Workers spending their lunch break at the gym may be commonplace in most Western countries, but in Sweden some employers are pushing the idea even further, making on-the-job exercise compulsory.

Every Friday, employees of fashion and sportswear retailer Bjorn Borg leave their desks at the company's Stockholm headquarters to get their weekly workout at a nearby gym.

There is no getting out of it: for more than two years the company founded by the Swedish tennis legend has made on-the-job exercise mandatory at the initiative of chief executive Henrik Bunge, a 44-year-old built like a wrestler.

"If you don't want to exercise or be a part of the company culture, you have to go," says Bunge, without batting an eye. So far no one has quit because of the requirement, he adds.

The main aims of the policy -- shared by other firms such as city water company Kalmar Vatten and construction consultancy Rotpartner - are to boost productivity and profitability while fostering camaraderie in the work force.

In 2014, a University of Stockholm study showed that exercising during the workday was advantageous for both employees -- who were healthier and more concentrated - and the employer.

The study found there was a 22 percent decline in work absences, not negligible in a country where the average person is on sick leave four percent of the time, twice the European average.

Rosy-cheeked and smiling, the 60 Bjorn Borg employees taking part in this week's gruelling yoga session head to the changing rooms, their endorphins soaring."Most of us think it's a really good part of the work week," says employee Cecilia Nissborg.

Swedes have long been known for their healthy outdoorsy lifestyle. Long walks to pick mushrooms or berries, or just for pleasure, regardless of the weather, are part of their everyday lives.

"In Sweden there's this idea that you'll be healthy, strong and happy if you get a lot of exercise, if you spend a lot of time in nature," says Carl Cederstrom, an economics researcher at Stockholm University and the author of "The Wellness Syndrome", a critique of the pervasive ideology of wellness.

He notes that it is a common belief in Sweden "that if you exercise and take care of your body, you're a better person".

Swedes get more exercise than anyone else in Europe. A 2014 Eurobarometer poll found that 70 percent of Swedes exercised once a week, and 51 percent two to three times a week. At the bottom of the rankings, only 22 percent of Bulgarians exercised once a week.

Swedes also generally see being in shape as a duty to oneself and society, an expectation dating to the 1930s, when a cult of youth, vigor and "social hygiene" flourished, Cederstrom says.

But people also see it as a "responsibility you have to your employer", he adds.

Since the late 1980s, most Swedish companies subsidise their employees' sporting activities -- from golf to water aerobics -- contributing up to 500 euros ($615) per year, which is tax deductible for the employer.

And some, like at Bjorn Borg, go so far as to organize exercise classes during work time.

Bunge is convinced the workplace he has created has made employees happier and more productive, noting that all the company's key numbers have gone up since the new regime was introduced.

Mandatory workouts, usually in a group, also have other benefits.

They bring together all the departments of a company, allowing employees to put their work responsibilities aside and get to know each other on an equal footing.

"When we go into the gym, we're all on the same level. Your place in the company has no importance, everyone is equal," says Ida Lang, who works in Bjorn Borg's accounting department.

For Cederstrom, while the search for wellbeing and performance through physical activity is not unique to the Scandinavian country, "Sweden is really extreme when it comes to companies that make exercise on the job mandatory".

It is a development he finds worrying.

"When you start to think that you're a better mother or a better father or a better friend if you exercise, you can get to a point where you think that people who don't live healthily, who are overweight or who smoke are less good people," he says.