Wednesday, November 14, 2012

Standing still – like balancing a baseball bat on the tip of your finger

from...DontFall.ca Posted on November 2, 2012

It’s amazing that we’re able to stand upright and not fall down. Old or young, the weight of your body is perched high above your feet. Have you ever tried balancing a baseball bat on the tip of your finger? Or a hockey stick? Or a golf club? It can be a challenge. This is a nice analogy to how we stand upright on only two feet.

To keep the bat (or stick, or club) from tipping over, sooner or later you end up moving your hand around – side-to-side, front to back. Madly, you are trying to keep your finger under the bat, the bat on top of your finger. Eventually you can’t keep it up and the bat topples over. It drops to the ground, or perhaps you catch it. Why does the bat move around and eventually fall off your finger? Gravity, of course, is one reason. Gravity tries to pull the bat down to the ground. But if the bat was perfectly balanced on your finger, shouldn’t it just stay there? Perhaps. But it won’t be perfectly balanced for long because your finger is always moving, disturbing the balance of the bat. And then you end up chasing it around until eventually it falls.

Like the weight of the bat is above your finger, the weight of your body is above your feet. And because of many different factors – including perhaps your own breathing, wind blowing against you, “noise” in your nervous system, and other factors – your weight is swaying around above your feet, just like the bat sways around above your finger. To try to keep the bat balanced, you move your finger and chase the weight of the bat. You are trying to keep your finger under the bat’s “centre of gravity”. To control the sway of your body over your feet, you contract and relax muscles in your feet, throughout your legs, and your trunk. Your nervous system controls the activation and relaxation of these muscles so that your body’s centre of gravity stays above your feet, the feet being the “base of support”. If your body’s centre of gravity is allowed to move away from your feet, or outside of your base of support, you either fall or you catch yourself (which is called a “balance correcting response” – more on that another time, but as a teaser, the speed of your reflexes when you are performing a balance correcting response is faster than the response time of an Olympic sprinter when the starting gun goes off!).

As you get older, you sway more. Previous research has demonstrated that, older people who are at risk of falling also sway more from side-to-side when they are standing still. Why do older people sway more than younger people? We’ll talk a lot more about this later, but for now, some of the reasons have to do with the speed at which electrical signals move along the nerves, how quickly information from your sensory systems (touch, vision, etc.) is processed in the brain, and changes in the quality of your sensory information – for example, vision changes as people get older, as you know.

All of this just to stand quietly, without moving, without taking a step, without falling. As your body sways, your muscles contract and relax to keep your body from swaying too far. Even when you’re just standing still, your body sways forward and backward – 1-2 centimetres – and side to side – about 1 centimetre. More, or less. You can feel this sway in your feet if stand quietly and concentrate on the sensations from your feet. If you close your eyes, you’ll feel that sway increase. But if you do close your eyes, keep one hand close to a chair or a railing to grab, so you make sure not to fall.

Armed now with this knowledge, what can you do to reduce your risk of falling?

...Keep your muscles as fit and strong as you can. Go for regular walks – don’t avoid the hills. Muscle strength is important, but so is muscle endurance. Please check first with your doctor to make sure that this level of exercise is okay for you.

...Throw in an uneven surface to walk on from time to time – but be careful (if you’ve fallen in the past year, perhaps avoid this). There is some scientific evidence to suggest that if you challenge your balance control system you may be able to slow or prevent decline in your balance control, and reduce your risk of falling.

How does your nervous system know what muscles to turn on and off, and when, while you stand? Sensory information from three of your five senses (I know of nothing to indicate that you can either smell or taste your way to better balance!), information from two senses that you may not have ever heard about, and your brain. As I mentioned above, this sensory information changes, as we get older. We’ll talk about this soon. So come back and keep reading. And please tell your friends …

We will be sharing some of these postings on falls with you...Visit DontFall.ca often form more information.