He limps, but no one notices
His left leg is shorter than his right.
But that does not stop him from competing in triathlons because he wants to prove that he is normal.
Mr Alex Tung, 47, was hit by a car when he was 14 years old.
His left thigh bone was fractured, but his doctors decided to let the bone heal without operating on it. Instead, they stretched the leg at intervals using weights.
Mr Tung, now a professional swimming and triathlon coach, told The New Paper: "My doctors said I was young and didn't need surgery as my bones would heal quickly on their own."
It didn't quite work. His left leg is now 4cm shorter than his right.
He said: "I actually walk with a limp. But over the years, I've managed to fool everyone that I'm normal."
When walking and running, he places more weight on his right leg to even out his stride.
Next month, Mr Tung, who is married with two boys, aged 14 and 18, will take part in Ironman, a gruelling triathlon, in Western Australia.
Participants have to swim 3.8km, cycle 180km, and run 42km - all within 17 hours.
Mr Tung took part in his first triathlon in 2004 and his first Ironman in 2005.
This would be his fifth time at an Ironman challenge. Each time, he hopes to better his performance. He said: "This time, I hope to finish everything within 13 hours."
But this year, he found out that he is suffering from an illness that causes pain in his lower body.
Said Mr Tung: "My doctors told me that I shouldn't take part in the event. But I've done it many times, and know what I'm doing."
He said his family is supportive because they trust that he knows how to take care of himself.
What drives him to go for such gruelling races again and again?
"I want to prove to myself and everyone else that I can achieve my goals despite my past injury.
"The training also helps me to keep my figure. I can eat whatever I want and still stay slim."
Every step is painful
Every step is painful
He has flat feet and an extra bone on each foot.
But despite this, Dr Anthony Thian, 46, is taking part in his first Ironman on Sunday.
Said the general practitioner, who is single: "It's painful, but it's manageable. I can still push on."
He was born with the deformity - an extra bone in the arch of each foot.
The bones jut out, making his feet too broad to fit into normal shoes.
So Dr Thian wears special fore-foot running shoes that help him to land on the ball of his feet, thus taking some weight off his ankles.
Even then, his ankles swell each time he runs because there are no support points to cushion the feet when they land.
Two years ago, he needed steroids injected into his feet before a marathon as they were swelling badly after his training.
He said: "It's always going to be more painful for me. Naturally, I'll be slower, and have to train harder."
Dr Thian said: "As a doctor, I'm fully aware of the dangers and risks of participating. But life is not only about being safe and careful.
"It's about doing something that is difficult and seeing if you complete it, as a personal achievement. Every step I take is painful. But I feel great when I run.
Refuse to let her health problems drag her down
She feels like vomiting when she exercises and her legs retain water.
But Ms Chua Wee San, 35, said: "I'm a strong person, and refuse to bow to these conditions."
The tax manager has oesophageal reflux, in which stomach juices rise up and irritate her throat.
She said: "The more rigorous the exercise, the more the acid accumulates. That's when I feel like vomiting."
The avid runner was also born with thyroid disease, a hormonal problem. She sometimes experiences swelling in her thighs and calves.
The condition has worsened over the years.
Ms Chua also suffers from gastritis, a stomach inflammation.
Gastric pains hit her when she runs or swims over long distances.
She has been on long-term medication since the start of the year for these problems.
She said: "There's so much medication that I usually carry it around in a Zip-loc bag."
"But I refuse to let these problems drag me down or affect what I can do in life," she said.
Triathlons also have a special meaning for her. It was through the training that she met her husband, logistics executive Benson Ng, 38, five years ago.
They were married two years ago .
Said Ms Chua: "He encourages me, and has always been there for me."
This article was first published in The New Paper.