The 36-year-old waves to a member on a nearby machine just as another high-fives him on his way out.
Almost everyone seems to knows Rivera, who has Down Syndrome and lives in a group home in Englewood.
The karate black belt has made training at Retro part of his routine on Tuesday and Thursday evenings for almost two years, and if you ask him why, he'll tell you: "It's for combat."
But for his father, George Rivera, 72 of Hackensack, fitness serves a greater purpose in his son's life.
"I hope he can inspire other people who have disabilities."
"I’ve always believed in exercise and felt this is something that’d be good for him," he said. "The other option is for him to sit in front of the television eating."
And so, Rivera's trainer, Enrico Addeo, makes his way over to the smoothie bar and they walk together onto the floor.
Addeo guides Rivera through his warm up before moving on to bicep curls, push-ups and some resistance machines — once something that intimidated Rivera, his father said.
There isn't anything Rivera can't do in the gym. His passion is unwavering and it shows in every workout.
"He cares more than most," Addeo told Daily Voice as Rivera finished his curls. "And 10 reps is too little, he always wants to be sweating."
Working up his strength in the gym and at the dojo took years of work. The greatest challenge, however, came in January 2015, when Rivera lost his mother to cancer.
"I had him involved in every aspect of her health and explained everything about cancer and how to keep her as comfortable and happy as possible," the elder Rivera said. "When she died I took him to the hospital to say his last goodbye.
"I explained it's okay to grieve and to be sad. It's a big loss."
Rivera speaks about his mother often, Addeo says. They talk through many problems, working through the sets.
Working out keeps Rivera physically and mentally fit, his father said.
Most importantly, it provides him with structure, discipline and confidence.
"It changed my life forever," Rivera said. "I feel like I'm doing something with my life."
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