Pick up dumbbells with both hands, lift them to shoulder height, and then do expansion exercises with both hands. When lifting dumbbells horizontally with both hands, the dumbbells must touch each other, and when unfolding backwards, open your hands and align with your body. Remember, dumbbells can't be put down. You should finish the extension exercise you started talking about while holding the dumbbell horizontally all the time. Just do it twice a day, once in the morning and once in the evening. 10 should be able to see the effect. If you are thin, the dumbbell should be 10 kg per hand. If you are strong, the dumbbell in each hand should be no less than 15 kg. Of course, if you think the dumbbell is too light, you can add weight yourself.