While this is somewhat of a complicated question to address and answer, it can be said that these can actually make swimming easier. Now, they do isolate your arms and allow you to work out your upper body. So, in theory, it would seem that they would actually make swimming harder. Yet, here is the thing; due to the buoyancy that they provide, they can make it easier to float and subsequently swim. For the most part, however, not too many users out there buy these training tools for this reason.