Upon entering the world of exercise, you’ve likely heard one of the following terms at least once: high-intensity interval training (HIIT), high-intensity intermittent exercise (HIIE) or sprint interval training (SIT). You’ve also likely encountered both fitness enthusiasts and qualified exercise professionals praising the approach – and you would perhaps like to try, but wait a second…what exactly is HIIT?
Simply put, HIIT is a form of interval training, implementing a strategy alternating short periods of vigorous anaerobic exercise with noticeably less intense short recovery periods. Just like with any popular exercise approach out there, if you simply ask Google for help, you will likely find tons of contraindicating articles and opinions.
We strongly believe that if used correctly, HIIT is a very powerful tool for your weight loss and fitness journey. The evidence is on our side – all categories of athletes, amateur or hardcore professionals can greatly benefit from incorporating HIIT workouts into their current regime. Compared to “classic” endurance training, HIIT promotes much higher rates of fat loss , exceeds the benefits of moderate intensity endurance training  and helps well-trained athletes overcome performance plateaus by eliciting performance enhancements .
Of course, used correctly is the key here, and there are simply too many false claims around. Today, we’re going to examine the evidence behind the concept of HIIT training and debunk some common myths. From there, you can see for yourself if HIIT training is for you at this point in time!
The Beginning Of HIIT Training
The concept of interval training is quite young, but far from new: modern HIIT workouts were invented in 20th century to improve running performance . What begun as simply alternating fast and slow runs, has quickly evolved into a regime much closer to HIIT we’re used to today. Over time, bursts of intensive exercise and rest periods between them became progressively shorter, and maximal exercise efforts increased from 75% to nearly 100% of the individual’s performance capacity .
Moreover, HIIT, once designed for runners, has become a widespread tool for athletes of all sorts, particularly engaged in multi-sports, such as soccer, football, basketball, hockey, tennis, and swimming . For these athletes, HIIT has become an effective measure as a successful technique for improving cardio-vascular endurance . Exercise professionals have quickly discovered that compared to HIIT, steady long distance training at only 70-80% of maximum heart rate can be detrimental to strength and power . At this point, sport-specific variations of HIIT were developed for many various disciplines.
TABATA : The King Of HIIT Training
In 1996, a true HIIT legend was born when Izumi Tabata of the National Institute of Fitness and Sports in Kanoya, Japan published the results of his study on the effects of High Intensity Interval Training.
One of Tabata’s most famous findings demonstrated that 20 seconds of all-out cycling followed by 10 seconds of low-intensity cycling for four minutes was as beneficial for VO2 max (maximal aerobic capacity) as 45 minutes of long, slow cardio performed four times per week . Moreover, Tabata method of training resulted in improvements to anaerobic capacity, whereas, the steady state training failed to demonstrate such improvements .
Key findings of the famous Tabata study were the following :
- Interval training may help achieve substantial VO2 max improvement
- HIIT has unique anaerobic benefits for athletes, which cannot be achieved with steady cardio alone
- Tabata training sessions required to facilitate the benefits are much shorter compared to “classic” steady state cardio
These benefits have helped HIIT – and Tabata protocol training in particular – quickly gain enormous popularity among both athletes and trainers.
What does this mean for fat loss?
Research on overweight individuals clearly demonstrates that HIIT has amazing benefits when it comes to fat loss. When compared to an endurance-based exercise program of much higher energy cost, HIIT still demonstrated a much more pronounced reduction in subcutaneous fat storages . This illustrates that HIIT-style exercise protocols are much more efficient compared to steady state cardio.
Moreover, HIIT appears to induce beneficial changes in muscle tissue. In the same study, muscle biopsies were obtained from both groups before and after training . Both programs appeared to induce comparable changes in the citric acid metabolism . However, the activity of the activity of muscle glycolytic enzymes was increased by the HIIT program .
Together, the results of the study suggest that “for a given level of energy expenditure, vigorous exercise favors negative energy and lipid balance to a greater extent than exercise of low to moderate intensity” . In addition, “the metabolic adaptations taking place in the skeletal muscle in response to the HIIT program appear to favor the process of lipid oxidation” , which means HIIT training sessions provide considerable benefits for weight management.
Why Intervals Might Not Be Right For You
As we’ve discussed above, HIIT was initially developed for highly trained athletes looking for ways to enhance their performance. Because of that, implementing HIIT for untrained exercise amateurs poses certain risks which need to be considered when designing an exercise plan.
Individuals who have been living relatively sedentary lifestyles or had prolonged periods of physical inactivity may not be able to start their exercise journey with HIIT without building up certain levels of endurance first. This is because vigorous physical activity in such individuals may pose an increased coronary disease risk.
The same risk applies to those with family history of coronary disease, cigarette smokers, individuals with high blood pressure and diabetes. It may be still possible to commence HIIT training, but only after receiving medical clearance.
For previously sedentary individuals, going straight into HIIT, which sometimes incorporates complex moves performed at very high intensity, poses additional risk of injuries. To avoid that, it’s better to establish a foundational level of fitness (3-5 times a week of aerobic training, 20-60 mins duration per session).
If you’re unsure if HIIT is for you, the best thing you can do is to contact a qualified personal trainer. Upon performing a thorough assessment, your personal trainer will be able to develop an appropriate exercise plan tailored to your own needs and abilities. Personal trainer will also, if needed, recommend you to see a health practitioner before commencing a new exercise program.
How Does HIIT Compare To Other Forms Of Cardio?
Regardless of where you currently stand with your fitness level, the main benefit of HIIT is perhaps the fact that it provides similar or greater benefits compared to steady state cardio, but in shorter periods of time . This is because HIIT workouts tend to burn more calories than traditional workouts and the effects last even after the workout is over .
The post-exercise period, or “EPOC”, stands for excess post exercise oxygen consumption . EPOC tends to last for about 2 hours after the exercise session is completed, where the body is restoring itself to pre-exercise levels, and thus using more energy . As HIIT workouts are vigorous in nature, HIIT-induced EPOC stage tends to be substantially greater, adding about 6 to 15% more calories to the overall workout energy expenditure when compared to steady state cardio .
Is HIIT The Latest Fitness Fad?
We get this very question a lot. First of all, HIIT definitely not the latest fad – we’ve discussed how stale yet effective the concept actually is, remember?
Furthermore, by definition, a fad is “an intense and widely shared enthusiasm for something, especially one that is short-lived; a craze.” In contrast, HIIT has been around for a while after various names, so its lifespan is definitely considerable. Also, unlike many actual fads, the concept of HIIT is based on good quality evidence (remember the Tabata study?), not some city myths.
Although HIIT is currently the fitness worlds flavour of the month and a passing fitness trend (under this particular name at least), it still has its benefits like all other forms of exercise! So have a chat to your personal trainer and decide for yourself if it’s worth giving a go.
- Tremblay, A., et al (1994) “Impact of exercise intensity on body fatness and skeletal muscle metabolism”. Metabolism. 1994 Jul;43(7):814-8.
- Sijie, T., et al (2012) “High intensity interval exercise training in overweight young women.” J Sports Med Phys Fitness. 2012 Jun;52(3):255-62.
- Laursen, P.B. & Jenkins, D.G. (2002). “The scientific basis for high-intensity interval training: optimising training programmes and maximising performance in highly trained endurance athletes.” Sports Med. 2002;32(1):53-73.
- Lacasse, D. (2010). “The Past, Present, and Future of Interval Training”. Source: https://seeadamtrain.wordpress.com/2010/04/14/exercise-the-past-present-and-future-of-interval-training/
- “High-Intensity Interval Training”. Source: https://www.acsm.org/docs/brochures/high-intensity-interval-training.pdf