A new film that premiered at the Tribeca Film Festival on Friday questions whether an NFL team was hypocritical in demanding that its cheerleaders maintain a wholesome image while decidedly selling their sex appeal to fans.

The focus of "Sidelined," a documentary short directed by Galen Summer, is the San Diego Chargettes squad from the late 1970s that was systematically fired after members posed alongside other NFL cheerleaders for Playboy.

In 1978, NFL cheerleading squads were in their nascence, trying to compete with the Dallas Cowboys Cheerleaders, who were at the top of the game (as detailed in a documentary that premiered last month, "Daughters of the Sexual Revolution: The Untold Story of the Dallas Cowboys Cheerleaders").

According to the film, teams recruiting women into cheerleading roles in the late 1970s made it no secret that sex appeal was one of the main things they were selling to football fans. The women themselves stress in the film that they knew that going in. As one local broadcast noted during cheerleading tryouts, "A press release inviting them said they should come dressed 'as sexy as they feel comfortable with.' Some felt very comfortable."

"It was probably the first time that sexiness was kind of being sold on TV," former Dallas Cowboys cheerleader Debbie Kepley said in the film. Competing against the Cowboys model yielded many teams to push the boundaries with skimpier uniforms; by that point, for example, the Chargettes had replaced skirts with white briefs.

So when Playboy came calling to do a feature on cheerleaders, some teams, including the Chargers organization, embraced the opportunity for added publicity. "They received us with open arms," former Playboy editor Jeff Cohen said in the film.

A film crew from Playboy visited one of their practices and recruited women to be interviewed in the magazine. In the course of those interviews, many were persuaded to pose nude or in various states of undress. The result was a spread in the December 1978 issue entitled "Sex on the Side Lines: NFL Cheerleaders Bare All."

At the time, the Chargettes were not making money for appearing at games. Playboy offered a payout starting at $500 for posing topless and up to $1,500 for posing nude. "I'm a girl with no financial help, living on my own, working, trying to go to school," said Lynita Shilling, a former Chargette who was 20 years old when she posed topless for Playboy. In the film, she described how nervous she was walking into the photo shoot, where she was offered a glass of wine to calm her nerves.

Despite the fact that the teams themselves invited Playboy to recruit women for the magazine, the former cheerleaders in the film say there were no team officials present at the photo shoots.

As the film details, the Chargers fired the entire squad before the Playboy issue published. "It wasn't so much what the girls did -- it's what the guys did to the girls," Rhonda Bosworth, then-director of the Chargettes, said in the film. The firing came directly from assistant general manager Paul "Tank" Younger.

"I was in shock, because I felt betrayed. And I couldn't understand: If it was wrong, why didn't he stop it?" Jill Fleming, one of the fired Chargettes who didn't pose for Playboy, said in the film.

Said film director Summer: "Their biggest response was, 'We don't understand why this happened. We thought we were following the rules.' Not only did they think that the team had OK'd the pictorial, but they didn't really even see anything they were doing as going against everything that they had been told up to that point, which is dress a certain way, show your body off in a certain way.

"[The Chargers] wanted to have their cake and eat it, too," he said.

According to Summer, at the time, there weren't explicit rules prohibiting the Chargettes from posing for Playboy. (The Cowboys, however, did have such rules, as shown in "Daughters of the Sexual Revolution.") Fast-forward to the present day and NFL cheerleading squads boast a bevy of rules prohibiting members from fraternizing with players or posting provocative photos on social media. In 2011, former Indianapolis Colts cheerleader Malori Wampler sued the team for discrimination after photos emerged of her appearing at a Playboy event in a painted-on swimsuit, which took place before she joined the Colts. In March, a former New Orleans Saints cheerleader filed a gender discrimination complaint with the Equal Employment Opportunity Commission against the team and the league based on the Saintsations' eight-page booklet of rules, saying that they enforced a double standard by requiring different behavior from the women on the squad than the men on the team.

For its part, "Sidelined" isn't just a film about the seeming hypocrisy in the way NFL teams use women's sexuality to sell the game -- it's also about sisterhood. Those who come to the film with preconceived notions about cheerleaders might change their tune after hearing some of these women describe why they joined their squads in the first place. For example, former Chicago cheerleader Jackie Rohrs, who had posed in the Playboy issue, was older than other women at tryouts and hid both her age and the fact that she had an 8-year-old daughter.

"I felt that my life wasn't over. I felt that I could still do something creative, fun," Shilling said in the film. "That sisterhood was really important to me, and I thought I'd never have that again." To Shilling, making the squad "meant that I'd have another chance at developing bonds and friendships with other women."

The film's climax captures a reclamation of this sisterhood in a 2016 reunion Shilling has with other former Chargettes. For decades, she had been carrying a heavy sense of guilt for posing for Playboy, blaming herself for the other women being fired -- in essence, for breaking up the family. (After disbanding the Chargettes, the team established its dance team, the Charger Girls, in 1990.)

"It really was this sisterhood. That's why it was so important to lose it," Summer said. "She felt like she took it away from everybody."

"Cheerleading didn't just involve being on a field on a Friday night," Shilling said in the film. "It also involved a sisterhood, kind of a small family. That's why I loved it so much."