I keep reading this thread title as 'does anyone retch...'
Must get my eyes tested.
Back to the thread I guess it depends what you are stretching and how. Depending on what you are doing, certain muscles will be extended and certain muscles will be flexed. They will all have build ups of lactic acid and other chemicals which are residues of exercise, especially anaerobic exercise. So after cycling always stretch quads, hamstrings and bum. This is v important because tightness in these areas can lead to back injury. Cycling is also quite low impact though so stretching isn't completely necessary.
If I go running I always also stretch out my calves and ITBs because they can get very tight especially with all the impact.