Originally Posted by
moogyboy
Physically, I'm 5'9", 260 lb (again, don't laugh, I'm more stocky than fat), 43 years old, not really much in upper body strength but fairly strong legs, and my sciatica and middle-back act up sometimes (sucks getting old).
You have some back trouble, so it'll be helpful to learn to take the bumps with your legs. Visit a BMX park and watch how the people ride, and note their body position on their bikes. They are out of their seats and in the attack position whenever the terrain gets rough.