The world of professional sports is becoming more and more welcoming and inclusive of the LGBT community.

Below, we showcase six men and women who helped fuel that change. Some were out on the field, others couldn't be open while they were playing, but all blazed trail in professional sports and LGBT advocacy.

Watch Mind/Game: The Unquiet Journey of Chamique Holdsclaw on May 3 at 10/9c on Logo TV.

David Kopay

Joe Namath might have made waves by cheekily wearing hosiery in a 1974 Hanes pantyhose commercial, but the big bombshell came a year later when former Redskins running back Dave Kopay came out in his bestselling autobiography.

Decades before Michael Sam, he became the first openly gay player in the NFL, though he was not out while in the league.

“I got very, very few hate mails.” Kopay, now 73, told Outsports. “Mostly the mail that poured in was amazingly supportive and [people] telling their own stories."

But as he sought work as a coach, Kopay found himself effectively blacklisted and became a successful Southern California businessman instead.

Kopay continues to make meaningful contributions as a board member of the Gay and Lesbian Athletics Foundation and a Gay Games ambassador. In 2007 he announced plans to leave a million-dollar endowment to his alma mater, the University of Washington, for the school’s LGBT Center.

Martina Navratilova

Arguably the greatest female tennis player of all time, Martina Navratilova won 18 Grand Slam singles titles and 31 Grand Slam doubles titles before retiring in 2006—and remains the only player—male or female—in to hold on to the Number One ranking for more than 200 weeks.

And for most of her brilliant career she was an out gay woman.

Navratilova came out publicly in 1981, when it was unheard of, and has remained a staunch advocate for the LGBT community ever since.

In an essay for Sports Illustrated, Navratilova had this message for fellow gay athletes: Come out.

“It is beautiful out here and I guarantee you this—you will never, ever want to go back. You will only wonder why it took so long."

Renee Richards

In 1976, Renee Richards was primed to be in the U.S. Open when judges learned she had been born male. The United States Tennis Association attempted to ban her, citing a women-born-women policy, but Richards filed suit and, in a landmark case, the New York Supreme Court ruled in her favor.

Despite the victory, Richards endured public scrutiny, the loss of family and friends, and brutal discrimination from the tennis world.

"[It] didn’t stop the WTA from trying to Richards her from pro tournaments until she sued, or 25 of the 32 women in the field from withdrawing from the first tournament she played, at age 41. Crowds rooted against her," ESPN writes. "If Richards turned on a TV at the time, she could’ve found Johnny Carson and Bob Hope snickering on The Tonight Show that Richards was her own "mixed doubles team"

Eventually Richards left tennis and returned to a successful ophthalmology practice in California, but her very public battle blazed a trail for future trans athletes like MMA fighter Fallon Fox and NCAA basketball player Kye Allums.

Glenn Burke

You can thank baseball player Glenn Burke for the high five: In 1977, Burke ran on to the field to congratulate Dodgers teammate Dusty Baker on a game-winning home run. Rather than a hug or a handshake, Burke offered an upraised hand and Baker slapped it. The high five went on to become a famous symbol of camaraderie and athletic celebration.

Ironically, Burke was often denied such camaraderie from coaches and teammates during his four-year career in professional baseball.

He was outgoing, funny and an incredibly gifted athlete—the fact that Burke was gay was an open secret among his Dodgers teammates and managers. And while Burke maintained players didn’t care, Dodgers general manager Al Campanis reportedly offered to foot the bill for a lavish wedding.

To which Burke responded: “To a woman?!”

He also had a troubled relationship with Dodgers manager Tommy Lasorda, who was furious Burke was hanging out with his son, Tommy Jr., in West Hollywood.

After only two seasons with the Dodgers, Burke was traded to the Oakland A’s, where he was underutilized and isolated. (Some teammates reportedly even refused to shower with him.)

The final “out” in Burke's career came in 1980, when Billy Martin was hired as the A’s manager. Early in his tenure, Martin stood in the dugout, looked straight at Burke and declared, “I don’t want no faggot on my team.”

By the end of the season Burke was released from his contract.

Free from clubhouse homophobia, Burke was at least able to come out publicly. He even competed in the first Gay Games in 1982, in track and field, and then in the 1986 Games in basketball—proof of what a well-rounded athlete he was.

In later years he struggled with drug addiction and homelessness, and finally succumbed to AIDS in 1995. He always maintained that prejudice against homosexuality “drove me out of baseball sooner than I should have [gone].”

Still, he took pride in his achievements, telling People magazine in 1994, “They can’t ever say now that a gay man can’t play in the majors, because I’m a gay man and I made it.”

Sheryl Swoopes

How’s this for a trailblazer: Swoopes was the first player signed to the fledgling WNBA, back in 1997. During her 14-year professional career she received three league MVP awards, won three Olympic gold medals, and even had a shoe named after her—the Air Swoopes.

She also became involved with a woman romantically and, in 2005, made their relationship public. Swoopes explained that she wanted to someday marry partner Alisa Scott.

“It doesn’t change who I am," she told ESPN Magazine. “I can’t help who I fall in love with. No one can...Being intimate with [Alisa] or any other woman never entered my mind. At the same time, I’m a firm believer that when you fall in love with somebody, you can’t control that."

Swoopes and Scott haven since split and, in 2011, the former baller became engaged to Chris Unclesho. She is currently head coach for the Loyola University women's basketball team, the Ramblers.

Matthew Mitcham

At the 2008 Beijing Summer Olympics, China's formidable men’s diving team was expected to make a clean sweep. Then came the 10-meter platform competition, and 20-year-old Australian underdog Matthew Mitcham pulled out a near perfect final dive—the highest single-dive score in Olympic history.

After learning he’d won the gold, Mitcham leapt into the stands to hug and kiss his boyfriend. He had come out publicly less than six months prior, and was one of only ten out gay Olympians at the 2008 Summer Olympics.

Mitcham's victory in the 10-meter dive was easily the highest profile win ever by an out gay man in an Olympic event. (While Greg Louganis was a diving star in the 1984 and '88 games, he didn't come out as gay until 1994.)

It was a powerful human interest story and yet, even though that kiss was captured by live video feed, NBC opted not to show it—or even Mitcham’s medal ceremony—in its Olympics telecast.

After his historic performance, Mitcham was inundated with letters from gay teens inspired by his athleticism and openness, an experience the gold medal winner described as “extremely humbling."

Watch Mind/Game: The Unquiet Journey of Chamique Holdsclaw on May 3 at 10/9c on Logo TV.