Well, as you guys know I'm all in favour of studies and books. But I'm also in favour of experience. As
Rippetoe points out,
"We all know that 40 milligrams of Dianabol a day is a pretty effective dose for a weightlifter. How many peer-reviewed studies support this? Zero. How many anecdotal reports? About a hundred thousand. You're an idiot if you avoid anecdotal data, pure and simple."
Recent studies tell us that back squats put more shear force through the knees than front squats [
source 1], that Valsalva offers no benefit compared to forced exhalation [
source 2], and that
"the squat, regardless of technique variation, produces minimal activity in hamstring muscles" [
source 3].
These are all things which experience tells us are nonsense. So when a study or ten tell me that stretching after a workout has no effect on DOMS, well I'm happy to stick to experience.
My experience of a decade's workouts in the military, and my experience of training others now in civilian life, tells me that people who stretch after a workout tend to suffer less soreness the day after that workout than people who don't.
My experience is also that the bouncy short duration and/or "dynamic" stretching
before a workout is worthless for most people. However, people who are particularly stiff with a reduced range of motion may benefit from static longer-duration stretches before a workout to improve that range of motion.
Most of those who stretch do the bouncy momentary one, and don't get a proper stretch; this will definitely help neither with recovery nor with flexibility. They then conclude that stretching is useless. This is rather like those who squat with poor technique, and then conclude that squatting is bad for their knees and doesn't work their legs much.