High-Intensity Interval Training

The Science Behind High-Intensity Interval Training (HIIT)

High-Intensity Interval Training, popularly known as HIIT, has taken the fitness world by storm. And for a good reason. But what exactly is HIIT, and why is it so effective? This article takes a deep dive into the science behind HIIT, its benefits, and how to implement it into your fitness routine, whether you’re a beginner or an advanced athlete.

What is HIIT?

HIIT stands for High-Intensity Interval Training. It involves short bursts of intense exercise followed by recovery periods of lower intensity. The idea is to push your body to its limit during the high-intensity intervals, which typically last from 20 to 90 seconds. This structure allows you to pack in a potent workout in a shorter amount of time compared to steady-state cardio, making it a go-to option for those with a busy lifestyle.

The Science Behind HIIT

HIIT works by leveraging your body’s physiology to deliver efficient workouts. When you engage in intense physical activity, your body taps into stored carbohydrates (glycogen) for energy. After your glycogen stores are depleted, your body turns to fat for fuel during the recovery periods. This shift in energy sources results in significant calorie burn and fat loss.

Furthermore, HIIT creates an afterburn effect, known as Excess Post-exercise Oxygen Consumption (EPOC). During EPOC, your body continues to burn calories at an elevated rate for hours after the workout. This effect is significantly higher in HIIT than in moderate-intensity continuous training, further enhancing its fat-burning potential.

Benefits of HIIT

HIIT offers a myriad of health benefits, making it a valuable addition to any fitness regimen:

  • Efficiency: One of the main draws of HIIT is its efficiency. With HIIT, you’re packing a high-intensity workout into a short amount of time. This approach is ideal for people with busy schedules who may not have an hour or more to devote to exercise each day. In as little as 20-30 minutes, you can get a full-body workout that combines cardiovascular training and strength training, helping to improve your fitness levels and burn calories. Additionally, the intense nature of HIIT workouts means they often feel more engaging and less monotonous than longer, steady-state workouts, which can increase adherence to an exercise regimen over time.
  • Calorie Burn: HIIT workouts can lead to significant calorie burn, both during the workout and afterward. This is due to the afterburn effect or Excess Post-exercise Oxygen Consumption (EPOC). When you push your body during the high-intensity intervals, your body uses more oxygen than in a steady-state workout. As a result, your body continues to burn calories at a higher rate post-workout as it recovers and returns to its resting state. This can lead to greater overall calorie burn and aid in weight loss and fat loss goals.
  • Cardiovascular Health: Regularly participating in HIIT workouts can offer significant benefits for your cardiovascular health. The high-intensity nature of the workout pushes your heart and lungs to work harder, helping to improve your cardiovascular fitness over time. Studies have shown that HIIT can improve VO2 max (the maximum amount of oxygen your body can use during exercise), lower resting heart rate, and reduce blood pressure levels. These improvements can reduce your risk of heart disease and other health complications related to cardiovascular health.
  • Fat Loss: HIIT workouts can also lead to significant fat loss. The combination of high-intensity exercise and recovery periods forces your body to switch between different energy sources, which can help to increase fat burn. During the intense intervals, your body taps into carbohydrate stores for quick energy. Once these stores are depleted, your body turns to fat stores during the recovery periods. This cycle can help to increase overall fat burn, making HIIT a powerful tool for weight loss.
  • Muscle Preservation: One of the significant advantages of HIIT over traditional steady-state cardio is its ability to help preserve muscle mass. During steady-state cardio, your body can begin to use muscle protein for energy, leading to muscle loss. In contrast, the quick, high-intensity bursts of a HIIT workout are designed to use carbohydrate stores, preserving muscle while still promoting fat loss. This is crucial for maintaining a healthy body composition, improving athletic performance, and enhancing daily functional abilities.

Implementing High-Intensity Interval Training into Your Routine

Before you begin HIIT, it’s crucial to get the all-clear from a healthcare provider, particularly if you have any pre-existing health conditions. Once you’re ready to start, here are some sample HIIT workouts tailored for different fitness levels:

Beginner Level High-Intensity Interval Training

Beginners should start with more extended periods of low-intensity exercise and shorter bursts of high intensity. A workout could look like this:

  • Warm up for 5 minutes with brisk walking.
  • Sprint for 30 seconds.
  • Walk for 2 minutes.
  • Repeat the cycle for 20 minutes.
  • Cool down for 5 minutes.

Intermediate Level High-Intensity Interval Training

As you gain strength and endurance, you can shorten the recovery periods and increase the high-intensity intervals. An example of an intermediate HIIT workout could be:

  • Warm up for 5 minutes with light jogging.
  • Run at high intensity for 1 minute.
  • Walk for 1 minute.
  • Repeat the cycle for 20 minutes.
  • Cool down for 5 minutes.

Advanced Level High-Intensity Interval Training

For advanced exercisers, HIIT can involve challenging exercises and shorter recovery periods. Here’s an example of an advanced HIIT workout:

  • Warm up for 5 minutes with light jogging.
  • Perform burpees at high intensity for 45 seconds.
  • Rest for 15 seconds.
  • Repeat with different exercises (jump squats, mountain climbers, etc.) for 20 minutes.
  • Cool down for 5 minutes.


Implementing these HIIT workouts into your routine can significantly enhance your fitness levels. However, it’s crucial to remember that rest and recovery are as important as the workouts themselves. Aim to incorporate HIIT into your regimen 2-3 times a week, allowing your body ample time to rest and recover.

How NATEFIT Can Help You With High-Intensity Interval Training

In your fitness journey, remember that guidance can be a game-changer. Working with a personal trainer can ensure that you’re performing exercises correctly and efficiently, reducing the risk of injury. For instance, Nathaniel Ernst specializes in strength training and can help you incorporate HIIT into a routine that meets your specific fitness goals. Similarly, Tyson Linford can guide you through weight management and functional training, complementing your HIIT workouts.

At NATEFIT, we offer online coaching that provides you with professional guidance and support wherever you are. With online coaching, you can receive professional guidance to perform HIIT workouts safely and effectively.

Additionally, consider scheduling a consultation with our personal trainers. A consultation is a significant first step towards a personalized fitness program that caters to your unique needs and fitness goals.


In conclusion, HIIT is a scientifically-backed, efficient, and versatile workout method that offers numerous health benefits. Whether you’re looking to lose weight, improve your cardiovascular health, or simply spice up your workout routine, HIIT could be the perfect addition to your fitness regimen. With the right guidance and a tailored approach, you can harness the power of HIIT to reach your fitness goals faster. Reach out to a personal trainer in Calgary to start your HIIT journey today.

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