A 16-year-old from New Zealand has set a new world record for the fastest mile run by an under–18 athlete.

Sam Ruthe crossed the finish line in an extraordinary 3:48.88 minutes at the John Thomas Terrier Classic in Boston, United States on Saturday, outpacing a field of professionals to win the invitational heat on an indoor track.

“I didn’t feel like I was going that fast to be honest. I still don’t believe it… I’m completely stoked,” Ruthe told the track broadcaster Flo Track after the record-breaking outing.

Approaching his final lap, Ruthe was in second place behind Belgian Pieter Sisk. But with a burst of speed in the final 100 meters, he surged ahead to finish 1.43 seconds quicker than Sisk.

The teenager said the Boston race was only meant to be a “rust buster” to shake off the cobwebs after making the 9,000-mile (14,500-kilometer) journey from his home country three days earlier.

“There’s definitely more in the tank… I’ve got three more races and could probably go a bit faster,” he said immediately after the race.

Ruthe caught the attention of the athletics world last March, when he became the youngest athlete on record to run a sub-four-minute mile, clocking 3:58.35 in Auckland.

His performance In Boston on Saturday also set a new New Zealand record for any age, surpassing Olympic gold medalist John Walker’s time of 3:49.08, which he ran in Norway aged 30, more than four decades ago, according to Athletics New Zealand. Walker was the first man in history to run a sub–3:50 mile.

“I really didn’t expect to get Walker’s national record (today),” Ruthe told CNN Sports. “I hoped to get it one day but that was a real surprise as I thought it may have been three or four years away. I feel like I’m the luckiest person in the world.”

The teen athlete comes from a family of runners. His parents Ben and Jessica Ruthe are both national-level champion athletes in New Zealand and his grandmother Rosemary Stirling is a 1972 Olympian.

“To see him achieve (the record time) so early and at such a level is wonderful but comes with significant challenges,” Ben Ruthe told CNN Sports.

“The time he ran today, for example, is faster than anyone has ever run in New Zealand, so (to keep developing) he needs to travel for racing and quite considerable distances. It took 50 hours to get to Boston from home but all well worth it to get good competition,” he said.

The Boston University Track and Tennis Center is widely considered one of the fastest indoor tracks in the world, known for producing several national and world records.

But running indoors was an “unusual” experience for Ruthe, because New Zealand does not have indoor tracks.

“I was a bit worried about tight turns and tactics because of the sharp turns on a short track but I got into a really good spot early and it all just felt good,” he said.

Ruthe’s time now ranks as the 11th-fastest indoor mile for all ages, but he is still 3.7 seconds off the indoor world record set last year by Jakob Ingebrigtsen, 25, who ran a time of 3:45.14 in Liévin, France.

Athletics records set on indoor 200m tracks and outdoor 400m tracks are kept separate, according to World Athletics, because they are not directly comparable, due to differences in track size, tighter indoor turns and varying weather and facility conditions.

Ruthe said he “definitely felt” the advantage of running on the indoor track and being able to follow other runners, an experience he rarely gets in New Zealand, which helped pull him through the race.

“Nice not to worry about the wind like we have to on our long island in the middle of an ocean at home,” he said.

Last week, Ruthe clocked 3:53.83 seconds at the Cooks Classic in Whanganui, New Zealand, finishing behind his training parter Sam Tanner, a Kiwi Olympian, but breaking the world outdoor record for a 16-year-old, adding yet another achievement to his growing list of milestones.

The Boston race is the first of four mile races Ruthe plans to run this month, before he returns home for New Zealand’s national championships in March. (CNN)

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