A 51-year-old fireman collapsed and died when on a midnight run in Sam Ka Tsuen sports ground in Kwun Tong.
The man, Tong, had been running on a football field near his home when he was found unconscious by security staff at 12.03am yesterday.
He was taken to United Christian Hospital by ambulance but was certified dead upon arrival.
Sources said the veteran with 31 years of service had a history of illness, though an autopsy should help determine the cause of death.
The Fire Services Department confirmed an off-duty principal fire officer at Ngau Chi Wan Fire Station had died after collapsing at a sports ground in the early hours of yesterday.
The chairman of the Hong Kong Fire Services Department Staffs General Association, Jerry Nip Yuen-fung, said Tong was married with a son and a daughter. The family resided in a disciplined services quarter in Yau Tong.
Yuen also said the department does not require firemen to go through regular health checks, but they must pass a running test every year.
"They are regarded as fulfilling fitness requirement if they pass the test," he said.
But as for determining whether an officer is suffering from an illness "they must pay for health checks to find out for themselves."
Firemen are usually required to finish a 4.8-kilometer run in under 30 minutes, but allowances are usually made for older officers.
Asked if regular health checks should be made compulsory, Nip said his colleagues would welcome such a policy if the department offered free services.
Lobo Louie Hung-tak, associate head of the Education University of Hong Kong's Health and Physical Education Department, said most sudden deaths during exercise are caused by heart problems, with coronary heart disease being the most common cause.
He said for those aged 35 or above, as in Tong's case, reasons of sudden death may be related to acquired factors such as the "three highs" in blood pressure, sugar and fat levels or hidden congenital heart disease.
He advised people to undergo annual cardiac checks to assess their heart functions and whether their blood vessels have narrowed, which can cause blood clots.
He also advised people to undertake moderate aerobic exercise to strengthen their cardiovascular functions.
"Do moderate-intensity exercise two or three days a week and jog for half to an hour each time," he said. "However, if you feel persistent wheezing or chest discomfort you should stop immediately."