As a weightlifter, I struggle like heck to find bluetooth headphones that work at the gym. The only small decent 'phones that properly grip (comfortably) one's ears I have ever found are the Philips SHS3300BKs. Once you have attached them via the clever little hooks to the back of your ears, they stay there and they sound fantastic. I can't wear those dreadful stupid bud type things on their own because, my dear dimwitted earphone manufacturers, not all humans have that the protruding skin and cartilage platform that allows them to mount and "lock" the buds near your ear canal. The SHS3300BK can be found for £20 (beware of people auctioning them at higher costs) and are excellent value for money, but they aren't bluetooth. So I fixed that by buying a seperate bluetooth receiver, and they worked a charm in the gym, mostly....
As a general tip (I am an electronics engineer and a physicist) you can tell if an earbud based 'phone will produce bass properly wthout muddying up the trebles because they have a bass port (a tiny hole) drilled into them in their backs. Without that, forget it, you ARE wasting you money on whatever "earbud" 'phones you are considering. "Waterproof" is a word you don't want to read in the spec of any gym enabled pair of 'phones because they won't have that port. Why are you swimming or showering with 'phones on anyway? Stupid life risking thing to do.
If you are weight lifter, like me, and you bought a seperate bluetooth receiver so you can use your beloved decent yet tiny 'phones, no matter where you put the receiver on your body (pocket, chest etc.), sooner or later its switches get pressed down by your clothing when you lift a heavy weight, causing them to turn off or select random tracks via your phone. Some-or-other receiver manufacturer simply has to supply a receiver with lock mechanism to disable the controls and the world's gym earphone problems would all be over, but no, that is to simple and obvious a solution especially to whom, I would imagine, are people who design these things but never actually use them themselves.
These phones (SHQ7900CLs) above hinted they had a bass port (assessed by looking at the pictures). The pictures also imply they have a proper hook (like the SHS'a) to hold onto your ears successfully. Wrong on both counts. The sound quality is awful and murky as predictable without the port. The hooks are flippy-floppy little latex "will decay or snap off in 2 minutes of real world usage" soft stretchable stupid things that don't grip your ear and as soon as you lie back to do any sort of press movement, out they pop, dangling around your neck or falling onto the bench making you look like a complete and utter idiot (almost as stupid as those who wear fullsized headphones to the gym and then have to endure the phone's weight pulling them off their head when they too, attempt presses of any sort).
These thing are NOT worth the asking price. They are awful stupid things which are no better than the £20 bluetooth jobs you can find elsewhere on this site. I have yet, over decades of attempt, yet to find a working solution other than keep using my SHS's with a dangling receiver.
COME ON YOU HEADPHONE MANUFACTURER'S! Talk to someone who knows what it feels like to use 'phones with bluetooth in a gym instead of fooling yourself into thinking you have made a usable product! It's hardly rocket science. I am sick to death of wasting what must be now over £300 on useless manufacturer attempts at "sport" headphones. Philips, your products are some of the best, usally exceeding in performance the cost of the item, but you should be ashamed of these.