January 29, 2024

Why is HIIT such a great workout and the science behind it

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Why is HIIT such a great workout and the science behind it
Cory McKane
Blog Post Summary:

High-Intensity Interval Training (HIIT) has revolutionized the fitness world, gaining recognition for its efficacy in delivering impressive fitness results in a short period.

High-Intensity Interval Training (HIIT) has revolutionized the fitness world, gaining recognition for its efficacy in delivering impressive fitness results in a short period. Beyond its reputation as a time-efficient workout method, HIIT's effectiveness is deeply rooted in scientific principles that make it a powerful fitness regimen. In this comprehensive guide, we delve into the science behind HIIT, exploring the physiological mechanisms and reasons why it stands out as a top-tier workout strategy.

Understanding HIIT: A Brief Overview

HIIT involves alternating between short bursts of high-intensity exercises followed by brief recovery periods or low-intensity activities. The intensity during these intervals pushes individuals close to their maximum effort, making it a demanding yet time-efficient workout method.

The Science Behind HIIT's Effectiveness:

1. EPOC and Increased Calorie Burn

HIIT's signature benefit lies in its ability to elevate the body's metabolic rate, leading to a phenomenon known as Excess Post-Exercise Oxygen Consumption (EPOC) or the "afterburn effect." During HIIT, the body experiences an oxygen debt due to intense exercise. Post-workout, the body works to restore oxygen levels and repair muscles, leading to continued calorie burn for hours, even after the workout ends. This elevated metabolism aids in fat oxidation, contributing to weight management and fat loss.

2. Metabolic Adaptations

HIIT induces metabolic adaptations in the body, enhancing mitochondrial function and increasing the production of enzymes involved in energy production. These adaptations improve the body's ability to utilize oxygen efficiently, leading to improved aerobic capacity and endurance.

3. Cardiovascular Benefits

HIIT's intense intervals challenge the cardiovascular system, leading to improvements in heart health, stroke volume, and overall cardiovascular fitness. Studies have shown that HIIT can be as effective, if not more, in improving cardiovascular health compared to traditional steady-state cardio exercises.

4. Muscle Fiber Activation and Growth

HIIT engages both fast-twitch and slow-twitch muscle fibers. The rapid, explosive movements during high-intensity intervals activate fast-twitch muscle fibers responsible for explosive power and strength. Moreover, the prolonged time under tension during HIIT contributes to muscle hypertrophy and endurance, leading to comprehensive muscle development.

5. Hormonal Response

HIIT triggers a beneficial hormonal response in the body, including increased production of growth hormone and improved insulin sensitivity. These hormonal changes aid in muscle repair, recovery, and help regulate blood sugar levels.

6. Time Efficiency and Adherence

The efficiency of HIIT workouts, often lasting between 15 to 30 minutes, makes them more feasible for individuals with busy schedules. This time efficiency promotes adherence to workout routines, increasing the likelihood of regular exercise and long-term fitness success.

The HIIT Protocol: The Key Elements

HIIT's effectiveness relies on several key elements:

1. Intensity

The intensity of HIIT is crucial for triggering physiological adaptations. High-intensity intervals should push individuals to near maximum effort, followed by recovery periods that allow for adequate rest before the next bout of intensity.

2. Work-to-Rest Ratio

The work-to-rest ratio determines the duration of high-intensity intervals and recovery periods. Common ratios range from 1:1 to 1:4, where the high-intensity interval duration is matched or varied in relation to the recovery period.

3. Exercise Selection

HIIT can incorporate various exercises, such as sprints, bodyweight movements, cycling, or plyometrics. The choice of exercises influences muscle engagement and workout intensity.

Applying the Science of HIIT:

1. Tailoring Workouts

Customize HIIT workouts based on fitness levels, goals, and individual preferences. Beginners may start with shorter intervals and longer rest periods, gradually progressing as fitness improves.

2. Planning Progression

Gradually increase the intensity, duration, and complexity of HIIT workouts to prevent plateaus and ensure continued fitness improvements. Progressive overload is key to achieving ongoing results.

3. Recovery and Rest

Prioritize recovery between HIIT sessions to allow for muscle repair and prevent overtraining. Balancing intense workouts with adequate rest is crucial for overall fitness progress.

4. Consistency and Adherence

Consistency is key to reaping the benefits of HIIT. Incorporate HIIT sessions regularly into a well-rounded fitness routine for long-term success.


The scientific foundation behind HIIT underscores its effectiveness in improving cardiovascular health, boosting metabolism, enhancing muscle strength, and promoting overall fitness. The physiological responses triggered by HIIT, such as EPOC, metabolic adaptations, cardiovascular improvements, and hormonal responses, contribute to its status as a highly efficient workout method. By understanding the science behind HIIT and applying its principles wisely, individuals can harness its benefits to achieve their fitness goals and embark on a journey toward better health and vitality.


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About the Author:

Cory McKane
Cory is a huge fan of fitness - and an even bigger fan of helping you with your fitness. He's started on his journey with WeStrive back in 2015 and has been building it ever since.

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Written by
Cory McKane
CEO | WeStrive
Huge fan of fitness - Even bigger fan of helping you with your fitness. I've been building up the WeStrive platform for over 5 years and I'm excited to keep building out the greatest Health & Wellness platform on Earth.

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Why is HIIT such a great workout and the science behind it