One of the biggest problems as you get older is that your hamstrings actually shrink, and this is what causes most folks lower back problems, I know I have been fighting it for the last 5 years. Lots of streching will help, I do 20 min in the morning and 20 at nite but I also work out 3 to 5 times a week by either going to the gym or riding my bike.
Bottom line - stretch your hammys.