The Navy Physial Fitness Test requires sit and reach, situps and pushups, and a 1.5 mile run. I used to laugh every time because NOBODY ever warmed up before the run. Just try maxing out on pushups and feel how pumped your arms are, and then run an all out 1.5 mile. It takes a little extra time to divert the blood down to the legs, no doubt contributing to accelerated oxygen debt. I used to try and explain how a few strides down the road prior to the run portion would benefit them in the run, but nobody ever took me up on it that I can remember.
A couple of weeks ago I ran very well in a 5K- the best I have felt in a long time. Besides stepping up my long runs, another difference was that a small group of us did 2.4 miles prior to the 5k in memory of Ryan Shay, taking us to 5.5 miles. This was about double my normal warm-up jog.
Was that the difference? Who knows, but I think it's worth repeating to find out.