Yi Jin Jing(易筋经Yìjīnjīng) is another form of exercise handed down from ancient times. In Chinese yi means change, jin means "tendons and sinews", while jing means "methods". This is a relatively intense form of exercise that aims at strengthening the tendons and muscles, so promoting strength and flexibility, speed and stamina, balance and coordination(Co-ordination is the ability to use the different parts of your body together efficiently) of the body.
This exercise pays great attention to the coordination of movements, respiration and mind so as to guarantee(something that is a guarantee of something else makes it certain that it will happen or that it is true) that qi circulates freely and smoothly. As with most exercises, there is an enormous variety in form, the most popular being the "12-postures of Changing Tendons" devised by Pan Wei in the Qing dynasty (AD 1644-1911). See the picture below for reference.