For what I know, cooldown is okay and a bit useful after a hard endurance training, in example, intervals or some other constant high pulse exercise. But I have never thought it as absolutely necessary. Or at least is it necessary to actually think about the issue and always save time for it. It might be also good to get the all the lactic acid and other waste off your legs and other muscles with lighter work and this cool down. I think this problem could be a bit overaexaggerated here, as it might cause something and can, in the worst and rarest case, lead to something bad. Stretching for sure ain't a must, and when it's done inproperly, it might cause more damage than it actually helps.
Every endurance exercise
This caught my eye. I for one don't take cooldown so seriously because I don't think I'm training in the actual zones where I would need to cool down. My average pulse for a workout is somewhere along 145 or below, and only in rare cases I have to breath more heavily. Never exhausted after a work out. So it's not too much of an endurance exercise. But is my usual running exercises either? What is considered as an endurance exercise to fit the previous standards? It must take higher heart rate or far more duration in running for you to actually faint or have heart problems when you stop. And also does your own endurance effect on the reguirement of a cooldown? Ain't my circulatory and respitarory systems more accustomed to hard exercises, and then better at adjusting the blood flow and breathing when, in example, comparing to some obesed non-athlete?
After running, for example, a slow, restful walk for several minutes helps prevent blood from pooling in the extremities
Many people, me including, already do this on common basis. I usually walk, dress up and ride my bicyle home. That's all the cool down I need. I would say there are many cases where this already happens without people actually noticing. It's hard to imagine someone who actually stops moving for several minutes straight after endurance exercising.
So yeah, I'm a little sceptic but if someone who knows more can share some light on this issue. I would remember this topic has been mentioned here before a month back or so.