The subject of "stretching", as it applies to muscular hypertrophy is not commonly discussed – although it certainly should be. Why? Because performing stretches at the wrong times can actually hinder progress by decreasing performance, as well as cause injuries like "pulls" and "strains". Conversely, well-timed, specific stretches can set the stage for accelerated muscle growth!
I am not exactly sure when this myth started, but the majority of exercisers still believe that they should perform static stretches (note: dynamic stretching is a different subject) prior to lifting weights - however, this is a mistake!
Stretching a "cold" muscle can result in injuries ranging from minor strains to actual tears - not a great way to begin a workout! And if that is not enough to prevent you from stretching as soon as you get into the gym, then ponder this fact: Research indicates that stretching the muscle you are about to train (or are currently training) can cause a significant loss of strength during all of your lifts (for that body part)!
Thus, while stretching may feel good, and help to increase blood flow a bit, you would be better off giving the target muscle a light massage between sets instead.
So, rule #1: Do not stretch the muscle you are about to target prior to starting your workout. And rule #2: Do not stretch the muscle you are in the middle of training during the workout.
Now, before I move forward, I should mention that utilizing stretches correctly during a workout will actually increase strength and improve recovery between sets, allowing one to lift heavier, and/or achieve more reps.
The key lies in stretching the antagonistic muscle (to the one you are working on) rather than the one being targeted. For example, it is advantageous to stretch the hamstrings after each set of leg extensions, the biceps after skull crushers, or the lats after bench presses.
What about after training a specific muscle? Are there any advantages to stretching the body part you just smashed? Absolutely my fellow gym rats!
One of the most underutilized "secrets" in the world of bodybuilding is the use of intense stretching of the trained muscle immediately after completing your workout for it.
Now, when I say intense stretching, I do mean that it should sting quite a bit (although you must know your body well enough to realize if you are going too far), with each extreme stretch lasting for 30-60 seconds before slowly being released.
Some examples of intense stretching would be holding the bottom of a chest fly while grasping moderately heavy dumbbells, hanging from a chinning bar with a close (V-handle) grip while having an assistant pull down on your waist, or lowering into the deepest stretch position of a sissy squat.
In other words, you have to be willing to push beyond the light stretching you might normally be used to in order to make this technique maximally effective.
At this point you may be asking, "So how does this extreme stretching help ignite hypertrophy."
Studies have demonstrated that this specific form (and timing) of stretching can actually hasten anabolism via greatly increased activation of satellite cells and the enhanced release of powerful growth factors (hepatocyte growth factor, myogenin, IGF-1) within muscle tissue. Sounds to me like an easy-to-use, valuable tool to put into your arsenal of hypertrophy heighteners!
So, to summarize what I discussed above: Don’t stretch a cold muscle before training, and don’t stretch the muscle you are in the middle of training. However, DO stretch the antagonistic muscle to the one you are targeting during your workout, and once the session for the body part is complete, finish it off with two or three intense 30-60-second-deep stretches.
Getting muscles to grow is not easy, so it is vital that you make sure and approach hypertrophy through every pathway and mechanism possible.