I am a road cyclist. When I push big gears (up the hill ) I have great pain in my back. I noticed that bigger the gears are, more I seat on the back end of the seat, like a DH position for example. Please help, because I don't know what to do. I tried many seats and different seat position but didn't help.

Dear dvince,

What you described as a pain in your back… is a back problem. Adjusting your seat may be a component of reducing factors that antagonize your problem, but, it is not and shouldn’t be the sole factor in treating your condition.
It is clearly an over use syndrome, as most conditions are, unless you encountered some kind of trauma that you omitted from your post.
In this situation, you must identify whether or not you have any “core stability” issues. This means evaluating the abdominals, back extensors and lateral flexors. Once this is found, you can develop a plan of action to reverse the excess tissue strain and ride more comfortably again and improve your pace. In addition to evaluating your core stabilizers, evaluating the hip and lower extremities such as the gluts and hamstrings would be prudent as they also contribute to core stability because of their attachment sites on the pelvis.
I am a chiropractor and deal with structural, postural and repetitive stress disorders routinely. This is most likely a pure biomechanical problem involving the kinetic chain of muscles and joints. I would caution you as I have others, don’t fall into the trap that this is “only a muscle”. Another trap is taking pain relievers… the pain may go away but you’ll retain your imbalance and suffer with a recurrence down the road or worse, you’ll just suffer with decreasing performance over the years and blame it on just getting older. Hope this helps you out.

Hi,

Are you using drop handle bars and a traditional 'racing' posture?

I have had lower back problems for some years and got great advice and help from an osteopath. (My doctor was useless). I had to frequently get off my bike and lie down and do stretches to cope with even a couple of hours riding.

Reluctantly last year on the osteo's advice I changed my traditional drop bars on my traditional touring bike for 'butterfly' bars which you see a lot in Germany. This gives a much more sit up straight posture that is so so comfortable. I can ride for 12 hours a day with no back problems at all. I do not notice any difference in how far/how strongly I can ride.

Of course if you've already got flat bars none of the above will be any help. Sorry.