I've got Shure E3c earphones and, while they sound great and are actually pretty comfortable, they do TOO good a job isolating you from the world for me to be comfortable wearing them while jogging or bicycling. That's probably true for most "in-ear", isolating headphones, whether from Shure, Etymotic or whoever. I, for one, want to be able to hear the idiots on the road that are trying to kill me!