It's not the circulation, but the attempt to ease the compression pressure on the small metatarsal bones, and hence the pressure on the nerve. Doing up the laces or straps tight, or trying to shoehorn a foot with a thick sock into an undersized shoe cramps the sides of the feet in particular.

If it was a circulatory issue, I have no doubt one's toes would be blue.

Early on in my long-distance riding days, I rode around 800km from Canberra to Melbourne in five days, and could hardly walk on my left foot at the end for reasons I could not fathom. It was not until I got to the Paris-Brest-Paris event in 2003 that I talked to another Australian rider about his issues with hotfoot (or Morton's Neuroma) and how he had solved them.

Essentially, he created a button in the bottom of his shoe. I built up buttons in both my shoes with layers of electrical tape on the eve of the 1200km event, and was surprised at how effective they were in helping to spread the metatarsals apart and allow me to ride without foot pain.

On my Shimano MTB shoes, I use the credit card trick (actually, a thick piece of plastic cut to the shape and size of a CC -- I found the CC plastic to be a little brittle). Even then, I can sometime be caught out by wearing a slightly thicker pair of socks compared with those I am used to.

I'd also moved the cleats back as far as the would go, and that is how I have ridden ever since. Mashing the pedals can exacerbate the issue, but once you get it on a ride, even spinning with light pressure on the pedals won't really help relieve it.

But, having spent a little time away from LD riding, I also have found there is a certain "conditioning" of the body that is needed to enable me to ride comfortably again. This has applied to both feet and butt...