The A2 pulley keeps your flexor tendons close to the bone. It takes the highest stress in crimping, is sensitive to angle drift, and fails when load increases exceed structural adaptation. Stable angles and slow progression protect it.

PIP and DIP joints control the shape of the finger and therefore the path of force. Angle instability, not load, is the main cause of pulley stress and tendon overload in climbing.

The force line is the path load takes from muscle to bone. Joint angles, hold size, and pulley direction determine how force is distributed. Sharp angles overload structures; smooth angles protect them.

Finger strength relies on two flexor tendons and a series of pulleys that guide them. The PIP and DIP joints determine force distribution, and understanding this structure is essential for safe, effective finger training.