To bike - particularly on serious uphill sections - can entail serious lower back pain. Just as with getting a prosthetic arm to fit and work for me, getting a bike to fit me and work for me seems to be tedious and hard work, and requires attention to detail. That does not mean it should not be done however. All I am saying is it takes attention and love to detail. And, possibly, know-how.
At first, a rather small uphill ride (+400m) would cause serious back pains.
Here is how I addressed that.
Do not blame the bike? Blame the bike!
It is said that one should not blame the bike. (link)
While it is true that there are those that tend to suffer from lower back pains, there are those that get them increasingly when riding harder, and while it is true that get them really easily when getting tired muscles, it is also true that those benefit a lot from a perfectly set up bike in a particular way. My tendency to get lower back pains on awkwardly set up bike geometries is increased due to the arm disability, so all eyes are on that geometry. So of all people that benefit from a real close look there, I would really be one. Even more so: I benefited tremendously from using my hex Allen keys or my Alien to play with the setup till cows come home.
Setting up bike correctly
The pelvis needs to be tilted forward and the pelvis - lumbar spine transitional region needs to be rather straight. It is bad to have too much of a curve there. So the saddle needs to be more or less horizontal - i.e., parallel to the ground.
When pedaling, the pelvis should not tilt or swivel - neither upwards, nor, downwards, nor sideways. For starters, the saddle height should provide for that.
- The balls of the feet at the lowest pedal position, knees should be slightly bent.
- The heel of the feet at the lowest pedal position, knees can be totally straight but the pelvis does not even nudge a bit sideways.
With every pedaling stroke, the arms play a role as well.
And with that, the saddle - handle bar distance must be so small that:
- Upper arm angle from the vertical about 10 degrees.
- Lower arm angle about 45 degrees (really I do not care whether you think that is from the horizontal or vertical).
That is not a given with an arm "limb" difference.
Why would that be an issue at all?
Because one handed riding is not trivial.
- When riding one handed, a backward saddle tilt provides great stability. Horizontal and definitely forward saddle positions make for great improvements for the lower back, but strain is shifted to elbows, shoulders and upper back. So with that, we have a real problem here. Optimally, you can distribute your loadings between lower back and arms / neck, so all areas are overused equally ; )
- With a prosthetic arm, you may have asymmetric arm lengths such as me - so try to get the 10 / 45 degree thing right as much as ever possible.
After I implemented that (basically by maxing out my saddle forward and tilt options and so on) I was practically pain free when riding that (+600m, nice trail back down, see below).