I have a stretching routine I go through. If I do all stretches, one after the other without breaks in between, it takes roughly two hours to do. There are stretches that target the hamstrings. Now that I am getting older, I am beginning to have some discomfort with muscular tension. The stretching exercises are very effective in relieving tension, tightening, and stress. There is a book named "Sports Stretching." It will let you know how to get at the hamstrings. The muscles definitely change as you age. When I was in my thirties I worked out with weights quite a lot. I got very strong and toned. Now, no matter how much I work out, the muscles just cannot do it anymore; they just do not pump up the way they did when I was younger.
If the hamstrings tighten too much, it can cause problems with your range of motion. Try some serious stretching for a while. You might just be surprised at how much difference it can make. There are also stretching routines targeting the particular muscles used in certain types of sports activities, including cycling.