On average, Americans spend more than 12 hours a day in a seated position, slumped at a desk, flopped on a couch or hunched over a device like Gollum over his ring.

Remember a few years back when everyone started saying sitting was the new smoking? Science now knows sitting for more than eight hours a day with no physical activity has death risks similar to those for obesity and smoking. And if it doesn’t kill us, it leaves us with weak abdominal muscles, tense shoulders, migraines, varicose veins and low back pain.

It isn’t that we are sitting too much, but that we are sitting all wrong.

To fix the problem with our bodies, we need to set both our physical posture and our mind’s inability to stay focused on the present moment.

We have to anchor the brain in the physical sensations of the body to improve the body’s alignment.

Proper posture aligns the ears over the shoulder and the shoulders over the hips. The chin should be parallel to the earth, the chest open to facilitate proper breathing, and the navel pulled slightly back in toward the spine to engage the muscles of the core.

If sitting in a chair, sit all the way so that your lower back is touching the backrest at all times and the feet are resting on the floor. This may require some adjusting to your desk, chair or workstation.

Better still is either squatting or sitting cross-legged on the floor.

Americans have spent so much time sitting in chairs we have lost the pelvic mobility necessary to allow for floor sitting, but these two positions are fundamental building blocks of human movement.

Squatting flexes the ankles, knees and hips to stretch some of the most overworked muscles in the body. Ideally, you do the squat with your feet facing forward and your heels close to the ground. It places the spine in a neutral position and strengthens the core.

If you haven’t done this for a few decades, go slowly and savor the incremental improvements over time.

Sitting cross-legged rotates and stretches the hip muscles while strengthening the muscles of the back to refine your posture over time.

Have you ever heard of the Sitting-Rising Test? This life-expectancy test requires you to start standing, sit down in a cross-legged position and then stand back up again. The wrinkle? You cannot use your hands to help you at any point.

The two basic movements in the sitting-rising test (lowering down and standing back up) are each scored on a one-to-five scale, with one point subtracted each time you use a hand or knee for support; both scores together yields a 10-point scale.

People over the age of 50 who scored fewer than eight points were twice as likely to die within the next six years compared with those who scored higher; those who scored less than three points were more than five times as likely to die within the same period compared with those who scored more than eight points.

I use it all the time with my yoga therapy clients, and it is deceptively challenging.

Now that you have the physical alignment down, let’s circle back to how to stay mentally present in the sensations of the body.

We can only maintain good posture with present-moment awareness. When you’re mindlessly scrolling Facebook or three episodes in a Netflix binge, you’re probably also slack-jawed and hunched over. We don’t need to sit down; we need to sit still. Intentionally sitting still has a profound physiological effect on the body to reduce pain and enhance the body’s immune system, enabling it to better fight disease. Research suggests mindful sitting helps reverse heart disease, the number-one killer in the U.S.

When the body is still and the breath deep, the blood pressure drops, the heart rate slows and the adrenal glands stop releasing cortisol, the fight-or-flight hormone.

Sitting down also humbles us and gives us a different perspective; it’s the main reason monks kneel to meditate or pray.

Think of all the great spiritual leaders who were also great sitters.

Buddha sat under the bodhi tree.

Jesus sat in the garden.

Mother Teresa sat quietly with the sick and dying, holding their hands.

Gandhi sat still as a form of revolution.

One cold, December day, Rosa Parks changed the social structure of our country by sitting still on a bus.

How could we change our world if we sat still (and sat well) for a few minutes each day? If every man in the world sat down and cleared his mind for a few minutes?

If every woman took a deep breath to decompress? Could every couch become an alter? Every threadbare carpet a mosque? Every bus seat a church? Every patch of grass a cathedral?

At the least, our backs will feel better.

Erin Smith is the owner of the OM place in Winchester, the author of “Sensible Wellness” and the online host of the OM channel. Follow her on Twitter @erinsmithauthor.