(CNN) After years on a treadmill of stressful and demanding assignments for high-powered institutions such as the World Bank, development and policy expert William Powers hit a brick wall.

The self-confessed "work junkie" took a year out living off-grid in a North Carolina cabin, experimenting with a slower lifestyle, and upon returning to his native New York, decided that he could not go back to the grind.

"I could never work 9-5 again," says Powers. "That kind of work seemed like a form of slavery -- giving up your mental, emotional, and intellectual capacities."

Powers slashed his working hours from over 50 a week to just 20, limited to Tuesdays and Wednesdays, with a five-day weekend. His time was split between freelance consulting, writing and speaking jobs.

Two theories were critical to making the new arrangement work. ' Parkinson's Law ' - that work expands to fill the time available, and entrepreneur Richard Koch's ' 80/20 Principle ,' which argues that we achieve 80% of productivity in 20% of our time -- and vice versa.

"I gave myself very short deadlines on everything I needed to do," says Powers. "I thought about what were the most effective things I could be doing and fired other clients. I got rid of superfluous work strands, and though my hours were reduced by 60%, my income went down by only 20%."

Strictly adhering to the new routine -- observing technology fasts and ignoring out-of-hours emails -- recharged the New Yorker's frazzled psyche as he was able to spend time with his family, get out of the city, and eat well, but also ensured that his reduced working hours were put to good use.

"I would get to my virtual office Tuesday morning refreshed," says Powers. "I would be focusing on tight deadlines and because of 80/20 I would be doing the work that was most interesting to me."

Work less, achieve more

With a new release of his book "New Slow City," Powers wants to convince others of the benefits of changing routine.

He argues that a new paradigm is needed to replace the eight-hour, five-day week that has endured since Henry Ford introduced it in 1914. The productivity of US workers has almost doubled since the 1970s but Americans are still working some of the longest hours in the world.

"I realize not everyone can do it because the cost of living is so high in cities that some people are just scraping by with two jobs," says Powers. "But if cultural creatives and opinion leaders make the change it can (eventually) flip to everyone."

Powers went cold turkey after being a workaholic but recommends that others make more gradual adjustments, such as experimenting with shorter deadlines and taking the saved time off:

"In the U.S. our identities are shaped around two things; being workers and consumers. It's about opening up little spaces for creativity and free time that will help you to go in a new direction."

Powers is far from alone in promoting new practices. The " Gothenburg experiment " has seen the Swedish city implement a six-hour day for public workers, with many private firms joining in, on the basis that what is good for staff will improve their work.

"Today we get more done in six hours than comparable companies do in eight," wrote Maria Brath , CEO of tech start-up Brath. "We believe it comes with the high level of creativity demanded in this line of work. We believe nobody can be creative and productive in eight hours straight."

Brath points to rising revenue since the shift as evidence of its value. She also notes benefits beyond staff morale, such as offering an advantage in recruitment and retention, and improved profile and reputation for the company.

Forward-thinking U.S. companies such as 37signals and Treehouse have implemented and maintained four-day weeks, noting an improvement in staff morale, retention and quality of output.

The global race...to slow down

Recent studies support the shift, with OECD figures showing that shorter weeks in France and Germany have resulted in higher productivity per hour than British counterparts working longer. The correlation extends further to show that productivity sharply declines from the second hour.

Excessive hours have also been shown to be counter-productive, with Stanford Professor John Penceval's research concluding that working over 55 hours a week "increases the probability of errors, accidents, and sickness that impose costs on the employer."

British think tank the New Economic Foundation (NEF) has proposed a 21-hour week as the basis of a new working model with greater emphasis on staff well-being and sustainability.

"There are social, environmental and economic imperatives to change the normal routine," says Anna Coote, Associate Director of the NEF. "For the economy it's better to spread paid work across the population to reduce unemployment and have less people on benefits (welfare). You would have a stable, committed workforce and there is some evidence that people are more productive in a shorter working week."

Coote believes cultural changes makes the vision more likely, with modern workers open to changing routine, as well as the possibilities of automation to reduce the workload. The growing threat of climate change could slow the wider imperative for constant economic growth.

The social policy expert wants to see more incentives for employers to consider a new model and research into what might convince them, such as paying taxes by the hour. She proposes transition steps such as reducing hours at both ends of the age scale.

One recurrent criticism is that low paid workers would lose out from shorter hours, but Coote feels this can be addressed.

"(Change) must go hand-in-hand with efforts tackle low pay. The answer is not for lower paid people to keep working long hours to keep a roof over their head -- it's to have better hourly rates."

This would be fair reward for productivity increases that have not yet benefited the low paid, she argues.

Coote is under no illusion that employers will flock to a new model -- but believes that within 10 years it could become widespread. Comparing the campaign to those for women's voting rights and against public smoking, she believes that major social change is often imperceptible until a dam breaks and the unthinkable becomes standard practice.

If so, working life could soon become far more adventurous.