High-intensity interval training (HIIT) usually refers to high-intensity exercise in a short period of time, followed by a period of low-intensity exercise or rest. Studies have found that high-intensity exercise in a short period of time can improve fat burning better than high-volume endurance training. Sprinting is a good example. Sprinting is intense exercise in a short period of time, followed by walking or rest. The most commonly used program is the Wingate protocol: do 4 to 6 30-second high-intensity sprints with a certain degree of difficulty, rest for 4 minutes each time, train 3 days a week, and continue for 2 to 6 weeks. This method looks simple, but it is very effective.
Benefits of high-intensity interval training (HIIT)
- Fat loss
After HIIT exercise, excess oxygen consumption (EPOC) will occur in the body, which will last for 12-72 hours, and the largest energy source of EPOC is fat. It can achieve the effect of lasting fat loss.
- Improve aerobic exercise endurance
HIIT will quickly increase the body's maximum oxygen uptake and hemoglobin content, thereby improving aerobic endurance.
- Lower heart rate
HIIT is a high-intensity exercise. During exercise, the heart rate is required to reach more than 85% of the maximum heart rate. Some movements will reach the maximum heart rate, which is a great challenge to the cardiovascular system. The cardiovascular system will also undergo adaptive changes. The content of myocardial contractile protein and myoglobin increases, a large number of capillaries in the myocardium are newly formed, the blood supply increases, the myocardial fibers become thicker, the myocardium becomes thicker and stronger, the heart contraction force increases, the heart capacity increases, and the heart's stroke volume also increases. As the myocardial strength becomes stronger, the heart capacity increases, and the stroke volume increases, the heart's diastole will be prolonged, and the myocardium can get enough rest to avoid overwork. This is also called exercise-induced sinus bradycardia. The average heart rate of an adult is 75 beats per minute, and the normal range is generally 60 to 100 beats per minute. When an athlete is at rest, the heart rate can be lower than 60 beats per minute, and some athletes can reduce their heart rate to 36 to 40 beats per minute at most. The heart is energy-saving.
- Increase lipase activity
After HIIT exercise, adrenalin, growth hormone and norepinephrine in the body accelerate the transport, decomposition and excretion of lipids.
- One of the most effective ways to control visceral fat and subcutaneous fat.
Many studies have shown that compared with aerobic and anaerobic exercise, HIIT exercise is most effective in controlling visceral fat and subcutaneous fat, especially reducing abdominal fat.
- Improve cardiopulmonary function
Cardiopulmonary function is the ability of the human heart to pump blood and the lungs to inhale oxygen, and the ability of both directly affects the activities of organs and muscles throughout the body. It is the source of human power. Its quality is the most core indicator for assessing cardiovascular diseases, respiratory diseases, endocrine diseases, etc. HIIT exercise can quickly improve cardiopulmonary function.
- Enhance the ability of nerves to control muscles
The advanced stage of HIIT is a series of complex movements. These movements require changing the state of the body in a very short period of time, and require a high ability of nerves to control muscles.
- Improve coordination and agility
There are many coordination and agility exercises in the HIIT action library, such as rope ladder training, multi-point training, etc. Long-term training will enhance its agility and coordination.
- Shape the body
Most of the HIIT actions are freehand exercises. It can not only enhance the strength and dimension of large muscle groups, but also maximize the exercise of small muscle groups, making your body more stable and controllable. The muscles trained in this way will not be too stiff, and can integrate strength, speed endurance, agility and coordination.
Scientific research behind HIIT
A study in the Journal of Applied Physiology found that 7 HIIT training sessions over a 2-week period can improve the burning state of body fat and increase the ability of skeletal muscle to burn fat. Many studies have shown that HIIT can not only reduce subcutaneous fat, but also reduce visceral fat.
An article in Cancer Research pointed out that women who exercise moderately for 45 minutes 5 times a week can not only reduce 2% of body fat, but also significantly reduce serum estrogen. Serum estrogen is the main cause of breast cancer, endometrial cancer, and ovarian cancer in women.
Studies published in the British Medical Journal and the Journal of Oncology show that high-intensity exercise can improve cardiopulmonary function, muscle strength, aerobic metabolism and mood, and can also reduce fatigue in patients undergoing chemotherapy for advanced cancer. A study in Physiological Reviews found that short-term, high-intensity exercise for several hours can enhance the activity of natural killer cells (a type of white blood cell that can kill cancer cells).
HIIT is also better than moderate-intensity aerobic exercise for heart disease. A study in the Australian Family Physician and Circulation journals suggests that HIIT can reduce low-density lipoprotein cholesterol while increasing high-density lipoprotein cholesterol. HIIT can also improve endothelial cell function, blood pressure, left ventricular function and glucose regulation.
HIIT is also a special exercise method for regulating insulin, growth hormone and glucagon. Studies in the European Journal of Applied Physiology, the Journal of Applied Physiology and the Journal of Nutrition and Metabolism have all shown that intense exercise can increase the release of growth hormone, which helps balance insulin and glucagon. The growth hormone released after exercise, like glucagon, burns fat and helps build muscle.
Exercise smarter
When we carry out a specific exercise plan, please think about what kind of exercise is suitable for your body first, and make sure that there are no health problems that affect exercise, or make sure that the exercise you choose can improve your health. Therefore, before you start, you may need to consult an experienced health care physician.
Here is a relatively effective exercise method that only takes 20 minutes each time and can be done on a treadmill at home.
Turn on the machine and start walking at low intensity (level 2) for 2 minutes. This slow walk is an adaptation to the machine and also a warm-up exercise; after 2 minutes, increase the speed of the treadmill to medium intensity (level 4 or 5), which is from fast-paced walking to super-fast walking or jogging, and this speed lasts for 1 minute; then do high-intensity exercise, increase the speed of the machine to level 8 or 9, and run at the fastest speed for 1 minute. At this time, the heart rate will rise and the muscles will feel swollen. When the time is up, slow down quickly and return to the low-intensity state at the beginning for 2 minutes. Repeat this step 5 times, and then relax yourself with 3 to 5 minutes of low-intensity walking, or just walk on the treadmill for a while, and then take a short break. Over the next few hours, your body will begin to burn fat.
Whatever your exercise, figure out how to do low-intensity, moderate-intensity, and high-intensity exercises in phases. HIIT can be done on a bike, treadmill, vibration machine, or other exercise machine, or you can do it on your feet.
When is the best time to exercise?
Whether you are doing HIIT, weight training, or any other form of exercise, do not do it on an empty stomach. The safest time to exercise is 1 to 4 hours after a meal. If you do not eat before exercising, you may not have enough energy to exercise, and cortisol will break down muscle while maintaining fat because the brain cannot use fat for energy.
Some studies have found that exercising in the afternoon is best, while others recommend exercising in the morning. Try to avoid exercising in the evening, which can increase cortisol and disrupt sleep. Choose a time of day that works for you, and plan to eat a snack or a small meal with protein and some form of complex carbohydrate at least 1 hour before exercising. If you eat too much or too soon before exercising, you may feel nauseous. Be sure to eat a serving of protein and a serving of carbohydrates after exercise to prevent the effects of cortisol and to provide glycogen (muscle glycogen) to your muscles.
