I'm currently training for the Boston Marathon and so Im running a lot more hills. I have to say that I did not think these CW-X were anything more than superhero looking tights and only bought my first pair because I got it on sale. However, I love it! I was able to notice a difference in not just much less muscle fatigue but also it does help me keep my form much more than ordinary running tights. Prior to this (like most runners) I was just wearing your standard black running tights and was not aware of the difference in muscle fatigue until I got my CW-X insulator tights. Bottom line, I highly recommend it. FYI, I think this insulator version is best worn when it is about 50'F or less. I think anything more than 60'F and it is probably going to be too warm for you.