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The complete HIIT guide to your best workout yet

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September 10, 2018

High-intensity interval training (HIIT) is a form of exercise that’s caused a lot of buzz lately. Let’s take a look at why this training method has got everyone talking, from beginners to workout experts. This is everything you need to know about HIIT.

HIIT basics

HIIT workout - training for beginners

What is HIIT?

HIIT is short bursts of intense exercise, followed by regulated, lower intensity periods of recovery.

Whether you’re a beginner or a more seasoned exerciser, chances are you will have heard the acronym ‘HIIT.’ In the last few years, this style of training has taken the fitness world by storm. But, what exactly is this whole HIIT thing and what makes it so popular? And is it better than Crossfit or circuit training?

In this post, we’ll look at some of the reasons HIIT should be making a regular appearance in your workout schedule.

What does HIIT stand for?

HIIT stands for ‘high-intensity interval training.’ Other names for this kind of training are high-intensity intermittent exercise (HIIE) or sometimes sprint interval training (SIT), but the most commonly used term is HIIT.

The idea with HIIT is to push yourself into your body’s maximum training zones. Then, take rests to allow yourself to partially recover, before pushing hard again. It’s all about putting your body (and your mind) to the test and redefining your limits. 

How will I know if I’m hitting my maximum training zone?

You should be reaching somewhere between 85 percent – 100 percent of your max heart rate during the peak of your work periods in a HIIT session to get the best results. Yep, it ain’t no walk in the park (more like a sprint)!

If you want to know more about maximum training zones, we’ve found a simple max heart rate calculator. This will allow you to work out your max heart rate based on your age.

To track your progress and make sure you’re pushing yourself hard enough during your HIIT workouts, a wearable workout tracker or heart rate monitor is a great option. Various kinds of trackers are available, right from high-end (who said you couldn’t look fabulous in your active wear?) to budget options. Check out a few of the most popular ones here.

The most important thing you need to know about HIIT

The beauty of HIIT is that it doesn’t consist of just one prescribed workout. HIIT refers to the way you approach the workout. In theory, the principles of HIIT can be applied to any training, and this can be either with weights or without.

Many gyms offer their own version of HIIT training as group fitness classes. These can be a great way to get started with HIIT safely under the supervision of an instructor. Or you can do HIIT at home if you’re a bit more experienced. At BMF, we incorporate HIIT into our sessions. Find out more here.

HIIT without machines

HIIT is an extremely adaptable training technique, which means it can be done pretty much anytime, anywhere, and doesn’t rely on fancy equipment to make it one of the most effective training styles around.

Some of the best HIIT workouts are the ones with the simplest moves. When you’re not worrying about complicated technique you can focus more on giving it everything you have and sending your body into those new training zones where it will adapt.

All British Military Fitness workouts are HIIT-based training, with the added fun of being based outdoors in a team atmosphere. When getting in those extra few reps seems impossible, seeing the rest of your team in the same boat is great motivation to keep on pushing.

Check out a few simple HIIT workouts we’ve put together for you:

 HIIT workout BMF X-ERT military fitness training exercise 1

HIIT workout BMF X-ERT military fitness training exercise 2

HIIT workout BMF X-ERT military fitness training exercise 3


5 HIIT benefits for beginners


There are plenty of studies that show HIIT brings a wide range of benefits when it comes to improving metabolic health and cardiovascular fitness, and torching fat. HIIT is effective because it isn’t just about getting that Nicki Minaj bum, it’s about the overall health and fitness of the whole body.

Here’s five reasons why HIIT is brilliant for beginners (and everybody else, too!):

1. Lose weight and feel the burn

One of HIIT’s claims to fame is its well-known ability to burn fat and aid weight loss. Many beginners tell us that losing those love-handles is why they’re looking to prioritise exercise. With so many different methods out there, it can be tricky to find the right one, so, here’s the facts without the fluff:

The secret behind why HIIT is the ultimate fat burner when it comes to exercise is something called EPOC – or Excess Post-Exercise Oxygen Consumption.

This might sound technical but simply put, it just means the rate that you burn calories in the hours after your workout. In fact, this EPOC effect, or afterburn, from high-intensity workouts has been shown to last up to 36 hours:

HIIT training afterburn diagram - military fitness

HIIT requires a lot of effort. It’s intense and not supposed to be easy. But, after all that effort your body will do the rest and burn, baby, burn. Even if you are just slumped on the couch marathoning Brooklyn 99 on Netflix. How do you think Terry Crews stays in shape at a desk job?

What, HIIT could even shift my belly fat?

One study, which followed a group of 40 adults for eight weeks showed a significant reduction not only in total body fat but most significantly, in abdominal girth, in a test group that performed regular HIIT workouts.

2. HIIT workouts build muscle as well as burn fat

OK great, HIIT burns fat. But, what else does it do? While steady state cardio training – such as going for a long run or an elliptical trainer workout – have been shown to encourage muscle loss, HIIT allows you to maintain your hard-earned lean muscle mass while ensuring weight loss comes from fat stores. Win-win.

As we see in this Pennsylvania State University research group, adding just two HIIT sessions per week into their training schedule resulted in a huge 21.9 percent increase in back strength in just six weeks.

This was compared with a group who continued their usual, steady state cardio exercise. This group also built muscle and gained strength but to a much lesser extent.

High-intensity interval training vs steady state training

3. Enjoy healthy, happy hormones

HIIT workouts cause a spike in two key hormones: epinephrine and norepinephrine. We all know exercise gives you that ‘happy feeling’ caused by endorphins, but this is more than a feeling (more than a feeling!). These two hormones are both responsible for driving lipolysis, a.k.a. the breakdown of fat.

4. Reduce cholesterol

In the same study as discussed above, HIIT training helped reduce triglycerides, or bad cholesterol, by 14.5 percent in just six weeks. Reducing this kind of cholesterol helps lessen our risk of heart disease. Clogs shouldn’t be in your arteries, or on your feet. Just, avoid them altogether…

 HIIT gets rid of clogs and improves heart health (image: a pair of clogs)

5. Improve insulin sensitivity (it’s a good thing!)

You might hear the word ‘sensitivity’ and think this is a bad thing, but when it comes to insulin, being sensitive is actually good. Being insulin sensitive means our bodies are more responsive and need a smaller amount of insulin to lower our blood glucose levels.

Not to mention that people with low insulin sensitivity, also known as insulin resistance, have a higher chance of developing metabolic diseases such as obesity, diabetes and heart disease.

 HIIT - results from a workout with military fitness techniques


Is HIIT better than other forms of exercise?


HIIT vs circuit training

Although HIIT can use some of the same equipment and exercises as circuit training, they key difference with circuit training is that it is lower intensity and there are no timed recoveries.

In circuit training, you simply move from one exercise to the next, with no prescribed rest period in between. Circuit training usually involves resistance-based exercises such as dumbbell presses or weighted squats, which are great for building strength and lean muscle.

However, the aim is not to push yourself into high-intensity training zones. So, circuit training does not have the same cardio benefits as HIIT training and does not result in the EPOC effect where you burn calories long after your workout is finished.

According to NHS guidelines, adults should aim for two weights or resistance-based workouts each week that focus on building lean muscle mass and increasing our bone density. So, strength-based circuit training is a beneficial addition to your workout schedule, but it shouldn’t be confused with HIIT training.


In contrast to HIIT, which we know is all about short, sharp intervals and timed recoveries, Low Intensity Steady State (LISS) training is at the other end of the spectrum when it comes to exercise.

You know those people that get to the gym and beeline straight for the nearest elliptical trainer and spend the next hour working up a healthy ‘glow’ while reading an issue of the latest Hello magazine?

Yeah, that’s LISS.

The problem is that while you might be able to burn calories during a LISS workout, the benefits stop as soon as the workout does. Doing long, low-intensity exercise simply doesn’t kick your metabolism into overdrive, creating that all-important afterburn effect.

Obviously, if you’re an endurance athlete with a specific goal that you’re working towards then LISS might be part of your training schedule. But if you’re a recreational exerciser looking to take your fitness to the next level and really change your body shape, you’ll get far more benefit – in less time – with a HIIT workout.

Our advice? Don’t waste hours slogging away on the cardio machines. Give your body a shake up with HIIT workouts.

HIIT vs Crossfit

Crossfit and HIIT workouts utilise two different training styles that will give you different results depending on what your goals are. Crossfit is all about the time you are spending working out – doing things faster, pushing the limits. HIIT is as much about the intervals when you are not doing high-intensity exercise as it is about the exercise itself.

Crossfit is based on a method of training called High-intensity Power Training (HIPT). This means you push yourself to your limits, trying to reach a certain number of reps within the timeframe of a workout, or completing workouts as fast as possible.

HIPT definitely packs a punch but can be inconsistent, with some Crossfit workouts lasting only a few minutes, and others lasting hours. The nature of HIPT combined with the competitive aspect of Crossfit means you have to be careful not to push yourself too hard. Don’t try and beat your ‘score’, or time in a workout at the expense of good form, or, even worse, injury.

If Crossfit and HIPT is something you’re interested in, it’s worth starting slowly, taking time to master the basics and most importantly: finding a coach that knows their stuff and has your safety as their top priority.

British Military Fitness workouts, on the other hand, are based on the principles of High-intensity interval training (HIIT). The key difference with this kind of training lies in the intervals. These are crucial when it comes to getting you the results you want.

Training in this way means that you can get the most out of the times that you’re pushing your heart rate and your fitness into new zones. Using planned intervals of rest means you can achieve a very intense, very effective workout, in a shorter space of time.

The winner?

Every form of exercise has benefits and drawbacks. Some ways of working out will be effective for one person, but not another, and each method might get you closer to certain goals at a faster or more steady rate. But, for overall, sustainable fitness, we’ve got a favourite at BMF (drumroll, please):

Yeah. It’s HIIT.

HIIT vs crossfit


Is HIIT the right choice for me, then?


HIIT for beginners, over 50’s or those with high BMIs

It’s understandable that if you’re just getting started with fitness, the idea of high-intensity interval training can sound kind of well… intense.

Don’t be overwhelmed by all this talk of maximum training zones and peak heart rates. The thing about HIIT is that the intensity is individual to you – meaning your maximum training zone is going to be different to another person’s. It’s about being honest with yourself. As your fitness improves, so too will your capacity to hit new zones.

If you’re older and looking to get into fitness for the first time, or you’re embarking on a new fitness routine to combat a serious health condition like obesity or diabetes, it’s best to get the advice of your local doctor on whether HIIT is right for you. It might be the case that your doctor recommends starting with some lower intensity cardio and weights. This would build a foundation level of fitness first, before jumping straight into high-intensity workouts.

When to avoid HIIT

HIIT is a great adaptable type of training that offers benefits to exercisers of many different ages and abilities. And, because workouts are usually based around simple, body weight movements, there’s less chance of injury than with a training style like Crossfit, for example.

However, there are times when HIIT might not be the way to go. How to know if HIIT isn’t the right choice? Before starting your HIIT journey, make sure you have considered if you fall into any of these three categories:


If you are already an experienced exerciser with a good level of fitness, it may be fine and even beneficial to continue with HIIT workouts if you’re pregnant. However, if you’ve never done HIIT before, starting a new high-intensity schedule when you’re pregnant may not be safe, so consult your doctor first.

Recovering from a severe injury or serious illness

 This is one that requires a bit of common sense. If you’re recovering from a serious health condition or injury then jumping straight into HIIT might not be the best option for you. Talk to your doctor first and take it easy! This is your personal fitness, so getting competitive isn’t worth it.


Doing HIIT will build some lean muscle and increase strength, but it’s essentially a form of cardio training. If you’re a bodybuilder looking to increase size and gain a lot of muscle mass in specific areas ahead of a competition, it’s a good idea to monitor the amount of muscle mass you’re wanting to maintain.

HIIT is for everyone - beginners and experts

Don’t worry, HIIT workouts are not dangerous

As with any kind of exercise, overdoing it or performing movements with bad technique all because you want to reach that weight-loss goal faster can have damaging effects. But, as long as you have the right coaching and don’t overdo your training, it’s unlikely that HIIT will be harmful for you in any way.

BMF HIIT: our approach to safe training with HIIT

Our instructors at British Military Fitness are all ex or current serving members of the armed forces who have been highly trained to plan and deliver HIIT workouts. They might be some of the fittest humans on the planet, but they’re also masters of motivation. They know good technique and they know when to push you at just the right times.

And they are totally cool with you giving them the evil eye after they tell you to do ten more push-ups. (As long as you do the push-ups.)

At your first British Military Fitness HIIT session, your instructor will ask about any injuries or conditions you might have, assess your fitness level and tailor the options through the workout to suit you. We like to keep our class sizes small so you get that one-to-one experience.


Top tips for getting started with HIIT


I’m a keen bean - should I do HIIT everyday?

So, if HIIT has all these great benefits, we should be doing it as much as possible right?


To get the most out of any HIIT workout, you need to be pushing your body harder than you’re used to. ‘High-intensity’ remember?

We’re not just talking about getting a glow on. To hit maximum training levels, you need to be reaching outside of your comfort zone to that place that feels… well… pretty horrible.


For this reason, we don’t recommend doing HIIT every day. It’s an intense type of training. Your body needs enough time to recover in between workouts so you can carry on hitting those max training zones. If you’re getting to a HIIT workout 2-3 times a week, you’ll see great results while still allowing yourself to recover and avoiding burnout and injury.

HIIT is about getting out of your comfort zone

The importance of recovery – a.k.a. the ‘interval’ bit

In HIIT sessions you’ll be pushing your body to its max, and for this reason it’s important to allow yourself time to recover between sessions.

Failure to do this will not only make you tired, sore and more susceptible to bad technique and injuries, but will also sabotage your gains. If your body’s working against you because it’s hurt, that’s not the kind of resistance training we encourage!

When your body becomes too tired to continue hitting those peak training zones, your HIIT workouts will become simply ‘vigorous training’ workouts, and you won’t see the same results.

The best food to eat after a HIIT session

Diet and exercise go hand-in-hand. HIIT workouts are intense and are intended to totally deplete your body of energy. Refuel the right way within a couple of hours of your workout to help promote lean muscle synthesis and stop your energy levels from crashing.

The ideal meal should be something high in protein, with healthy carbs and fats in there too. It’s always best to eat natural sources of protein but if you’re on the go and need something to carry you over until dinner or breakfast time, then a protein shake can be a great option too.

If you’re serious about getting great results and want to nail your nutrition, check out our BMF nutrition plans.

What to eat after a HIIT session

BMF X-ERT and HIIT workout sessions

The general idea is to get more value and benefit from your workout by putting in an increased amount of effort over a shorter period of time. HIIT workouts last about 30 minutes, but can be a little longer or shorter.

You want to be reaching peak levels of effort and finishing a HIIT workout having totally emptied your tank, so you shouldn’t be able to sustain a HIIT for hours on end the same way you could doing lower-intensity cardio.

At British Military Fitness, our instructors are trained to plan and deliver safe, effective HIIT workouts. Each workout is different, so you’ll never do the same thing twice. Not only does this stop you from getting bored with the same old workout but also keeps your body guessing – forcing it to adapt and your fitness to keep improving.

A BMF HIIT workout will have:

  • Five to seven minutes to warm up and prepare your body for what’s to come and prevent you from getting injured;
  • 30 Minute HIIT session of bodyweight and some functional equipment exercises;
  • 8 – 10 minutes of cooldown, flexibility and stretching. This helps your muscles recover so you can push hard again in your next session.

At British Military Fitness we run 600 outdoor HIIT workouts every week, in 120 UK parks, rain or shine, seven days a week.

Find a HIIT workout near you and sign up for your free BMF trial here.


Topics: HIIT, hiit classes, hiit training