Finishing a marathon is challenging enough as it is, but for one runner, it is a matter of faith.
"I literally put my life in his hands every time I run," says blind runner Wong Yiu-tong, referring to Ng Kam Yiu, who guides Wong with the aid of a rope.
Failing eyesight brought on by a hereditary disorder forced Wong, 59, to retire early from his job as a transport worker for a soft-drink company.
He became depressed as he tried to come to terms with his new limitations.
But once he mastered doing chores, and even cutting up chicken on his own, there was another issue that worried him.
"Many of my friends who went to the same centre for the blind became obese because of the lack of exercise. Some of them died young," Wong said.
"This worried me; I thought I would soon go the same way if I didn't do something about it."
So Wong started running. For four years, he has trained three times a week - with the help of Wong and another guide - come rain, hail or shine.
"Many associations for the blind fail to realise that blind people can exercise if they have the right method," he said.
In Wong's case, that means the right guide. Ng, an assistant officer with the Correctional Services Department in his forties, trains with Wong every Tuesday and Thursday night for an hour. They usually follow their sessions with a late-night snack.
Last year, they ran their first Standard Chartered Hong Kong Marathon and also competed in the Taipei Fubon Marathon.
Ng acts as Wong's eyes - but this extends beyond giving him directions and adjusting the guide rope. Ng also describes their surroundings and makes sure messages of support from fellow runners are passed on.
"I'm really impressed by his resilience and the incredible amount of trust he puts in me," Ng said.
"This trust makes me more aware of the inmates putting their lives in our [correctional officers'] hands and reminds me to make sure I am taking good care of them."
The pair are hoping to do better than last year's effort and aim to finish the full marathon on February 16 within four hours and 10 minutes.
The Correctional Services Department will be represented by 130 staff members competing across various distances in this year's event. Officer Anson Chan Kwok-cheung, coach of the department's distance runners, hopes his 10-member team will finish in the top three in this year's uniformed services race, which will be held at the same time as the 10-kilometre race.