoyed this article and found it useful, don’t be afraid to share it around social media.


#trainingvariety #training #fatloss #intensity #fitness #healthyexercise #exercise #hiit #gym

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