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WHY HIIT?

You might wonder why you put yourself through a gruelling 30 minute workout, which leaves you covered in sweat and your lungs working harder than normal.

HIIT (High Intensity Interval Training) is a form of training used to increase anaerobic capacity....the rate at which you can perform effectively, without oxygen. Before it became fashionable to do HIIT workouts, athletes would embark on this style of training with the use of sprints....sprint, rest, repeat.

A typical HIIT workout pushes you into you 80-100% Max Heart Rate (MHR) for a short period, followed by a rest period at a lower intensity.


Nowadays HIIT has become the go to workout, with so many variations of the; exercise, rest, repeat format. Aside from it being a quick workout that can fit easily into your day, it does have other physiological benefits if used correctly.

1. Burning calories.

2. Increasing anaerobic capacity

3. Releasing endorphins

4. Improving fast twitch muscle fibre recruitment.

5. A change in your body composition

Burning calories

You burn calories every minute of the day - some exercises/activities burn more than others and you may have found that during a HIIT session you're not burning as many calories as you think you should.

HIIT sessions, whilst increasing your anaerobic capacity, also increase your EPOC (Excess Post-exercise Oxygen Consumption) - which simply put, is the calories you burn after a workout, for the next 24 hours. So, whilst you may not think the calories burnt during the session are top heavy, you are consistently burning more calories for the next 24 hours than if you went for a steady pace jog for 30 mins.

You may have 'felt this' through hunger! so what is really important (if you are trying to achieve results) is to keep your intake in check, ensuring that you're not over eating to compensate for that extra burn created.

Increasing anaerobic capacity


To work anaerobically, is to work without oxygen. We spend our whole day working aerobically - a limitless supply of energy provided through the use of oxygen. We rarely push ourselves out of this zone ...Why? Because it feels hard and uncomfortable, it also is not needed for general daily living.

When we do push ourselves into this uncomfortable zone, we are encouraging our bodies to work in a zone that is abnormal and challenging.


Imagine yourself in a race…comfortably pacing yourself around the course and finishing in an ‘okay’ position….with anaerobic training you can push harder and faster – meaning you can overtake when you need to, push up the hill faster and recover quicker – thus finishing in a ‘great’ position and hitting a PB!



HIIT training allows you to increase your anaerobic capacity by getting used to this uncomfortable zone and training your body to recover better from these short bursts of high intensity. You are not expected to be at 80-90% of your maximum heart rate for long…you have to drop back down to a more comfortable (oxygenated) area at some point.


What you will find with more anaerobic training….is that you also increase your aerobic capacity…meaning you can work at a higher intensity and still remain in your aerobic zone – because you are better at utilising oxygen.

For example; on a treadmill – if you normally run comfortably at 9.0km/h…overtime this should increase and 9.5km/h would become your new comfortable pace.

Releasing endorphins

Lets face it – sometimes the thought of doing a HIIT session is terrible! But the feeling afterwards and even during, outweighs that every time.

The high release of endorphins and adrenaline leave you feeling positive, motivated, and with a huge sense of achievement.

Improving fast twitch muscle fibre recruitment.

We have three types of muscle fibres within our bodies – simply put – fast twitch, slow twitch and a middle ground.

Aerobic activity – day to day movement recruits slow twitch fibres – full of oxygen.

Anaerobic (HIIT) style activity – fast explosive movements – recruit your fast twitch muscle fibres…this means that when you need to react to something, you can!

Imagine the need to sprint for the bus that’s just leaving, or chase after a child that’s ran in the opposite direction (in my case!!)

Encouraging the recruitment of these muscle fibres gives you a much better balance within your muscles, stops atrophy (diminishment) of fast twitch fibres and makes your movement more dynamic.

A change in your body composition.

Body composition refers to your body fat % and your muscle mass. Including HIIT into your training routine encourages you to burn fat (during and afterwards) and improve your muscle mass, this will in effect change your composition – meaning that you should start to look a bit leaner and see more muscle definition (as long as you’re eating effectively to support your training)

The number on the scales might not necessarily change, but your clothes fitting and general appearance should improve.

I hope this has helped with your understanding of HIIT!

Remember everyone can do HIIT training – you just have to make the exercises and intensity relevant to YOUR fitness levels…not the person next to you!

You can catch a session with me

Monday 12pm

Wednesday 7:30am

Hollie 😊



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