Silicon Valley veteran Bonnie Crater has one question she asks everyone who applies for a job at Full Circle Insights, a marketing performance management solutions provider she founded: “What hobby is important to you?"

If they don’t have a ready answer, they don’t get the job.

It’s that simple for Crater, who is an avid tennis player and volunteer for the Bay Area Lyme foundation, which she also founded.

"I've learned that we are all much better and more productive at our jobs when we have a release outside of work," she told Business Insider. In founding Full Circle Insights, she “wanted to create a company with a different culture to prove that you can start a company that runs well and also encourages a healthy work-life balance.”

It’s a balance that proves elusive for many people. A quarter of all employees view their jobs as the number one stressor in their lives, and seven out of ten American workers report that they struggle with work-life balance, according to research funded by the Centers for Disease Control and Prevention (CDC).

But perhaps the fix is a simple one, and one that has nothing to do with working less. The researchers, who were studying IT workers at a Fortune 500 company, found that by allowing the sample group more flexibility in their schedules, work-family conflict was reduced significantly – even though the employees continued to work roughly the same number of hours. This finding underscores the fallacy in how many people equate balance with a 40-hour workweek, or a reduced schedule of three or four days a week.

Instead, it’s about recharging outside of the office in order to function more efficiently inside it. TaskUs co-founder Bryce Maddock competes inIronman events; Bark & Co. co-founder Carly Strife spends most of her spare time with her dog and loves riding her motorcycle; Tumblr CEO David Karp flies drones around his Brooklyn, NY neighborhood.

When work and life are in balance, CEOs and entry-level employees alike feel more energized, at home and at work. An emotional connection to a hobby, or to the community, generates happiness, and that leads to positive results on the job. A study from the University of Warwick found that happiness gives people the drive to work harder and increases their productivity by 12 percent.

Achieving balance is obviously a benefit. But how can we do it better?

Work-life balance is like a marathon

Marathon runners are known for their regimented approach to the sport, which requires them to log hundreds of miles in any given training cycle. Effective training regimens are structured around cycles that incorporate taking breaks – periods of prescribed rest, or reduced mileage, that allow the body to absorb the work the runner has done and repair damaged muscles. These periods of relative rest are designed to allow the runner to return to more rigorous training feeling refreshed both mentally and physically.

These breaks are crucial to helping the runner become stronger, and the runners who return to this distance over and over again find joy in both the resting and the training. It’s a measured approach that holds true whether you’re training for a marathon or sitting down to do work.

A vision of a balanced work and life

If a runner over-trains during a training cycle, the running that he or she does becomes less effective. This burnout can take the form of an injury or mental fatigue.

In much the same way, when an employee’s life balance is tilted too far into “work,” he or she risks becoming physically ill. In order to give his best at work and home, balance is required. That lets our bodies stay healthy on a physiological level.

Maintaining a state of happiness and relaxation isn’t just good for our mental well-being — it also makes us better at our jobs. Scientists at the University of Washington found that meditation training helps information workers stay on tasks longer with fewer distractions, while also improving data retention.

Other researchers have found that employees who unwind from work stress during off-work times are better at dealing with conflict and are more engaged in their work. When people are stressed and overwhelmed, it’s difficult to deal well with difficult situations. They react defensively and have less empathy for other points of view.

Balance also creates more efficiency — not only does it provide more energy with which to do the work but it also provides motivation to finish task efficiently, because employees have something to look forward to when they are done.

Balance doesn’t necessarily mean working fewer hours

Achieving balance doesn’t mean striving for a four-hour day or clocking out at 36 hours each week. There are going to be peaks and valleys in workflow: Sometimes doing the job well will require putting in a 60-hour week; at other times, the balance will tip in the other direction.

Ultimately, balance is a cycle of work - rest, work - rest. Just as in training for a marathon, the periods of thoughtful rest are critical to making sure you come back to the work stronger than ever.

So test out the research for yourself. This week, make time for something you would typically say you don’t have time for. That could be 20 minutes of exercise, a trip to an art museum or a night spent at your book club. Set aside that time to recharge, rebalance and refresh, and see if it gives you renewed energy when you return to work.