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Sitting kills. That’s the headline you’ve seen on , , and even over the past few years. With the —and even treadmill and —people are treating sitting as “the new smoking.” In 2010, that found sitting for just an hour increased one’s risk of all-cause and cardiovascular disease mortality, and other studies have linked prolonged sitting to , , , muscle degeneration, soft bones, high blood pressure, , , , and . And a daily hour-long workout probably won’t save you, according to a .

We reviewed the scientific literature, spoke with experts, and assembled the definitive guide to choosing a chair that will keep you healthy, listed from worst to best. Plus, we outlined the ultimate daily office routine.

#5: The Stability Ball

When the stability ball became trendy in the mid-2000s, its supposed health benefits were based on two theories: Without a backrest, the user must sit upright with feet flat on the floor, ensuring proper posture and circulation. And second, because the ball is squishier than an office chair, you must engage your abdominal and back muscles to stay upright.

But the reality is that stability balls, when used in isolation, can do more harm than good. “I wouldn’t recommend sitting on a yoga ball for long,” says Jason Zhao, clinical director at in Corvallis, Oregon. “It’s easier to lose good posture on these, and the increased muscle activation puts more pressure on the spine.”

#4: The Kneeling Chair

The —a stool-like structure that provides support for your forward-facing knees—was “trendy in the 1980s and 1990s, but they’ve fallen out of favor,” says , a pain management physician at in Warrenton, Virginia. Claims that the downward-sloping seat and dropped-knee position rotate the pelvis forward and therefore align the spine in an ideal, natural S-shape . Like the stability ball, however, the kneeling chair will than a conventional chair and , even as it distributes your weight onto your knees and off the lumbar curve.

#3: The Standing Desk

: Ben Franklin, Virginia Woolf, Winston Churchill, and Ernest Hemingway used them. But recently they’ve been to oversitting ills. Humans developed a lumbar curve because we’re bipedal, so working upright must be healthy, right? Well, it’s complicated.

Research shows that working upright , all without ruining your focus, as well as . But being on your feet for too long poses its own risks: it inhibits proper circulation and adds pressure to your hips, legs, and spine, which . And, unfortunately, research shows that .

#2: The Saddle Stool

You know this style of seat—your . All things considered, the saddle stool is pretty great. The backless design increases muscle activation—much like a stability ball or kneeling chair—and the saddle will rotate your pelvis forward, which maintains the spine’s natural lumbar curve. Wheeled saddle stools are also the only chairs that effectively prevent slouching: because the stool is designed to be raised higher than a conventional chair or stool top and because the wheels give it mobility, leaning forward would launch the chair out from under you. Research shows that the saddle stool is also great at . The only downside: eight hours on a stool is .

#1: The Ergonomic Office Chair

When you read something about how , most of those articles reference the plain old office chair, which indeed is not great. Most scientific studies that praise the competition—stability ball, kneeling chair, saddle stool—compare it to standard office chairs as well. However, —which may look like a normal office chair but are customizable in various ways and are designed to support your lower back and promote good posture—are perhaps the healthiest way to spend the workday, especially when paired with short bouts of standing and walking.

Most office workers do not properly adjust their chair to fit their body, and a on office chairs discovered that after volunteers were given an ergonomic model and instructions on correct posture and usage, like relaxing their shoulders and adjusting the seat according to their height, most of their previous musculoskeletal symptoms resolved.

Two trustworthy associations certify chairs as authentically ergonomic: the and the . Both calculate suitable shape via slightly different methods, so on their varying guidelines. Before purchasing a chair, make sure it’s HFES 100 or BIFMA G1 certified.

The Perfect Day

Despite the ergonomic chair’s many benefits, it’s not perfect, and spending too much time in one can, indeed, be as bad as smoking. That said, here’s what the ideal nine-to-five grind should look like.

Sit, Stand, Walk

Everything in moderation. Because the standing desk and chairs each have benefits and drawbacks, the key, experts say, is to alternate between standing and sitting. A or is the perfect solution.

Research is ongoing as to how long you should sit or stand at work, but a recent says to stand for a total of two hours a day and slowly ramp up to four. The key is to accumulate those four hours in chunks. , a professor of ergonomics at Cornell, the proper sit, stand, walk ratio for each half-hour of work is 20:8:2—sit for 20 minutes, stand for eight, and finish with a two-minute walk around the office. That rotation gives you the positive posture benefits of both sitting and standing without the painful consequences of doing either for a long time.

How to Sit

Buy a customizable, ergonomic office chair that has rests for your head and arms, plus plenty of lumbar support. Stay an arm’s length away from your computer monitor. The screen should be centered, just below eye level, and tilted . This will keep your head and neck in position and reduce eye strain. Alternate between sitting at 90 degrees (upright) and . “People don’t realize that leaning back in a chair is healthy. It take pressure off your spine,” says Zhao.

Keep your spine against the backrest, shoulders relaxed, and arms on the armrests. In addition to promoting good posture and decreasing musculoskeletal strain, this position will keep your chest open, which and therefore ensures good memory and circulation. Keep your feet flat on the floor with your thighs parallel to the ground. Don’t cross your legs—you won’t be in proper spinal alignment, and doing so also .

How to Stand

When standing at your desk, raise the table or viewing stand so your screen is just below eye level. Stand erect with your legs, torso, and head in line; relax your shoulders; and keep your upper arms close to body.

How to Walk

During your two-minute walking breaks, head to the kitchen: with your co-workers will boost natural levels of oxytocin—which keeps you —and reduce cortisol, a stress hormone. If you don’t like walking, force yourself: send your documents to a printer at the far side of the office. At noon, find a healthy lunch spot near a park: through someplace green will buoy your mood.

Drink Lots of Water

Drinking four to six cups of water usually ensures hydration, which in turn regulates proper blood pressure and and . It will also make you pee—another opportunity to walk.

Fidget

Contrary to what your teacher told you, fidgeting—like toe tapping and heel bouncing—is helpful. Jiggling will help each day, by engaging your muscles, and improve lower-limb circulation. To stay focused, enhance creativity, and ease stress, try clicking your pen or tinkering with a slinky, a stress ball, or two .

The Takeaway

“There’s a lot of good research about sitting and standing at work,” says , an associate professor of kinesiology at the College of William and Mary. “There are a lot of gimmicks out there, but it comes down to movement and fit: get an ergonomic chair that fits you and get up out of it often. That’s really it.”