Siblings Matt and Becca Hamilton, who will compete in curling mixed doubles as well as the men’s and women’s events take a selfie after a news conference. (Aaron Favila/AP)

The 40-pound granite stone at the heart of curling is nearly impossible to lift — heavier, somehow, than any 40-pound bag of garden mulch or dog food because its entire mass is crammed into a rock no bigger than a bistro chair cushion with a small handle attached.

But the point of curling has nothing to do with lifting this stone. It lies in making it glide effortlessly over a sheet of pebbled ice and come to a stop with a sniper’s precision by releasing it with the gentlest touch, as if it were a baby sparrow, while applying the subtlest directional spin.

So the Olympic debut of mixed doubles curling here at the 2018 PyeongChang Winter Games raises the question — at least to all but curling practitioners — why isn’t curling a coed sport in the first place? If it rewards touch and control more than strength, what makes curling a gender-specific sport, apart from a history and tradition that date back to 16th century Scotland?

In other words, if an elite men’s curling team faced an elite women’s curling team, would it be a fair fight?

No, as it turns out, for two reasons that have to do with strength, as a handful of Olympic curlers and coaches explained Tuesday. And no for a surprising third reason, according to performance-based evidence gathered in Canada, whose men’s and women’s teams are defending Olympic champions: a male advantage in curling strategy that’s not fully understood and is the subject of ongoing research.

It’s not simply that Canada’s top male skips (the chief strategist of a curling team) are more aggressive play callers than the top female skips. The difference is more nuanced, according to Kyle Paquette, director of sports science for Curling Canada, suggesting to some that top male curling skips may see angles better and anticipate three or four shots ahead better than their female counterparts.


Stones await competitors at the Gangneung Curling Center. Competition gets underway Thursday morning in PyeongChang (Wednesday night Eastern time). (Jae C. Hong/AP)

Angles play a significant role in curling, much as they do in pool.

“Let’s say we have a half-dozen rocks in play,” said Paquette, who holds a doctorate in human kinetics. “Male skips will just sometimes see shots that top female skips won’t see at times. I would [like to] say that works vice versa, to a certain degree. But we’re not certain at this point.”

According to Paquette, Canadian curling officials had the country’s top men’s team plays its top women’s team 15 or 20 years ago. The result wasn’t close. They repeated the experiment 10 years ago and got the same lopsided result.

Nonetheless, he believes that strategy plays a more significant role in curling success than strength. That’s why Curling Canada is working to develop a metric that assesses the curling IQ or curling savviness of a skip, Paquette explained, equating it to an NFL quarterback rating. The ideal curling metric would capture the myriad factors behind successful skips and help coaches close any performance gap.

“The data suggests that even tactically, there are [gender] differences in terms of game-calling,” Paquette said. “To be honest, we’re not quite sure why at this point.”

The strength advantage is easier to understand and comes into play in specific yet significant facets of the sport.

For starters, men would have the edge in a curling battle of the sexes because core muscle strength affects the speed with which curlers propel themselves from the “hack” (akin to a starting block) and reach the point where they are required to release the stone. A top male curler can cover that distance in about five seconds, whereas a top female takes about seven seconds.

Power also is an asset as stones accumulate near the bull’s-eye-like target at one end of the ice and the roughhousing begins. Curling teams amass points by placing stones in concentric rings on the ice and knocking opponents’ stones out of scoring position. When it’s essential to send a rival’s stone flying, strength helps.

“If the other team has a couple of rocks in the rings [scoring position], generally the male curler is going to be able to move more granite, so to speak, and throw a little harder,” said Matt Hamilton, 28, of McFarland, Wis., a 6-foot-2 curler who is on the men’s team and will compete with his sister Becca, 28, in the inaugural Olympic mixed doubles event.

Mixed doubles curling kicks off the 2018 Olympic competition Thursday (Wednesday night Eastern), the day before the Opening Ceremonies, with the Hamiltons facing a Russian husband-and-wife duo in the first of seven round-robin games. Of the eight countries that qualified for the mixed doubles event (Canada, China, Finland, South Korea, Norway, Olympic Athletes from Russia, Switzerland and the United States), four advance to the playoffs.

Mixed doubles curling differs from traditional four-person team curling in many respects. The games last 90 minutes as opposed to three hours (better suited for TV broadcasts) and are faster-paced and more dynamic. Rather than start with an empty sheet of ice, mixed doubles curling begins with two stones pre-placed — one in the center of the target (or “house”) and one nearby, “guarding” the other stone — so the game “cuts to the chase,” as it were, of knocking stones out of position.

The hope of the sport’s international governing body is that the addition of mixed doubles will spark more interest and increase the countries that compete — a surprisingly broad cohort that already includes Brazil, Mexico, Guyana, Qatar and Israel, among others.

Already, the Hamilton siblings have rare exposure at home, as guests of Jimmy Fallon on “The Tonight Show” in the run-up to the Games.

“I love the [mixed doubles] sport because it’s fast, it has always got rocks in play and there’s always stuff going on,” said Derek Brown, a Scot who is director of high performance for USA Curling. “The traditional game has been around for hundreds of years. When mixed doubles came along, people weren’t so sure, but when you see it, it’s just exciting.”