HIIT and Sprint Interval: 20-minute intense workouts for get in shape and endurance

Run for about half a minute as if you were being chased by a lion. Rest for about half a minute. Repeat a few times. This is how you get the fancy sprint interval and HIIT workouts. It’s time-efficient, great for shaping and burning fat, building endurance, preserving muscle and even keeps your brain functioning young! Sounds too good to be true? It’s primarily recommended for hobby athletes, but has also been used by elite athletes for a long time. Read important details about sprint interval and HIIT and incorporate them into your workouts!

Interval, repetitive training, sprint interval, HIIT, sprint: Which is what?

To clarify, there are important differences between the above terms.

A sprint is a full effort, very short exercise that you only do once. Or repeated a few times if it’s not a race but a workout. In a workout, it is characterised by much longer rest periods of 5-20 minutes and full recovery than the workload. It is a method of developing pure speed and explosiveness. E.g. 30-60-100-200m runs, but often even 400m is called sprint.

Interval, repetition training is similar to each other, usually consisting of repetitions of 30-60 second up to 6-10 minutes intervals and rests, at high, but not necessarily maximum intensity. With rest periods equal to or slightly shorter than the work interval, with full or partial heart rate recovery. It is primarily an endurance method. For example, in kayak canoeing we often had 10×4-6 minute or 3x2000m workouts.

Sprint intervals and HIIT (High Intensity Interval Training) are a mixed genre between interval training and pure sprinting. It is characterised by a maximum workload of 30-60 seconds and rest periods of about the same amount or less, repeated many times. Heart rate does not go back to baseline, which is one of the essential elements. It’s hard to define them precisely because there are so many variations, so it’s more of an umbrella term for both.

HIIT is said to be at or near maximum effort intensity (85-100%), with very short rest periods, lot of sets. Whereas sprint intervals are said to be 100% effort at each stage, so it’s a bit harder. Less sets and longer rests until you are able to run again close to 100%.

Both are suitable for endurance and strength-endurance development, for shaping the body, but for speed and explosiveness they are not nearly as good as pure short sprints. E.g. the classic Tabata protocol is 8x (20″work and 10″rest) or 4-6x (30″work and 30-60″rest).

Ancient roots

Cavemen may have had to sprint at full speed after prey or run away from a bloodthirsty predator. Sometimes several times, with short rests in between. In addition, lifting and carrying heavy objects and tree-climbing are ancient, natural movements, all of which require strength and speed, repeatedly.

What is it good for?

HIIT and sprint intervals are both time-effective methods of shaping the body, strength-endurance and endurance development.

Both involve alternating short bursts of work at or near maximum intensity followed by short rest periods to push yourself almost to the limit in a few minutes. So you can develop endurance with less time investment just as well as you can with traditional continuous long-duration exercise, plus you burn body fat more efficiently and even build some muscle, or at least not lose fast muscle fibres. Too good to be true?

Several studies (see references) have demonstrated the benefits of these methods over traditional low-to-moderate intensity, continuous aerobic exercise. Intense exercise methods were equally effective in improving aerobic endurance (low-to-moderate intensity exercise) and also improved anaerobic endurance, i.e. the ability of muscles to tolerate acidosis. Intense intervals effectively improve mitochondrial function and increase the number of mitochondria as well!

In addition to the short workout time, an added benefit is that it’s a more playful, enjoyable alternative if you’re bored of long, monotonous workouts. During a short workout, less oxidative stress is put on the body, fewer free radicals are produced, and insulin sensitivity is improved. The high effort mainly uses fast muscle fibres, so there is no “muscle loss” as with many low-tempo workouts, where slow fibres are almost exclusively used, leading to a long-term loss of muscle mass and strength.

Exercises involving intense muscle contraction (sprints, weight training) are much more likely to trigger growth hormone (GH) and testosterone production after exercise than slow, low-intensity forms of exercise. GH boosts the use of fats for energy production, often referred to as the ‘hormone of youth’ because it slows down the inevitable ageing process.

Older people should therefore not be discouraged from using it, and it is highly recommended for them because of its beneficial effects on the hormonal balance, with medical approval, a suitable training history and a gradual approach. It also has a beneficial effect on brain function, as high intensity exercise constantly challenges the areas of the brain responsible for movement, and new neural connections can be formed.

Short intense workouts burn fewer calories compared to a long run during the training period, but the recovery process continues for the day or two afterwards, so you burn more calories overall. See EPOC – Excess Post-Exercise Oxygen Consumption.

It’s good for your running technique and general movement coordination if you learn to move your limbs in a faster way than jogging. Especially if you try to keep this up as you get more and more tired with the number of sets.

What are the disadvantages?

A promising and practical form of exercise, but not a ‘sixpack in 10 minutes’ magic workout for everyone.

One of the drawbacks of sprint interval and HIIT training is that it is tempting because of its time efficiency and for many people it would be more time-efficient, but it is not a recommended method for complete beginners. It’s worth training regularly for a few months beforehand, with basic strength training and slow-to-moderate intensity endurance training (walking, jogging) for longer periods.

Another disadvantage compared to traditional aerobic (cardio) training is that it has a longer recovery time, so you can’t do much of it and it’s not worth doing it every day. Too much of a good thing can be not so good…

Another problem: It doesn’t really improve your cardiac output (the amount of blood per minute delivered to the heart), as opposed to the traditional long, continuous method, which is an excellent way to do it. For the long-term health of the circulatory system, it’s also worthwhile to do low-intensity exercise of longer duration. Long walks and hikes, for example, are excellent ways to do this.

One more thing: In endurance sports, long, continuous, low-to-moderate intensity work is part of the training, and you can’t get away with just relying on sprint intervals. But you can combine the two in a smart way!

How to do it?

You can vary the method widely in terms of durations, distances, training frequency, nutritional status (on an empty stomach or with replenished glycogen stores) and form of exercise.

Running is probably the most practical, but you can also do cycling, indoor cycling, swimming, rowing-ergo, elliptical, treadmill, assault bike, for beginners fast walking. It can even work with bodyweight or weight training. For example, burpees, jumping jacks, push-ups, rowing, squats, etc.

You’ve done well if, by the end of the workout, you feel like you can’t do any more, you’re out of breath and would like to breat through your ears, your heart rate and lactic acid levels have skyrocketed.

A few ideas

HIIT: 85-100% intensity in each intervall, very short rest periods, like 10-30″, high number of sets. 

Tabata: 1-3x (8×20″ work / 10″ rest)

30-60 x (8″ work / 12″ rest) 

10-20 x (50-100m run / 10-20″ rest)

The Sprint Interval is a bit more advanced workout with always 100% intensity, longer rest 30″ to 2-3min and less repetitions

4-8 x (30″ work and 60-90″ rest) 

1-2 x (400, 300, 200, 100m run and 1-3 minute rests)

8-10 x (50-100m run and 60-90″ rest)

A few important advice

  • Not recommended for complete beginners or if overweight. You should first be able to move and run for at least 30 minutes continuously. Heart disease is also a rule-out!
  • In addition to basic endurance, it is also worth building up a basic level of strength and mobility first, so that your muscles and joints can cope with the intense workload.
  • In case of any muscle injury, fix it first.
  • Learn and keep polishing your sprinting technique. It’s quite different from jogging!
  • Warm up thoroughly first!
  • Keep to a gradual progression (volume, intensity, training frequency), otherwise you could risk injury due to the high stress on the muscles.
  • For this type of training, it is particularly important that the pre-exercise meal is removed from the stomach if you do not want to see it again.
  • The work portion should be near maximum or 100% intensity that you currently have in you! At first, 70-80% effort can of course work as an introduction for a few weeks and gradually increase the intensity and volume as the weeks go on.
  • Rest can be completely passive (you’ll wish for it) or very light exercise, walking.
  • One set of the Tabata protocol is enough for beginners, more advanced people can do two, three or four.
  • The maximum total duration of the workout should be 20-30 minutes.
  • Stop the workout when performance is dropping about 20% below your best. It is also a good idea to stop for the day if your body gives you any indication that you shouldn’t push yourself any further or if you feel a strong loss of motivation for the next set.
  • If you’re doing other types of exercise, one or two sessions a week is enough, but no more than 3-4 a week is worth it anyway. More than that can lead to injury and overtraining.
  • Traditional aerobic exercise should not be completely discarded and it is worth doing this type of training from time to time, as time and sporting goals allow.

My experience

I’ve been replacing most of my long runs with 15-30 minute intense sprint intervals and HIIT workouts for about 10 years now, so I’ve gained some experience. I only do them 1-2 times a week in addition to strength training and have had a great experience. I only do classic longer continuous runs a few times a year.

In recent years my SunnyFitness “handyman” workouts have mainly focused on developing movement skills, maximal strength and relative strength, and as a side effect, maintaining a muscular, lean, proportionate physique all year round. Sprint interval type training is better suited to strength development than long endurance workouts because there is not a big counter adaptive stimulus, so I develop better indicators of strength.

As an elite canoeist, there is a place for longer interval and continuous runs, as kayak canoeing is largely an endurance sport. There came a time when I no longer had the goal of excelling in elite sport, only in the handyman-generalist fitness and I wanted to keep the endurance I had developed over the years to a high level (or rather lose as little of it as possible).

99% of the time I run barefoot on sand or grass. I’m totally out of shoes ???? If the terrain is more gravel, I’ll put on a thin-soled, flexible, minimalist 5 finger or surf shoes. But for OCR races, I mostly prefer to go with a traditional trail running shoe so I don’t waste time being careful.

The good news is that my endurance and general work rate is still well above average. E.g. Cooper test above 3000m, 21km mountain running race no problem, OCR races above 10km are also easy to complete (finishing in the top 3-10% of the field). I could run a marathon even if I woke up from my sleep. I also stop my training only because I have to go somewhere, otherwise I would continue with a few more sets.

I like that sprint interval workouts are short, time efficient and enjoyable. I used to do a lot of monotonous, long endurance work, it’s a real relief to run fast and intensely. Plus, my metabolism is spinning hours after the workout, I can eat almost anything and still burn fat!

If you’d like a personalised training plan for intense intervals or other sports goals to get you in the best shape, email me! There are many variables and many ways to make mistakes, some of which I have tried. You don’t have to test for years to see what works. I’ll help you put together a gradual, periodized plan that fits with your other workouts and lifestyle. With nutritional and lifestyle advice if needed. (info@mihalysafran.com)

Go for it!

If you’re in the mood because you don’t have time to run for hours, and good body composition and strength are important, sprint interval and HIIT training is for you! It’s tough, but enjoyable if you like the tired but euphoric feeling that comes with intense workouts. It’s also great if you want a change of pace or can’t stand monotony.

The best form of exercise for intense intervals, in my opinion, is running, because you should also practice sprinting as a natural movement. Do it outdoors if possible, because you should spend more time in natural light. If for some reason this is not feasible, of course all the other forms of exercise and gyms mentioned above will do. The point is that this method also works only if you do it regularly! Keep moving!

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Contact me, if you would like a personalised, time efficient training plan or advices on how to train: CLICK HERE!

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Mark W. Pataky, K. Sreekumaran Nair: Too much of a good thing: Excess exercise can harm mitochondria,
Cell Metabolism, Volume 33, Issue 5, 2021, Pages 847-848, ISSN 1550-4131,

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