Regrowing the Tendons
The true strength of the body is held and expressed through the tendons, rather than the muscles. Over the long term, the tendon strength holds up and requires much less maintenance and caloric fuel than building muscles. The practice of strengthening the tendons also allows the joints to open, grow stronger, and store more energy. The raw energy that is stored in the tendons and joints can be transferred into higher spiritual and creative energy.
Iron Shirt 2, or Tendon Nei Kung, involves a series of moving postures that stretch and open tendons along the major tendon lines of the body. Some of the major tendon lines that benefit are the pinkie, thumb, and tendons of the wrist. Tendons are connected throughout the body, so these postures create tendon strength and joint opening for the whole being.
-From The Alchemist’s Tao Te Ching