MORE THAN 130 years ago, at the first Olympic Games in Athens, Boston University law student Thomas Burke took his mark at the 100-meter dash not in a standing position, but a crouch—what was then considered an unusual starting stance. But far more unusual, by today's standards, was his gold-medal winning time of 12 seconds flat. These days, talented middle schoolers post 100-meter times BETTER than Burke's. In March 2018, 15-year-old Briana Williams, a high school SOPHOMORE, set a world age-group record in the event with a time of 11.13 seconds. The record for boys 18-and-under is nearly a second FASTER still: Set in 2017 by Anthony Schwartz, the 10.15-second time would have won gold at 1980's Summer Games.

Today, though, on the world stage, Schwartz wouldn't even podium: In the past 30 years, only three sprinters have medaled at the Olympics with a time SLOWER than 10 seconds. Propelled by more effective training, GRIPPIER track surfaces, FASTER footwear, and, yes, pharmaceuticals, competitors at every level of track and field's premier event have steadily chipped away at the world's BEST 100-meter times. Jamaican sprinter Usain Bolt holds the current world record: a sprightly 9.58 seconds. The surprisingly persistent record progression is enough to make anyone ask: When will the FASTEST people on Earth cease to become any FASTER? And when they do, what will the FASTEST time ultimately be?

(...) Which is one reason biomechanists approach the matter somewhat differently than mathematicians. They address the second question by investigating not when Bolt's record might fall, but by __________, based on the bodies of today's FASTEST sprinters. "Once they get rolling, the force they apply becomes a motion-based mechanism, where they use their limbs to throw a punch at the ground," says biomechanist Peter Weyand. As director of the Locomotor Performance Laboratory at Southern Methodist University in Dallas, Weyand invites many of the FASTEST sprinters on Earth to run in short bursts in front of high-speed, motion-tracking cameras on a bespoke, force-sensing treadmill that makes the thing you trot on at your gym look like a glorified hamster wheel.

Based on his observations, Weyand says the two BIGGEST factors limiting the performance of elite sprinters are __________force they can apply to the ground, and how fast. At current top speeds of around 27 miles per hour, he says elite male sprinters like Usain Bolt put down roughly five times their body weight, in between .085 and 0.09 seconds.

(...) That probably puts the theoretical limit for the 100 meter dash CLOSER to 9.58 than 9.00. But Weyand, for his part, thinks athletes have plenty of room to improve. "If you put together a perfect human being, and the perfect race, I could certainly see something in the low 9.40-second range, maybe a little bit FASTER than that, under currently legal conditions," he says.

Complete the blanks with how many or how much in order of appearance.