(Bloomberg Business) — Swedish trucking company Scania believes in the 24-hour employee. Scania workers aren't just expected to be their best selves at work, they're expected to be their best selves all the time. To help employees attain that ideal, Scania offers an extensive workplace wellness program to its 5,000 employees that includes access to an onsite gym, a team of health care professionals, and seminars in which employees can learn techniques for healthier living.

"Scania cares for its employees both on and off the job," a human resources manager in 2011 told a researcher of its approach to workforce wellness. "We try to help them live healthier. Our interest and care does not end when they leave work."

But according to researchers Andre Spicer and Carl Cederström, Scania's efforts didn't always have the intended effect. Over the last 4 years, the two have studied wellness programs at hundreds of companies, including Scania. In their new book, The Wellness Syndrome, they describe how the company's extensive wellness efforts stressed some employees.