The Science Behind HIIT Workouts

The essential breakdown behind the fitness results and health benefits of HIIT classes.

If you’re reading this, you’re probably wondering: What is a High-Intensity Interval Training (HIIT) workout? Why does HIIT lead to better results than traditional exercise? What are the health benefits of HIIT for your body? And what is the science behind HIIT?

HIIT workouts consist of short intervals of maximal effort alternated with low-intensity recovery periods. They’ve made waves in the fitness world in recent years for its revolutionary effectiveness, efficiency and health benefits. When you break down the science behind why HIIT classes are so effective, however, it’s clear that it’s much more than a fitness trend that will come and go. Here are a few of the scientific explanations behind the most popular fitness and health benefits that comes from HIIT workouts.


Ultra-Efficient Calorie Burning

Due to the versatile nature of individual HIIT classes, it’s impossible to say exactly how many calories participants burn in a given session. A high-quality session led by trained instructors can burn up to 1,000 calories. Not only does HIIT burn more calories than traditional cardiovascular training such as running or biking, but it does so in a much more efficient manner.

One study published to the National Center for Biotechnology Information (NCBI) has shown that an HIIT routine burns 25-30% more than steady-state cardio. In this study, HIIT participants were put through a routine that consisted of 20 seconds of maximal effort followed by 40 seconds of rest. This means that although the HIIT participants were actually only exercising for ⅓ of the time as the running and biking group, they were burning more calories.

Considering the overall short time period of HIIT workouts, they’re simply far more efficient than traditional cardio training. The high-intensity intervals can easily exceed the weight and fat loss benefits of steady-state cardio with a much shorter time commitment.

Metabolic Rate

One of the most well-documented physical reactions actually happens following the HIIT session when your body’s metabolic rate increases. This is known as post-exercise oxygen consumption (EPOC) in which your body burns more calories and fat for 24 to 48 hours following the HIIT class due to its intense nature.

EPOC greatly improves the aerobic stamina and power in your heart (the key to a long and healthy life) ad increases your oxygen consumption in a way that you burning fat up to 9x faster than normal. This afterburn effect alone can be far more effective for weight loss than a jogging or training session, and shifts the attention of your metabolism to fat for energy rather than carbs.

Maintain and Strengthen Muscle

HIIT classes are far more dynamic than any type of workout on the market. While a HIIT session does have endurance benefits that exceed cardio exercises, they’re very much a complete full-body workout that also includes elements of weight and strength training.

As the most popular option for weight loss, steady-state cardio can burn muscle mass as body fuel in addition to fat. HIIT workouts provide the endurance benefits of cardio while building on the strength gains at the same time. While obviously you won’t develop as much muscle as you would engaging in pure weight training, this means that HIIT workouts are ideal for those who don’t want to lose their muscle gains while allowing them to reap the benefits of fat loss. No longer do those in pursuit of a healthy lifestyle and their dream body have to choose between weight training or cardio.

The intense nature of HIIT classes also leads to a dramatic increase in muscle-building anabolic hormones, making it a great way to develop lean muscle. Of course, the particular details of a HIIT program depends on the specific program, but the bottom line is that the flexibility is unmatched. It’s just about choosing a program that matches exactly what you want and need for maximum results.

Improved Oxygen Consumption

Long periods of running or cycling at a consistent rate typically aim to improve your body’s overall ability to use ability. They key in HIIT sessions lies in pushing your heart over 80% of its maximum for an induced surge in your body’s level of growth hormones and organic compounds. This leads to transformative fat loss and muscle-building growth. Oxygen consumption also directly correlates to an athlete’s overall endurance ability.

Pushing yourself to this level is very hard to do when exercising alone, but it’s far easier when alongside supporting teammates and a motivating instructor who wants to get the best out of you. The interval training gets your heart beating fast because of the rest intervals. This keeps improves your aerobic stamina and power and greatly improves blood flow throughout your entire body.