“Naturally, you are afraid of losing fitness, if you reduce your training,” Cheng said. “But you have to listen to your body, and take a step back. Relaxing, doing different sports, and enjoying other parts of your life, leaves you fresh for the new season.

“There are always things to improve, and I want more this year.”

Cheng splits her time between triathlon and working at running her No Limits personal training company. The balancing act was tested when she devoted up to 24 hours per week, over a prolonged period, training for the fearsome World Championship course in Hawaii.

She completed the 140.6 miles in 11 hours and three minutes, missing her sub-11-hour target by the slimmest of margins in December. The time positioned her 317th, among the world’s best 2,039 competitors. In her 30-34 age-group, she placed 70th out of 237.

“I would love to be able to go back and recover those three minutes,” Cheng said. “But I proved to myself what I was capable of, I achieved my dreams, and the weeks after the race were the happiest of my life.”

Cheng, who is hunting for sponsors, has set herself the ambitious goal of “creating a triathlon culture in Hong Kong”.

She coaches a mix of experienced amateur triathletes and complete novices, and advocates the idea of “triathlon as a lifestyle”.

“Triathlon builds character and resilience … succeeding in triathlon equips you for the challenges in your work and life,” she said. “When I compete, I am motivated by setting a good example for the athletes I coach. I want to inspire them and show what can be achieved with discipline and hard work.”

Formerly visited by nerves before a race, a sense of calm washed over Cheng, 33, before her slog across the water and scorching, undulating roads of Kona, in the west of Hawaii.

She was “super happy to be there”, and needed to reserve every shred of energy.

“It was a rolling course, and hot and humid, with a strong headwind,” she said. The three-mile ‘Energy Lab’ in the second half of the closing marathon running leg, where the air temperature hovers around 35 degrees, “felt like being trapped in a maze”.

“Late in the run, I felt like I could not move my legs,” Cheng said. “I had to walk through the aid stations, and put ice all over my body. When I finished, there was a huge sense of accomplishment, I felt empowered.

“But I have never been so tired. I had to lie down in the recovery area, and for 20 minutes could not move. I did not sleep properly for a week afterwards, my body was drained, and full of energy gels and drinks.”

Cheng’s family were watching a live broadcast, and a screengrab of her crossing the line quickly arrived from her mum, the 1984 Olympic swimmer Liang Weifen.

Cheng grew up fascinated by a wooden trophy Liang won at a race in Hawaii.

“I searched for information about the swimming competition to see if I could find her name,” Cheng said. “In a magazine I bought online, there was an article about her winning. In the next column, there was an advert for the Ironman World Championship. It felt like what I was doing was fate.”

Cheng found the pool where Liang competed in 1981, and after some gentle persuasion was allowed to retrace her mother’s breaststroke exploits.

“It was at a university 10 minutes from where I was staying,” Cheng said. “They originally would not allow me in the pool, but when I told them the story, they let me swim one kilometre, before I left for the airport.”