BEIJING (AP) — Russia’s “Quad Squad” of figure skaters will try for an Olympics podium sweep by landing the thrilling quadruple jumps that remain rare in the women's competition. But could skaters one day add a fifth rotation to their jumps?

Sports experts say it’s not clear what the human limits might be on the number of rotations a skater could complete. Quadruple jumps have become standard in the men's competition since Canadian Kurt Browning landed the first one in 1988. For women, Japan’s Miki Ando achieved the feat in 2002.

Yet the quads on display in women’s skating at the Beijing Games only came onto the scene in a big way in the last few years.

Here's a look at how the jumps are achieved.

WHAT DETERMINES THE ROTATIONS IN A JUMP?

To get in as many rotations as possible during a jump, experts say skaters need to launch themselves as high and far into the air as possible to maximize their spinning time.

The speed and strength needed for launching — and landing — is partly why quads are more common in men’s skating.

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But a factor that could favor women is a skater’s body dimensions. A skater with a narrow frame, for example, might have an advantage over those with wide shoulders, said Rajiv Ranganathan, an expert in body movements at Michigan State University. That could let them hold their bodies more tightly with their arms in the air, allowing them to achieve more rotations.

WHAT DO QUADS ENTAIL?

A quadruple jump entails four rotations, as the name implies. But exactly how skaters achieve the feat can vary.

In recent years, it’s become more common for skaters to start spinning before they launch off the ice, said Polina Edmunds, who competed in the 2014 Olympics in Sochi. That spin – known as pre-rotation – is another reason why quads in women’s skating aren't as rare as they once were.

“The line is blurred right now because we’re not looking at or penalizing pre-rotation,” she said.

There’s a push in the skating community for pre-rotation, which might consist of a half turn or more, to be factored into scoring, Edmunds said. Currently, the technical panel looks at whether the landing is clean.

HOW ARE SKATERS AFFECTED?

Landing quadruple jumps can be extremely stressful on bodies.

With basketball or volleyball, for example, players land more gradually starting with the front of their feet, which helps spread absorption of the impact, said Karl Erickson sports performance coach at Mayo Clinic. With skating, the landing is more abrupt and on a single foot tied into a skate.

“It’s a crazy amount of force that they have to be able to absorb quickly and land gracefully," Erickson said.

Since skaters are rewarded for attempting quads even if they don't land them, they can feel pressured to try them, Edmunds said.

“More young girls are going to be attempting these quads, even at the cost of them landing wrong and risking themselves injury,” she said.

Edmunds also noted the young age of the skaters landing quads in women’s skating, a reflection of the advantages of being small. Russian favorite Kamila Valieva, the leader after the short program, is 15 years old. Her teammates, Anna Shcherbakova and Alexandra Trusova, are both 17.

WHAT ABOUT THE DRUG SCANDAL?

A sample taken from Valieva weeks before the Olympics tested positive for a drug that's banned by the World Anti-Doping Agency.

The drug, trimetazidine, is intended to help increase blood flow to the heart, which would typically help older people with heart disease, said Dr. Michael Fredericson of Stanford University’s School of Medicine.

For athletes, he said the increased blood flow could potentially help boost endurance, allowing them to exercise intensely for a longer period of time. He said it's not clear what benefit it might bring a skater.

Lawyers for Valieva have cited contamination from the heart medication her grandfather was taking.

HOW MANY SPINS COULD A SKATER POSSIBLY ACHIEVE?

It’s not known how many more rotations a skater could achieve. But past assumptions about the limits of human performance — such as the 4-minute mile — have been proven wrong, noted Michigan State’s Ranganathan.

The next leap forward in jumping appears to be the quad axel, a 4 1/2-revolution jump that Japan’s Yuzuru Hanyu fell on last week, when he tried to become the first to land the forward-starting jump in competition.

Still, Ranganathan noted the height needed for spins in skating jumps.

“That may eventually place a limit on how many rotations we could possibly achieve,” he said.

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AP Sports Writer Dave Skretta contributed to this report.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.

Miki Ando

EXPLAINER: How figure skaters deliver quadruple jumps