Back pain

When i first started my current job(tree surgeon) I used to suffer from horrible back pain at the end of each day, mainly due to having to pick up fucking huge logs and shit all day, when i started climbing the bastards as well things got better in some respects and worse in others: months of groundwork had strengthened my back to the point where picking stuff up was no longer a problem but working the tree and holding chainsaws at full stretch caused different back pains.

Was told that any repetitive exercise: tree climbing, picking up heavy shit, riding a bike in a bad position builds muscle imbalance, so the pain usually comes from the muscles opposing the good uns.

Solution: work the opposing muscle groups in whichever way you see fit. Tree climbing gives you monster forearms but does fuck all for your shoulders so i began rock climbing as well. It's the true king of all round workouts, think of it as playing around like a kid combined with yoga. Depending on the type of climbing you do you can target specific muscle groups, or avoid them entirely to allow you to climb to some extent while injured.
Lack of core strength as mentioned above is also a biggy, i found slacklining to be the best for this(not really a gym kinda guy) again, wicked fun and sorts you out a treat.

Not a doctor, but my physio is way happier with me than he was 6 months ago. No gym, no giggling at the back of yoga class(my mate tried to teach me but i just laughed my arse off for some reason) and other than the odd twinge when i know i've pushed it too far its all good.

Prob not that relevant to cycling but i think the main thing is to do a wide range of exercise that works your back/core in as many ways as possible so you don't surprise it. That said, i'll never rock a lo-pro and my bars are pretty high on my tourer. Sense over style.