top of page
  • Coach Paul Kuck

High Intensity Interval Training (HIIT) - What You Should Know.

It would be ridiculous to claim that I invented HIIT. But yours truly are one of the earliest advocates of this training method and have implemented it in my clients' exercise routines (both strength and cardio versions) right from the beginning when I developed my Body-Transformation-Programs in 1998. Hence I can qualify myself a subject matter expert in this popular training method.


The real origin of HIIT


Despite all the buzz in recent years, HIIT is not really a new concept, in fact it has been around for about for several decades now. The origins of HIIT training can be traced back to 1912 where it was used by the best Olympic runners at that time, usually the Scandinavian athletes, in their own training. The true researchers of HIIT are Saltin and Astrand who published their first study in 1959 and all of the subsequent HIIT techniques from then on were, more or less, borrowed from their original research.


How is HIIT done


HIIT exercise sessions are typically performed with 'cardio' type exercises (e.g. running, cycling). It consists of:

  • a warm up period, followed by

  • several cycles of high-intensity (hard) exercise separated by low-medium intensity (easy) exercise for recovery, then

  • a cool down period.

Typically, sessions last under 30 minutes, with times varying based on a participant's current fitness level. Essentially, it means a short workout of alternating easy and hard works.

HIIT are now used in strength workouts too.


My personal HIIT testing with great successes


I had come across this in a fitness journal (name forgotten) somewhere in 1992. The enlightening article was in line of my thought about certain exercise physiological principle that no one was applying at that time.


Everyone followed flawed unproductive exercise routines found in fitness magazines which often are not fully grounded in science.

The newly discovered exercise theory got me very intrigued and decided to put it to test through some sample routines. True to the article and to my delight, I had achieved very impressive results from them. I had lost a significant amount of bodyfat and also skyrocketed my cardiovascular fitness within a short span of time. I also attributed it to my 3rd place win in National Bodybuilding (junior) in 1992 by combining it with some specialised strength training and of course, mindful nutritional intake. Also bear in mind that most bodybuilders then were probably training 6-7 times a week, with minimum 2 hours each session, plus a heavy dose of illegal anabolic stuff (steroids that is). As for me, I trained naturally with nothing more than 3 weekly sessions of hourly workouts of HIIT and Strength Training.


In the same year (1992), I got enlisted into the Army into a specialised unit that required greater fitness level than normal units. The timing needed for 2.4km running component was below 9.15min (instead of typical 9.45min) in order to secure a 'Gold' for the army fitness test . During the 2.5 years stint there, everyone had to clear several such tests at regular intervals. And I had on all occasions gotten gold with running timings of between 8.15min and 8.45min, quite impressive feats considering:


I only did a couple (quite literally 2-3x) of HIIT sessions before all the tests.


I had a muscular built (how many bodybuilders you know can really run not to mention, excel at it? A few fellow bodybuilders of my age I knew then couldn't survive one lap around the stadium of non-stop slow jog) and


I am never a runner (genetically, passion or otherwise). My ex army buddies can attest to these facts. I was nicknamed 'Baby Hulk' for my built and 'PTI ' (physical training instructor) for my generally fitness.


About Tabata Protocol and CrossFit - They helped to popularise HIIT


A fellow advocate and a very reputable early researcher of interval training, Professor Izumi Tabata (田畑泉), who created the highly popular Tabata training protocol (a form of HIIT), only came to scene in 1996. CrossFit is a another branded regime that incorporate HIIT along with other exercises in their their training routines, it only started in 2000. So you can see I got into HIIT even before these 2 hugely popular HIIT household names (Tabata and Crossift) started to appear.


Tabata and his colleagues (1996) conducted a research that compared moderate-intensity continuous training at 70% of maximal oxygen consumption (VO2max) for 60 minutes, with HIIT conducted at 170% of VO2max. HIIT consisted of eight, 20-second all-out exercise bouts followed by 10 seconds of rest for a total of 4 minutes of exercise. The study found that HIIT improved aerobic capacity to a similar degree as moderate-intensity continuous training, but also resulted in a 28% increase in anaerobic capacity.


My Master's Degree research in HIIT and connection with my business: Fitness Tutor


HIIT was one of the primary reasons why I became a personal trainer and started my personal fitness training business in Singapore (1998) when I realised that this form of training would have the potential to offer far better results for my clients, as compared to what the others were doing at that time (i.e. promoting low-intensity method, eg doing slow walk on treadmill and doing aerobic workouts as the best way to 'burn-fat'. It was a widespread flawed training method, although that was based on a legitimate exercise physiological fact).


In 1999/2000, I got enrolled in a Master's programme in the science of Exercise and Nutrition. During this period, I took the opportunity to further my understanding the science and art of HIIT. I physically went to many university libraries, visited online ones, and dug out all relevant books and journals, subscribed to some, and devoured all the information like a hungry wolf.


I then designed my version HIIT protocol and tested it some clients and friends whom I had recruited for this research purpose. The outcome was very positive, which I had expected. I collected the data, analysed them statistically, and documented them into the thesis for my final year project (see below). Note: Chester University was a college of University of Liverpool at the time.


During this period, I had also written several pro-high intensity articles like 'Anaerobic or Aerobic - which is the better way for weight loss' (published on Ministry Of Health's Healthy Lifestyle Portal).


Subsequently in 2005, I got Certified as 'Lifestyle and Weight Management Specialist' by American Council on Exercise in which the programme also strongly promoted the use of HIIT for fitness and fat-loss. Till today, I am still fine-tuning it because there are still many ways to make it even better.


Fast forward to recent years, like fashion, a wave of HIIT Tsumai suddenly swept the fitness industry out of the blue. Within a couple of years everyone was raving about it. Magazines started splashing articles about it and its benefits. Exercisers switched their usual training mode from low to high-intensity. Every gym I know started to push HIIT to therir members. Fellow fitness trainers, started to jump on the bandwagon and claimed to be experts. Some of these were the same guys who had, not too long ago, strongly opposed the use of HIIT and defended their preferred low-intensity training methods or mocked at me during the earlier years when I preached about HIIT. Some even called it 'ridicules training method'. Imagine my vexation.


Let bygones be bygones, I hope these newly converted 'experts' do know what they are doing stay true to the principles of HIIT. However, judging from the way they have conducted the training on their clients and themselves, I cringed. Almost all of them are doing it wrong in some aspects. They seem to have completely no clue what HIIT is all about. It's either just random exercises put together or they just blindly followed the videos found on the internet which in my book, spells disasters in the making. The customised training part is completely missing in the equation. They have switched from misapplications of a valid scientific theory to misutilization of another great one. What they do would either not produce any desired result and/or may cause serious injuries to the exercisers


I will shed some light on how to and how not to do HIIT.


First, let's talk about the Benefits of HIIT


There are hundreds, if not thousands, of studies pointing to the effectiveness's and benefits of HIIT. Here are just some of them:

  • Improved health - Interval training substantially improved a number of metabolic and cardiovascular risk factors, and a whole list of others.

  • Increased endurance — Interval training trains your heart to pump more blood to the muscles and it trains your muscles to extract oxygen from it more efficiently, making all your other workouts easier to handle

  • More efficient workouts — If you have limited time, such workouts are superb time savers, allowing you to accomplish more in a short period of time.

  • Greater fuel efficiency — This type of training systematically taps the body’s different energy systems (phosphagen, glycolytic, and mitochondrial respiration), thus effectively burning fat and carbohydrates.

  • Better performance — Working at high intensities raises your lactate threshold and improves your performance

  • Reduced risk of injury — Because you're varying intensity, you may be able to avoid overuse injuries or overdoing it with longer workouts

  • More fun - Interval workouts have much more variety than other workouts, making them less tedious

  • Fat loss and muscle gain - Studies show that interval training, may burn more fat and build muscles, if you work hard enough, can increase afterburn. Look at the bodies (compare their muscle to fat ratio) of sprinter (who uses interval training) and that of a long-distance runner (who uses traditional low-intensity steady state training) and you can get the picture.

  • Balanced of hormones - It can boost testosterone, reduce estrogen etc along with other favourable changes in hormones

Now comes the interesting part...


Unbeknown to many, yes many so-called 'HIIT experts' even, there are actually two kinds of HIIT:

Performance Interval Training (PIT) and Fitness Interval Training (FIT). Can consider this as a modified HIIT.

PIT, as the name implies, is typically geared towards well-trained athletes who are seeking to enhance their performance for sports. Most scientific protocols (e.g. Tabata) use this approach for research and programming. It involves the exercisers to push themselves during the 'high-intensity'/hard phase near to/to their absolute maximum limit. Apparently, this is very demanding, requires a lot of mental and physical strength, and may necessitate the standby of the puke bucket.


Such interval training , I repeat, is strongly recommended only for the professional/highly motivated/seasoned exercisers, and NOT for the average 'just-want-to-keep-fit' Joe.


FIT, on the other hand, is highly recommended for most gym users. For this form of interval training, as you would have guessed, the exercisers need not push themselves to the extreme during the 'hard' phase. They just need to periodically increase intensity throughout the workout. Such increase in intensity is capped when the lactate threshold (slight breathless is felt) is reached, after which the intensity is decreased. In a nut shell, the high intensity here is actually not very high, as compared to the PIT. This picture may explain more.

The difference in training for HIIT (recreational exercisers vs athletes).
HIIT: Recreational exercisers vs Athletes

But everyone one is doing PIT

Many HIIT practiced in many gyms are often done in similar fashion as PIT, pushing the exercisers to the absolute limits, disregarding the capabilities and/ goals of the exercisers as stated above. So much for 'tailoring' a program. In fact, one can often see slogans like 'go hard or go home' plastered all over the place, prompting the exercisers to go as hard as possible, else it's deemed as a wasted workout. By doing so, they do not realise they could be doing more harm than good. This is akin to eating a buffet - eat as much as you can to get the money worth. It just doesn't work that way.