I think it would be very hard on the back to keep the feet on the pedals at all
times. Think of the strain in a three-hour opera! I have found, over the years,
that dragging your feet around the pedals with your heels on the floor results
in a lot of noise. Playing pedally sections in a pianissimo or in a recording
session requires any creative solution you can come up with to avoid pedal
noise. I “tip-toe”, or just remove my shoes entirely. The size of your feet makes
a difference, too. As far as I know, this rule of keeping the heels on the floor
originated with Salzedo, a man, playing in flat, quiet shoes.