SOUTH PORTLAND — When Dan Guiliani crouches low in the shot put circle, his knees bent and upper body leaning slightly forward, he sets in motion a fluid maneuver you wouldn’t expect from someone who’s 6-foot-3 and 270 pounds. Hopping from one foot to the other and back again, he turns twice in the tight circle with increasing speed before he fires his right arm over his head like a catapult, launching a 12-pound ball out to the field beyond.

The carefully choreographed spin move creates a powerful torque that has helped Guiliani, a 17-year-old junior at South Portland High, throw a shot put farther than any Maine high schooler before him.

The spin technique is somewhat unconventional for high schoolers, most of whom use a glide move. Even more unconventional is Guiliani’s progress – he has improved on his best effort by a stunning 21 feet in 15 months.

On May 19, he threw a personal best of 66 feet, 5 inches. Until this spring, the state’s all-time outdoor best was 60-33/4 (set by Dan Smith of Thornton Academy in 2009). In a sport where records typically are broken in incremental fashion, Guiliani’s throw topped Smith’s mark by nearly 10 percent.

Heading into Saturday’s state track and field championships, no other shot putter in Maine has thrown as far as 57 feet this spring. Guiliani, ranked No. 4 in the nation, says his sights are set on 70 feet, a distance rarely achieved by U.S. high schoolers.

Guiliani’s rapid improvement has longtime track and field observers doing a double-take.

“Either he hit a growth spurt all of a sudden or, to improve by 20 feet – I’ve never heard of anyone doing something like that,” said Bill Kulis, who coached Sam Bombaugh of Falmouth (Massachusetts) High to a fourth-place finish at nationals in 2010.

University of Florida associate head coach Steve Lemke, who has mentored 14 NCAA throwing champions and been an assistant coach on four U.S. Olympic teams, said the nation’s best throwers typically improve at a more gradual pace.

“You never really know how someone will make a change … but that’s a heck of a big jump,” Lemke said. “That’s a huge jump for one year. You don’t see that very often.”

Matt Bryan, who coached Nick Demaline of Swanton, Ohio, to a second-place finish at the high school national championships last year, said: “Over the course of four years you see that kind of progress, of 20 to 25 feet, not in one year.”

Auburn University throws coach Knut Hjeltnes, who competed in the discus at three Olympics, said: “That is really an unbelievable improvement.”

To all of them, Guiliani, a soft-spoken and polite young man, responds with conviction.

“I’ve progressed through hard work,” he said. “I spend 95 percent of my time working on the shot put. This is my life. This is what I do. This is important to me.

“I’m not surprised at the improvement. Because I think if anybody spent that much time working on something, they would get very good at it. And I want to see how far I can go with this.”

GETTING ACROSS THE CIRCLE

As a sophomore in 2014, Guiliani placed seventh at the Class A indoor state championships with a throw of 44-11 1/2. That success fueled his interest in the shot put. South Portland Coach David Kahill started working with Guiliani to get him to use his legs more in his throw, though Guiliani was still using the glide technique.

“I didn’t get drastically stronger or bigger. But I was getting across the circle faster,” Guiliani said of last spring. “I was more stable, more balanced. I really started to follow through.”

Last June, he won the Class A outdoor title with a throw of 53-6, the first time he had thrown over 50 feet in a meet. A week later, he threw 54-10 to place second at the New England championships.

“Last year when he won states a lot of people thought 53-6 was out of nowhere,” Kahill said. “He hadn’t broken 50 at a meet, but he had done it in practice. It didn’t come out of nowhere.”

After making such a big improvement, Guiliani was hooked. He watched the New England champion, Evan Dombrowski of Danvers, Massachusetts, use the spin technique to throw 55-1 1/2, and decided to change his approach.

“His throw was effortless with the spin. I was in shock. I wanted to learn that,” Guiliani said.

Guiliani committed himself last summer to a better diet, harder weightlifting sessions and learning the spin technique.

He worked on breaking down the spin move every day last summer from videos he found online. Even during double sessions of high school football practice in August, Guiliani still devoted three hours a day to the shot put.

He also spent more time in the weight room and improved his numbers there: From 275 pounds in the bench press to 405; from 315 pounds in squats to 555; and from 455 pounds in the dead lift to 570.

“That’s the other half of it. I got stronger,” Guiliani said.

Guiliani kept a detailed log book of what he ate and began taking protein shakes. He broke down YouTube videos of the world’s best throwers to see how they mastered the spin.

“He works tremendously hard in practice and on his own. Before school I’ve driven by and seen him in open fields. His mom says he’s destroyed the yard,” Kahill said.

‘JUST INCREDIBLE’

By the time the indoor track season started this winter, Guiliani had remade himself as a thrower.

“We took what he had done and improved on it,” Kahill said.

Kahill helped Guiliani get even faster and become more stable, which gave him added power. They worked on his foot placement. Toward the end of the indoor season, the two realized his feet were too close together, and when Guiliani put them slightly farther apart, he gained greater balance and acceleration.

Guiliani threw 58-7 1/2 to win the Dartmouth Relays in January. He fouled on all three of his throws at the indoor state championships, but rebounded two weeks later to win a meet in Orono with a throw of 62-4. That topped the state’s all-time best indoor mark by a high schooler, set by Portland’s Ed Bogdanovich in 1977 (62-1).

“Even at the Dartmouth Relays when I threw 58 feet, my feet were very close,” Guiliani said. “A lot of that throw was upper body doing the work. When I moved my feet farther apart, I could feel the power at the finish. There is a crazy difference. That’s how I jumped from 58 to 62.”

Steve Vaitones, a high school official with USA Track and Field for three decades, said many factors could lead to the kind of improvement shown by Guiliani: if an athlete changed coaches, attended elite camps, or switched to the spin.

But he added: “60 feet is a rare distance in general.”

The national high school record of 81-3 1/2 was established in 1979 by Michael Carter of Dallas, who went on to win a silver medal at the 1984 Summer Olympics.

However, since 1956, only 24 other high schoolers in New England have broken 60 feet in the shot put, said Larry Newman, a senior correspondent for Track and Field News.

Guiliani has caught the attention of longtime track observers in Maine, too.

“(Former state champion) Dan Smith and Ed Bogdanovich together threw 60 feet maybe five times in their careers. (Guiliani) did it twice at his last two meets,” Thornton Academy Coach George Mendros said earlier this spring.

Mendros said the kind of rapid improvement Guiliani has seen is not uncommon for high school athletes – but at a much lower level of competition.

“I’ve only seen that with lesser athletes. Then it’s a lot easier. To improve that much at that level is just incredible,” Mendros said.

Bogdanovich, who has held the Class A indoor state record for 38 years, said his progress was more measured.

“It takes years of daily hourly practices,” said Bogdanovich, who went on to compete for the University of Pennsylvania and win an Ivy League title. “The typical high school kid, if they stick with it, if they practice over the summer, a good measure of improvement for them is five feet a year.”

In high school, Bogdanovich threw 53-8 as a sophomore, 58-9 as junior and 62-1 as a senior, using the glide technique.

Then again, Bogdanovich said, “Not many people did the spin back then.”

‘TREMENDOUS ACCELERATION’

Guiliani said his peers have made occasional jokes about him using performance-enhancing drugs, but nobody has made serious accusations.

“I’ve had cases where people have said things, but I don’t let it bother me because it’s not true,” he said. “It’s cheating. It’s not right. It’s obviously unhealthy.”

Kahill, a history teacher at South Portland, said Guiliani is not a towering, muscle-bound presence compared with the nation’s best throwers.

“The development of Danny’s overall technique is pretty clear. Anyone who has watched Danny throw doesn’t have any suspicions at all,” Kahill said.

Jim Spier, who co-founded the New Balance Indoor and Outdoor Championships for high school athletes, said in cases where exceptional coaching is added and the switch is made to the spin, great gains can be made.

“I have noticed similar things over the years,” said Spier, of Chapel Hill, North Carolina. “The girl who set the national school record last year, Raven Sander, threw 42 feet as a junior and the next year threw 55 feet. It’s unheard of, but what she did was change from the (glide) to the spin, and she got very good coaching to help her improve her technique. It can happen.”

Kahill says Guiliani now does the spin nearly perfectly, getting faster as he whirls around.

“The final thing he does exceptionally well is at the very end he gets his last foot down with tremendous acceleration. Other people in the spin maintain the speed or decelerate,” Kahill said of Guiliani, who also throws the javelin and is ranked No. 1 in the state in the discus.

Guiliani, who did not compete at the 2015 indoor nationals because of a wrist injury, will not compete at outdoor nationals this month. Instead, he plans to attend an elite camp led by former Olympians in Washington state this summer. He said it would be too costly to attend both the camp and the national meet in Greensboro, North Carolina.

Right now, Guiliani is intent on throwing a personal best at the state meet Saturday. He does not plan to repeat the setback he suffered at the indoor state meet, when he fouled out of the competition.

“I got too pumped up. I was very nervous because I was seeded first,” Guiliani said.

“Since then my first throws are very conservative. I just put one out there to get one on the board. Then I let loose for the next five throws. But sometimes the first throw ends up the best. So now I think being calm and relaxed might be better.”