Stretching to Aid Growth
When your goal is to build muscle, flexibility is also important for several reasons. Flexibility in your muscles and joints will allow for optimal flow of blood and nutrients into the areas being worked. This will help to repair muscles and get rid of waste products produced during exercise.
Stretching Between Sets
In between sets is a good time to stretch. Not only does it allow you to do something productive while you are resting, it will also enable you to perform the next set in a more optimal fashion. This is because stretching the muscles after a set helps to remove lactic acid which is what causes the burning sensation when training, thereby helping you to recover for the next set.
When to stretch?
Always do some type of warm-up for 5-10 minutes before stretching. It is acceptable to stretch before and after exercise(time permitting). I recommend stretching after the exercise to decrease soreness and improve flexibility as well as prevent injury.
Full Range of Motion for Stretching Muscles
When performing exercises, it is important to perform them through the fullest range of motion possible. This will cause your body to recruit more muscle fibers as well as to stretch the muscle being worked in a dynamic fashion, particularly on the eccentric or lengthening phase of the movement.
Stretch Tight Muscles Before Stregthening Weak Muscles
If you have a group of opposing muscles, one of which is tight, and the other which is lengthened and weak, such as the pecs being stronger than the muscles in the back, then, before working the longer,weaker muscles stretch the short tight muscles. This helps correct the imbalance and develops symmetry in your physique.
Symmetry and Stretching
Another important reason for stretching is to aid in balanced muscle development throughout the body. If one group of muscles is tight and overdeveloped, while another is lengthened and underdeveloped, not only will this look poor aesthetically, but it will contribute to potential future injury. For example, overworking the chest, relative to the back will cause you to have rounded shoulders and look like a gorilla, in addition to causing low back problems.
Typical Tight Muscles to Stretch
There are certain muscle groups which are notoriously tight in a number of people. They are hamstrings, calves, low back, pectorals, neck extensors, upper trapezius.