Defined as repeated bouts of high-intensity exercise performed above the lactate threshold, followed with either low-intensity exercise or complete rest, High-intensity Interval Training (HIIT) is key to boost performance in athletes
BYLINE: Laurens Zweers
What happens as you push your pace out of your comfort zone during workout and again return back to the resting phase? Well, it takes your workout or fitness to another level. And, as the name itself suggests, High-intensity Interval Training (HIIT) lets you experience the same. It is known as one of the best ways to boost the performance in athletes by quickly improving cardiovascular and metabolic parameters. It is a type of interval training exercise. HIIT is defined as repeated bouts of high-intensity exercise performed above the lactate threshold, followed with either low-intensity exercise or complete rest.
The origin
Interval training was first introduced in the first half of the 20th century as a higher intensity form called sprint interval training, which reached near maximum heart rate. This was used to improve the performance of Olympic athletes. During the 1950s, research by physiologists advanced and the interest in this phenomenon started to grow. Next, it was picked by team sports as a preparation tool. Due to the research, technological advancements and the global rise in interest towards sports, HIIT has earned its place today among the top training methods in the world.
Understanding the problem
The problem with this form in training is the indefinite number of possibilities to train and the variety and needs of specific sportspersons and sports. The variables that can be modified are the number, the intensity and duration of the exercises as well as the type and length of the pauses. With understanding of the underlying physiology, a trainer can adjust these variables to achieve the desired stimulus as and to maximise the body´s response.
Decoding the training counselling
The most important way to train is dependent on the sport and where the athlete needs improvement. There are four pillars on which training counselling is based upon. The first one consists of the specific requirements for greatness in the sport. Are there known benchmarks available from top athletes? The second pillar is the profile of the athlete. Due to the combination of aerobic and anaerobic components in sportsmen, both components should be assessed and addressed in training. How does he score on specific tests? Where does he need improvement? Where does he differ from the benchmarks from the top athlete? The third pillar consists of the long-term goals for the athlete and the fourth one is the complete planning, included with periodisation and competition.
In 2019 Laursen and Buchheit published a reference work on HIIT training (science and application of high-intensity interval training). The book is based on known science and their long experience in the field. In their book, they describe three main targets for HIIT training, which can be improved by six different types of HIIT sessions.
The three main physiological targets for HIIT training according to Laursen and Buchheit are as follows:
- Aerobic oxidative metabolic response targets cardiac output, aerobic enzymes, mitochondrial function, respiratory work
- Anaerobic glycolytic metabolic response target changes in energetic flux, lactate kinetics, and glycogen depletion.
- Neuromuscular and musculoskeletal strain targets muscle function and muscle strength, power, and changes in movement characteristics.
The different types of HIIT sessions consist of:
- Only aerobic stimuli
- Aerobic and neuromuscular stimuli
- Aerobic and anaerobic stimuli
- Aerobic, anaerobic and neuromuscular stimuli
- Anaerobic and neuromuscular stimuli
- Only neuromuscular stimuli
Within a certain sport, one kind of HIIT training would be better to achieve the intended goal and therefore this training will be used more often.
The recovery interval
The resting period is essential to achieve the intended stimulus. Not only the length but also the type of rest plays a role. If you are doing a combined aerobic and anaerobic HIIT session, there are multiple energy systems that need recovery. The Creatine Phosphate (PCr) stock needs to build up and the pH needs to increase again. Herein lies a problem. The PCr recovery rate is about 5 to 8 minutes with passive recovery and the pH normalises faster, if there is an active recovery of moderate intensity. The choice between active and passive recovery is thus dependent on the desired physiological stimulus. During HIIT training of high intensity, passive rest is recommended, since otherwise the training would be over faster than the intended stimulus could be achieved by the complete depletion of PCr. A simple rule to apply is the usage of passive rest with rest intervals lesser than 2 to 3 minutes and active rest with longer breaks.
Planning
Another problem with HIIT training is the impact it has on the body. Most athletes use HIIT as an extra tool for training. Suddenly, introducing multiple HIIT sessions in a week without considering the influence on the athlete or on the other training sessions will cause more harm than benefit. As these training sessions are quite intense, they should be programmed and there should be enough rest after HIIT as the body needs to recover to prevent fatigue, overtraining and injury. Research from Rutgers University demonstrated that the knees, shoulders, and ankles were the most commonly involved injuries.
Conclusion
HIIT training can be a powerful tool to achieve the athlete’s full potential. Important considerations to change the variables of the training and thus the stimulus are the physiological needs for the sport and the needed improvements of the athlete. It is paramount to plan the different sessions and to implement enough rest to prevent overtraining and injury. Due to the indefinite variety, there is more than one way to achieve greatness.
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