I really like these Vibrams for doing cross training and short distance running. It definitely allows the smaller intrinsic foot muscles and joints to get worked out in ways that wearing normal athletic shoes does not. I wear a size 9-9.5 US and ordered the 42, but they were a little too big especially in the toes. If I had longer toes, this size would have worked fine. I also felt like my heels were almost coming out while I was doing weighted sled pushes, even with the laces tied tight. The extra length in the toes wasn't much of an issue for short runs and other resistance exercises. In any case, I still like how they felt so I will be returning them for a size smaller. If you aren't used to barefoot training, I would definitely recommend using the Vibrams slowly over time so you don't get any lower extremity pain.