Stairs.. the toughest challenge?

I know I can't be alone in this....

I have built myself up to an hour on the stepper. I have coped with the boredom, the pain... and the laughter from a work colleague who came to check if I had accidentally glued my feet to the stepper and needed assistance....

So why did three flights of stairs at work this morning have me gasping for breath and reaching for oxygen??

Maybe this lunchtime I should just walk up and down the stairs for my training. It could be interesting as I am known for being clumsy and have already gone down a flight on my arse in December...

Stairs.. the greatest challenge ?? Or Just the subconscious way of your body saying "No, turn back" when it thinks of work....