For three months, Sim Kai Xiong trained hard for his first jiu-jitsu competition without his parents' knowledge. He was worried that they might force him to stop if they knew.
But about a week before the bout in February, the Nanyang Junior College student had to come clean when his training session clashed with a family dinner.
"I was afraid that my father would get angry. He did get upset, but I explained that I had to train to compete. He understood in the end," the 17-year-old recalls.
That was his first foray into combat sports.
As interest in these sports, including mixed martial arts (MMA), grows among teens here, some youngsters are finding that they have to fight an emotional battle against their worried parents before they can throw the first punch or kick.
Most mums and dads blanch because of safety concerns.
Mr Joshua Sim, Kai Xiong's father, says: "I told him, 'You've got to be careful. It's your passion and you can enjoy it, but if you get seriously injured, the people around you will suffer too.'"
But the 57-year-old, who is self- employed, eventually came around.
"If I stopped him, I would be preventing him from reaching his potential," he explains.
Kai Xiong went on to win his debut match - and his parents' support. In April, he won two boxing fights as well as his first mixed martial arts bout.
Gyms here say interest in mixed martial arts, in particular, has spiked among the young in the past three years. For example, Juggernaut Fight Club, an MMA training gym in Boat Quay, has seen the number of teens at its facility jump by about 40 per cent since 2011.
Most people who practise the sport are boys, although the number of girls is rising.
Clubs here attribute its growing popularity to the fact that more competitions are being held here, which raise the profile of MMA.
For example, the Ultimate Fighting Championship held its inaugural show in South-east Asia, UFC Fight Night, here in January.
One Fighting Championship (FC) holds matches here every year. Started in 2011, One FC, whose headquarters are in Singapore, is said to be the biggest MMA organisation in Asia.
Its most recent competition was held at the Singapore Indoor Stadium last Friday, featuring 20 top fighters from around the world.
Their children's safety is the top concern for parents, and sports clubs here say they take this very seriously.
Mr Arvind Lalwani, 34, head coach at Juggernaut Fight Club, says those who want to pick up contact sports should look at a club's training facilities and the credentials of its instructors.