Here's a thought - approach a staff member for the gym, and explain you need to get some videos filmed for from checks, not for social media, and could that staff member film some reps for you for that purpose? This way, it's clear you're not an "influencer", nor are you filming anyone for nefarious purposes.
They may say no, but then again, they may say yes. And if there are multiple personnel, you might be able to get a yes at some point. At the very least, you'll get information about your gym...