Many people think that the longer you exercise every day, the better. Let's hear what the experts say.

Zhang Ming

August 8, 2024 is the 16th National Fitness Day in my country. Life lies in exercise, and exercise requires science. When you sweat and work hard to exercise, you must also pay attention to scientific methods and methods. The following fitness misunderstandings must be avoided.

Does fat burn after 40 minutes of exercise?

There are three major energy substances in the human body, which are used by three major energy metabolism systems to provide the energy needed to maintain vital signs and carry out physical activities. The three major energy substances are sugar, fat and protein, and the three major energy metabolism systems are the phosphagen system, the glycolysis system and the aerobic system. Among them, only the aerobic system can use the three major energy substances to provide energy. In any exercise (including anaerobic exercise), the aerobic system is providing energy to the body, and there is no exercise that is only powered by one energy substance. It's just that in exercises of different intensities, the body uses different proportions of sugar, fat and protein for energy. Usually, the longer the exercise time and the relatively low exercise intensity, the greater the proportion of fat oxidation energy supply. Therefore, most people choose long-term aerobic exercise as a way to lose fat.

In fact, the human body is burning fat all the time, and most of the energy consumed in daily life comes from fat. Even when lying quietly, the body's energy supply mainly comes from fat, but at this time the body needs less energy, the fat burning rate is low, and the consumption is not obvious.

Will regular running make your calves thicker?

Many people feel soreness in the calf muscles after running for a long time, and mistakenly think that their calves have become thicker. This is actually due to the frequent exertion of the calf muscles, fatigue and increased blood flow, which creates an illusion. As long as effective stretching is performed, this feeling will gradually disappear. In fact, long-term long-distance running training can also make the calves thinner.

To achieve the effect of changing your body shape through long-distance running, it is recommended that you regularly do aerobic running for 30 minutes or more, and stretch your muscles after running. We can use steps to do straight leg dorsiflexion, use walls to do bent leg dorsiflexion, and use stools or railings to do back leg plantar flexion to relieve discomfort after exercise.

The longer the exercise time, the better?

Exercise is good for health, but the longer the exercise time, the better. Quality is always more important than quantity. After each exercise, our joints and muscles will repair themselves. But if the exercise frequency is too high, the joints and muscles cannot recover in time, which can easily cause injuries. For example, chronic injuries such as "tennis elbow" and "meniscus wear" that everyone is familiar with, and even acute sports injuries such as "Achilles tendon rupture", are mostly due to the gradual accumulation of chronic injuries caused by long-term excessive exercise, which manifests in the form of acute pain. Therefore, it is particularly important to control the frequency and duration of exercise. According to the "Healthy China Action (2019-2030)": It is encouraged to carry out moderate-intensity exercise more than 3 times a week, more than 30 minutes each time, or a total of 150 minutes of moderate-intensity or 75 minutes of high-intensity physical activity.

Is fasting more effective in reducing fat?

The so-called "fitness on an empty stomach is more effective in losing weight" is a misunderstanding. Although fitness on an empty stomach can consume more calories in a short period of time, it is easy to cause insufficient energy supply to the body if the duration is too long. For some patients with chronic diseases, especially those with diabetes, it is not scientific and harmful to the body to exercise on an empty stomach. When exercising on an empty stomach, a large amount of free fatty acids will be produced in the blood, which may cause acidosis and arrhythmia, and even lead to sudden death. Therefore, people with poor gastrointestinal function, prone to hypoglycemia, people over 60 years old, as well as patients with diabetes and heart disease should not exercise on an empty stomach. It is recommended that such people try to add a meal before exercising in the morning. It is recommended to eat easily digestible carbohydrate bread, biscuits, rice porridge, etc., or eat an egg and drink a cup of yogurt. It should be noted that you should not eat too much before morning exercise. As long as you don't feel hungry, it is fine. It is not recommended to eat too much fat and dietary fiber.

Is it only effective if you sweat profusely?

Generally speaking, the greater the intensity of exercise, the more sweat you produce. This is because as the intensity of exercise increases, the human body will produce more heat and a large amount of metabolites - carbon dioxide and water. In order to maintain normal body temperature, the human body must increase the amount of sweat to dissipate the excess heat. Therefore, the intensity of exercise is directly proportional to the amount of sweat.

However, you should not exercise just for the sake of sweating. Excessive exercise intensity may cause high blood pressure, increased heart rate, myocardial ischemia and hypoxia, and physical exhaustion. For ordinary people, the maximum heart rate for men is "220 minus age", and the maximum heart rate for women is "210 minus age". The safety warning line for exercise is 75% of the maximum heart rate, and it should be lower for the elderly.

The manifestations of appropriate amount of exercise are: moderate sweating, slight fatigue, slight comfort after exercise, pulse recovery within about 10 minutes, good appetite and sleep, and full of energy the next day. If there is a lot of sweating, palpitations and shortness of breath, extreme fatigue after exercise, poor appetite and sleep, pulse cannot recover within about 15 minutes, general weakness the next day, and lack of interest in exercise, then it is a manifestation of excessive exercise. Although fat people sweat a lot during exercise, their ability to tolerate water loss is relatively poor. In other words, if the exercise time is not long, fat people will become tired prematurely due to metabolic disorders. If you are a person who sweats profusely after a little exercise, you should see a doctor as soon as possible.

(The author is an associate researcher at the Institute of Sports Science of the State Sports General Administration)