When is best to do stretching exercises in order to help building up muscle? Any times one should avoid or concentrate on?
My soccer coach has always taught to do dynamic stretches before workouts and static stretching afterward. If you do static stretching before you work out you actually are at risk in straining your muscles too much, but if you do it afterward it helps work out the lactic acid in your muscles so they become stronger and if you leave the lactic acid in you it can slow you down in the long run, ( for example: If you're in a season and you don't get all the lactic acid worked out your next training/game will not be your best performance) My team stretches about 10 minutes dynamically before hand and 30 minutes after, static stretching afterward also helps with flexibility
Well, AFAIK stretching exercises are best to be done after you have done your workout. Tiny rips are made in the muscle(which are not painful, nor dangerous) and the body needs to heal them. The muscle grows because it needs to strengthen the muscle fibers in order to prevent other tiny rips.