For most American workers, three-day weekends are akin to Loch Ness monster sightings--rare enough to seem precious, yet frequent enough to prompt somewhat predictable daydreaming about what could be. You've got science backing you up if you're craving an extra day per week away from the office.

Bye-bye, stress. Hello, better health.

Some  40 percent of Americans report that their work is "very or extremely stressful." Chronic exposure to stress at the workplace can increase your risk for mood problems, metabolic/appetite abnormalities, disrupted sleep, high blood pressure, heart disease, stroke, immune system dysfunction, and more, mainly because of increases in the hormone cortisol. Not surprisingly, reports of absenteeism, high health care requirements, and accidents/injuries are higher among workers who put in lots of overtime. Getting away from the office for an extra day gives you a chance to chill out and engage in activities that can combat this assault on your well-being. Countries in which a three-day weekend is fairly normalized have some of the highest rates of happiness in the world.

Skyrocketing productivity.

Contrary to what most executives fear, productivity can actually increase with implementation of a four-day workweek. Some of this connects to the improved physical functioning you might experience simply from being less stressed-out. It also links to how the brain "recharges" during sleep. Whenever you catch some z's, cerebrospinal fluid floods into the brain, washing away toxic proteins that build up during the day. The results are better decision making, improved learning, fewer errors, and a bump in organization. Assuming you're not just shifting to a 10-hour day to get one off, a four-day workweek can let you unwind better before you hit the hay, making your sleep more recuperative. It also means you have an extra day to get more pillow time if you need it. Additionally, psychology plays a part. Business leaders who use a four-day week indicate that workers gain a sense of urgency with the less-common schedule, tackling projects sooner and doing more to optimize their efficiency.

Other worthy considerations.

Four-day workweeks have non-physical benefits. They give you more time for relationships, for example, and let you have more time to think independently (translation: innovation). Companies can also save money by not operating facilities for a fifth day, and cutting hours by just 10 percent could potentially reduce carbon emissions by as much as 15 percent.

Taking back Fridays starts with you.

Other countries are proving that four-day workweeks have multidimensional benefits. If a three-day weekend isn't the norm where you work, just share the science with your leadership -- it'll put their anxieties to rest and initiate change that helps everyone.