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The History of Cardio HIIT and Cardio ISOMETRICS

HOTWORX made the decision early on, prior to the opening of its very first studio, that the use of isometrics and HIIT would be the most effective approach to infrared fitness training, and therefore, would be the basis for all of the workouts that would be offered in each of the patented HOTWORX workout saunas. Let’s take a look at the origins and evolution of those two disciplines of training.

High-Intensity Interval Training (HIIT) is a relatively modern approach to fitness training that has gained significant popularity for its efficiency and time effectiveness. HIIT is associated with cardio training because of the demands it places on the cardio system during the high intensity intervals that involve explosive spurts of movement. HIIT provides for an excellent cardio conditioning result. The development of HIIT can be traced back to several key milestones:

The foundations of HIIT were laid down by early research exploring the benefits of interval training. In 1912, Danish physiologist August Krogh and his wife Marie Krogh conducted experiments that highlighted the physiological adaptations induced by interval-based exercise. However, the concept didn't gain widespread attention until the latter half of the 20th century.

A pivotal moment in the development of HIIT was the work of German track and field coach Woldemar Gerschler and his colleague Hans Reindell in the 1960s. They introduced the concept of "Gerschler Fartlek," a form of interval training involving alternating periods of high-intensity effort and recovery. They experimented with intervals of fast and slow running. Their approach was later refined by Swedish physiologist Per-Olof Åstrand, who developed the "Åstrand-Rhyming Test" for assessing cardiovascular fitness. The Astrand Test involves the use of a sub-maximal cycle ergometer aerobic fitness test. It is based on the relationship between heart rate during workouts and the percentage of maximal aerobic capacity and was a precursor to the modern day more advanced VO2 Max testing methods.

Dr. Izumi Tabata, a Japanese researcher, conducted a groundbreaking study in the mid-1990s that greatly contributed to the popularization of HIIT. His study focused on a specific interval protocol: 20 seconds of all-out effort followed by 10 seconds of rest, repeated for four minutes (a total of 8 cycles). This approach, now known as the "Tabata Protocol," demonstrated significant improvements in both aerobic and anaerobic fitness.

Dr. Tabata is often referred to as the "father of HIIT" due to his groundbreaking research and development of the Tabata Protocol, which is a very specific form of High-Intensity Interval Training. His work has had a profound impact on the way fitness enthusiasts and professionals approach cardiovascular training.

The results of his study showed that the Tabata Protocol led to significant improvements in both aerobic and anaerobic fitness, which sparked interest in the concept of HIIT. HIIT became popular as an effective and time-efficient method for improving cardiovascular fitness and metabolic capacity.

As a result of his pioneering work, Dr. Tabata is widely recognized for his contribution to the development and promotion of HIIT, and he is often credited with helping shape the modern understanding of this training approach.

In the 2000s, fitness experts, trainers, and researchers started experimenting with various interval training protocols, adapting the principles of HIIT to different forms of exercise, including running, cycling, bodyweight exercises, and more. The flexibility of HIIT, which allows customization of work and rest intervals, made it appealing to a wide range of individuals with varying fitness levels and goals.

Over the past couple of decades, HIIT gained immense popularity due to its time efficiency and effectiveness in improving cardiovascular fitness, boosting metabolism, and burning calories. The fitness industry embraced HIIT, and many gyms and fitness programs, including that of HOTWORX, incorporated HIIT workouts into their offerings.

In December of 2016 executives from HOTWORX corporate experimented with cycling inside of a HOTWORX infrared workout sauna. It was clear from that first Hot Cycle test session that they were onto something. Since that innovative moment, HOT CYCLE, a fast and effective HIIT session, has become one of the most used workouts of the entire HOTWORX lineup.

HIIT’s effectiveness has been supported by numerous scientific studies, highlighting its ability to improve cardiovascular health, increase aerobic and anaerobic capacity, and promote fat loss in a shorter timeframe compared to traditional steady-state cardio workouts.

As HIIT gained prominence, numerous adaptations and variations emerged beyond the, "Tabata Protocol,” such as "Turbo Training,” and, of course, HOTWORX. These protocols differ in terms of work-to-rest ratios, exercise type, and overall intensity levels. I laugh when I think back to my football training in high school when we were practicing HIIT for conditioning but there was no such official protocol for it. We were running drills that were definitely interval training with high intensity. We would line the entire team up in full pads at the end of practice and then we had to run in a single file line. When coach blew the whistle the player at the end of the line would have to launch into a full speed sprint to get to the front of the line and then the whistle would blow for the next player, and so on until the entire team had ran one full out sprint to the front. Then we would do it again until coach felt like we were conditioned enough for that practice.

The bottom line is this, HIIT works! And it works especially well when combined with infrared energy and heat.

Any fitness history lesson has to wind up with a discussion of the integration of technology. The digital age has certainly played a role in the development of HIIT. Fitness apps, online workout platforms, and wearable devices have made it easier for individuals to access and engage in HIIT routines, monitor their progress, and customize workouts to their specific needs. HOTWORX incorporated technology in a big way since the opening of its very first location in Oxford, MS in 2017. Through the use of its Burn Off App, the franchise allows customers to track their workouts with their Apple Watch or Fitbit and view their results in a rolling 90 day challenge that resets every 90 Days. A 90 Day Challenge should always be happening for your routine. Once you finish one challenge, it’s time for a new one.

The development of HIIT is a result of contributions from researchers, coaches, athletes, and fitness enthusiasts who have refined and popularized interval training approaches over time. Its effectiveness, adaptability, and time efficiency have solidified HIIT's place as a widely practiced and well-studied method of cardiovascular and metabolic training.

Now let’s move over to a discussion about isometrics. What about the history of Isometrics as it relates to cardio?

Any dialogue regarding the development of modern isometrics has to begin with yoga. Yoga was the first disciplined form of isometrics with its origins in Ancient India.

Yoga, as traditionally practiced, is not typically considered a primary form of cardiovascular training. However, in recent years, certain styles of yoga have been adapted and modified to incorporate more vigorous movements and sequences that can elevate heart rate and offer some cardiovascular benefits. Certainly, HOTWORX has invented a way to elevate the cardio experience of yoga and other isometrics through the combination of heat and infrared energy into the the yoga/isometric workout environment. Let’s explore the history of yoga and its evolution as a potential form of cardiovascular training.

Yoga originated thousands of years ago in India as a holistic practice that aimed to achieve physical, mental, and spiritual well-being. While not understood at that time, one byproduct of yoga was conditioning for the heart.

The earliest forms of yoga focused on meditation, breathing exercises, and static postures to promote self-awareness, mindfulness, and flexibility. These practices were not primarily designed for cardiovascular conditioning.

Hatha yoga emerged as a branch of yoga (10th-15th Century) that integrated physical postures (asanas) and breathing techniques (pranayama) to prepare the body for meditation and spiritual growth.

While Hatha yoga introduced physical movements, its pace was generally slow and deliberate, and it wasn't designed with the same emphasis on cardiovascular exercise as modern forms of cardio training. HOTWORX yoga and isometrics, with its athletic style and infrared heat, gets the heart rate to the right range for cardiovascular conditioning quickly and allows customers to maintain the appropriate heart rate at the right level for fitness.

As time passed, yoga continued to evolve and expand throughout the world beyond Hatha. As yoga spread to the West in the 20th century, various styles and adaptations emerged to suit different needs and preferences. Some of these styles began incorporating more dynamic and flowing sequences that can raise heart rate and promote muscular endurance.
Styles like Vinyasa, Power Yoga, and Ashtanga Vinyasa Yoga include sequences of poses that are performed with coordinated breath, resulting in a more dynamic and physically demanding practice. Other forms such as Bikram and HOTWORX developed to use athletic postures with very strict holds and sequences. These modern adaptations often involve faster transitions between poses and more physically challenging sequences, leading to an increased heart rate and accelerated cardiovascular benefits.

While certain styles of yoga can elevate heart rate and contribute to cardiovascular conditioning, they may not offer the same level of intensity and sustained cardiovascular effort as traditional cardio exercises like running or cycling unless they are surrounded with an infrared energy and heat environment like that of a HOTWORX sauna.

Yoga's emphasis on mindful movement, flexibility, balance, and focus remains central to its practice, but cardiovascular gains can be a major byproduct of certain styles including that of the HOTWORX 3D Training Method with sequences that can contribute to significant cardiovascular benefits.

Beyond the yoga discipline, isometric exercises, while also not typically associated with cardiovascular training, have been historically used more for strength development and rehabilitation rather than specifically for cardio. Isometric exercises involve contracting muscles without joint movement, such as pushing or pulling against an immovable object to allow for a zero impact workout. However, I can provide information on how isometric exercises have been used and their potential relationship to cardiovascular fitness below:

Isometric exercises have ancient roots too, as they were practiced in various forms of martial arts, yoga, and other disciplines for centuries. These practices used static postures to build strength and stability.

In the early to mid-20th century, isometric exercises gained attention in the field of physical therapy and rehabilitation. They were used as a means to rebuild strength and muscle function in individuals who were recovering from injuries or surgeries. When you think about the combination of isometrics performed within an infrared sauna, you can easily conclude that the results will be dramatic. HOTWORX brought that discovery to the fitness table!

In the 1950s and 1960s, some researchers began to explore the potential cardiovascular effects of isometric exercises. There were hypotheses that isometrics might elicit a cardiovascular response due to the increased muscle tension and potential impact on blood flow.

While isometric exercises can generate muscle tension and engage a significant number of muscle fibers, they are not typically used as a primary method of cardiovascular training. Traditional cardio exercises like running, cycling, and swimming are more effective at increasing heart rate, but when you combine isometrics with heat and infrared energy from an IR sauna it too becomes an excellent cardio conditioning experience.

In modern fitness practices, isometric exercises are still used primarily for strength building and muscle engagement. They can be incorporated into routines to enhance muscular endurance and stability, but they are not typically utilized as a standalone cardio training method. HOTWORX disrupted that notion. HOTWORX isometrics provide for an incredible cardio workout!

Infrared HIIT + Infrared Isometrics = The one, two punch for cardio fitness.


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Stephen P. Smith, MA
CEO and Creator of HOTWORX, Author, Former National Collegiate Bodybuilding Champion and Arena Football Player, Certified Professional Trainer


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