41 into 36 for Ghisolfi

Stefano Ghisolfi, one of the best climbers in the world, reports on Insta that he has size 41 in regular shoes but only 36 in his La Sportiva Futura.

Please explain how this is possible?
It is painful to wear them only the very first time. I put the plastic paper that comes with the shoes under the heel to slide the heel in. But after two or three times they enter normally and from the second day it is not that painful anymore Sometimes for training, I use one number bigger to keep them on longer. Otherwise, I just take them off every attempt.

So how would it be to climb in size 39?
They would be too large and inaccurate. The feet would move too much inside the shoes.

Another example of these "Geisha" shoes is Adam Ondra squeezing in his 44 size feet into 38.5 shoes. At the same time, Ondra has said that on competition slabs and volumes you do not want that much pressure on just the toes so then he has much bigger shoes. It should be mentioned that when it comes to ordinary climbers, you will not benefit much, but pain, going down in sizes. I have 39.5 and I climb in 38.5 in La Sportiva and I even have a pair of Testarossa size 41 and the difference for me is not that big.