I'm not crazy about these. They ride up really bad, to the point where I have to adjust frequently. They DO wick sweat, but who cares if you're faced with a major wedgie? I think it's because they don't really have a seam.
As far as sizing, I think they run a little small. Out of the package, they seemed WAY too big. But on, they're actually quite snug. If I went up a size, I think they'd be a little too loose. But I definitely couldn't go down a size. Maybe trying a L would help with the riding up, but they're kind of expensive and I'm not thrilled with them enough to take the risk. I hate trying on underwear because with the other pair on, it's hard to tell the fit really well!
I probably would recommend finding another pair of moisture-wicking undies. These just aren't comfortable, although they do work from a sweat perspective.
Moving Comfort Response:
Could be a defective pair. I personally wear the same underwear and love them. They do seem to fit a fuller behind.
Jen from Norwalk, CT
Average Height (5'4"-5'8")