HIIT For Fitness: Fact or Fiction?

A Somewhat Typical Story…

With the holidays fast approaching, Jane wanted to get fit, shed that extra weight she had put on and perhaps even gain some muscle in the process.latestfitnessgadgets_fitness_holiday_pic

She had heard about HIIT for fitness before but didn’t bother with it. She decided she knew what to do to achieve the fitness she wanted.

She wanted to go about it correctly so she had the best chance for success. She took her time to clearly articulate her fitness goals and measure her progress.

==> See blog on Setting and Conquering Goals

She decided to go out for a jog every day and watch her diet as most of her friends were also doing the same. She didn’t dither long and got started on her fitness plan.

About 6 weeks into her plan, she discovered that while she lost weight in the initial weeks (which was very exciting), the weight loss gradually slowed and had plateaued. The routine had gotten a little boring and at times she felt weak and exhausted during the day.

On the verge of giving up and puzzled at this, she decided to investigate how the human body responds to exercise.

What she found had her very excited and brought her enthusiasm right back. She had discovered HIIT for fitness!

She decided to give HIIT a go and was quite simply blown away by the results.

By the time her holidays started, she had achieved her goal weight, added muscle definition to her frame, and was very proud of her achievement…

The above story with a happy ending is fictional but is not very far from the truth for many of us who have tried HIIT. Did it resonate with you?

The questions really are, did Jane actually benefit from HIIT or was it just her enthusiasm and other factors that helped her achieve her fitness goals?

Even if HIIT did benefit her, how so? 

Also importantly are there any downsides to HIIT?

In this article, I hope to answer the questions above. Hopefully, you will tune in to what I’m saying, learn and benefit from it.

What is HIIT?

High-Intensity Interval Training (HIIT) simply put is an exercise plan that alternates between short, intense burst of exercise followed by low-intensity exercise or rest. This exercise pattern is repeated until the end of the HIIT session.

Before we dig in, let’s understand a few terms that will be used as this article unfolds.

Some Important Terms

Aerobic exercise is any form of low to medium intensity exercise that uses free oxygen to meet the metabolic needs of the body. Typically, aerobic exercises can be performed for long durations. We are all familiar with this exercise form – going out for a walk or a run would be an aerobic activity.
Anaerobic exercise is any physical exercise where one goes out of breath very quickly (in seconds typically). Anaerobic training means training without oxygen instead metabolic pathways provide the required power. The exercises are short in duration and high in intensity lasting from a few seconds up to a couple of minutes.

This form of exercise causes lactate to form which allows glucose breakdown to produce energy. The muscular development in this exercise form is very different from aerobic exercise.

VO2 max is a measure of maximum oxygen intake by a person. It is an indicator of cardiovascular fitness and a powerful indicator of future health.
Insulin sensitivity measures how sensitive the body is to insulin. Diabetics, for example, have low insulin sensitivity and require larger amounts of insulin to keep the blood glucose levels stable.
Aerobic (cardiovascular) fitness is an important component of physical fitness and is the ability of the heart, lungs and blood vessels to provide adequate oxygen to all parts of the body and the ability of the body to use the oxygen for movement.

HIIT For Fitness In Action – Some History

I first saw HIIT for fitness in action back in Feb 2012 when I watched Michael Mosley’s show The Truth About Exercise on BBC’s horizon program.

In the program Michael Mosley (co-author of The Fast Diet) was put under a radical, time-saving exercise routine (HIIT) which improved his body’s insulin sensitivity by a remarkable 23% coupled with a 10% improvement in his cardiovascular fitness.

The HIIT protocol required him to get on an exercise bike and cycle as hard as he could for 20 seconds followed by a resting period and repeat it 2 more times. And that was it for the day.latestfitnessgadgets_exercise_bike

A grand total of one minute of intense exercise!

After doing it 3 days per week for 4 weeks, he completed 12 minutes of HIIT (1*3*4 = 12 minutes) and his blood sample showed a sharp increase in insulin sensitivity by 23%. Also, his cardiovascular fitness improved by 10%.

It made me question quite a number of things that I thought I knew about exercise. For example, I assumed that the more exercise you do it’s better for you. Well after the program I realised that may not necessarily be true.

Forget several hours, we are talking just a few minutes a week to get remarkable health and fitness benefits!

Sounds too good to be true?

The Magic of HIIT

There are two important health factors that can be dramatically improved through exercise.

The first is insulin sensitivity. Insulin removes sugar from the blood. It controls fat and when it becomes ineffective, the person becomes a diabetic.

The second important factor is aerobic (or cardiovascular) fitness measured as VO2 max. It’s a measure of how good the heart and lungs are at getting oxygen into the body. It’s not just an indicator of how fit the person is, but also a powerful predictor of future health.

In other words, if a person can improve their VO2 max and insulin sensitivity, he/she will improve fitness levels and probably live longer.

Contrary to conventional thinking, the HIIT protocol has shown that its is possible to improve these health markers with a remarkably short amount of exercise.

In a period of just a few minutes per week, you can dramatically improve your insulin sensitivity and your cardiovascular fitness.

The Science Behind HIIT

How can such a short amount of exercise have any benefit at all?latestfitnessgadgets-glucose-structure

Without going into the too much technical detail, I have explained what actually happens below.

The key thing about this form of (anaerobic) exercise is, in the absence of free oxygen, it breaks down the glycogen stores in the muscles where the glucose is stored.

When that happens, a signal is sent from the muscle to the bloodstream for more glucose. This is done by producing insulin to shift that glucose which brings down the blood sugar levels significantly.

What’s really good about the HIIT protocol is unlike walking or jogging where you are probably activating 20-30% of your muscle tissue, here you are activating 70-80% because of the high maximum intensity nature of the exercise.

The scientists researching the effects of HIIT on fitness believe that ultimately it’s the intensity that counts. It breaks down the stored glycogen in muscles much more effectively than moderate exercises like jogging.

What’s In It For You?


HIIT is an exercise protocol that you cannot afford to ignore. The two key factors of health that are influenced by exercise are positively impacted in a very short period of time.

HIIT will improve your glucose and therefore your insulin sensitivity.

When you are at your VO2 max, your cardiovascular system improves in fitness.

The two factors together go a long way in improving your health, fitness, and longevity.

Getting Fit – The Conventional Way

Getting fit is an imperative. Exercise is the best way to achieve this goal.latestfitnessgadgets-gym (1)

Exercising extracts fat from the blood and make it available to the muscles where it is consumed. This is good.

If you don’t exercise regularly, the fat remains in the blood and eventually lodges itself in your system.That’s the start of bad things.

Exercise switches on genes that make an enzyme called lipoprotein lipase (LPL) and this controls the amount of fat in the blood.

The trouble is in order to produce that result, we actually need to spend many hours per week exercising. While this can be done occasionally it is not easy nor practical to sustain this level of exercise commitment long term.

Rising Popularity of HIIT


If you do long sessions in the gym or jogging and that’s what you enjoy, great. But most of us don’t.

HIIT may be the new kid on the block but it’s making waves. It is a form of exercise protocol which is very effective and can easily fit into your busy life and is something you can honestly imagine doing for the next few decades without a break.

HIIT would suit everyone and can easily be tailored for people of all fitness levels and special conditions, such as overweight and diabetes.  It will help a lot more people get those vital health benefits.

HIIT workouts can be performed on all exercise modes, including running, cycling, walking, swimming, elliptical cross-training, and in group exercise classes.

HIIT workouts can be done even at home.

Negatives of HIIT

Injury is one of the main concerns. If you have been leading a sedentary life, be cautious when you sign up for an HIIT workout. Know yourself and your limits.

If you have a pre-existing medical problem, you must have a checkup before you start. This is necessary because of the high-intensity nature of the exercise.

Final Thoughts

The health and fitness benefits of HIIT are backed by research and evidence. Scientific research worth millions are in progress learning more about HIIT and its impact on the human body.

It’s a newly evolving field of study that has really taken off in the last few years.latestfitnessgadgets_fitness_holiday_original

… Jane (remember her?) may not have been too concerned about her blood sugar levels and her cardiovascular fitness when she started on an HIIT program to lose weight to get prepared for a summer beach holiday.

Unbeknownst to her, she inadvertently started on an exercise form which benefitted her far more than she was aware of.




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