Originally Posted by
razorjack
Ok, so i didn't add more info before.
-yes i had a bike fit last year, i believe good, person is known in my city and recommended (for sure my saddle is not too high or too far back)
-i ride all the time, maybe a bit less in winter. this year: 4kkm distance, 65km elevation)
-before, some discomfort could appear earlier, so at the end looks like body gets stronger.
-i doubt i pull my pedals on such long climbs (i try to keep it at 80%FTP)
-mine standard (weekdays) rides are shorter - 2-3h, with 10-20min climbs.
I belive it's connected with hip flexors (
Psoas?) - I stretch them (sitting work, sitting on a bike, bad bad bad
) - maybe not enough?
that's why I ask about other muscles, which i could train/make stronger to support my body.
Wear a heart rate monitor and make sure you avoid rapid increase / drop in heart during the entire ride. Muscle fatigue, pain, etc, is strongly linked to allowing your heart rate to rise and fall too rapidly. It means the muscles are starved of oxygen at some point and it's oxygen you need to avoid accumulation of lactic acid on your core muscles. The core muscles is the source of the lower back pain.
Another cause of lower back pain is poor lower back posture on the bike. The lower back should be arched slightly upward, not arched down. If your lower back is arched down, you're putting more load on your core muscles and can cause accumulation of lactic acid. If you're having a hard time arching your lower back upward, reducing stem length will help.
And finally, start getting used to spinning higher cadence with smaller gears.
I had exactly the same lower back problem as you did for two years. We also deal with similar circumstance, seating long periods at work. What solved it for me is started monitoring my heart rate and avoid heart rate spikes and improved my lower back posture. I tried a lot of things like stretching, core muscle strengthening workouts on the gym. They did not solve the problem entirely.
If you're riding regularly and doing climbs, you're already working out your core muscles already. The problem with off-bike core strengthening exercises is you may need recovery periods for it and can mean no riding or at least an easy ride without any climbing.