Despite my jokey reply above, I do intend to start doing some light upper-body exercise and some stretching.
I can cycle a long way on the flat without problems but when I do rides including more than (say) 2,000 metres of steepish climbs, my back inevitably starts to ache. It doesn't seem to matter how much cycling I do, my back and core muscles never seem to get as strong as my legs so my back packs up first.
I have been doing DIY for my sister at her new house, including demolishing some stud walls and blocking up a redundant doorway. I was shocked how hard I found it to do a bit of sawing, hammering, and helping take stuff to the tip!