Now, with a silver medal hanging around his neck, the 24-year-old light-flyweight from a small Caribbean port town plans to buy a new home for them with about $60,000 (£46,408) in Olympic prize money awarded by the Colombian government.
"My life has changed a lot through boxing," said Martínez, a relative unknown who surprised boxing fans by reaching Sunday's final which he lost to Uzbekistan's Hasanboy Dusmatov, the first boxer from outside the Americas the Colombian has ever faced.
Already 16 before he donned a pair of gloves, Martínez at first did not tell his parents about his new hobby. He was particularly worried about informing his father, an evangelical pastor and construction worker whom he feared would see boxing as violent.
"How could that be -- that a pastor's son is out there swapping punches?" Martínez recalled thinking.
Gradually, though, he won his parents over, especially because Martínez, one of six children, by that point was also putting the family's food on the table. After his father was injured lifting a concrete block, the younger Martínez began doing construction work of his own and also fixing bicycles.
"I was in charge of the family," he said, explaining how he won them over.
Now, he has the support of the thousands of yellow-clad Colombia fans who packed the Rio arena for Sunday's bout and many more Colombians back home, who are cheering a silver that represents the Andean country's first boxing medal in 28 years.
"We are making a little history," Martínez said after the fight.
Smiling despite a unanimous decision that awarded the gold to Dusmatov, a southpaw and winner of last year's Asian championships, Martínez paraded around the ring with his arm around his victor, pointing at the winner in tribute.
Although his family was unable to travel to Rio de Janeiro to watch him fight, Martínez said he was looking forward to returning, claiming his prize money and investing in a new house for his parents.
Would he have preferred gold?
"Yes, I came for more," he said. "But silver is still enough for me to buy them a home."
(Reporting by Paulo Prada, editing by Neil Robinson)
