1. Hand Taiyin Lung Meridian: This is a meridian that starts from the chest, passes through the arm and finally reaches the finger. When practicing the spiral arm, the arm swings up and down, rotates and stimulates this meridian.

2. Hand Yangming Large Intestine Meridian: This is a meridian that starts from the finger, passes through the arm, and finally reaches the head. When practicing arm flexion, the up-and-down swing and rotation of the arm will also stimulate this meridian.

3. Hand-Sun Small Intestine Meridian: This is a meridian that starts from the finger, passes through the arm and finally reaches the head. When practicing arm flexion, the up-and-down swing and rotation of the arm will also stimulate this meridian.

4. Three-way meridian of hand shaoyang: This is a meridian that starts from fingers, passes through arms and finally reaches the head. When practicing arm flexion, the up-and-down swing and rotation of the arm will also stimulate this meridian.

5. Pericardium Meridian of Hand Jueyin: This is a meridian that starts from fingers, passes through arms and finally reaches the heart. When practicing arm flexion, the up-and-down swing and rotation of the arm will also stimulate this meridian.

Generally speaking, Tai Ji Chuan's first arm bend mainly acts on the meridians of human hands and upper limbs, including lung, large intestine, small intestine, triple energizer and pericardium.