I went to physical therapy for a good 3-4 months.
Therapist: Your hamstring doesn't seem to be getting better. Maybe you need an MRI.
Me: thinking, "Duh!", but nodding in agreement.
My MRI showed a bulging disc in my back that puts pressure on my sciatic nerve. I also learned I'm deformed. Most people have 5 lumbar vertebrae. I have six. One chiropractor described the spinal column as a tower of blocks. You get too many blocks and they all fall down. My spinal column is just not as stable as most people's. I weeble. I wobble. But I don't (usually) fall down.
Five doctors and 5 cortisone spinal injections later, all they could tell me was that if it hurts, maybe you shouldn't do it. No running. No biking. No swimming. Not even much walking. I went from running 50 to 70 miles per week to being a couch potato.
This whole fiasco lasted almost 2 years. About that time we moved from Colorado to Idaho. I decided, "It hurts when I do things, it hurts when I don't do things. Screw it! I need to do something!" So I started walking. At first I could only go 5-10 minutes. Slowly, I built up to an hour. I also found a chiropractor who put me on traction. The combination of traction, walking, and core strengthening exercises did wonders!
About a year ago I purchased an inversion table and was able to drastically reduce my chiropractic bill. The table functions like a traction machine for me, so I can skip all of those chiropractic appointments.
Also, riding horses seems to help, too. (Gosh, Stableboy, honey, I'm sorry! I know you'd like some help stacking those hay bales and putting up that fence, but I really need to go ride my horse. It's physical therapy for my back, you know!)
Over the last few years, I've been able to incorporate some running into my workouts, but I have to be careful. If I do too much, I start to have more hamstring pain and have to back off. My workouts now are about what my warm-ups used to be!
I'm feeling pretty good right now, so I've got my fingers crossed. I doubt I'll ever be able to complete a marathon again, but a 5K? Maybe. I may not be "as good as I once was", but maybe this summer we'll see if I can be "as good once as I ever was!"