HIIT Workout Guide: The Science, Benefits & Workouts Ideas

High-Intensity Interval Training (HIIT) is a fitness trend that combines interval training and high-intensity training, to produce great results in a shorter amount of time. Interval training is not a new type of training, runners have been practising interval training for 100s of years, alternating between jogging and sprints to build their endurance.

The HIIT workouts and classes you know today, like Tabata and Grit classes, are the same - repeated bouts of high-intensity exercise followed by a bout of recovery. What changes between HIIT workouts is the exercises, equipment, interval timing and workout length. To get the full benefit from HIIT training, in the high-intensity bouts you will need to aim to get your heart rate up to at least 80 per cent of its maximum capacity. You can measure your heart rate using technology like a Fitbit or smartwatch.

Why Do People Choose HIIT Workouts?

The single biggest benefit of HIIT training is improved cardiovascular health. You can boost your cardio in a shorter amount of time than you could with continuous exercise.

And with most people pressed for time, a long workout is not always possible, and short ones just don’t seem worth it. The good news about HIIT training is that you can increase your endurance in less time. Yay for no more long 60-minute jogs around the park!

HIIT workouts also allow for a lot of variety, since you can use strength equipment, cardio machines or no equipment at all. You can also do HITT workouts at home, in the park or in the gym, it’s a workout you can do anywhere.

It’s understandable why high-intensity interval training is so popular, you can reach your cardio goals in less time and you can always mix up your workouts to keep them interesting.

The Science Behind HIIT Workouts

It’s important to understand the physiology behind high-intensity interval training so that we are aware of the benefits and risks.

High-intensity interval training involves working out with maximum possible effort with the aim of reaching VO2 max. VO2 max is the uppermost rate at which your body can utilise oxygen for energy during exercise. Research has shown that interval training leads to larger improvements in VO2 max compared to other forms of training in a smaller period of time.

So what does improved VO2 max mean for you?

By doing HIIT workouts you are effectively training your body to use oxygen more efficiently. This means you become more aerobically fit, which means your heart can pump blood better, which in turn helps to prevent heart disease.

Another interesting physiological effect of this type of training is what’s called the ‘afterburn effect’. This is where your body continues to burn calories for a period of time after your workout. There is research to support that HIIT leads to higher calorie burn post-workout compared to other forms of training.

So how does this work? The short intense bursts of movements used in HIIT overload the body compared to continuous exercise. The intensity makes your body utilise its anaerobic system for energy as the aerobic system cannot supply oxygen quickly enough for your body to convert it to energy.

During your rest periods or low-intensity periods, the body begins to utilise your aerobic system again. So essentially in HIIT workouts you are using a combination of both systems and improving them both. Because you are using your anaerobic system, your body works post-exercise to replenish the oxygen. In this process, your body is continuing to burn calories after you’ve finished your training.

What Are The Other Benefits to HIIT Workouts?

On top of achieving a healthy heart in an efficient way, HIIT workouts provide other benefits including:

Weight Loss

HIIT is a time-effective way to burn calories. Due to the intensity, you use a lot of energy, which means you are burning calories. However, HIIT workouts are not proven to cause more weight loss compared to continuous training. This is why it’s important to combine exercise with a healthy diet, as it’s easier to lose weight by cutting calories in your diet vs trying to burn off excess calories.

Better Mitochondrial Function

HIIT workouts help your body to become more efficient on a cellular level. It helps boost the function of your cells’ mitochondria (your cell’s energy-releasing powerhouses), resulting in more overall energy and more efficient use of energy produced.

HIIT workouts also increase the production of proteins for the mitochondria, which otherwise deteriorates over time. This means that HIIT can slow down aging at a cellular level!

So HIIT Workouts Are Great - But Should You Do Them All The Time?

HIIT workouts should not be performed more than 3 times per week. Since each workout routine can vary in length, do no more than 40 minutes per week. You should also avoid doing your HIIT workouts back to back. Try to space them throughout the week to give your body enough time to recover. The high intensity of the workouts requires a lot from the body, which means you need more time to rest and refuel between sessions.

If you are starting HIIT workouts from a sedentary state, it’s recommended that you do less intense workouts. Try to build your strength and cardio with continuous training first.

Why?

HIIT training can be demanding mentally and physically. Any more than 40 minutes of truly highly intense exercises can lead to a higher risk of stress and injury on the body. Overtraining your body in this way can lead to symptoms such as depression, anxiety and a decrease in sleep quality.

So yes, there is such a thing as too much HIIT.

The Best HIIT Workouts

By this point, you’re probably wondering what a HIIT workout looks like. Well, they can look like many different things, from cycling on exercise bikes, running on a treadmill, push-ups on an exercise mat.

As long as the workout includes intervals of high-intensity exercises combined with periods of rest or lower intensity movements, then it’s a HIIT workout. Always remember to incorporate warm-up and cool-down exercises with any workout.

We’ve put together some home HIIT workouts to get you started.

#1 Weight Vest HIIT Workout

This workout uses basic bodyweight exercises with the addition of a weight vest to add resistance which in turns burns more calories. To make this workout low impact remove the jumping from the exercise e.g. regular squats instead of jump squats and you’ll still get a good workout by wearing the weight vest.

Interval: 40 seconds/20 seconds rest
Rounds: 2-3

1. Jump Squats x 40 seconds / 20 rest
2. Burpees x 40 seconds / 20 rest
3. Jump Lunges x 40 seconds / 20 rest
4. Lunge Drive x 40 seconds (20 sec per leg) / 20 rest
5. Lateral Shuffle x 40 seconds / 20 rest
6. Knee to Elbow x 40 seconds / 20 rest
7. Shoulder Taps x 40 seconds / 20 rest

#2 15 Minute Treadmill HIIT Workout

In this workout, you will combine cardio and strength exercises for 15 minutes. To complete this HIIT workout you will need dumbbells, resistance bands & a treadmill.

Interval: 1 min low intensity / 30 sec high intensity / 1 min strength
Rounds: 6

Visit Our 15-minute Interval Training Treadmill Workout for full instructions and tips for this workout.

#3 25 Minute Balls to the Wall HIIT Workout - Slam Ball, Wall Ball & Med Ball

Exercise balls are great pieces of equipment to incorporate into a HIIT workout, as you get both cardio and strength gains. In this workout, we have used the 4kg wall ball, 3kg slam ball, and a 4kg medicine ball.

Interval: Complete reps / 1min rest
Rounds: 3

Round 1: Wall Ball Exercises

• Wall ball throw X 15-20 reps
• Wall ball sit-ups X 10-15 reps
• Wall ball kneeling cross-body throw X 10-15 reps each side
• Repeat: 2-3 times
• Complete as quickly as possible – then rest for 1 minute

Round 2: Slam Ball Exercises

• Slam ball floor slam X 10-15 reps
• Slam ball shoulder toss X 10-15 reps
• Slam ball sprawl X 10 reps
• Repeat: 2-3 times
• Complete as quickly as possible – then rest for 1 minute

Round 3: Medicine Ball Exercises

• Medicine ball reverse crunch X 10-15 reps
• Medicine ball alternating twisting lunge X 20 reps total
• Medicine ball reverse burpee X 10 reps
• Repeat: 2-3 times
• Complete as quickly as possible – then rest for 1 minute

If you need to take small rests between each repetition that's fine! It’s important to always exercise within your body's limits to keep yourself safe.

#4 10 Minute Spin Bike HIIT Workout

To complete this spicy spin class you will need a spin bike and lots of enthusiasm!

#5 Plyometric Box HIIT Workout

There are loads of exercises in this video, we recommend picking 5 exercises that work best for you and changing them up each workout. To do this HIIT workout you will need, plyometric box, a 10kg power bag and a 4kg medicine ball.

Interval: 30 seconds/30 seconds rest
Rounds: 3

Frequently Asked Questions