HIIT Explained: High Intensity Interval Training – The Complete Overview

High-intensity interval training is one of those workout trends that people swear by. If you want to see results fast and you don’t have hours to spend in the gym, then the idea of fitting your workout into a 30-minute period is likely to be very popular.

HIIT principles are now being applied to other workout styles so you might see HIIT spin classes at your local gym, or you might see HIIT boxing workout videos on YouTube. If you’d like to find out more about this style of exercise and figure out if it’s right for you, read on to discover the science of how HIIT works.

What happens during a HIIT workout?

By studying the way the body responds to exercise, scientists have discovered that pushing yourself to 100% effort for 15-30 seconds followed by a period of rest is the best way to increase athletic performance.

When you are working out, your body takes in oxygen and uses this to break down glucose for energy. By pushing yourself harder, you might not have enough oxygen to do this. You enter something known as the anaerobic zone where your body produces lactic acid in place of oxygen. Anaerobic workouts are more effective because they encourage the body to use its natural energy stores (fat) in order to fuel itself.

If lactic acid is allowed to build up in your body, it can lead to pretty nasty side effects including cramping and nausea. This is the bodies way of telling you to stop doing what you are doing. In HIIT workouts, you enter the anaerobic zone, but then your body is able to rid itself of lactic acid during the recovery phase. Over time, your body will become more effective at using energy.

What happens after a HIIT workout?

When you are done with most workouts, the benefit ends when you stop moving. You can go back to your daily life and maybe not even notice that you worked out the day before. With a HIIT routine, you’ll know about it the next day. By pushing yourself to maximum capacity for short stretches of time, you break down your muscles in the best possible way. Over the next couple of days, your body will be busy repairing those muscle proteins, which also expends energy.

This is known as excess post-exercise oxygen consumption (EPOC) which means you continue to take in more oxygen and burn more calories long after your workout has finished. By pushing yourself to the maximum for short bursts, you can actually stretch out the impact for longer.

Is it dangerous?

Yes, but only in the way that any exercise is dangerous when done incorrectly. To be effective in your HIIT goals, you need to learn to listen to your body. Most people think that they are in tune with their bodies and that’s why they stop working out when things get hard. You need to learn to know the difference between pushing through your barriers and pushing yourself too hard. If you are returning to exercise for the first time in a while, don’t launch straight into an advanced HIIT workout.

How can I maximise the impact?

Big muscles use more energy than smaller muscles, so while you might be aiming for overall muscle tone, make sure you work your biggest muscles every time you work out. Your glutes and quads are some of the biggest muscles in the body, so make sure you push these to the maximum during every workout.

You can also increase the impact by incorporating something known as HIIPA into your daily life. This stands for high intensity incidental physical activity and it includes anything that would raise your heart rate when you’re in your everyday clothes. This can include taking the stairs instead of the lift or shovelling snow from your driveway. Scientists highlight the importance of this activity because you need to maintain an active lifestyle outside of the gym. A HIIT once a week is good, but only if you are active outside of this time. You can’t rely on HIIT workouts to fix a sedentary lifestyle.