Rugby sevens is fast. It's simultaneously rough and refined. And often, it's just downright spectacular.

Everything about the game is fast: seven-minute halves played by seven-member teams whose players streak, pass, catch, and tackle up and down the field. At the Rio Olympics, the men's and women's tournaments will each be played over three days packed with a breathless schedule that resembles a Netflix binge-watching session. Every half-hour, another game begins. In the early rounds, teams will play twice in one day.

The sport, which alongside golf is making its Olympic debut this year, shares the rough-and-tumble, no-pads-necessary attitude of traditional 15-man rugby. The game demands a specialized athlete, as Matt Cleary wrote last month in The Guardian. While speed is the biggest thing, "you also need optimal VO2 capacity, the ability to suck large amounts of oxygen into the lungs. You need to get up when you're down, repeatedly. You also have to make decisions when it feels like your lungs could shoot out your mouth."

Put it all together, and it's easy to imagine sevens becoming a break-out fan favorite of these Olympic Games.

Rugby sevens' appearance at the Games represents something of an Olympic comeback for rugby. The traditional version of the sport was played at four Olympics between 1900 and 1924. The U.S. took back-to-back golds at Antwerp in 1920 and Paris in 1924. The winning streak comes with an asterisk, though: The 1920 tournament was a two-way competition between America and France. Four years later Romania became the only new country to join the fray, guaranteeing at least that all three medals would be awarded.

Suffice it to say, the lack of international interest did not bode well, nor did the retirement of Pierre de Coubertin, the father of the modern Olympics and a driving force behind rugby's inclusion in those early years. There was also the matter of the brouhaha that followed the U.S. victory in 1924, when French fans — who'd been threatening American players throughout the game — rushed the field. A U.S. reserve player was knocked out after being hit in the face with a walking stick, and later, while the American flag was being raised, the national anthem was drowned out by boos and shrieks. Pelted with rocks and bottles, the Americans left the field under police escort. The sport was not re-upped for 1928.

Now rugby is back after a 92-year drought. (The International Olympic Committee's decision to admit sevens came in 2009, when rugby and golf beat squash, karate, softball, baseball, and roller sports for a spot in 2016.) It will also be on the docket in 2020, after which it will be reevaluated.

Women's play will take place Aug. 6–8, and men's Aug. 9–11. The tournaments — which each include 12 teams — start round-robin style, with every team in a four-team group facing each other. The best two in each group, plus two third-place teams, advance to the knockout stages.

The basic rules go like this: The ball can be kicked forward or passed backward or laterally. Teams earn five points for crossing the goal line — what's known as a try — similar to a touchdown in football. They then get two points for a conversion afterward, which involves drop-kicking the ball through the uprights. Players can try for a three-point, drop-kick-goal at any time if they think they're in range. And if a serious foul has been committed when the posts are within reach, players have the option to kick for a three-point penalty goal. (Speaking of which, players who land in the penalty box, or sin bin, are sidelined for two minutes.)

All of this unfolds on a field, or pitch, roughly the size of a football field. It's also the same size as the pitch for regular, 15-man rugby. Hence the need for stamina.

On the men's side, the big contenders are Fiji, Australia, South Africa, and New Zealand — but Fiji is the favorite for gold. The team is ranked number one in the world, and took its second straight world series title in May. A podium-owning moment would be historic for the country, as no Fijian athlete or team has ever medaled in the Olympics.

That's not to say the U.S. men couldn't work their way in there. The team is led by captain and British transplant Madison Hughes, who scored the most points in the 2015-16 rugby world series with 331. Carlin Isles is another to watch: A former track runner, his 100-meter time would have qualified him for the 2012 London Olympics if he'd been from any country other than the U.S.; he decided to try sevens after seeing some videos on YouTube. Then there's Nate Ebner, a Super Bowl ring-wearing special teams member of the New England Patriots. He inherited a love for rugby from his father, and played for the junior national team before going to college and switching sports.

Among the women, Australia, the 2015-16 world series winner, along with New Zealand, Canada, and England, are favorites. The U.S. women, ranked sixth in the world, are longer shots.

One other thing to note about sevens: the costumes. That's not rugby lingo for the teams' uniforms; it refers to actual costumes, worn by the fans, part of the festive atmosphere that's come to permeate games. As the pics from this Sydney tournament shows, spectators turn out as everything from Star Wars storm troopers to hula dancers, cave men, and lifeguards. So when a break in the action comes — brief as it may be — keep an eye on the stands.