Its important to loosen up your muscles before training, it increases your temperature and increases blood flow to your muscles, giving you a boost of energy, Its like winding up a spring..Warming up can also help reduce muscle soreness and lessen your risk of injury.
Stretching after exercise is required to place your muscles back to where they were before you trained. To seat them correctly. If you don,t, you could cause muscle cramping and pain.
And very unsatisfactory in the long term.. So very important
Good Training