Svec - Balance: a dizzying journey through the science of our most delicate sense

W HEN IT COMES TO BALANCE, ballerinas, circus performers, surfers, and gymnasts have nothing on you.

From the moment you wake up in the morning, daily life is a harrowing high-wire act. Its more than simply sitting upright or standing firmly on your feet without toppling over, although those are the most apparent aspects. To sit upright and not topple over requires having a solid sense of which way is up, so you can avoid falling down. It also means knowing where your body is in space and how to organize and move your muscles so that you can maintain your position. It requires a kind of internal gyroscope to keep the head level, a method for detecting gravity (so we dont fall victim to its pull), and a way to link what we see with how we move (so life doesnt look like a herky-jerky handheld video). Each step we take is a miracle of balance as our bodies compensate for hundreds of tiny changes in weight distribution and body position.

Without realizing it, we areeach of us (most of us)a hair away from collapsing in a heap on the floor. I mean that literally. There are groups of tiny sensory hair cells in the core of the vestibular system within the inner ear that sense movement, acceleration, and gravity. When something goes wrong and those hair cells send the wrong message to the brainas happens with Mnires disease or benign paroxysmal positional vertigo (BPPV)the result is incapacitating vertigo and dizziness.

But the sense of balance extends way beyond the inner ear. Nearly every cell in our bodies plays a role. Simply standing in place requires contributions from our eyes, ears, brain, nerves, joints, ligaments, blood, and bones in a symphony of coordination. Take away one factor and the body can usually compensate. Take away two and we may end up in a heap on the floor.

And yet, we dont think about this remarkable, exquisite ability we have until we find ourselves in unusual situations that stress the system, such as crossing an icy mall parking lot when youre overloaded with shopping bags. (I speak from experience.) All of a sudden, your firm footing is lost on the slick pavement and you have to think about each step, while simultaneously adjusting for the weight of your purchases. You plant a foot, pause, make a balance judgment, slowly lift your other foot until you know whether youre solid, take the step, plant the foot, and so on, until you reach your car. Its exhausting. And for a handful of people with a very specific proprioceptive disorder, a carpeted room is as challenging as that icy pavement.

So when you think about it, theres not much difference in physical skill required to walk a tightrope as there is in... well, just plain walking. I have spent the past year talking with physicians and researchers, visiting their offices and labs, learning about what balance really means. How do we accomplish this pure physical poetry every minute of every day?

What I discovered is that we dont have a sense of balance. We are balance. Balance gives us our place and space in the world, but it also contributes to our sense of self. After all, a dream of flying is impossible if you dont know which way is up.

I was inspired to write this book because of what happened to my mother. Back in December 2012, after a day of shopping, she lost her balance walking up the three little steps that led from the garage into her home. She fell backward onto the concrete garage floor, directly onto her head. Her only other injury was a slight scrape on the side of her arm, which flailed out in an automatic attempt to keep from falling. Just moments earlier, she had been lively, alert, and stable. But just three little steps and a quirk of balance later, she was unconscious.

Im happy to report that my mom had a miraculous recovery (the neurosurgeons words, not mine), despite skull fractures in two places and three areas of bleeding in her brain. We still dont know what made her lose her balance. Testing showed she did not have a stroke, had taken no medication or alcohol, and wasexcept for these most recent injuriesentirely healthy.

So why did she fall? And, perhaps more importantly, how come more of us dont fall? What keeps our balance steady? What happens when balance fails? Why are we so certain that we can come home from a trip to Bed Bath & Beyond and not end up in an ambulance? And what, exactly, does it take to knock us off our feet?