If Congress is a boys’ club, the House Members-only gym might be its inner sanctum.

It’s where you’ll find lawmakers, usually so confident and guarded, at their most vulnerable: red-faced, short of breath and often naked.

The gym got a star turn this week when pictures of naughty texter Rep. Anthony Weiner surfaced.

In one of the photos, the New York Democrat is shirtless, a towel wrapped around his waist, against the backdrop of what appear to be the industrial-gray lockers of the Members’ workout lair.

But it wasn’t the first time the gym has seen titillating action.

Rep. Eric Massa, the New York Democrat who resigned after admitting to tickle-fights with male staffers, once described an incident that took place there in which then-White House Chief of Staff Rahm Emanuel poked him in the chest and harangued him for not supporting the president’s budget.

Massa was showering, he said, and Emanuel, now the mayor of Chicago, didn’t even have “a towel wrapped around his tush.”

Throughout the years, the gym has been the setting of unwelcome displays of flesh, talcum powder gone awry and massages administered by a hungover Hungarian masseur.

But for all that drama, and for all the mystery surrounding the gym (only Members can enter, and an Architect of the Capitol spokeswoman wouldn’t say a word about it, citing “security purposes”), some who use it say there’s usually just not much inside to get worked up about.

Little in the way of deal-making happens, some say, and mostly it’s a scene that could play out in bland hotel gyms anywhere: a bunch of middle-aged guys on treadmills or stationary bikes, reading newspapers and exchanging pleasantries.

Rep. Joe Walsh (R-Ill.) describes the facility, located in the Rayburn House Office Building, as a low-key setting where Members typically keep to themselves.

“I’m not seeing any hijinks,” he says. “Maybe that was the case back in the ’70s or ’80s when things were looser. Now, it’s just a quiet place where guys go to work out and clear their heads.”

Walsh belongs to the “couch caucus,” a not-so-elite club of Members who sleep in their offices, a group that some estimate to be in the dozens. Those lawmakers typically shower and change daily in the House gym, and many throw in a workout for good measure, often just to kill time in the ghostly office buildings.

There’s a group of lawmakers that meets in the mornings for P90X workouts, a grueling fitness routine whose founder, Tony Horton, has become a celebrity and frequent visitor to Capitol Hill, where he’ll sometimes lead sweaty groups of lawmakers in the House gym. Rep. Paul Ryan (R-Wis.) once boasted to Roll Call that the sessions had helped him keep his body-fat percentage to an impressively taut 6 percent to 8 percent.

And a group of mostly freshmen have a regular weekly basketball game in the evenings.

Dues for the Member gym are $240 a year, and the facility is overseen by a “gym committee” headed by Rep. John Sullivan (R-Okla.). Women have their own gym, a facility that was spruced up in 2008 after calls for parity with the guys’ fitness center. The women’s gym is smaller and geared more toward cardio equipment than heavy-duty weights.

Women, Sullivan says, are welcome to use the larger gym if they like, too.

Sullivan says the committee selects and purchases equipment to meet the needs of the gym’s patrons and pays for it using their dues. He looks for quality gear that will stand the test of time, he says (i.e., no fad items like ThighMasters). Five gym staffers, employees of the Architect of the Capitol, man the facilities, but Sullivan himself enjoys pitching in, helping to make sure colleagues are using proper techniques on the machines.

Rep. Jesse Jackson Jr. (Ill.), the Democratic co-chairman of the gym committee, is quick to defend the gym against those who might say it’s a cushy perk, noting the use of private funding. And asking 435 Members to find private facilities in which to work out isn’t really feasible, he says, because of security and privacy concerns.

“It makes sense that they would want to exercise in the bubble of security provided by the Capitol Police.”

Regulars say it’s a safe haven from rabid politics, too, a rare place where Members from opposite sides of the aisle can bond. “It builds camaraderie,” Sullivan says. “I’ve got guys from both parties that I see at my locker, and we talk all the time.”

And as for excitement in the gym? Not so much. In fact, Sullivan and Jackson both note that those photos Weiner shot actually violated the rules of the gym, where signs warn patrons that photography isn’t allowed. “And these are not paper signs,” Jackson says. “They’re carved onto placards.”

Sullivan says he’s heard stories from years past. “You hear about the guys who used to drink in there, maybe 30 years ago,” he says. “Now the only thing we’ve got down there is V8.”

Still, the facility has been the setting for some entertaining tales over the years.

Massa apparently isn’t the only one who finds nude encounters with one’s colleagues to be a little off-putting. Rep. Thaddeus McCotter once explained why his patronage of the House gym was so short-lived.

The Michigan Republican — a known chain-smoker — told Fox News in 2009 that he found the facility’s lack of ashtrays a deterrent. And then there was a too-handsy exchange he had with a fellow Member: “The one time I was there, my first trip, someone sort of was talc-ing themselves,” he said during an interview on Fox News’ “Red Eye.” The guy “offered their hand, and I just said, ‘Hey, we’re cool, dude.'”

And allegedly poking Massa wasn’t the only workout Emanuel got at the House gym. He was known for crack-of-dawn workouts that continued long after he left Congress to become President Barack Obama’s chief of staff. Former colleagues surmised Emanuel kept up his workouts at the Congressional facility as a way of keeping tabs on them.

But perhaps the modern Members’ gym, with its flat-screen TVs and fancy machines, isn’t as colorful as it used to be. Among the tales from the gym’s history are those of Ace Kovaks, a Hungarian immigrant who was the longtime “House masseur,” known for frequently coming to work with a hangover — and for his vigorous rubdowns.

Former Rep. Jim Weaver (Ore.), who served from 1975 to 1987, wrote to Roll Call last year to pay tribute to Kovaks, who he said was a favorite of then-Vice President George H.W. Bush. “A barrel-chested man with biceps the width of a lodge pole pine, he gave you a rub that left you a lump of rubble,” Weaver recalled in his letter.