"It's always been my passion," the 22-year-old tells PEOPLE.
Collin was working at Bob's Gym North in Evansville, Indiana when he observed personal trainer Glenn Ubelhor practicing poses for an upcoming bodybuilding competition. Eventually, he started going into a practice room to try the poses himself.
"I knew that it was my responsibility to befriend him and show him what bodybuilding is all about," Ubelhor, 48, tells PEOPLE. "I started showing him some different moves and giving him advice on diet."
When they first started working out, says Ubelhor, "Collin was morbidly obese and incredibly introverted and shy. He was extremely depressed at that time." But slowly he began to change. "His parents saw that was coming out of his shell, and he was this new Collin."
Collin's mother Jodie hired Ubelhor to begin working with her son on a regular basis.
"The more I talked to him, the more I realized that he was really serious about this," says Ubelhor. "I said, 'Do you really want to be a bodybuilder?' And he said, 'I've dreamed of it my entire life.' He told me his dream was to be on a bodybuilding stage and to perform. That's all he wanted. I said, 'I can make that dream come true.' "
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Ubelhor put Collin on a strict diet – eliminating the McDonald's he was used to eating – and amped up his training. Thanks to his hard work and dedication over the past year, Collin has dropped 62 lbs. and is now ready to compete in the Kentucky Muscle Strength and Fitness Extravaganza on November 14.
"He's still going to grind out every single day until he gets on that stage," says Ubelhor. "He's focused. All he cares about is being able to get on the stage, put on a show, and inspire and motivate people."
Jodie says she is proud of all her son has already achieved.
"Collin has never given up, never quit, has heart and dedication," she tells PEOPLE. "Collin never had any doubts about his end result. He knew he could achieve his goal. I do, however, think he surpassed his own bar that he set for himself."
Adds his father S. Carter, "What I personally find amazing is the amount of people that Collin inspires each and every day from near and far, and to some extent he has no idea he has that power. He is just being himself – a 22-year-old man with Down syndrome, trying to conquer this world one day at a time."
And that means taking the bodybuilding stage later this week.
"I'm looking forward to going on stage," says Collin, "and having the time of my life."