Subject: How is weight distributed across a heavy object when climbing staircase

Imagine that two people are carrying a heavy piano (with uniform weight distribution) up 
a staircase.  Both people are equally fit, but the person near the bottom must strain much 
more than the person near the top of the stairs.  Why, and how much more?  What 
principles are involved, and how would I calculate the difference in burden?

Re: How is weight distributed across a heavy object when climbing staircase