Amy Kneale this tight hamstring of yours may not be tight at all. With Cyclists, i have found that the majority of tight hamstrings are due to what's termed "neural tension" (can't get into it right now but it has a lot to do with that bike position we get into. You would get a lot of results via ART (active Release Technique) and self-treatment of Nerve Flossing. I recommend Dr. Matt Diamond from Allied Spine & Sports Chiropractic. He and I can teach you how to Nerve Floss. Dr. Diamond has the highest obtained ART certification. He is available on Fridays. You can reach him at 315-498-6888