YiMy experience with the 535:
I've used them at the gym and my current pair will probably become my gym beaters now, but given the cable connector, it could result in problems over extended use with things like corrosion or the cable being yanked repeatedly if you're the type of person to run into that issue too often. The connector is intended to allow the cable to be replaced in the event of damage (or for customization); it's not really intended as any sort of safety release.
That's just my hunch. I've used my 535s for 3 years at the gym and had to replace the cable once, but they still work. Just don't be surprised if you start noticing repeated wiggling of the cable leading to an uneven connection between the cable and the earpiece over extended use (think years), which can eventually lead to sound cutting out randomly during gym sessions. Mine work and I've adjusted myself to that inconvenience by buying a replacement cable whenever it becomes something I can't fix, but this is my way of saying your mileage will definitely vary.
bryantThe cable degeneration was one of my worries but I found identical replacements on amazon for $35. Considering you only replaced your cable once in 3 years of usage, that just gave me confirmation for the go ahead.
Yilol...but for real, these isolate, right? and humans dont sweat inside their ears. this should answer your question. If you should take $1k IEMs to a GYM is another question... I bicycle with them every day and its a joy ride :)
bryantI use my FAD Heaven VI's for my almost daily, very lengthy long-walk/run (30-40 min.) + commute (30 min.) going to and from my university. I love them too much to let them just sit there (what's the point of buying if you don't use them?). I know it's crazy since the FAD's cable feels so...delicate (not flimsy, and definitely not fragile), and the strain relief is, in a word, "meh." Shures/Westones/UEs would have been better choices. Sadly, my earholes are too small for any of those so...yeah...FADs.