Lower back pain, 1 side, power imbalance, outside only

I’ve recently started to develop pain on outdoor rides (not indoor, even though the bike is the same). It is in the right side of my lower back.

This coincides with a slight discrepancy on my Assiomas: it’s always 50/50 or 51L/49R on the trainer, but is usually more like 52-53L/48-47 R on the road, and just spinning easy early in a ride can be as much as 55/45.

There’s obviously a muscular imbalance or postural issue behind it, and I find it hard to believe the back pain and power imbalance aren’t related (as the onset has been almost the same). But

  1. What is it? and
  2. Why am I only getting it outdoors?

Any guidance gratefully appreciated

Obviously must be something that only affects you outside. Things I would check:

  • alignment of your handlebar / stem with your front wheel. (—> is your stem in line with the front wheel. On the trainer you can correct, outside you will ride somewhat crooked if not)
  • same shoes inside and outside?
  • does your bike lean on towards one side on the trainer? (Since you are having the issues outside this is not a likely reason)
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Same shoes, alignment of stem is fine.

But… you might be on to something with the trainer alignment. The floor in the room I use has a very slight slope from one side to the other, leaning to the left. I wonder (as I ride more inside than out) if I’ve developed a compensation which then affects me outside? Hmm…:thinking:

Other thoughts:
Are your outside rides simply longer?
Are you riding on the hoods when riding inside or do you use the bar? Outside you have to use hoods / drops in order to brake and therefore position would be more stretched.

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Generally they’re longer but the back discomfort kicks in after 40-50 minutes and I’m routinely doing 90 on the trainer with no issues.

I suspect I am on the hoods/drops more outside, but I don’t do my indoor sessions exclusively on the tops by any means, so you may be right, but I’m not sure.

Thank you for the suggestions though.

It may be because you use your stabilizer muscles more outdoors because you’re more dynamic than when you’re on the trainer, which is more static. I have significant problems in my back on outside rides and have been seeing PTs for about two years now with some improvement, but still the problems. I have weaknesses through my right side, which contributes to the problem. Good luck!

(Functional) Leg length discrepancy or saddle being too high can cause these types of issues, but strange that it’s only outside.

I don’t know exactly know what the problem is but out side you’ll be leaning, steering, engaging your core etc more than you could do on a static trainer. Which is probably why problem only manifests outdoors.

This may not be the case for you at all but I am just adding my 2 cents to the pot here. I know I tend to ride at a lower cadence when outdoors. I’m not sure why, but I’ve been trying to catch myself when I notice it and move at least one gear up. Lower cadence obviously adds more stress to the knees and in turn can affect your hips and lower back, thus putting more emphasis on any imbalances you may have. Could potentially be a piece of the puzzle?


You have back pain like 40% of the population… The most common musculoskeletal issue. Cyclists aren’t immune. The problem is internal to you and not your bike, trainer, stem alignment and whatever else this forum conjures up. Stay away from the amateurs and see a physical therapist.

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see a fitter, could be a fit issue.

see a PT, could be a number of things there that can be corrected with some exercises/stretching.

I’m not saying this describes you but most people have back pain because they sit way too much (like all day) and they have postural imbalances from all that sitting (tight hip flexors) and flabby abs.

If you couple cycling with the average body you end up with over developed quads and a greater muscle imbalance. What can be done?

Core work and general body conditioning
Weight lifting and strengthening the posterior chain
Stretching hip flexors if needed - yoga?

If any of that sounds familiar google “lower cross syndrome” for further reading.

I doubt the slight imbalance measured in the pedals means that much.

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Yup - sit too much and have tight hip flexors, as well as over-developed quads relative to my hams and glutes. I’m quite proud of having visible abs :rofl: but I know that doesn’t mean I have a strong core.

I’ve started some yoga and ham/glute work so thank you for confirming my suspicions and the tips :+1: