What does aerobic exercise mainly consume?

From the perspective of energy supply substrates, mid- to low-intensity aerobic exercise mainly consumes glycogen and fat in the body, and a very small amount of protein participates in energy supply. The consumption ratio of the two will fluctuate with the duration and intensity of exercise, and there is no absolute fixed ratio.

I have been running for three years. When I was preparing for the half-marathon, I looked at the energy supply data of the sports watch every day. The physical feeling was particularly obvious: when the pace was stable at 6 and a half minutes and the heart rate was stuck at about 65% of the maximum heart rate, the proportion of glycogen energy supply in the first 30 minutes was basically 6. Above 0%, most of it is muscle glycogen stored in muscles, and a small part is liver glycogen used to stabilize blood sugar. Last time I measured my fasting blood sugar before running and it was 5.2. After running for 30 minutes, it dropped to 4.4. This is because liver glycogen has been mobilized. If you continue to run for an hour, the proportion of fat energy supply will exceed 55%. The last time I ran the half marathon, I was so hungry that I wanted to eat a buttered European bun. This is because glycogen was depleted and the second half of the race was completely dependent on fat for energy supply.

However, there has been a lot of quarrel on the Internet about aerobic consumption. The most common controversy is that "the first 20 minutes of aerobic exercise only consumes glycogen and does not burn fat." Some people say that this statement is completely a rumor. The sports watch I wear shows that the energy supply ratio of fat is about 30% when I walk for 5 minutes. It is just a low ratio. There is no situation where it is not consumed at all.； The other school actually simplifies the expression. What they want to express is "after 20 minutes, the proportion of fat energy supply exceeds that of glycogen, and the fat loss efficiency is higher." In fact, there is no fixed value at this time inflection point. People who have exercise habits all year round have high glycogen utilization efficiency, and the proportion of fat energy supply may increase in about 15 minutes. People who rarely move may take 30 minutes to reach the inflection point, and they cannot be stuck for 20 minutes.

In fact, if you give an analogy, you will understand. Glycogen is like the change you carry in your coat pocket. You can use it when you take it out. It is convenient but the stock is limited. If you just go downstairs to buy water or walk around the community for a short period of time, you can basically spend the change.； Fat is like the money you deposit into your bank card. You have to go through two more steps to redeem it when you withdraw it, but the deposit is very sufficient. If you go out for a whole day or run a long distance, you will definitely spend most of the money in your bank card later. As for the protein consumed, it is equivalent to selling the small silver jewelry hanging on the keychain for two steel pennies when you really have no change. The amount consumed under normal exercise intensity is minimal, and you don’t have to worry about losing muscle after running a few times.

If you want to burn more fat with aerobic exercise, you don’t have to endure the exercise for a long time. Keep it at an intensity that allows you to speak normally but not sing smoothly. It’s very efficient if you exercise for about 40 minutes. If you really can’t spare the time, you can stand more, take two less subway stops and walk two more steps. If you add up, you can burn a lot of fat.