The first way to thin your arms is to hold dumbbells or mineral water bottles filled with water in both hands and hang them naturally at your sides. Lift your arm up slowly. When your arm is perpendicular to the ground, your arm is close to your ear, and your arm swings back slowly until your body can bear it to the maximum. Then slowly put down your arm forward. Repeat the exercise 15 times. If you feel sour after practicing your arm, it proves that the action is in place. Do it 45 times a day and practice it 3 times a day. The second way to thin the arm is to lift the right arm and bend it backwards until the palm is placed on the left scapula. Lift your left arm, press the elbow joint of your right arm with your left hand, and keep this action for 10 second, then put down your arms and repeat the action with your left hand. Repeat the exercise 20 times a day. The third method is to stand with thin arms and feet open, and the width is about shoulder width. Straighten your hands forward, straighten your upper body, and use the strength of your arms to rotate your hands clockwise and counterclockwise at the same time, 20 times in each direction. Keep practicing every day. When drawing a circle, remember to use the strength of your arm, not your palm. If you feel sour after practicing your arm, it proves that the action is in place. The fourth way to thin your arms is to adjust your breathing and stand on your knees. Inhale, with your left hand straight up and perpendicular to the ground. Put your right hand behind your head and grab your left elbow. Inhale and press your left arm down for 5 seconds. Exhale, the left arm grasps the right elbow, forming a posture of holding the elbow with both hands. Put down your hands, then raise your right hand and repeat the action. Repeat 10 times on each side. After repeated practice, keep your elbows behind your head. Inhale, stretch your arms out vigorously, and keep your hands in the elbow position. Keep this action 10 minute. Exhale, lower your arms and relax. This method can not only thin the arm, but also tighten the back muscles, soften the shoulder joint and prevent scapulohumeral periarthritis. It is very suitable for women who sit in the office all day.