They were playing one of the those new Nintendo systems that allow you to control the game by actually waving your hands. (Movement of the remotes directs the on-screen action.)
"We just went at each other, throwing punches," he said by phone Tuesday. "Ten minutes later, we're dripping with sweat. We couldn't even breathe. I'm thinking 'Oh, my God - this thing is working us out pretty good.'"
What would happen, he wondered, if he devised an exercise regimen based solely on the Wii?
This was the spark that led DeLorenzo, a 25-year-old-computer programmer, to begin a six-week routine of daily, half-hour work-outs on the Wii's boxing, tennis and baseball games. (He avoided golf, which he deemed not worth the time.)
The experiment ended Monday. The results can be followed on his blog, called WiiNintendo.net. He also posts a video there that shows how one works the Wii with ones hands. The site, which is independent from the manufacturer, also acknowledges some of the Wii mishaps people have suffered. The only damage DeLorenzo chronicles is to his laptop, which once caught a remote that slipped from his hand and flew across the room.
He tracked his weight, body mass index, calories burned per session, body fat percentage, heart rate, as well as something called "Wii fitness age" -- some with measurement devices sent to him for free after a New York Times column mentioned his experiment in passing last month.
The idea, DeLorenzo says, was to keep to his normal habits, with the exception of the 30-minute workout. "I ate Christmas dinner," he says. "I had drinks. This was my only exercise - I didn't jog or bike. I just walked around the city."
Go to his site to check out the intimate details, but the headline is that his waist melted from a 34 and a half inches to 31 inches. "I might actually have to have a belt on," he says.
He lost a total of nine pounds off the 180 he's weighed for the past two years. Before and after photographs (he's pretty dedicated to this project; there are charts and a video, too) show a man who has lost his love handles.
And when he began the experiment, the machine told him he had a Wii age of about 46. Six weeks later, he played like a 20-year-old.
So what's next? More of the same, says the man who got his first Nintendo system at age 5 on Christmas, 1986. He's addicted.
"I didn't do it yesterday," he says. "I kind of felt guilty, like I'd missed the gym. I play video games normally. I will keep something up."
There's been a healthy side-effect. His 42-year-old father was impressed enough that he went out and bought a Wii for himself.