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A Guide to Exercise: Understanding HIIT Workout Basics

Director Cardiology, Fortis Escorts Hospital
Nov 25, 2018 4:56 AM 5 min read

Having previously discussed the benefits of High Intensity Interval Training (or HIIT), we shall now review the basic principles and commonly deployed protocols of HIIT workouts for beginners and experts.


Before we go further, just a reminder - HIIT is not a specific exercise in itself.


It is rather a broader principle driven training routine, which can be applied in a variety of ways: stand-alone or as a combination of aerobic exercises with and without weights; free weights; kettle bells; machine based or bodyweight exercises.


Would advise you to read why HIIT workout is the ultimate resistance training routine to familiarize yourself with its physiology before reading on.


Now with that behind us, let us start where it all starts.


The Four Guiding Principles of HIIT


  1. Intensity
  2. Duration
  3. Progression
  4. Frequency


We’ll look at Intensity, Duration, and Progression in the purview of resistance training, and Frequency from the perspective of a broader routine, but parallels can be found across exercises as would be elaborated through future articles.


A Guide to Exercise: Understanding the Basic Principles of HIIT




The underlying idea is to exhaust all possible muscle fibers being exercised.


There are 3 broad types of muscle fibers:


  1. Slow twitch fibers: which have more endurance, which fatigue slowly, but recover fast (recovery in about 90 seconds).
  2. Fast-twitch fibers: which are more powerful, which fatigue quickly, and recover slowly (4-10 days for complete recovery)
  3. Intermediate-twitch fibers: a large group falling in between a. and b.


The ideal exercise should engage all types of muscle fibers sequentially and exhaust them.


The quantum of load is important here. If the load is too light, some slow-twitch fibers would recover by the time the fast twitch fibers come into play. Conversely, if the load is too high, the fast-twitch fibers would get exhausted before the slow twitch have been stressed, deeming the exercise as "over" in only 2-3 reps. Read my article on " How to Incorporate HIIT Workout in Your Daily Routine " to get more details. 


Hence, moderately heavy stress must be placed on the exercising muscles; which means about 50-60% of the *1 rep max.


The aim is to do 12-20 reps of the exercise in one intense, all-consuming set (with the broader acceptable range being 8-25 reps).


*1 rep max is the maximum weight that can be lifted in one rep, say 100 kg on the bench press (for example). 
50-60% of 1 rep max would hence imply (for the aforementioned example) as lifting 60 kg, which can perhaps last till 15 reps.
So a 60 kg lift for 15 reps becomes the load for the work set (defined later). The penultimate rep should take all of one’s strength and willpower, with the last rep being barely possible with the entire reserves of one’s body and mind. 
This is what is meant by intensity, which when accurately deployed gives the desired results.


The set would end only when there is complete muscle failure, at least positive failure (meaning complete inability to lift the weight), though an ideal regimen often involves negative failure (lowering the weight under control). But only try this if you have a trained spotter, not if you’re exercising alone.


A Guide to Exercise: Understanding the Basic Principles of HIIT




Duration has two aspects to it.


First, the duration of the set which should be between 45-90 seconds for best results (range 30-150 seconds).


Second would be the duration of the workout, which may last a maximum of 45 minutes, though ideally this should be under 30 minutes.


After 45 minutes, the body’s testosterone starts falling and cortisol rises, so the returns start diminishing.


Aim to do only 1 work set per exercise, to failure. Since this is meant to be an exhausting set, any further stress on the muscle can perhaps result in injury, without any gain.


A Guide to Exercise: Understanding the Basic Principles of HIIT




A progressive increase in either the load or the number of reps is essential.


This means that from one workout to another, there must be progress in the work performed – either the load should increase, or the same load be lifted for more reps, or perhaps the previous load and reps should be aimed to be finished in lesser time.


After one has determined the optimal recovery time (range 4-14 days) for the body, it is possible to continuously progress for months (and ideally years), provided you are committed and eat well.


Case study in Progression:

Say you’re able to perform 15-18 reps of the exercise comfortably. For the next round your load may be enhanced by 2.5 kg or 5 lbs for upper body exercise and double that for squat and dead lift, depending on the weights you use. 


After a few months, you will reach a plateau depending on your initial fitness and strength; the higher one's fitness is at the time of starting, the earlier one is likely to plateau. Now would be the time to slow down but attain definite gains - increase by one rep per week till one can again perform 12-15 reps with a higher weight, say 70 kg for the athlete in the above example. This is likely to result in a substantial gain in 6-12 months, and is a highly achievable goal.


After this, one can change the exercise a bit: for instance start incline press instead of the bench press, or change to dumb bell press or body weight training (difficult push-up variants, dips etc. ) for a few weeks. 


You have to exercise regularly, while changing the routine a bit, but stressing the same muscle groups, in order to achieve the best results.


A truly Zen concept, as Danny Kavadlo says. 

 A Guide to Exercise: Understanding the Basic Principles of HIIT




Frequency is dependent on the type of exercise being performed.


The hallmark of HIIT is to allow complete recovery before the next workout.


Typically, aerobic exercises such as running can be done thrice a week, while weights should be lifted at most once a week.


Generally, it is better for people who start exercising late (after 30), to begin slowly, possibly consult a physician before kicking-off in case one is otherwise used to being sedentary. Learn all the exercises gradually to build a reservoir of strength and endurance, before graduating to HIIT.


Next week, I will elaborate on applying the principles of HIIT on specific exercises such as running, kettle bells, free weights etc. Stay tuned!


This is a recurring column published every Sunday under the title: A Guide to Exercise.



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