I've been running 30-40 mpw for the last two years without a single running related injury. Did a few test runs in Vaporfly 4% and felt like I was floating -- best feeling shoe ever, nothing else is like it. Like sex without a condom for the first time. Raced a 70.3 in them and by mile 10 the soles of my feet were completely numb. After the race had horrible peroneal and Achilles tendinitis. It hurt to even walk. Took a month of running and am finally getting back into it. It was like gonorrhea, such a let down. I've rationalized it away by telling myself I got injured because I sprained my ankle a few days before the 70.3 so perhaps my form was a bit off. And then ordered the Next% and will race IM in them next season. Hopefully I have better luck this time around as the shoe locks down much better in the heel and across my midfoot.