During or after an intense weight training session your body is in a stage of metabolism called catabolism. This is where your muscle fibers are being broken down for the energy required to remove waste during exercise, repair damage caused to the muscles (protein synthesis) and replace used up stores of muscle glycogen. High protein and carbohydrate intake is important after an intense workout with emphasis being placed on complex carbohydrates, protein will very dependent on how intense the weight training session is. The greater the weight training session the greater the demand for protein. If these nutrients are not ingested within the proper time and in the right amount the result will be continued catabolism and tissue break down.