Originally Posted by
carpediemracing
Things you may need to do with your bike:
1. Bars too low or too far away or both
2. Although counterintuitive, bars may be too high or too close. Sitting sort of upright can really stress your back. It's like sort of leaning over the kitchen sink to wash dishes - I have to stand straight up else my back starts to seize in just a few minutes. On the bike I have a longer, lower position, appropriate to my body dimensions, and on my bike I have no back issues even though I have some actual back issues.
I would bet on
#2 before
#1 . The dishes analogy is a good one. The issue is that your pelvis ends up rotated back, as though you were sitting up, and you bend forward at your belly button. This puts a lot of pressure on your lower back. Here's an example, me from before I changed my fit to correct for this issue:
Look at my hips and the very lower part of my back - it looks like I'm sitting on a beach cruiser. And then above that, I bend waaaay forward at my belly button to get low. Not that you care much about aerodynamics right now, but in addition to causing a lot of discomfort, my ability to get as low as possible was compromised by this position because I was relying on the flexibility of my middle spine, not my hips, hamstrings and glutes, to get low.
For a road position, the forward lean needs to come as much as possible from rotating your pelvis forward on the saddle. This is true even for a mild forward lean. Obviously, different body types and flexibility levels will effect the details of the fit.
As for fixing it, handlebar reach is one element, saddle setback is also important. Handlebar height per se is less important, but may contribute as well. I addressed my problem by swapping to a longer stem and sliding my saddle back a bit. I may need to consider sliding it back a bit more at some point, but it's best not to make huge changes. Anyway, this pulled my pelvis forward and released a lot of the tension from my back. Pedaling hard still puts those lower core muscles to work, so I do feel that when I've been hammering for a while, but it's definitely improved. My back and neck, notably, don't hurt AFTER I'm done riding anymore.
All that said, it is also possible that you need to adapt, as well. Cycling does use those muscles as I said. But if you're literally unable to continue after 15 miles or so, I think fit needs to be seriously considered. Even when I was relatively new to riding (before I developed that fit issue, which came later when I got a new bike and shortened my position by almost 2 cm) I could easily ride that far without back pain to the point of having to stop. Sure, my back got tired, but it was not in pain. I would definitely look into the fit issue.