It might help to loosen your shoes as you get further into your ride.

How do your shoes fasten? I wear Sidi Dominator shoes (mountain bike shoes even though I only ride on the road), and they have 2 velcro straps and 1 "click-in" strap. I can loosen or tighten all of the straps while I am riding, so if I need to make adjustments I don't need to stop.

--- Denise