Will working more than 8 hours a day increase productivity? originally appeared on Quora - the place to gain and share knowledge, empowering people to learn from others and better understand the world.

Answer by Bernie Klinder, Entrepreneur, Investor, Consultant, on Quora:

There's an old saying within academia that "in theory, theory and practice are the same. In practice, they are not."

So in theory, if you work more than 8 hours a day, you should see an increase in productivity in relation to the extra hours you put in - if you're a machine. But most of us are not machines. We get tired and distracted and our work slows down and gets sloppy as the day goes on. There have been several studies showing that longer work hours actually cause a decrease in productivity.

The initial concept of the work day was driven by the natural sunlight available - people worked from sunrise to sunset. With the invention of artificial light during the industrial era, factory owners had the grand idea of forcing people to work longer shifts and longer hours in a week. However, Henry Ford discovered that longer hours didn't translate into increased productivity and implemented the 8 hour work day and eventually 40 hour work week in his factories.

To this day we still use this factory work day/work week as our mental model and apply it to a modern work environment - and it's completely wrong and counterproductive. Modern work (especially knowledge work) doesn't have to be done in one continuous 8-hour block, and recent studies have shown that we are often more productive with frequent and longer breaks throughout the day.

Many people who work from home and set their own schedules already know this. When I was a professional freelance writer, I would work around my energy levels, not some artificially imposed schedule. I worked about 10 hours a day, but it was a few hours in the morning with a two-hour break in the afternoon, followed by a work sprint, followed by an evening break, and maybe another hour or writing or editing when inspiration struck me. If I was feeling burned out on a nice sunny day, I would take the day off and head to the park or the beach and make up the time on a rainy or snowy day (we had a lot of those in Cleveland.) If I was tired, I would take a 90 minute nap. That may sound like I'm slacking from a traditional workday, but at one point my editor told me that he had a team of 12 people that couldn't keep up with the pace I was working.

The concept of work sprints and managing your energy versus your time is a concept that is gaining a broader acceptance among productivity experts. The key is to really focus during your sprint, and keep the distractions to a minimum. Start with the Pomodoro method of a 20 minute sprint and a 5 minute break. Use the defined break time to reward yourself with your favorite distraction - social media, YouTube, a coffee break, a walk outside, etc. Then get back to the next focused sprint. If you're really into the work you're doing, don't take a break until you feel like you need one. Focus on the task at hand, and resist the urge to multitask, check email, answer the phone, or respond to distractions. Over time, your sprints will get longer and your productivity will increase.

You may find that this will make you more productive without putting in more hours, and that a longer work day or work week isn't necessary. Use your productivity gains to spend less time at the office and more time living your life.

Extra hours at the office in sprints are okay - consistent 70-80 hour work weeks are not. If you still want to work more hours, watch for signs of burnout and fatigue and make sure those extra hours actually are more productive and not just time spent at your desk looking busy to impress the boss. As a former Paramedic, I've seen lots of people have early heart attacks and health problems due to job stress. But I've never met anyone who was on their death bed wishing that they spent more time at the office.

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