Ever noticed how pumped your legs are after a good, hard effort? That's a lot of blood, and some extracellular fluid (was blood plasma...). During exercise, the force of the muscle contractions help push the blood back to the heart, and the venous pressure is necessarily low. If you suddenly stop this pump, and the vasculature is still dilated from exercise, you get hypotension. This is because the Frank-Starling mechanism works on pre-load; basically it's a reflex that causes your heart to pump the more it is stretched (filled). If it is suddenly underfilled, because venous return is compromised, stroke volume suddenly falls.
When you're young and your blood vessels adapt much more quickly, it usually doesn't go so far as to make you pass out or anything. As you get older, the odds of something negative happening is greater. Aren't they always?
Just turned 25, and I can definitely see the value of a good warm-up and my foam roller a lot more than I could even 5 yrs ago. I figure it's only a matter of time before I personally value an active warm-down, as opposed to objectively seeing its merits.
Last edited by tadawdy; 11-05-09 at 12:56 AM.