Hello!
New to this forum. I've been running in vff kso for a few months, taking it easy to start with. Just walked with them for the first couple of months. I think my form is quite ok, I'm landing on the ball of my foot.
Weather started to get colder here in Finland, so I bought a pair of vff treks. Figured their a bit warmer, and have a better grip when it starts to get slippery. So yesterday I ran in them for maybe about 4 km, and had sore heels afterwards.
Pretty sure I wasn't heel striking. I was running part on asphalt, most on gravel road. Weather was cold, temps around -2C, no snow yet but the gravel road was very hard, ground starts to be a bit frozen. I was running in long trousers and only a t-shirt, felt really good

Could this have something to do with the more agressive tread on treks? Maybe that digs into my heels somehow?
Actually now that I think about it, the soreness isn't exactly on the heel, more like on front of the heel.
It's not a bad pain, slight soreness.
What do you think?