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High-Intensity Interval Training


In the ever-evolving world of fitness, one training method has gained significant attention for its efficiency and effectiveness: high-intensity interval training (HIIT). This approach involves alternating periods of high-intensity exercise with short recovery periods, challenging the body to its limits. In this article, we will delve into the mechanisms and benefits of HIIT, programming guidelines and provide sample protocols using the Technogym Skillmill.


Before we dive into the benefits, let’s establish a solid foundation by understanding what HIIT entails. HIIT involves performing short bursts of intense exercise, typically ranging from 10 to 60 seconds, followed by brief recovery periods. This pattern is repeated for a specific number of sets or a predetermined duration. The exercises can vary, including activities such as sprinting, cycling, bodyweight exercises etc. The key principle of HIIT is to push your body to its near maximum effort during the high-intensity intervals, creating a metabolic and physiological response that yields numerous benefits.


Metabolic Changes: HIIT stimulates various metabolic pathways within the body. During intense exercise, there is an increased demand for energy, which leads to the activation of anaerobic metabolism. This results in the production of ATP (adenosine triphosphate) through processes like glycolysis. HIIT also promotes an increase in mitochondrial density and oxidative capacity, enhancing the body’s ability to utilize oxygen and produce energy aerobically.

EPOC (Excess Post-Exercise Oxygen Consumption): HIIT induces a phenomenon called EPOC, where the body continues to consume oxygen at an elevated rate even after exercise. This is due to the need for the body to restore energy stores, remove metabolic byproducts and repair muscle tissue. EPOC leads to a sustained increase in calorie expenditure post-exercise. Keep in mind that the amount of calorie expenditure is not considered as significant as previous studies may have indicated.

Hormonal Response: HIIT triggers the release of various hormones that play a role in metabolism and fat burning. One important hormone is catecholamines, such as adrenaline and noradrenaline, which increase lipolysis (breakdown of fat) and stimulate metabolism. HIIT also promotes the release of growth hormone, which aids in muscle growth and fat oxidation.

Cardiovascular Adaptations: HIIT elicits significant cardiovascular adaptations. It improves heart function by increasing stroke volume (the amount of blood pumped per beat) and cardiac output (the amount of blood pumped per minute). HIIT also enhances vascular function, improving the flexibility and dilation of blood vessels, which can lead to better blood flow and lower blood pressure.

Muscle Fiber Recruitment: HIIT recruits both fast-twitch and slow-twitch muscle fibers. The high-intensity intervals activate fast-twitch muscle fibers, which have a high capacity for force production and power. The recovery periods allow for the activation of slow-twitch muscle fibers, which have a higher capacity for endurance. This combination leads to improved muscle strength, power, and endurance.

These are just a few of the scientific principles underlying HIIT. It’s important to note that the specific adaptations and benefits may vary based on individual factors such as fitness level, training history, and genetics.

HIIT is a potent tool for enhancing cardiovascular fitness. The intense bursts of exercise during high-intensity intervals push the heart to work harder, improving its ability to pump blood efficiently. Additionally, HIIT has been shown to improve the function of the endothelium, the inner lining of blood vessels, promoting better blood flow and reducing the risk of cardiovascular diseases.
Contrary to popular belief, long-duration cardio exercises are not the only way to build endurance. HIIT has been found to be equally effective, if not more so, in improving aerobic capacity and endurance. The intense nature of HIIT places a significant demand on the body's energy systems, including the aerobic and anaerobic pathways. As a result, the body adapts by increasing its oxygen utilization, improving the efficiency of energy production and enhancing endurance performance.
Time is a precious commodity. One of the major advantages of HIIT is its time-efficiency. HIIT workouts can be completed in a fraction of the time compared to traditional steady-state cardio sessions. The short, intense bursts of exercise followed by brief recovery periods allow for a highly effective workout in as little as 20 minutes. This makes HIIT a convenient option for individuals with busy schedules, enabling them to squeeze in a challenging and effective workout without sacrificing their other commitments.
One concern often associated with traditional steady-state cardio is the potential loss of muscle mass. HIIT, on the other hand, has been shown to preserve muscle mass while promoting fat loss. The intense nature of HIIT stimulates the release of growth hormone and other anabolic hormones, which play a crucial role in muscle preservation and growth. Additionally, HIIT triggers metabolic adaptations that enhance fat oxidation and improve insulin sensitivity, making it an effective strategy for individuals aiming to improve body composition. There is more research to be done in this area and there is a lot of nuance so please keep that in mind. By no means should steady-state cardio be eliminated from your program as the benefits outweigh any potential muscle loss.

High-intensity interval training (HIIT) is a game-changer in the world of fitness. Its unique combination of metabolic and physiological responses leads to a multitude of benefits, including increased fat loss, enhanced cardiovascular fitness and improved endurance. Whether you’re a seasoned athlete or a fitness enthusiast, incorporating HIIT into your training regimen can take your fitness gains to new heights. Embrace the power of HIIT and witness the transformative effects on your overall fitness and well-being.


A main go-to for our HIIT training here at Woodside is the Technogym Skillmill. The non-motorized belt, dual handlebar and performance monitoring make this piece an exceptional option for HIIT. The Skillmill, located in The Playground, allows us to seamlessly work between resisted pushing and pulling, sprinting, athletic movements and walking for active recovery. Below are programming recommendations and sample protocols utilizing the Skillmill that you can integrate into your program.


The recommendation for HIIT programming sessions per week can vary depending on individual goals, fitness levels and overall training program. However, the general consensus among fitness experts and researchers is that performing HIIT workouts 2-3 times per week can yield significant benefits while allowing for adequate recovery. This frequency strikes a balance between providing enough stimulus to elicit physiological adaptations and allowing the body to recover and adapt to the high-intensity demands of HIIT.

It is important to note that HIIT is a highly intense form of exercise, and it places considerable stress on the cardiovascular and musculoskeletal systems. Therefore, it is crucial to listen to your body, monitor your recovery and adjust the frequency of HIIT sessions accordingly. Some individuals may benefit from starting with 2 sessions per week and gradually increasing to 3 sessions as their fitness level improves and their body adapts to the demands of HIIT.

Additionally, it is recommended to incorporate other forms of exercise, such as strength training and low-intensity cardio, into a well-rounded fitness routine. This approach ensures a balanced and comprehensive approach to overall fitness and reduces the risk of overtraining or injury.

Ultimately, consulting with a Woodside Personal Trainer can provide personalized guidance and help determine the optimal frequency of HIIT sessions based on individual needs, goals and training capacity.

Session One | Sprint, Push, Pull, Shuffle
Time to Complete: 20 Minutes
Interval: One Minute On, One Minute Off
Rounds: Four
The Protocol:

  • Dynamic Warm Up
  • 1A. Sprint
  • 1B. Complete Rest
  • 2A. Resisted Push
  • 2B. Complete Rest
  • 3A. Resisted Pull
  • 3B. Complete Rest
  • 4A. Shuffle Left
  • 4B. Complete Rest
  • 5A. Shuffle Right
  • 5B. Complete Rest

Session 2 | Peaks and Valleys
Time to Complete: 15 Minutes
Interval: By Minute
Rounds: Five
The Protocol:

  • Dynamic Warm Up
  • Work – Resisted Push – 1 Minute
  • Recovery – Walk – 1 Minute
  • Work – Sprint – 20 Seconds
  • Recovery – Walk – 40 Seconds

Our Training team can help you incorporate high-intensity interval training into your workout routine. To learn more click here or email us.

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