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.

The second secret of thin arms:

Lift the right arm, bend the left scapula to the back, press the joint of the right arm with the left hand, touch the left scapula, then lift the right arm and change sides from left to right. Do this 20 times a day.

If you feel sore in your arm when you first do it, it means you have moved to that part.

The third secret of thin arms:

1. Stand with your hands straight forward and your feet shoulder width apart.

2. Draw a circle with both hands and draw a circle outward for 20 times. 3. Draw a circle inward 20 times.

4. Don't draw too big a circle, use the strength of your arm, not your palm.

The fourth secret of thin arms:

1. Stand up straight, spread your feet about shoulder width, spread your arms to both sides, and slowly turn forward. The point is to tighten the muscles on the upper arm.

2. Stand up straight, spread your feet about shoulder width, spread your arms to both sides, and turn around slowly. This is mainly to tighten the muscles of the arms and chest.

Don't draw the circle too big, so as not to hurt the joints of your shoulders.