If you are just starting to practice, take 10 kg first, which may feel a little light, but you can do it 50 times in a row! It is best to do it at high speed. If you are tired of the explosive power of your muscles, rest with your other hand. Besides, dumbbells can be used not only to lift weights, but also to practice boxing and swing rackets. When you feel that your arm is almost bent, increase the weight. If you start practicing, 20 Jin is definitely too heavy. I often exercise. Now, you can't lift 50 times in a row for 20 pounds. At the beginning, you may use up all your strength, but this will not only put too much burden on your muscles at once, but also make your muscles stiff and not explosive. If you just start practicing, the effect will be obvious. The next day, your muscles will be very sore because of the necrosis of a large number of old muscle cells. When new ones grow, they will become stronger and stronger. If it is not sour, it means that you are lazy or too strong. 10 kg is no longer enough for you. If you don't have dumbbells, you can also do push-ups and do them casually on the ground. Slow down when you go down and accelerate when you come up. Besides experience, the most important thing is persistence. Starting tonight, do it for half an hour before going to bed every night.