Basic Knowledge of Exercise for Weight Loss: Heart Rate, Time, and Oxygen – The Three Key Elements of Aerobic Exercise

Of all weight loss methods, exercise is hailed as the "healthiest way to lose weight." While it may not produce immediate results like other methods, it certainly doesn't have the side effects or rebound weight gain associated with them. Moreover, in addition to achieving weight loss, it also provides fitness benefits, which is unparalleled by any other method.

This chapter introduces several commonly used exercise methods for weight loss, such as rope skipping, swimming, running, mountain climbing, cycling, and aerobics, all of which are simple, safe, and effective. However, because exercise for weight loss is relatively slow, consistency is essential.

**Common Sense About Weight Loss Through Exercise**

Exercise can increase basal metabolic rate, causing the body to burn fat rapidly. After each exercise session, the body's basal metabolic rate can remain elevated for up to 24 hours. Therefore, exercising once every two days or three times a week for at least half an hour each time, burning more than 300 calories, will prevent the body's basal metabolic rate from slowing down. When combined with a diet, excess body fat can be effectively burned off.

If you exercise for only 15 minutes at a time, you'll burn carbohydrates, not fat; you'll only start burning significant amounts of fat after about half an hour. The longer you exercise, the more fat you burn, because the primary energy source for continuous exercise is fat, not carbohydrates. Conversely, bursts of intense exercise use carbohydrates, not fat, so this type of exercise is not beneficial for weight loss.

The body's pre-stored ATP energy can only sustain energy for 15 seconds, and it will be completely used up after running 100 meters. When running 200 meters, the energy for the remaining 100 meters must be provided by the rapid synthesis of new ATP from blood glucose under anaerobic conditions, with lactic acid as a byproduct. Sports such as running 200 or 400 meters, 100-meter swimming, tennis, and soccer utilize energy provided by the anaerobic breakdown of blood glucose, resulting in a large accumulation of lactic acid in the muscles after exercise. Lactic acid is the substance that causes muscle soreness after exercise. The blood glucose required for these types of sports is provided by starch, so they do not burn fat and are not beneficial for weight loss.

The energy provided by the anaerobic breakdown of blood glucose can only sustain the energy for 40 seconds, and it will be completely used up after running 400 meters. When running 800 meters, the energy for the last 400 meters must be provided by the synthesis of new energy substance ATP from blood glucose, blood fatty acids, and blood amino acids under aerobic conditions. Blood glucose is supplied by the breakdown of starch, blood fatty acids are supplied by the breakdown of fat, and blood amino acids are supplied by the breakdown of protein. This entire process requires oxygen, that is, oxygen is used to burn starch, fat, and protein to produce the energy substance ATP, which supplies the heat required for the latter part of the exercise. This latter part of the exercise is aerobic exercise.

Running 800 or 1500 meters, swimming 200 or 400 meters, boxing, and other sports all require the use of oxygen to burn starch, fat, and protein at the beginning. Therefore, the latter part of these sports is aerobic exercise.

Aerobic exercise is widely recognized as the best way to lose weight. Aerobic exercise doesn't just refer to aerobics routines; it also includes endurance exercises such as running, cycling, swimming, and rope skipping. Generally speaking, unless there are specific medical conditions, aerobic exercise is very effective for improving cardiovascular function and reducing fat for everyone. The key is to choose the type of aerobic exercise based on your existing physical condition and your personal interests. Below are some basic facts about aerobic exercise; understanding them will help you choose the appropriate exercise method during your weight loss process.

**1. Heart Rate**

Heart rate is the most direct indicator of the effectiveness and intensity of aerobic exercise. Many gym machines have calorie counters. However, in reality, these counters often differ significantly from actual calorie expenditure, and there is no constant ratio between calorie consumption and fat burning. Fat metabolism involves a series of complex biochemical reactions, and heart rate reflects the excitability of the sympathetic nervous system. Sympathetic nerve excitation promotes the secretion of a series of lipolytic hormones, thereby activating lipases, which break down fat stored in adipose tissue into free fatty acids and glycerol. Under sufficient oxygen supply, fatty acids can be further broken down into carbon dioxide and water, releasing a large amount of energy.

So, what heart rate is needed during exercise to effectively lose weight? Generally, it should be between 60% and 75% of your maximum heart rate. Maximum heart rate = 220 - your age. For example, if a person is 30 years old, their maximum heart rate should be 220 - 30 = 190. To achieve weight loss through exercise, their heart rate must reach 190 × 60% = 114 to 190 × 75% = 145, meaning it should be maintained around 114 to 145. Since maximum heart rate is an estimate based on physiological limits, the actual intensity should be adjusted according to the individual. Beginners can usually maintain 60% to 65% of their maximum heart rate. Ignoring your physical condition and blindly pursuing high intensity is detrimental to your health.

**2. Time**

Research shows that muscle glycogen is the main energy source for the first 15 minutes of aerobic exercise, while fat energy supply only begins to start 15 to 20 minutes after exercise. Therefore, aerobic exercise is generally required to last for more than 30 minutes.

**3. Oxygen**

Since fatty acids can be decomposed into carbon dioxide and water and release a large amount of energy under sufficient oxygen supply, oxygen is the key to fat loss in aerobic exercise. Sufficient oxygen intake must be ensured during exercise. However, this does not mean that maintaining deep breathing during exercise will ensure oxygen intake, because the amount of oxygen inhaled does not correspond to the amount of air inhaled. If many people do aerobics together indoors, you can imagine how much oxygen each person can get. Therefore, it is best to do aerobic exercise outdoors or in a well-ventilated indoor environment.

**4. Motion Frequency**

For those without a fitness background, exercising twice a week allows sufficient time for the body to rest and recover from fatigue. An effective aerobic exercise session begins to alter the biochemical reactions in your body. During the rest period, your body adapts to the new metabolic rhythm. After a period of time, you can increase the frequency to three times a week, or at most four times a week, depending on the situation. However, there is no need to go to the gym every day and exhaust yourself.