Using a hotel gym as a non-guest
 

So most hotel gyms (especially Holiday Inn's and the like) tend to sit pretty empty, while actual gyms are overpriced and crowded... does anyone have experience in using a hotel gym as a non-guest either just walking in (I'd imagine not) or having some sort of arrangement with a hotel?

I have found that many hotels, usually with larger gyms, offer memberships or day passes.

Sure beats committing theft of service.

The other issue, beyond what BearX220 calls, accurately, "theft of service", is liability. You go in there and hurt yourself... I'm not suggesting that the hotel should have any liability (though you know how things go these days), but, at minimum, they're going to have to deal with your "rescue".

I've noticed these too, but generally like you said at bigger hotels where the gym has its own branding and operations. I'm more talking about smaller airport-ish hotels where the gym is generally unattended and has nothing more than a door requiring a keycard. I'm thinking more of an informal arrangement with the property itself... anyone have any experience? Or should I just go down and ask?

As you mentioned, just strolling in can be tough as many properties do require keycard access.

For 5+ years, I had a yearly gym membership at a local hotel, which afforded me use of their locker rooms, cardio & resistance machines, pool, whirlpool, sauna, outdoor patio, and towel service.

I flew from Boston to O'Hare about once a month for around two years for a consulting gig in the early 1990s. UA, AA and probably others had non-stops, but the way Delta's Frequent Flyer Program (this was before SkyMiles began in 1995) worked then, for the same economy fare, I could get confirmed F seats and 5,500 FF miles (versus 1,734 for a non-stop round trip). The only downside was that I had to change at CVG (Cincinnati).

The return (eastbound) connection was quick and painless. Westbound, though, I had about a three-hour wait. My travel agent (remember them?) arranged with the local Hilton that I'd be able to take their shuttle van to the hotel, use the gym (usually to shower after a run, but in bad weather I'd use the equipment) and then take the van back. I never stayed there, I don't think he sent much business to that hotel, but I suspect he played the "I send Hilton a lot of customers" card.

So: if you know anyone who has any leverage with the hotel(s) whose gym(s) you want to use, you might ask them to do something like that.

Wouldn't the sensible plan be to call the hotels in the area and ask?

The only way to find out would be to ask. My guess is most hotels with small fitness rooms would say no because they can't predict when guests might want to use the facility, and their maintenance schedule (if any) is based on the levels of usage they get normally.

Frequently, I have returned to hotels later the same day I checked out and asked for a key to use the gym and I've never had any issue with this at all.

On at least 2 occasions, I approached Marriott properties near the airport and very frankly told them that I wasn't staying at the hotel on this trip, but that I am a very loyal Platinum Premier, and asked if they would mind giving me a key to the exercise room. In both cases, they were happy to oblige. In one case I walked over (hotel connected to airport), and in the other case, I called ahead and then took their shuttle over (at their suggestion). I thought this was excellent customer service.

One thing I have noticed, however, at least at Marriotts is a decreasing number of properties with showers available in the exercise room/pool area. That makes this plan more difficult to execute.