they may be too lose to use at the gym depending on how tightly they fit on your head. in my case i use them at home or when commuting. in the summer they feel like ear warmers! so I dont think it would be a good idea to use them at the gym. I recommend using sony headphones that go in the ear for gym purposes. I currently use: Sony MDREX58V/VLT In-Ear Headphones when I go to the gym : )
These are pretty comfortable on the ears. Sometimes, if I have worn them for an extended time. my ears get a little sore, but I wear glasses with glass lenses so that soreness may well be a result of the glasses rather than the ear phones. If there is a way that you could test these headphones, you should do so. I am very pleased with them.