It's not what you think. I mean actually put your Foot on a Ball.
If you watched the video from the re-re-re-redux blog about how to "hinge" over to get to your handlebar tops and basically thought "yeah, right, gigglesnort..." to yourself, I would not be surprised. Cyclists have notoriously tight posterior chains. To be clear, it's not just your hamstrings or your calf muscles or your glute, it's most certainly a combination of all them including the giant fascial sheet at your lower back (thoracolumbar fascia) and your latissimus dorsi.
I've done (and do) this little check-in exercise with all my cycling clients (and runners and yogis and people who sit down) as well as with groups at the Pink Street Cycling camps. It goes a long way to demonstrate how all the tissues of your body are connected. So we'll loosen up your tight glutes, hamstrings and lower back by rolling out the feet. Yes. I said feet. Watch the magic happen.