How long is the best time to run for aerobic exercise?

Let’s get straight to the conclusion: There is no “optimal duration” that can apply to everyone, but for healthy adults with no underlying diseases and no usual exercise habits, running for 20 to 60 minutes in a single session and accumulating 150 minutes of moderate-intensity running per week is currently the reference standard with the highest consensus among the sports medicine community and the general public. As for those who have clear needs for muscle gain and competition preparation, or those with old injuries or basic diseases, they can adjust according to their needs. There is no need to stick to this range.

Some people may ask, where did the lower limit of 20 minutes and the upper limit of 60 minutes come from? In fact, it's not determined by experts' heads. People who have actually run have a sense of it. When I first started running, I ran continuously for the first half month. Every time I went out, I was out of breath like a bellows, and all I could think about was "Why don't I lie down at home and drink milk tea?". My legs felt as heavy as lead. After running for about 20 minutes, I suddenly came around. The feeling of the wind blowing against my ears became more comfortable, and I didn't feel tired anymore. Later, after checking exercise physiology, I found out that the body mainly relies on glycogen for energy supply in the first 20 minutes, and it takes about 15 to 20 minutes to switch to a stable aerobic state where glycogen and fat are mixed for energy supply. If you run for 15 minutes and then go home, it is not that it is ineffective, but the aerobic efficiency is cut off as soon as it rises, and the price/performance ratio is indeed not high. Of course, if you are a novice who has not done anything for several years, running for 10 minutes and walking for 5 minutes at a time is totally fine in the first week or two. However, if you insist on running for 20 minutes, it will easily injure your knees and dampen your enthusiasm. The gain outweighs the gain.

As for the upper limit of 60 minutes, it does not mean that running for more than an hour will hurt the body. It is just that for ordinary runners, the marginal benefit will decline rapidly after exceeding this time. First, cortisol levels will rise, and the rate of muscle breakdown will catch up with the rate of fat consumption. If you originally wanted to save some muscle, you will lose money if you run for too long. ； In addition, after weight-bearing joints such as knees and ankles are repeatedly stressed for an hour, the risk of wear and tear will also increase significantly. There are several Buddhist runners around me who run a 10-kilometer pace of 6 and a half minutes every day, which takes about an hour. After running, they feel so comfortable that they can take a shower or eat cold noodles without any burden. Occasionally, they can run 15 kilometers on weekends when the mood strikes. But if I force myself to run for an hour and a half every day, within half a month, I will either have knee pain or mental exhaustion, and I will not even be able to cheer up for work. Of course, this upper limit does not hold true for professional runners. I know a brother who runs ultramarathons. His daily training starts at 3 hours. He has core and lower limb muscles that have been cultivated for many years, and he also has a mature supply strategy. Ordinary people should not learn it forcefully. If they fail to learn it, they will easily end up in the hospital.

If you are running to lose fat and your physical fitness can keep up, you only need to run for 35 to 45 minutes at a time. You do not need to run every day. If you run 3 or 4 times a week, with two strength training sessions in between, you will lose fat much faster than running for an hour every day. I had a colleague who ran for an hour every day for 20 days to gain body fat for a wedding photo shoot. He lost 1.8% of his body fat but had fluid in his knees. He even wore knee pads when he took the wedding photos, and he regretted it so much. If you run purely to relieve stress, you don’t need to limit your time. If you run around the park for 20 minutes after get off work and sweat a little, your mind will be clearer than sitting in the office with the air conditioner blowing all afternoon, and it will be more effective than drinking three glasses of iced Americano.

By the way, if you have high blood pressure, knee arthritis or other basic diseases, don’t blindly search for criteria and get stuck. It’s best to find a rehabilitation therapist or doctor to tailor a plan for you. I have a runner who suffers from degenerative arthritis. Now he runs for 15 minutes each time and relies on the elliptical machine to make up the rest of the oxygen. He can still achieve the effect of exercise without hurting his joints.

In fact, to put it bluntly, running is a very relaxing exercise. There is no need to stick to a stopwatch to make up for the time. I am in good condition today and run for 10 minutes. If I stop running for 15 minutes today, it is not in vain. Those who insist on making up 30 minutes every second or less will take away the fun of running. After all, exercise that can be sustained for a long time is the best exercise.