Many worried that because the headphones weren't connected physically, that they might feel loose, or be prone to falling out. The set I tried had the smallest buds (they come with "skins" with different-sized buds), and I normally pick the larger ones when using in-ears. My attempts at jumping up and down in the Sands exhibition center were met with bemused looks by those passing, but the headphones didn't budge. Whether this would still be the same eight miles into a run, ears full of sweat, I can't confirm, but Hviid assures me, the fit has been tested. Put simply, they ain't going nowhere.