CARLTON COUNTY, Minn. — Austin Nastrom, according to his friends, hit the southern terminus of the Superior Hiking Trail with a big grin at about mid-afternoon Tuesday.

The 24-year-old, who lives in La Crosse, Wis., and works for a company that coaches injured runners back to health, had spent the past 6 days, 8 hours and 30 minutes cruising the 310-mile route from the Canadian border to this deeply wooded spot off a single-lane muddy gravel road at the Minnesota-Wisconsin border.

It is the fastest known time for a supported athlete — which means he traveled with a crew of family, friends and a coworker who addressed his needs every 7-10 miles, he said. Some nights they camped; some nights they stayed in a hotel.

“Sore, very sore,” he said, when asked how he felt. His ankles were toast, he said, his left knee was swollen and his toes were in tough shape. The bottoms of his feet were fine, though.

Nastrom is an ultramarathon runner whose most recent race was the Ouray 100 Mile Endurance Run in Colorado (he finished eighth) this past July. He had been plotting to attempt the Superior Hiking Trail for about a year, he said.

“To see if I could,” he said. “I’ve done a few hundred-milers in the past. I wanted to triple the distance and push it to the limit.”

Individual trail challenges are gaining in popularity, Nastrom said, noting the recent attempts at the 2,189-mile Appalachian Trail. In 2015, Scott Jurek, who grew up in Proctor, set the supported through-hike record on the trail by completing it in 46 days, 8 hours, 7 minutes.

Nastrom started running on Wednesday, Aug. 28, hitting 60 miles on consecutive days. The past few, starting at sunup and continuing until sundown, were 40-milers. On Tuesday he closed with 20. He was familiar with parts of the trail from the Superior 100 course, and he also knows the Duluth segments. His favorite part, he said, is Ely’s Peak.

“That’s a tough spot to be,” Nastrom said.

He said he tried to eat a lot along the way, including pizza from Sven & Ole’s in Grand Marais and fast food tacos. On Monday afternoon he was spotted at the trailhead near Highland Street lying on a blanket and eating food from McDonald’s. It was dietitian-approved. His friend and coworker Rachel Turi, who was part of his crew, said he needed the sodium and the calories.

The trail ends in a remote spot near Mountain Goat Road, a seasonal gravel road that isn’t maintained. The final Superior Hiking Trail parking spot is 1.9 miles from the end. Nastrom’s crew parked in the lot but went out on the path to greet him. Also part of the group: Ajay Pickett, who currently holds the record for completing the route without support. He finished it in 7 days, 20 hours, 56 minutes in September 2018, bettering Mike Ward’s record of 8 days, 7 hours and 59 minutes. He did part of it on a broken leg.

Pickett said Nastrom crushed the supported record. Cam Schaefer of Apple Valley set it in mid-July, completing the route in 6 days, 18 hours, 45 minutes, according to Minnesota Public Radio.

“It’s truly impressive,” Pickett said.

Nastrom said he spent much of his time in the woods thinking “keep going, just keep going.”

“I underestimated it a lot. This trail has a way of breaking you down,” said Nastrom, who was headed back home immediately following his finish. He was scheduled to work on Wednesday.