I believe in stretching briefly between sets of exercise to allow for an active rest/recovery period. This increases flexibility and range of motion. I also feel stretching is an important aspect of the mind/muscle connection and brings awareness to sensations within the muscles.

Although I do not believe in stretching as a warm-up because this may lead to tiny tears and weakened muscles.

As we see here, research and athletes still haven't come up with a definitive answer on what the true benefits and drawbacks are.

If your goal is to prevent injury, Dr. Gilchrist said, stretching does not seem to be enough. Warming up, though, can help. If you start out by moving through a range of motions that you’ll use during activity, you are less likely to be injured...

Stretching the hamstring muscle, for example, teaches the muscle to relax when the knee is fully extended, Dr. Kenny said. But that is not what a runner needs. Instead, runners need to have their hamstrings stiff and activated when the knees are extended.

So for now, keep stretching those warmed-up muscles between sets of exercise, don't overstretch to cause tears, and don't bounce the stretches. Bouncing a stretch may induce a stretch reflex in which the muscle will suddenly contract to protect itself, and instead, creates injury.

Listen to your body, do what feels good, and always exercise safety first.