what a bother! do you do core work? all the cyclists I know with low back issues (that have resolved the pain) found strengthening the core, strengthening opposing muscle groups,..helps much..... I am 51 and have found I need to strength train all year round to be able to go hard and be relatively pain free....This guy has several good books on that theme- He is 57 and still racing exterra!

http://www.bicycling.com/mountainbik...riding-forever