Benefits of HIIT Training: What It Is and Why It Works

High Intensity

So first, the high-intensity part. This refers to the fact the exercises during HIIT are designed to push the body to the limit. Forget about your 45-minute monotonous sessions on the elliptical machine while listening to music. With HIIT, everything is completed in a much shorter session.

Depending on the exercise, each one is completed for a time period extending from a few seconds to a minute. The key is you are exercising so hard that the level of intensity just cannot be sustained for a longer period.

In the simplest terms, imagine running as fast as you can until exhaustion. Even professional athletes cannot sprint constantly for more than a minute—it’s physically impossible.

Each HIIT exercise pushes the muscles and heart hard in a short space of time. As this level cannot be sustained, it leads us to the second part of HIIT: the interval.

Interval

This describes the break between each intense burst, with either complete rest or low-level exercise. Depending on the workout, this can involve walking around, steady jogging, or completing anaerobic exercises, such as lifting weights. Again, this lasts for just a few seconds through to a few minutes. Then the intense part begins again.

Once the rest (or light exercise) interval is completed, you push your body to the max. This can involve the same exercise as previously finished or a totally different one—again, at full capacity followed by another interval.

This process is repeated. HIIT combines massive explosions of energy and cardio action followed by calmer exercise or complete rest sessions. In total, it’s unusual for these workouts to exceed 30 minutes. Often, they’re finished in less time.

Over the years, numerous types of HIIT have developed. Today, there are almost as many versions as there are exercises that can be completed in a HIIT workout. Some of these have undergone scientific testing, examining their efficacy. Generally, they differ in the amount of time dedicated to exercise and rest periods.

The most common forms are:

• Tabata: Formed from a study compiled by Professor Izumi Tabata, who examined Olympic speed skaters. Involves 20 seconds of exercise followed by 10 seconds of rest.
• Gibala: A HIIT workout that involves 60 seconds of exercise and then 75 seconds of rest, developed at McMaster University, Canada.
• Zuniga: 30 seconds of exercise followed by 30 seconds of rest, designed to fit maximum effort into the smallest amount of time.
• Vollard: Known as the 2×20, it involves two twenty-second intense cycling sprints.

These regimens are slightly different. Some are more beneficial for weight loss, others for stamina building. But all the studies have shown that they are effective in improving cardiovascular health.

How Does HIIT Work?

HIIT is less of a workout and more of a lifestyle choice.

Going to the gym, playing sports, or hitting the sidewalk for a lengthy run means being highly proactive. These pursuits take you out of the home and often require the dedication of an extensive period of time, taking you away from your usual daily routine.

HIIT doesn’t have to be like that. Just as your normal day-to-day schedule involves showering, cooking, and brushing your teeth, HIIT integrates in the same way. The fact that it’s so time-friendly allows it to fit seamlessly into your lifestyle.

What’s more, HIIT becomes a conscious decision to improve your health. Occasionally, we all consume foods that we know are unhealthy or spend too much sedentary time watching the TV. HIIT allows us to improve our well-being without making drastic alterations to our life. And numerous studies prove its cardiovascular and fat-shedding power.

History and Research

Although HIIT has gained popularity in the last ten years—mainly due to increased scientific research proving its efficacy and its uptake by professional athletes—in real terms, this method of exercise has been around for years. The Finnish Olympian Hannes Kolehmainen was using it as part of his training back in 1912.

Obviously, during any type of exercise, the muscles and heart are worked hard, which in turn promotes health benefits. However, it was long assumed that for optimal returns, the repetition and duration of these exercises were of the most importance.

However, research has indicated that short, intense bursts of exercise can provide greater returns than longer workouts. Intense workouts raise the metabolism, and with HIIT, this remains elevated for hours after exercise has been completed—known as excess post-exercise oxygen consumption (EPOC), or “afterburn.”

The Mechanism Behind HIIT Effectiveness

Here’s how it works. During your HIIT workout, your body gasped for oxygen. It needed it to push you through each and every exercise. Because you were working so hard, oxygen intake could not keep up with demand. Instead, it drew on your reserves of adenosine triphosphate (ATP) to power your body.

Once exercise is over, your body needs to restore ATP levels, replace glycogen (energy-giving muscle sugar), stabilize internal temperatures, and restore oxygen to preworkout levels.

All of this places increasing demands on the body, not only giving it a “resting workout” but also using more calories than after moderate exercise.

Hence, comparatively, HIIT has been shown to be more effective than standard exercise regimens for losing weight and improving cardiovascular health in relation to time spent.

Can Anyone Do HIIT?

As HIIT is cheap, can be completed at home, and is very time-friendly, it makes it a very appealing exercise for people of any age. However, there are some provisos.

Most importantly of all, remember that HIIT does place stress on the heart. That’s one of the reasons it’s so effective. Yet this can make it unsuitable for people with existing heart conditions. If you’re currently experiencing, or ever have experienced, any cardiovascular issues, it’s essential you check with your health practitioner first, before starting HIIT.

Second, if you haven’t completed any form of exercise for a long period, starting your HIIT regimen with the mother-of-all-sessions is probably going to do you more harm than good. Don’t plan to dive straight in with a 30-minute workout. Instead, complete maybe one to two exercises over a duration of no more than six minutes. Then gradually build it up.

Here’s a handy tip. The ACSM (American College of Scientific Medicine) has formulated a physical activity readiness questionnaire to determine whether you are able to commence exercise. Just answer seven questions. If you answer yes to any of them, you must consult with your physician prior to HIIT. In fact, this is a great general rule whether you are looking at HIIT, long-distance running, or weight training.

Once given the all-clear by your doctor, HIIT is still a very safe form of exercise. Numerous research papers have been printed on the effects of HIIT on people who have suffered from heart attacks and patients with diabetics or who are obese and usually do not exercise. In all cases, the science tells us that HIIT provides beneficial effects and does not worsen symptoms.

What Are the Benefits of HIIT?

Using HIIT as your exercise of choice promotes numerous advantages, both in physiological function and your lifestyle. Here’s what I found to be the most appealing:

Time-Friendly

With one session lasting around 30 minutes maximum, this isn’t going to make very strong demands on your time. I know you’re probably already stressed to make space for exercise in your schedule, but 30 minutes isn’t that long.

Furthermore, you are not exercising every day or doing numerous sessions in 24 hours. Just one period of HIIT is required on your training days, and ideally at a maximum of 2–3 times per week.

Pushing the body this hard means it needs time to recover, so rest days are as important as training days. But whatever you decide to do, there’s probably no other exercise regimen that is so effective with such a short commitment of time.

Do It Anywhere

If you have enough room to run intensely on the spot, you can complete HIIT.

Being able to do it in the comfort of your own home is convenient and also saves time and money from going to a gym. Even if you have zero equipment, you can do HIIT. The key is to ensure that whatever exercise you choose elevates your heart rate to around 80 to 95 percent of your maximum heart rate. (Here is a handy calculator.)

Excellent HIIT workouts that don’t require equipment can include squats, burpees, box-jumps, and push-ups. Naturally, if you are lucky enough to own a treadmill, an exercise bike, or a rowing machine, these can be integrated too.

Why not take your HIIT outside? For a start, this can enable you to do things you cannot complete in your living room or garage (such as sprinting). Furthermore, it’s healthy. Being in the great outdoors not only means breathing in fresh air (at least for many people) and boosts mental health.

Naturally, if you find the gym a conducive place to exercise, there’s more equipment there than you will ever need: weights, treadmills, climbers, rowers, cables, pull-up bars, etc. Some people find that, as there are fewer distractions at a gym (as opposed to their home), it can provide greater focus and improve workout sessions.

Inexpensive

One of the most appealing factors about HIIT is its versatility. It can be completed with gym-size exercise machines, free weights, or simply by using your own body for resistance. Even if you are on a tight budget, this does not prevent you from doing HIIT.

Furthermore, if you’re exercising at home, it means no gym fees, gasoline, or public transport costs.

Numerous Health Benefits

In many instances, HIIT has been shown to be more effective and efficient than other types of exercise. The benefits include:

• Energy expenditure: As already explained, HIIT works the metabolism for an extended period once exercise has finished.
• Weight loss: HIIT and post-exercise recovery time require fuel, which is found in your fat stores.
• Improving strength and endurance: A 2006 study illustrated that short, sprint-based training boosts stamina and power greater than standard exercise.
• Breathing benefits: Every liter of oxygen you breathe burns five calories. HIIT increases breathing rates, burning more calories and improving heart and lung function.
• Building muscle: HIIT boosts human growth hormone (HGH) production, a powerful muscle builder, leading to a lean yet tightly toned body.
• Reducing insulin resistance: Lowering the risk of developing type 2 diabetes.
• Improves and builds fast twitch muscle: Improving speed, reactions, and explosive power.
• Does not destroy muscle: Excessive “steady” cardio has been shown to break down muscle, whereas studies indicate HIIT builds it.

HIIT Workout

I have put together a powerful HIIT workout below, designed to exercise the entire body. It requires no equipment and can be completed in the comfort of your own home. Generally speaking, this workout should last just under twenty minutes.

Both the exercise and rest periods are for guidance only. As everyone has different levels of fitness and ability, these can be adapted to suit your own personal requirements. The key is that every exercise is performed at the most intense level you can manage.

These workouts should be completed 2–3 times per week. If you find after a few sessions that your fitness level is increasing, and you’re not working to your limit, naturally reduce rest time and increase exercise duration.

As with all exercise, you should always ensure that adequate time is spent warming up and cooling down. To this end, I have included some example sessions below.

HIIT Warm-Up

Warming up before exercise reduces the risk of injury, creates focus, and allows you to perform to a higher capacity during the workouts. Remember, this is a warm-up not a HIIT session, so complete every exercise at a moderate pace. Push yourself too hard and this will negatively impact your full workout.

In total, this warm-up should take no longer than 3 minutes.

Leg Swings

1. Stand up straight, looking forward
2. Your feet should be shoulder-width apart
3. Swing your right leg forward and backward twelve times
4. Complete for the other leg
5. Swing your right leg from side to side twelve times
6. Complete for the other leg

If you have issues with balance, do this exercise while holding on to the back of a chair.

Inchworm Walkout

1. This is the starting position:
   1. Stand with feet shoulder-distance apart
   2. Keeping your legs straight, bend at the hips until you can comfortably place both hands on the floor
2. “Walk” your hands forward until your back and legs form one straight line
3. Then walk hands back again until you return to the starting position
4. Complete ten times

Here’s a useful video guide to this warm-up.

Standing Jumps

1. This is the starting position
   1. Stand with feet a little less than shoulder-width apart
   2. Bend at the knees until your thighs are almost parallel with the floor
   3. Look forward
2. Propel yourself upward with your legs until you lift one foot above the floor
3. Land with the balls of the feet first and bend at the knees
4. Without resting or pausing, complete this exercise ten times

20-Minute Workout

Do each exercise for 40 seconds. After each one, rest for 20 seconds, then move onto the next one. Once you have finished every exercise, complete the entire workout again. Ideally, use a training mat to prevent slipping and reduce joint impact.

Remember: all exercises should be completed at the most intense level you can manage. Push yourself to the limit.

Butt-Kickers

1. Stand with feet hip-width apart, arms straight by your sides
2. Bending at the knee, “kick” your right leg backward so the heel of your foot touches your right glute muscle
3. Return foot to starting position
4. While the right leg is descending, kick back the left leg up to your left glute
5. Repeat

Here’s a quick video demonstrating this exercise.

Burpees

1. This is the starting position:
   1. Lay flat on the floor facing downwards, feet slightly apart
   2. Place palms flat on the ground underneath shoulders, as if in a push-up stance
2. Lift your chest, legs, and groin off the floor by straightening your arms
3. As you do so, “jump” both feet forward underneath your hips, bending at the knees
4. Using your legs for power, propel yourself upwards and swing arms above your head for extra momentum
5. Land on the balls of your feet, bend at the knees, and return to the starting position
6. Repeat

It sounds a little complicated, so here’s a short video demonstration.

Squat Jumps

1. This is the starting position:
   1. Stand with feet shoulder-width apart
   2. Crouch downward until your thighs are parallel to the floor
   3. Fold your arms
   4. Elevate elbows so both your upper and lower arms are horizontal in a Russian Cossack position
   5. Look forward and do not bend your back
2. Pushing with the balls of your feet, propel yourself as high into the air as you possibly can, straightening legs at the highest position
3. Land on your toes/balls of the feet
4. Immediately drop down to the starting position
5. Repeat

Mountain Climbers

1. This is the starting position
   1. Lie flat on the floor, facing downwards
   2. Place your palms on the ground underneath your shoulders in a typical push-up position
   3. Bending at both the knee and the hip, bring your right knee forward until it is below your stomach, creating almost an on-the-blocks sprinting pose
   4. Your left leg should remain straight and extended behind you
2. In one complete move, explosively propel right leg backward until it is straight, while simultaneously bringing left knee forwards and bending at the knee
3. Alternate between legs for the duration of this exercise

Side Lunges

1. This is the starting position:
   1. Stand with feet shoulder-width apart
   2. Face forwards
   3. Intertwine your fingers, arms should be bent at the elbows, keeping hands tight against upper chest
   4. At all times, ensure you remain looking forward, keeping back straight and chest pushed out
2. Keeping your left foot flat on the floor, take a large step to your right-hand side
3. Bend your right leg at the knee and crouch down, the left leg should be at full extension and locked out
4. Pause for one second then return to the starting position by powering through your right leg until vertical again
5. Complete this exercise on the left-hand side
6. Repeat

Push-Ups

1. This is the starting position:
   1. Lie flat on the floor facing downwards
   2. Place palms down onto the ground, slightly wider apart than your shoulders
   3. Lock out the arms completely
   4. Face floor throughout this exercise
   5. Ensure that your back, butt, and legs form one straight line
   6. The only parts of the body touching the floor should be the palms of your hands and the balls of your feet
2. Lower yourself down toward the floor until your arms reach a 90-degree angle, but do not bend hips or arch the back
3. Push back up again into the starting position using your arms
4. Repeat

Walking Planks

1. This is the starting position:
   1. Lie face downward on the floor
   2. Place palms on the ground, slightly wider than shoulder-width apart
   3. Lock out arms completely
   4. Keep your legs, butt, and back in one continuous straight line
2. In one movement, move your right hand 12 inches to the right while simultaneously stepping your right foot in the same direction
3. Move the left hand 12 inches to the right and do the same for your left leg
4. You should now be in the starting position again, although 12 inches away from your original spot
5. Repeat moving to the right until you have taken four “steps” (reduce if you lack sufficient space)
6. Complete again, this time moving to the left-hand side, until you return to your starting location
7. Repeat

Jacking the Plank

1. Start from the push-up position: palms flat on the floor, face downwards, arms extended and locked, and back, legs, and butt forming one straight line
2. In one movement, “jack” both legs outward and then inward again, being sure to face the floor and ensure your back does not bend
3. Repeat

Leg Raises

1. This is the starting position:
   1. Lie on the floor with your back touching the ground
   2. Keep your arms straight and against your side, palms downwards
   3. Legs and feet should be together
2. Ensuring that you keep your legs straight at all times, raise the feet approximately 12 inches above the ground
3. Lower again until feet almost (but do not) touch the floor
4. Repeat

Adaptations

If you wish, you can increase the difficulty level by incorporating additional weight into this workout.

In such exercises as butt-kickers, jacking the plank, and push-ups, a weighted backpack can be worn. You do not have to own specific weights: rice, sugar, or other dense materials can be used.

Additionally, if you own some small home dumbbells, you can hold them in your hands while doing squat jumps or side lunges.

A beneficial alternative to completing this workout at home is to take it into the great outdoors—a park is ideal. This can allow you to substitute some of the more stationary exercises for those that require more space.

For example, you can replace butt-kickers with a couple of all-out 20-second sprints. Also, try to incorporate outdoor facilities into your HIIT. Parks often have horizontal bars that can be used for pull-ups.

Adapting HIIT for your environment is very simple and can prove quite satisfying. Just remember, whatever exercise you are doing, hit it as hard as you possibly can.

HIIT cool down

Never underestimate the importance of cooling down. Exercising gently post-workout will help to prevent stiffness and aches and improve recovery times.

This cool down will take approximately 3–4 minutes.

Arm Swings

1. Stand with feet shoulder-width apart, letting your arms hang loosely by your sides
2. In a “windmill” action, swing your right arm in one complete circle in a forward direction and continue for 40 seconds
3. Repeat for the left arm
4. Return to the right arm, but this time swing backward for 40 seconds
5. Repeat for the left arm

On-the-Spot Jogging

1. Stand with feet hip-width apart
2. Commence jogging on the spot at a steady pace, thighs should not lift so high as to become parallel with the floor
3. Swing arms naturally throughout this exercise
4. Complete for one minute

Hip Bends

1. This is the starting position:
   1. Stand up straight with your feet hip-width apart
   2. Clasp hands in front of you so arms are extended with hands near your groin
2. Keeping the legs straight, slowly bend forward and lower hands toward your feet
3. At full extension, pause for two seconds
4. Slowly rise back up into the starting position
5. Repeat 20 times

HIIT training will both strengthen and tone muscles, however, it will not lead to large muscle gains. If you are looking to increase mass, include a couple of sessions of weight training into your weekly regimen, alongside HIIT.

Does HIIT help lose fat?

Exercising intensely requires energy, which can be stored in the body as fat. HIIT not only helps to burn this fat during exercise but is also proven to keep the metabolism running in overdrive post-workout. This means that belly fat can be lost, even once the training has finished.

How many calories does 30 minutes of HIIT burn?

Depending on the intensity of the exercise, your current weight, and physiological composition, you can expect to burn between 300 and 400 calories in a 30-minute HIIT session.

How many days a week should I do HIIT?

Ideally, complete 2–3 days of HIIT per week. Do not exercise on consecutive days. Having a rest from training allows the body to rebuild and recover.

Now go get to it

But it doesn’t have to be like that. HIIT is a powerful exercise regimen with scientifically proven benefits. It’s the ideal program for busy professionals, as it takes up little time, is cheap, and can be completed virtually anywhere.