TOKYO (AFP) - At the stroke of 1:00 pm, a group of Tokyo IT workers spring from their desks for a few minutes of rigorous bending, stretching and thrusting as a voice on the radio instructs them - "ichi, ni, san (one, two, three)".
The suited staff are taking part in a regular calisthenics drill implemented by Adoc International, while over at electrical equipment firm Fujikura, the staff can be seen dangling from multi-coloured monkey bars.
A growing number of Japanese companies are encouraging exercise breaks, in the hope of keeping employees limber - and productive - for longer, as the nation contends with a shrinking labour pool and one of the world's fastest ageing populations.
"Japan's population is quickly getting older and there are fewer and fewer kids - this is very big risk for companies," said Kenichiro Asano, who works in Fujikura's healthcare strategy group.
With almost zero formal immigration, companies need to keep staff fit in the hope they'll work past the usual retirement age.
"Keeping workers in shape is an important corporate strategy," said Asano, adding: "Good health means a sound society and a sound company."
The government wants to keep citizens healthy as the growing number of retirees with medical problems strains the public purse.
Adoc International's staff practice "rajio taiso", a stretching routine that is often learned in schools and dates back to the 1920s.
"We chose rajio taiso because it was the simplest exercise to put in place," said Clifton Lay, who works in Adoc International's human resources department.
"Most Japanese and people who grew up here already know it and have no trouble with the movements," he added.
Instructions for the three-minute exercise are also played daily on public broadcaster NHK, with different sets tailored for building strength or for the elderly and disabled.
Automaker Toyota has its own in-house version, while Sony employees - ranging from blue collar assemblers to top executives - are supposed to join in a group stretch at 3:00 pm daily, although it's not mandatory.
At e-commerce giant Rakuten, some 12,000 movable desks were installed when it moved its head office. Workers can switch between standing and sitting throughout the day.
"I get tired easily when I'm sitting too long so it's nice to be able to stand up from time to time," said 35-year-old Rakuten engineer Liu Xiaolu.
More companies need to adopt a health-focused mindset, said Koichiro Oka, a professor of health behaviour science at Waseda University in Tokyo.
"If you think it is all right not to move much on weekdays because you're exercising on weekends, you'd be wrong," he said.
"A lack of exercise during the week can lead to heart disease, diabetes and other health problems," he explained.
The rajio taiso routine is considered by many as a Japanese tradition, although the idea was actually borrowed from a similar programme sponsored by an insurance company in the United States.
It spread quickly throughout Japan, as workplaces, schools and local communities got into the routine.
The daily radio broadcast was temporarily banned by the Allied occupiers following Japan's defeat in World War II because it was seen as being too militaristic. But it was reintroduced in 1951.
Today, as many as 28 million Japanese are believed to take part daily.
"Doing these exercises in the morning when you arrive at work or just after lunch - when your head is not completely into working - let's you get ready and say 'OK let's do the job,'" said Adoc's Lay.