“The key message of our report this year is ‘active families, healthy kids’,” said Professor Stephen Wong Heung-sang, chairman of the university’s sports science and physical education department, who co-led the study.

“It’s time for us to reflect on whether we have sacrificed too much quality of life for economic advancement.”

Wong’s team, which released its findings on Thursday, analysed the latest data available for the study. The team assigned grades from A to F to indicate 12 performance levels of children in certain areas, including overall physical activity, organised sports participation, active transportation, sleep, obesity, community and environment, and government policies.

An A-plus grade meant more than 94 per cent of youths could achieve a certain goal while an F indicated fewer than 20 per cent met the standard, according to the “2018 Hong Kong Report Card on Physical Activity for Children and Youth”.

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The physical fitness of local youngsters was found to be poor, with an “alarmingly low” D grade, the same as mainland China, which was lower than many other Asian countries.

Japan scored A, Taiwan B minus and South Korea D plus.

Hongkongers also did a poor job in limiting children’s screen time to below two hours per day.

The score fell from a C in 2016 to C minus, while parental participation in physical activities with their children also deteriorated from D to D minus.

In the 2018 report, just 35.5 per cent of children aged 10 to 19 spent less than 120 minutes a day on a smart device, including for messaging, gaming, and watching television and movies.

In 2016, 58 per cent of boys and 61 per cent of girls aged between nine and 13 reported success in compliance.

Asked whether Hong Kong’s long working hours had affected parents’ opportunity to exercise with their children, Wong said: “There have been many discussions on parents’ post-work exhaustion, so we tend to believe that factor is real in Hong Kong.”

But he said no academic research had drawn such a conclusion. Wong also pointed to other factors including shortage of living space, and limited access to sports facilities in communities and schools.

“We need a social engineering project to change the situation,” Wong said.

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Professor Mark Tremblay, president of the Active Healthy Kids Global Alliance, a Canada-based non-profit organisation that has brought the physical activity report card to 49 countries and regions, said part of the project could be a marketing campaign to raise public awareness.

“The concern, of course, is what we are passing on to the younger generation of kids,” Tremblay said. “They see their parents working long hours, sacrificing time with their family, sacrificing perhaps their health. That’s scary.”

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Ng Ching-kong, headmaster of Stewards Pooi Kei Primary School in Fo Tan, said parents were changing but it was not easy.

Starting after the Lunar New Year, pupils in five out of six grades in the school would get time for a daily nap and exercise would become part of their “homework”.

“We are collaborating with Chinese University to see if such measures will improve our students’ conditions,” Ng said. “And by using this form of homework, we hope the parents can participate more in regular physical activities with their children.”