How To Scientifically Understand Hiit Training

How to scientifically understand HIIT training

Is HIIT effective? What is the most significant difference from normal training? Why are more coaches talking about HIIT?

What is HIIT training?

HIIT is the abbreviation of High-Intensity Interval Training. HIIT is an aerobic training mode that intersperses high-intensity exercise for 10 to 30 seconds with low-intensity steady-state exercise. For example, intermittent variable speedrunning, battle ropes, and self-weight movements are all HIIT.

The opposite of this training mode is normal uniform speed training. LISS (Low-Intensity Steady State) is a uniform speed training mode without any explosive exercise interval. For example, regular walks and cycling are all types of LISS.

To compare the fat loss efficiency of aerobic training, we experimented with HIIT and LISS through actual training.

EPOC (Excess Post-exercise Oxygen Consumption)

Before talking about HIIT, we must first understand a term called Excess Post-exercise Oxygen Consumption (EPOC) for short. In the recovery process after exercise, to repay the oxygen deficit during exercise, the body will increase its metabolic rate to balance and restore the excessive oxygen consumed during exercise to burn extra calories under static conditions after training.

In the promotion of many HIIT courses, it is clear that EPOC has become the most significant selling point of the course. On the one hand, the principle of EPOC is familiar with science, but whether its effect is as practical as in the publicity, it is necessary to examine specific data.

In an article published in the Journal of Sports Sciences in 2006, the specific oxygen consumption of EPOC was measured experimentally. The final result of the experiment is: when the subject has undergone 80 minutes of high-intensity training, the EPOC state lasts for seven hours, and the extra calories burned during this period are 80 calories.

A general HIIT course lasts 40-60 minutes. Based on the experimental results, the body will consume about 40-60 extra calories through EPOC after training, which is the calories of half a banana. From this point of view, EPOC is not the biggest advantage of HIIT.

Why is HIIT so popular?

The biggest reason is its high efficiency and time-saving.

In a 2017 study, the two groups of subjects trained for HIIT and LISS for ten weeks. However, the body fat loss rates of the two groups of subjects were similar; the HIIT experimental group only spent 40% of the LISS group for training. Are scientific experiments reliable? Let’s take a quiz.

Ryan has 15 minutes of HIIT training and 30 minutes of LISS training on the treadmill. Finally, we can see that Ryan consumed 300 kcal through HIIT. Among them, 35% comes from fat, a fat consumption of 105 kcal. After 30 minutes of LISS, Ryan consumed 250 kcal. 50% of it comes from fat, so the fat consumption in 30 minutes is 125 kcal. Ryan spent half of the time consuming almost the same fat calories as LISS through HIIT training.

In addition to high efficiency, the fun of HIIT is also one of the reasons why it is popular with the public. It may be tedious to keep lifting iron and running all the time. But intermittently arranging the lifting and running together seems to be a better thing to persist. If the fitness effect is better, it is best. In comparison, the various HIIT courses in the fitness market can attract users to continue to return to aerobic training. Users who like to challenge themselves can choose a more intense variable speed running type training. Users who need team support can choose small tools with a strong sense of community for cycling training. The diversity of HIIT also increases user adhesion.

Short comings

As more and more users practice HIIT, the shortcomings of this training mode also appear.

1) The first problem is the hardware requirements of HIIT.

Because experiments have shown that when the heart rate reaches 80%-95%, HIIT training can exert the maximum fat loss effect, so wearing a heart rate detector is a vital part of HIIT training.

2) The second major problem is the damage to joints and muscles caused by high-intensity training.

Especially for people with severe injuries or cardiopulmonary disease, LISS is a better way to lose fat than HIIT.

3) In addition, the arrangement of HIIT courses will be a major test for coaches.

How to arrange a comprehensive training program so that users of various fitness levels can exercise safely while still achieving the best heart rate of 80%-95%.

Movements for people with Joint pain

Here will demonstrate several high-intensity, low-impact movements suitable for people who feel discomfort in the knee and ankle joints when jumping.

  • Action 1: Pivot Squat/burst rotation squat

Squat down with your feet slightly wider than your shoulders. Pay attention that your knees are in the same direction as your toes when squatting. Don’t tuck in. Use your gluteal muscles to drive it up explosively when you stand up. At the same time, the torso and hips rotate in different directions, alternating directions each time.

  • Action 2: Reverse Table Top Toe Touches / Reverse Table Top Toe Touches

The feet are the same width as the hips, the hands are the same width as the shoulders, and the body faces up to form a reverse table style. Keep the core and hips activated and tightened; touch the left toe with your right hand, and touch the right toe with your left hand and alternate sides.

  • Action 3: Down Dog to Kick Back

Put your hands shoulder-width apart and your feet the same width as your hips to enter the Downward Dog Pose. While moving the body forward to form a high-level flat plate, bend one leg, use the strength of the core to retract the knees, try to touch the chest, and alternate legs.

Young People Love HIIT Fitness, But This Is Not For Everyone

The principle of HIIT exercise is very simple-to-make the body reach the “limit performance” in a short time. Due to the alternating peak intensity and shorter recovery period, this endurance training method becomes easier to lose fat and promote the enhancement of cardiopulmonary function. However, the hot HIIT is not suitable for everyone.

How To Scientifically Understand Hiit Training

High-intensity HIIT needs to be evaluated because, for some groups. It will form a potential heart burden and the risk of limb sports injury.

First, the heart rate soared after HIIT exercise. Especially obese people with high blood pressure and high blood lipids and new fitness people whose aerobic capacity needs to be improved will push the heart rate load to the limit in a short time. Most HIIT group courses are based on high-impact sports, which put excessive pressure on muscles, joints, tendons, and ligaments.

In addition, if you only do HIIT training, it is easy to form a bottleneck period in a short time, resulting in stagnant athletic ability. This situation can happen to exercise coaches who have been coaching HIIT for a long time, and even overtraining can lead to a decline in athletic performance. This is because their excessive exercise needs a “better” body to withstand, which is also the key to reducing the probability of injury.

Because exercises that constantly impact the limited heart rate test the human body’s ability to adapt to the exercise load, if the load that it bears needs to reach the “peak” for a long time, then the improvement of exercise capacity will be correspondingly limited.

How To Scientifically Understand Hiit Training

HIIT Fitness - Which Young People Fall In Love With

Through the global fitness trends released by ACSM, it can be found that HIIT fitness has been firmly in the top 5 positions for several consecutive years. The reason for its popularity is simple. Compared with an hour or more of training, HIIT can achieve the same or better results relatively quickly. The reason is that the movement unit is clear, high-intensity executable, and able to set the maximum training stimulation.

How To Scientifically Understand Hiit Training

As a “fat-burning artifact” that attracts young people, HIIT has been proven to have an “After-burn effect”: After a short and intense exercise, the metabolism is significantly enhanced, so it also achieves the goal of fat burning.

Because HIIT requires higher oxygen intake than general aerobic exercise, high-intensity interval training requires 3-4 times the higher physical performance than 30-60 minutes of endurance training at a constant intensity. Even though the primary burning substance of HIIT is carbohydrates, it can also consume substances other than carbohydrates, such as fat, because of the afterburning effect and the large consumption of calories.

In principle, almost all sports can be done as HIIT training. However, it is beneficial for endurance sports. For example, jogging, boxing, riding, etc., can all be divided into three-minute intervals, alternating between high intensity and medium speed. More importantly, this training method itself can also increase the fun.

HIIT Is Not Suitable For Everyone Because the Threshold Is Not Low

If HIIT is used as the main item of all daily sports, its limitations will be quickly discovered. Because HIIT has exceptionally high demands on the body, beginners usually lack sufficient aerobic capacity, connective tissue strength, and sufficient stability of joints. At the same time, the risk of doing HIIT is not tiny for some people.

Heart Burden

The effect of exercise often depends on the intensity of exercise. This is because exercise increases the demand for oxygen from the heart and cardiopulmonary system to the working muscles. But with high-intensity training, the oxygen demand will become higher and higher.

Generally speaking, this load makes the individual’s heart stronger. However, in a few cases, exercise will cause the heart to work exhaustively, eventually leading to a cardiac event (such as a heart attack). In addition, if the exercise individual has a family history of smoking or high blood pressure, heart disease, high blood lipids, high blood sugar, and heart disease, this will increase this risk.

Although a study published in the Journal of the American Heart Association in 2018 found that HIIT has a lower rate of cardiac events, even in patients with coronary heart disease or heart failure. But to be safe, if you fall into any of the above categories, you should consult a doctor before trying HIIT.

How To Scientifically Understand Hiit Training

Physiological damage

Exercisers who have just started to exercise, if HIIT is used as the core exercise content, they are prone to the risk of injury and muscle strain, and exercising too early can lead to burnout. At the end of a course, shortness of breath, dry throat, and even retching and nausea may occur in new gymnasts. This stress response occurs when muscles, tendons, and joints are suddenly exposed to abnormal loads during HIIT training. Due to the high intensity and rapid fatigue caused, HIIT training has a greater possibility of injury than moderate-intensity training.

High intensity can also cause overload, especially in inexperienced people. If the regeneration interruption time between motor units is too short, it may lead to overtraining syndrome. Because the individual’s muscles and other tissues are not enough to cope with the intensity of this exercise. The bodybuilder’s understanding of his own body is not enough to recognize when to stop training altogether.

Before trying HIIT, it takes at least two months to build strength and aerobic fitness. Or perform relatively low-intensity circuit training before HIIT.

Sports recovery and secondary injury

Due to the intensity of exercise and high impact, HIIT puts a lot of pressure on muscles, joints, tendons, and ligaments. If any form of sports injury has occurred, this may lead to subsequent secondary injuries. Then in the recovery from exercise, the gentle exercise form has better exercise value than HIIT. Similar problems will also appear in many fitness coaches who have been busy here for a long time. Long-term high-impact, high-intensity training requires enough time for exercise recovery even for advanced players with full experience and cardiorespiratory capabilities.

HIIT Training May Not Be The Choice For Entry Fitness

For senior fitness people, HIIT is a good training method: it provides a lot of strong stimulation to human cells in a short time, thereby actively regulating the body’s functions. But even those with a training basis need to adjust their exercise plan through steady strength training or slow aerobic exercise.

Cross-training can help joints, muscles, and tendons recover from the last exercise, play a balancing role, and promote regeneration that recovers a stronger state during the next exercise.

How To Scientifically Understand Hiit Training

It is generally recommended that HIIT fitness does not exceed three times a week. Because high-intensity training will cause more significant stress on the nervous system. The nervous system requires more regeneration time than muscles. Therefore, there should be 36 hours between training units. And HIIT is usually completed in a short time (less than twenty minutes). For example, Tabata only takes four minutes to complete. If you only do it three times a week, it means that HIIT will have less than one hour of exercise time per week.

According to WHO recommendations, at least 75 minutes of moderate-intensity exercise every week to maintain health. However, HIIT cannot be the only way to exercise. For beginners, if you want to perform high-intensity HIIT training, your body must first withstand this pressure and stably increase strength and endurance.

If you want to do simple HIIT exercises, you should choose the reduced intensity version:

  • Warm-up for 5-10 minutes;
  • Load phase: 15 seconds high intensity;
  • Recovery time: 45 seconds average load intensity.


If you have 20 minutes of high-intensity interval training, you can use this HIIT plan to achieve ten intervals. If the duration of the exercise load phase is different from this. The subsequent recovery phase should be twice or three times that.

As an alternative, the low-intensity steady-state training is represented by LISS (Low-Intensity Steady State training). It aims not to break out for a long time and shortly but to try to maintain a low intensity. Such as common swimming, hiking, cycling, etc.

It can help eliminate delayed muscle soreness, improve posture, burn fat, and optimize the body’s cardiovascular function. It benefits a variety of fitness methods.

The body composition analysis has become crucial for body health conditions and the technique to do so must be reliable. 3D body scanner has been introduced in the sports or fitness world making the measurement of body fat scales more feasible than ever!

More importantly, for most gyms, although there is already an endless stream of boutique fitness HIIT courses. There is no corresponding heart rate measurement equipment (such as a heart rate belt). Before starting a HIIT course, you must first ensure the health of the training individual. Besides, you will be able to detect various physical indicators in a timely manner.