That's where I catch up with Praiss. He wears gray sweat pants and a red Special Olympics T-shirt, and is a study in calm concentration as he lifts, presses, and pumps.
"David is very strong," trainer Blake Kondras says. "He bench-presses over 300 pounds, squat presses over 400, and deadlifts over 300."
There's more than mere strength involved, Kondras notes. Praiss has mastered techniques as well.
"Without the right form, you can't be as strong," adds the trainer, who lives in Bellmawr.
Praiss (pronounced price) lives with his parents in Haddon Heights.
"He started with track and field, swimming, and basketball," says his father, Donald, a retired urologist. "When he was 11 or 12, power-lifting started in the Special Olympics, and he was in there, too.
"He's a fantastic Alpine skier. And you know why? Leg strength. He'll do 500-pound leg presses - 30 or 40 of them."
Donald Praiss, 82, was determined that his son not spend his life like a young man he knew decades ago, who also had Down syndrome.
"All he did was sit in the backyard and do nothing," he recalls. "That really struck the heck out of me."
Adds Dorothy Praiss, "I'm just very proud of David. He has difficulty with language, but he never gets frustrated. He's such a good-natured fellow."
Although he is unable to read or write, David Praiss works at the Abilities Center of Southern New Jersey, in Westville, five days a week. His favorite tasks are those that involve heavy lifting, but he does maintenance and housekeeping as well.
"What he does, through his athletics and bodybuilding, speaks to the kind of determination and capabilities that people with disabilities have," says Susan Perron, president and CEO of the nonprofit training and employment center.
"It requires an incredible amount of self-discipline," adds Perron, who has known him for about 25 years. "It's really a tribute to him that even though getting older, he's still at it."
It can be difficult for strangers like me to understand David Praiss, who is nevertheless quite sociable. He seems to know everyone at the gym, and vice versa.
Magnolia resident Joe Wilson is a Royal Fitness regular.
"I've been going there for a lot of years, and David is always in there," Wilson says. "He is an inspiration."
"He's a fixture here," gym manager and co-owner Patrick Sieck says. "He takes his training seriously. He's an athlete, like all the other athletes."
Praiss finishes a set of bench presses. He stands up, unhooks the leather band around his waist, and grabs a bottle of water.
He is just one of the guys.
Contact Kevin Riordan at 856-779-3845 or email@example.com, or follow on Twitter @inqkriordan. Read the metro columnists' blog, "Blinq," at www.phillynews.com/blinq.