hiit workout

How HIIT Workouts Can Improve Your Fitness in 2021

HIIT workouts have been all the rage lately and many personal trainers across the world have included HIIT workouts into their training. If you’re new to fitness you might be wondering “what exactly is a HIIT workout?” and more importantly, “can HIIT workouts improve my fitness?” Keep reading to find out exactly how HIIT workouts can improve your fitness levels.

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Any form of exercise is good for you so long as you keep good form and don’t cause an injury.

We’re much more sedentary now than people living 100 years ago. Technology has changed the way we eat, sleep, entertain ourselves and work. Simply put, we don’t move as much as we used to and we aren’t getting the same amount of exercise as part of our daily lives.

Therefore, it’s important to make sure we get enough exercise in order to remain fit and healthy.

I know this isn’t always as easy as it sounds and you might think that you don’t have the time to spend hours in the gym. If that’s the case then HIIT workouts might be the answer to your problems.

office worker 1

What Is A HIIT Workout?

HIIT stands for High-Intensity Interval Training which is a form of cardiovascular exercise. 

The concept is quite simple, you alternate between short bursts of high-intensity activity, followed by a short rest period for a certain length of time.

For instance: 30 seconds of high knees, followed by 30 seconds of rest.

HIIT is the opposite of steady-state cardio, such as a nice leisurely jog where you control your energy to sustain your activity for longer. 

The idea is to push your body to its limits for your entire working duration. Then let your body recover in your short rest period by either slowing down or coming to a complete stop. 

This enables you to improve your muscle tone, burn fat, build strength, endurance and cardio fitness in a shorter time frame than other methods.

It’s not always easy to know when you are pushing yourself to near your maximum energy output, but a fitness watch will be able to give you an idea of your heart rate during your working periods.

It is crucial to let your body recover before the next working interval to prepare your body to work at its full capacity.

Who Can Do HIIT?

Most people will be able to do HIIT workouts and reap the many benefits attributed to this form of exercise. However, there are some people who reconsider using HIIT due to their health.

It’s not really a one size fits all approach. 

Those new to high-intensity training or who are unfit should be careful at first and allow their bodies to get used to this kind of exercise. Or consider low-impact high-intensity workouts.


Simply start with a 15-minute workout: 30 seconds work, 30 seconds recovery. Then gradually increase your intensity or overall duration. This will allow the body to become accustomed to high-intensity exercise.

Who Shouldn’t Do HIIT Workouts?

There are some people who should avoid high-intensity training due to health concerns.

Anyone who suffers from the following should avoid HIIT sessions until their health improves:

  • Anyone who is injured
  • Anyone who suffers from heart, joint or back problems
  • Anyone with bladder weakness
  • Pregnant women
  • Women in the first 6 months postpartum
  • People who can’t perform exercises with correct form

The list above is fairly self-explanatory but it must be said that those with health problems could cause more damage to their bodies.

If in doubt, you should seek advice from a medical professional prior to doing HIIT.

Advantages Of HIIT

Although HIIT workouts are shorter in overall duration, they come with a number of advantages.

  • HIIT is short and can be done in as little as 15 minutes
  • It’s good for cardiovascular health
  • Increases your metabolism
  • Can be done anywhere
  • Allows you to build muscle while losing weight
  • It can boost your mental health
  • It increases your blood flow

Will HIIT Workouts Improve Your Fitness?

Using intervals can boost your cardiovascular fitness. In simple terms it makes it much easier for your heart, lungs and vascular system to deliver oxygen rich blood to your muscles during exercise.

The fitter you are, the longer it will take for you to get out of breath and you will be able to workout for longer.

Can HIIT Replace Cardio?

This isn’t a simple yes or no answer I’m afraid and it will really depend on you.

A lot of the benefits of steady state cardio can be achieved with HIIT in a shorter period of time. 

If you’ve had a busy day at the office, the idea of a 20 minute or 30 minute HIIT will be much more inviting than spending an hour on the treadmill. 

That being said, the two styles of exercise are not mutually exclusive and a lot of athletes alternate between HIIT on one day and steady state cardio the next.

cardio 1

Your body is also quite sneaky. While you may see quick results when you first start using HIIT, over time your body adapts and it becomes harder to gain results at the same pace as before.

Therefore, shocking your body with different forms of exercise will help you to achieve further progress.

The key takeaway of this is to ensure there is enough variety in your workout routines.

It’s Not All About Cardio!

HIIT workouts aren’t just about cardio. 

Including bodyweight and weighted exercises into your HIIT routine will encourage strength and muscle building and can also lead to further calorie burning.

It also allows for a good variety of exercises in your workouts which can keep your body from getting used to one particular type of exercise.

Are Short HIIT Workouts Effective?

Short HIIT workouts of around 15 minutes are still an effective workout. So long as you are pushing your body to near its maximum efforts during your working interval.

One of the benefits of HIIT is that it can be done in a shorter time than other forms of exercise. And providing the HIIT sessions has been performed correctly – i.e working at 8 or 9 out of 10 – you will increase your cardiovascular fitness, your metabolism will be raised and your body will continue to burn calories for up to 24 hours after your workout.

Is Low Impact HIIT Still Effective?

Low impact doesn’t mean low intensity. You still need to exert the most energy you can with Low impact exercises.

Low impact simply refers to exercises that are a little easier on the knees, and requires less jumping around such as:

  • Swimming
  • Cycling
  • Rowing
  • Elliptical
  • Pilates
  • Yoga
  • Walking

There are many ways that you can adapt a workout to be more joint friendly and it will really depend on your abilities. However, here are some low impact versions of popular exercises to give you a few examples:

  • Swap full burpees for walk out burpees 
  • Instead of high knees, swap for marching knees
  • Use a chair to sit down into your squat
  • Perform seated tuck jumps

Is It Better To Do HIIT In The Morning Or Evening?

I’ve talked about the best time to exercise in this post, and the conclusion was that the best time to workout is when it suits your lifestyle.

If you typically have a busy morning rush trying to get the kids up and out to school, or you’re rushing off to the office, then trying to fit in an early morning workout might not be possible.

Likewise, if you have busy afternoons, you might only have time to workout late at night, or early in the morning when everyone else is in bed.

The most important thing is finding a time that suits your schedule to devote 15, 20 or even 30 minutes to exercising.

morning evening 1

There are many benefits to early morning, afternoon and evening workouts.

If you exercise in the morning this can lead to increased brain function and it allows your body to burn through more calories that you consume throughout the day.

Afternoon workouts can be good for you as your body has had time to wake up, you’ve likely had at least one meal so you may have more energy for your workout. Your motor functions will be more alert and you may be less likely to injure yourself.

Evening workouts come with many benefits too. It can be a great opportunity to destress from the day and focus on yourself for a short period of time. You will likely be well fed and energized for the workout and working out later in the day can lead to improved sleep.

Regardless of when you workout, HIIT will allow for a calorie burn for up to 24 hours. Working out in the morning or afternoon will help to burn through more calories that you have consumed, but working out in the evening allows your body to burn calories while you sleep and recover.

Should You Do HIIT Workouts Every Day?

Ok, so I mentioned a little earlier how your body will adapt to certain types of workouts and you may see less progress by doing the same thing day in day out.

That doesn’t necessarily mean you shouldn’t perform HIIT workouts every day that you exercise. Moreso that you should be mindful of what you want to achieve.

There are no real hard and fast rules to say you should or shouldn’t do HIIT workouts every day. However, I will say that you should aim to workout between three to five days per week in order to reap the benefits of exercise.

That being said, HIIT does put a lot of pressure on your body. Working out at near 100% day in day out will take its toll. 

If you happen to notice that you’re not able to put as much effort in then consider switching up your routine by alternating between HIIT and steady state cardio. Your body will react to different forms of exercise and you will still see results.

Similarly, if you like HIIT and you feel you can continue with this type of exercise, then as a precaution, I wouldn’t recommend exceeding five workouts per week. Your body will need time to rest and without ample rest you could end up with an unwanted injury.

How Does HIIT Change Your Body?

HIIT can change your body in a number of ways. 

Australian researchers found that a short HIIT workout was just as beneficial to your body as a 30 minute cardio session.

The study looked at mitochondrial changes of participants after performing different types of exercise: 30 minutes of moderate exercise, 20 minutes of HIIT and 2 minutes of HIIT.

Mitochondria are responsible for producing energy for your body. When you get older your energy production slows down. However, exercise creates new mitochondria and boosts your energy production.

The results showed that the shorter amount of time spent doing HIIT provided an equal response in mitochondrial function as the longer moderate exercise.

HIIT also allows you to burn more calories long after your workout. It increases your metabolism and ability to burn fat. Which can lead to weight loss as long as you’re controlling your calorie intake.

Does HIIT Target Belly Fat?

This is a question I hear quite often. The simple fact is that you cannot target fat loss from one specific area of the body.

Your body decides where it will lose fat from. Most top heavy women tend to lose fat from their bust first before seeing a reduction in other areas of the body.

Over a period of time, if you have fat to lose around your belly, you will likely see some results but again, you cannot target fat loss from one specific area.

Healthy Body

What Does A Good HIIT Routine Look Like?

A good HIIT routine is all in how you build it.

To create an effective HIIT workout, decide on a range of exercises, along with your work and rest intervals which should last between 15 minutes to 30 minutes in duration.

Some excellent exercises to include are:

  • Squats
  • Lunges
  • Sprinting
  • Star Jumps
  • Burpees
  • Pushups
  • Sit-ups
  • Ab Crunches
  • High Knees
  • Mountain Climbers
  • Planks

Alternate your working and resting intervals for 30 seconds each and carry out each round 3 times to build a 30 minute workout.

You can also include certain equipment into your HIIT routines such as dumbbells, exercise machines or resistance bands.

As a beginner, HIIT sessions are great for flexibility. Begin with a 15-minute workout and build up strength and stamina. Each week add an extra exercise or round for a longer workout whilst also increasing the intensity of each move.

If you’re struggling to create your own routine, there are a number of HIIT workouts available online. If you like the competitive element of following a workout video, turn to The Body Coach, Millionaire Hoy, and Caroline Girvan on YouTube.


It’s clear to see that HIIT workouts can improve your fitness levels. You’ll experience better cardio fitness, energy production, fat loss, and improved mood. You can save time, instead of spending hours in the gym you can complete a 30 minute HIIT workout and burn more energy. You’ll also continue to burn calories for long after your workout has finished.

Have you recently started to do HIIT workouts? Have you noticed a change in your fitness levels? Let me know in the comments!

How HIIT Workouts Can Improve Your Fitness
How HIIT workouts can improve your fitness

HIIT Workout FAQ

How many days a week should you do HIIT training?

You should do HIIT workouts between 3 to 5 days per week ensuring you have ample rest periods in between workouts. I.e 2 days working out, 1 day rest. This allows your body to recover.

Are HIIT workouts good for weight loss?

Short bursts of high intensity workouts can be more effective for weight loss than longer less intense workouts.

How long will it take to see results of HIIT Workouts?

You will start to feel the results of HIIT workouts after a week of consistent training. After 90 days you will see good results on your body. They key is to remain consistent. Stick to a steady workout regime of 4 days per week for a sustained length of time to see better results.

Does HIIT burn belly fat?

Your diet will play the biggest factor in burning fat, especially stubborn belly fat. However, burning calories through consistent exercise is crucial. HIIT workouts are an effective way of burning calories and fat.

16 thoughts on “How HIIT Workouts Can Improve Your Fitness in 2021”

    1. Louise O'Boyle

      HIIT workouts are great to get the blood pumping and combined with some weights will take your fitness to new heights! I hope you do get started up again and come back and let us know how you feel 🙂

  1. HIIT workouts are fabulous. Thank you for this post and encouraging people to try these. I’ve done some fabulous workouts both in the gym and at home. I also do a type of HIIT to get faster with my running. I run faster for a short time, then slow it down to an easy jog, then repeat. Sometimes I pick lampposts to do this, sometimes I set a timer on my watch. It’s great. HIIT also keeps my attention and prevents boredom.

    1. Louise O'Boyle

      I LOVE a good HIIT workout and it’s always good to spread the good vibes to everyone else 🙂
      That’s such a good idea about using lampposts instead of timers. I’ll be honest though, I’m not much of a runner but I do love some star jumps, squats and quick knees 🙂

    1. Louise O'Boyle

      If you don’t have much time on your hands but want a really effective cardio or bodyweight workout then this is the ticket for you 🙂

  2. I totally agree with your post! HIIT workouts are the best way to stay fit and not spend your life in the gym – a busy mom’s best friend!

    1. Louise O'Boyle

      Oh absolutely, I don’t have kids, but I also don’t want to spend my life in the gym. So for me this is the best way to keep fit but also fits in with my lifestyle 🙂

  3. Amy @ The Kent Krew

    Yes! I love HIIT workouts, and I know so many people get overwhelmed by the name alone, they see it as something wild. But it is one of the best ways to burn tummy fat!

    1. Louise O'Boyle

      I think the name does seem scary and I’ll be honest, when I first heard about it I was a bit frightened too but when I actually completed the first session I was thrilled. Sometimes trying new things can be daunting but the sense of achievement afterwards is totally worth it!

    1. Louise O'Boyle

      That’s exactly the way to do it. Balance a HIIT with other forms of exercise. It gets the blood pumping and the endorphins rushing. I love it so much 😀

  4. Amanda Bradley

    There are so many great benefits of HIIT workouts! My go-to exercise is always running and this type of workout is also easily adapted for running. The endorphins from cardio definitely keep me coming back! Thanks for this very helpful post!

    1. Louise O'Boyle

      Honestly, good for you. I can’t run to save my life and it’s something I’ve always wanted to do properly. I just can’t though. But HIIT is very easily workable with running. Simply run as fast as you can for 30 seconds then walk or jog for 30 seconds. As Patricia said, she sometimes uses lamp posts as her measurement. Whichever works 😀

  5. This is such a great and informative post! Thanks so much for sharing all these information about HIIT training.
    I personally rarely do HIIT as I feel like my body doesn’t really like it and doesn’t handle it well. Slower paced workouts work so much better for my body. But it’s good once in a while xx

    1. Louise O'Boyle

      As much as I love HIIT, it really isn’t for everyone and if your body can’t handle it then you are totally right to avoid it and do what works for you. Like I’ve said, I really cannot run. I can’t so although I’d love to be able to run the length of myself one day I just know that it’s unlikely to happen. Good for you for putting your body first though, everyone is different and you have to do what’s right for you.

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