Post workout, that is, after you have completed your workout/training represents what is known as the critical anabolic window. The physical stress that has been endured by the body during training results in fatigue, a depletion of amino acids in the body, and muscle fibres that have been damaged and pushed to the point of exhaustion.
Straight after your workout your body demands and requires replenishment of nutrients to assist with ithe growth, recovery and repair of its muscles and associated tissue. A post workout supplement is essential to provide this. Creatine supplementation post workout is effective in building muscle size and increasing strength by providing more energy to the muscles (or increasing ATP), thus allowing you to lift more in the gym and achieve your muscle building goals. Creatine shoudl also be taken pre workout for best results.
Further, an essential post workout supplements is Whey Protein. Whey Protein should be consumed within 30 minutes of training to provide the muscles with much needed protein to enable them to begin the process of repair and recovery. Whey Protein Isolate, or WPI, is the most rapid absorbing protein available and is recommended for use by athletes as an effective post workout supplement.