"Support each other, assholes!" Beth Amphetamine yells. It's the end of a sweaty August practice for the Windy City Rollers All-Stars, and the hawkeyed cocaptain is giving her teammates her idea of a pep talk.

In the league's practice space, on the second floor of a Humboldt Park loft building, black mats line the walls and the cramped makeshift track smells like boiled rubber. It's humid; the air conditioner is on the fritz.

The team clusters around Beth for a morale-building exercise: each member talks up one of her peers. "Beth gets hit in the face a lot and she gets right back up," one skater offers. "I get hit in the face a lot too. Her calling me a pussy and twisting my nipples makes me not want to get hit in the face."

Laughter ricochets around the huddle.

The All-Stars are used to laughing. It's easy to laugh when you're winning. Off the track, they're lawyers, research analysts for unions, clerks at Whole Foods. On the track, they're speed demons and monster blockers who've defeated nearly every top derby team among the 98 leagues in the national Women's Flat Track Derby Association (WFTDA, or "wooft-dah," for short). In September they won the North Central regional tournament for the second consecutive year. Their roster boasts two competitive indoor speed skaters—Beth (aka Lucinda Scharbach) and Kola Loka (Dakota Prosch). And they're one of only three teams that've made it to nationals every year for the last three years.

This year though, the stakes are higher and winning has been harder.

This session is the All-Stars' last before they meet the 5280 Fight Club, a traveling team of the Rocky Mountain Rollergirls league. The Denver team is an upstart practicing a cunning new style of derby often referred to as "western style." The style has emerged only in the last year, bewildering traditionally successful teams and sending WFTDA officials running to the rule book.

To outsiders, derby might look like a bunch of skaters whizzing around on a track, but the game is deceptively complex and treacherous. A jammer from each team is tasked with breaking through and then lapping a labyrinthine pack of blockers, scoring a point for every opponent she passes during a series of two-minute sessions called jams. Pack members do everything they can within the rules—including body blocking and hip checking—to discourage the other team's jammer from scoring while helping their own get through.

Cocaptain Varla Vendetta, aka Jamie Ramsay, sums up the "straightforward" style of derby as "people running fast and hitting hard." It's the style of play that regularly draws thousands of rabid fans to Windy City Rollers bouts: hair-raisingly quick, action-packed, body-slamming derby.

But in the western style, skaters in the pack move at a snail's pace, stand almost completely still, or even skate backward. Besides really messing with competitors used to a high-speed game, these techniques outrage derby purists, who feel they transform an intensely physical contact sport into a mind-numbing exercise in strategy.

But if the Windy City Rollers All-Stars want a shot at the national championships—to be held in Chicago at the UIC Pavilion the first weekend in November—they're going to have to figure out how to contend with the western style.

It won't be easy. Rocky Mountain is currently ranked first in the nation by the independent Derby News Network, while the All-Stars, who've had an uneven season, have oscillated between ninth and 11th.

The Windy City Rollers, formed in 2004, held some of their early bouts in the orchestra pit of the Congress Theater, an improvised setup half the size of what's now considered a regulation track. Back then the game was spiked with WWE-like showmanship. Some fights were staged—others were not. Punishment for penalties took the form of crowd-pleasing stunts. "We were kind of trying to reference how roller derby used to be" back in the 70s, says Varla, who's been with the league since the first year.

Windy City Rollers All-Stars

Gil Leora

Since then, women's roller derby has evolved into a more legitimate sport, and within it, the Windy City Rollers have been a force to reckon with. The league has five home teams, which compete against one another, and two traveling teams, the A-list All-Stars and the B-list Second Wind, which compete against all-star teams from other leagues. The "bartenders and punk rock chicks," as Varla puts it, have been joined by more serious-minded athletes. Mock-fighting and stunts have been written out of the game. As ever, at the end of the night, the bruises and stress fractures are real.

(Not that derby still doesn't attract its share of skeptics. "They don't take us seriously because we don't have penises," cracks Barbara Brawlters, a skater for one of the Windy City home teams. "And strap-ons don't count.")

The league's administration has also gotten more serious. It's still entirely run on volunteer labor, from the league owners to the medical team at practices and games to the fans who assemble and dismantle the track. But the bouts have moved to bigger and bigger venues, from the Congress to the Cicero Stadium to the UIC Pavilion, where an average of 2,400 fans attend each Windy City Rollers bout. Big-name advertisers and sponsors, including Chipotle, Pabst Blue Ribbon, Yelp, the Onion, and Blockbuster, have come calling. A local TV station has approached the league about broadcasting bouts, but though they'd like to get roller derby on the air, league officials have decided against taking on the associated costs for now.

Ironically, coming off all this success, the All-Stars are at a transitional moment. The average career of a derby skater is three to four years; many talented old-timers have left. And the emergence of the western style has thrown the All-Stars, as well as many other teams, for a loop. To win at nationals, Windy City will have to step back into the role of the scrappy upstart: pissed off, hungry, and batshit-desperate to win.

At the final practice before the Rocky Mountain bout, Beth Amphetamine hits one note over and over: strategy, strategy, strategy. She instructs the skaters to watch archived videos of previous Rocky Mountain bouts online. "Remind yourself: they don't skate forward," she says. Before dispersing, the players huddle for a cheer: "Kill Rocky!"

Two nights later it's the All-Stars who get killed. Not just killed—massacred, 151-56. Jam after jam, the 5280 Fight Club blockers methodically control the speed of the pack. When their jammer effortlessly glides through the slowed pack her teammates set up for her, it's like a knife cutting through butter. It's inarguably ingenious—and infuriating to watch.

At the afterparty, one fan delivers the ultimate denouncement of the bout: "It was like going to a Cubs game."

"It sucks losing," says Varla Vendetta, sitting on the concrete steps outside the space as practice lets out the Thursday after the Rocky Mountain massacre. Varla, who won the league's "Most Villanous" title in 2005, says good night to bleary-eyed teammates as they straggle through the doors. It's almost 11 PM, on a school night.

I tell her about a postgame conversation with Rocky Mountain star skater Psycho Babble, who'd remarked that there were only two teams she'd ever really wanted to play: New York and Chicago. Not coincidentally, both are known for their straightforward style.

"Oh really?" Varla responds, in a tone that implies it's not the compliment I thought it was. "Well, she definitely gave me more motivation then."

The Rocky Mountain defeat wasn't the All-Stars' only crushing loss this season. The other was a June bout against the Gotham Girls Roller Derby All-Stars—a 141-point defeat. The Chicago-New York rivalry is legendary in the derby world. At the 2008 nationals, New York defeated Chicago in the championship game, and no one here has forgotten it.

"We went through years when we didn't lose games, or we lost maybe one game," Varla says. "Now we're losing games, and we lost significantly. This year has seen our two biggest losses, I think, ever.

"The All-Stars never lose like this," she continues. "I think it makes people feel vulnerable, and then they get edgy."

In fact Varla and Beth devoted the end of tonight's practice to an impromptu therapy session. As I'd walked in, the skaters were gathered at the back of the space—a medical area cluttered with bandages, ibuprofen bottles, and single crutches—and the cocaptains had opened the floor to anyone who wanted to discuss the palpable tension and sour mood.

One skater suggested waiting at least ten seconds before criticizing or blowing up at a teammate.

Another cut to the chase: "Don't snap at someone! We know each other well enough. We can have normal adult conversations."

"It didn't start with snapping," someone else replied. "It started with, 'I'm embarrassed, this sucks.' Then people go out there to play and feel like shit. They get even more upset."

Varla Vendetta (left) in the bout against the Rocky Mountain Rollergirls' 5280 Fight Club

Gil Leora

The western style may not be the team's only obstacle—but it's a big one. The national scene first got wind of it last fall, watching the 2009 West division regionals. A month later at the nationals, the All-Stars were eliminated early by the Mile High Club of the Denver Roller Dolls—the league Varla says originally devised the strategy.

Western style goes by many other names: "slow derby," "stopper derby," "stroller derby," "cerebral derby." And it continues to evolve. But its dominant trait is the slow pack.

The slow pack challenges the competing jammer, used to skating at high speeds, to cut through a stopped or slow group of players without illegally hitting another opponent in the back. "They play very slow," says Beth. "They tend to create walls that are stopped on the track, which is a challenge for our jammers because if they clip you when they're stopped, (a) you go flying because of momentum and physics and (b) you're liable to get a back blocking major [penalty]."

"Players would just stop on the track and bait their opponents," remembers Helsa Wayton, aka Cheryl Runge-LoVerde, an All-Stars veteran who this year is skating with the city's other WFTDA league, the Chicago Outfit. "They basically let a jammer run up as fast as they can."

Another hallmark of the western style is skating backward. When a player hits an opposing jammer out of bounds, the jammer has to reenter behind that player. So if that player skates backward on the track before the jammer can hop in-bounds behind her, the jammer is forced to retreat farther to reenter, delaying her next chance to pass the pack and score points.

"It was almost as if they were exploiting the rule book," says blocker Di Richmond (Kelly Hendrickson).

Since 2009, actually, the rule book has been slightly revised, "in order to prevent people from staying stopped on the track the entire time," explains Beth. But less-extreme elements of the western style are apparently here to stay.

At the 2010 North Central regionals in September, most bouts showcased some degree of western-style derby. "Everyone is doing it more," says Helsa. "As a player, it's hard to say that you want to do it more, but you know you have to. Because it's going to be done by the other team."

At their next home game, September 25, the All-Stars play the Texecutioners, the traveling team of the Texas Rollergirls—the historic league that started the flat-track derby revival back in 2003. Thousands of fans stream into the UIC Pavilion to watch these two old-school dames go head to head.

Fweeeeeeeeh!

At the whistle, competing jammers Jackie Daniels and Olivia Shootin' John start off racing toward the pack, about 30 feet ahead. The Texecutioners' Olivia veers to the outside, but she's held off by the All-Stars' Amy Nonamey. Jackie swoops up front to become the lead jammer. Meanwhile Hoosier Mama and Varla keep Olivia entangled in the pack.

Jackie laps the pack again, scoring a grand slam of five points. As if that isn't enough, she scores another partial lap, managing to nab a few extra points before calling the jam to a close—a lead jammer's prerogative—and destroying Olivia's chance at earning any points for the Texecutioners.

The crowd spontaneously combusts. The score is 8-0.

The bout feels special, and not just because the All-Stars are leading. Both teams seem to have made a conscious decision to keep it old-school. For two thrilling hours the crowd is treated to the dizzying spectacle of loose, light-footed, exhilarating derby circa 2008. Opponents are high-fiving each other on the track.

The first jam sets the tone for the rest of the bout, which ends in an 88-62 win for the All-Stars. They couldn't have asked for a better final home game before the nationals.

Afterward players and fans are packed cheek-to-jowl at the Bottom Lounge in the West Loop. It's more crowded than usual because the second floor is reserved for a private function: there's a wedding party upstairs while downstairs the derby crowd parties down. The energy of the game still vibrates in the air.

Beth and I take our drinks near the entrance, where we're nonetheless yelling over the loud music and the celebratory din. "Texas is always a good game for us," she shouts. "We both play very similarly. Both teams can play slow derby, but we prefer fast derby."

It's a choice teams increasingly don't have the luxury of making. Earlier this summer the Philly Roller Girls' Liberty Belles beat Denver's Mile High Club. It was a squeaker, by only 13 points, but the takeaway was this: an eastern team beat the team that invented the western style at their own game.

"The quote unquote western-style derby is all over now, because we've all had to learn how to do it," says Helsa.

But for the All-Stars, the solution isn't just imitation. They already tried that. "You know, now we're kind of sitting back and saying it, well, screw it," Varla says. "We just want to play what our game is. If there are western teams saying our game is this slow-stop derby, we want to try to find an identity for ourselves as well."

Beth has seen more teams adapt elements of the western style, but she thinks the most effective teams now are those that can play a hybrid of straightforward and western-style derby. Not many teams just do western style anymore: "Yes, teams are still doing stopped style, but changing speeds a lot," she says, "slow-fast-slow."

This hybrid style may turn out to be the news at nationals. Derby's still a new sport, points out Dinah Party, aka Erin Karson, speaking as the league's official press contact. "As teams from various regions develop new strategy for game play, other regional teams pick up and learn. All derby has an ever-changing style that all teams learn and/or adapt in order to play the best game possible."

At the Bottom Lounge, when I ask Beth about the All Stars' toughest competition at nationals, she doesn't have to think about the answer. The memory of the 5280 Fight Club bout is still fresh. "Rocky Mountain I would say is the team to watch this year," she says. "They are a killer. They can stop on a dime together on the track, and then all together speed the fuck up. It's amazing.

"I find them terrifying," she adds. Except there's not an ounce of terror in her voice.