Don't know if this will help anyone but I discovered this the other day. After 25 miles into a ride, my feet (actually my toes) started to become numb. Rather than slow down/stop and stretch them, I started to pull on the upstroke when I cranked the pedals (rather than push down). The numbness went away almost immediately. After another 5 miles or so, it happened again, and I did the same thing. The numbness went away again. Ever since then, I use this technique when my feet go numb. Seems to work for me. Hope it helps.

Q