Heh, interesting stuff coming out here. I went to grad school at Univ. of New Hampshire. They have a top-notch Kinesiology dept
(
not what I went for, but I did a lot of volunteer stuff for their studies
). They do all sorts of studies on all sorts of movement stuff.
They had to scrap a funded study on stretching because not enough athletes would agree to not stretch. Which, I think, proves the mental aspect is at least as, and possibly more, strong than the physical aspect
pre-workout. That bold is very important. Let's break it down.
The OP is asking about stretching
pre-workout, if I understand correctly. As has already been stated here, static stretching
pre-workout (which should always be post-warmup
), has been shown to have negligible effect on much of anything. If you like it, it gets you prepped for your workout, do it, by all means! However, the time you spend in
static stretching will be time your body is cooling back down, so ease back into your workout with another warmup period.
As for swimming being a good warmup for running, that, too, has been answered. Warm muscles, heart rate up, good to go. Ease into the running to get your legs firing, then off you go.
Now, some of the responses are talking about stretching
in general. Evidence is fairly well overwhelming on the benefits of stretching both post-workout and as its own "workout." Proper static stretching, after an adequate warmup, is incredibly valuable in all sorts of ways, including just in daily life. Reaching for the can of soup on the top shelf, bending over to pick up the toys, having more energy, etc. etc. While it may not show up as a direct, measurable gain in your times for triathlon, stretching strengthens your muscles without the pounding of running and motions of cycling and swimming
(I'll try to hunt down that link
).
Anywho, summary: stretching warm muscles = good. Running after swimming, go for it. Do what feels good for you, never stretch to pain, and you'll be all set.