Having earned and accepted a Buckeye scholarship offer in March, the three-star prospect from Shaker Heights, Ohio, had little to gain other than perhaps a nasty case of heatstroke on a balmy day that more resembled late July than mid-June in Columbus.
But that's not how Underwood saw it, so he was at the Woody Hayes Athletics Center working out among more than 400 high school juniors and seniors from all over Ohio and beyond.
The morning was spent going from station to station performing a variety of drills for speed, agility and conditioning before an afternoon of individual work on football fundamentals.
"I got an opportunity to get coached by (Ohio State offensive line coach Jim Bollman)and get a feel for the Ohio State regimen," Underwood said after the camp. "They worked me out pretty hard. Ultimately, I just want to get better."
Asked the No. 1 lesson he learned during the day, he identified communication.
"If you've got tackles or ends twisting, you've got to be able to communicate with the man next to you," he said.
"He's a real cool guy," he said of Miller, the nation's No. 1-rated quarterback prospect. "A nice pickup.
"It's cool, because you get a chance to bond with the players that are going to be coming here with you. A lot of them are good guys, funny guys. They say that our class is by far one of the best classes yet. We have a lot of talent, so hopefully we can do some damage with this class."
Though Underwood mostly has played tackle at Shaker Heights, the 6-3, 310-pounder expects to be a guard when he reaches Columbus next year.
"Coach Bolls said there are really no boundaries to where I could play, but I think most likely guard because of my height," he said. "There are bigger guys here than me who are like 6-8, 6-7."
Underwood has modest goals for his senior season at Shaker Heights.
"Ultimately the goal is to win and for me to become a better leader," he said. "We lost like 40 seniors, so the goal is to get better and improve as a leader, to pull the guys together and try to get to the playoffs.
"Coach Bolls is just telling me to do what I do on the field but make sure I finish strong in the classroom."