I sort of recall the Big Three: Endurance, Strength, Flexibility. Stretching stiff muscles is not so beneficial, and if you overstretch a "cold" muscle, you might not be riding the next day. I like to stretch after a ride (then ice those knees depending)...your body's warm, its mentally/physically relaxing and just "feels right"...its one way to slowly flip the switch to off as mentioned in a recent thread.
An old stand-by on stretching was a book by Bob Anderson titled "Stretching". But there are many others...I'm sure Joel Friel's chapter is good, too.
I get too impatient so pre-ride for me is just a slow 2 or 3 beginning miles. There are also some good on the bike stretches for those longer rides when you start feeling squinched up.
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..... "I renewed my youth, to outward appearance, by mounting a bicycle for the first time." Mark Twain, Speeches
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