Yes, there is also the first secret of thin arms: often do some scientific sports of swinging arms, such as playing badminton, tennis, squash and so on. Girls mainly recommend playing badminton, while boys can actually do some comprehensive sports, such as playing basketball. The second recipe for thin arms: 1. Take a dumbbell or a bottle filled with water (or sand) and straighten it from front to back. Remember to do this next to your ear. 2. Put it down slowly and repeat this action fifteen times. When you finish, your upper arm will feel sour. That's right. Do it forty-five times a day, separately.