What are the Strategies?
As humans, we have evolved methods to take in order to preserve our bodies to the best of our abilities. One of these remarkable mechanisms is how we maintain our balance as a bi-pedal (two-legged) species. Its our bodies very own unconscious defense mechanism that helps us prevent against falls when the surfaces below us trip us up:
- Ankle Strategies
- Hip Strategies
- Step Strategies
Just before we get to those strategies though, lets touch on some major terms related to balance:
center of gravity: the spot on your body that acts as a balance point around which your body moves.
cone of stability: its an imaginary upside down cone surrounding your body that depicts the amount of movement your upper body can make without needing the step strategy to protect against falling.
base of support: what you are using to keep your body steady. In most cases, its your feet about shoulder width apart. But we can make it larger to give us more sturdiness (like many elders do), or we can make more narrow to challenge our balance like a gymnast on a balance beam.
perturbation: anything that acts to knock you off balance. It could be someone shoving you, or a rock that trips you, or an uneven piece of cement on a side-walk.
Strategy One: Ankle Strategies:
The first of our strategies is the ankle strategy. It works in quiet standing. The ankle joint it self is designed to move in all directions, therefore it is a great first line defense against falls. The ankle strategy is designed to use its surrounding musculature to keep you standing upright. If you look at an individual without shoes on standing still, you will see their foot making tiny movements to counter any changes in the body’s center of gravity. Think of the ankle strategy too when you step on uneven ground, you will notice sometimes your foot will autocorrect before you can even consciously realize you are starting to get out of your center of balance. Once it goes beyond a small perturbation that the ankles cannot correct, we move onto the hip strategy.
Strategy Two: Hip Strategies:
Defensive mechanism number two is that of the hip strategies. These come into play when the perturbation is too large for the ankles to control, but yet not big enough that a step would need to be taken to correct it. The hip joint can also move in all directions, therefore the hip is also a great joint to defend against falling because it can correct any medium to large perturbation in any direction. The hips work by swaying and moving the the trunk to wherever it needs to go so that we don’t fall outside of our cone of stability. A perturbation that would elicit a hip strategy might be something like stepping on uneven ground unexpectedly or tripping over a rock. In this cases, you might extend at the hips to correct against the forward moment from tripping.
Strategy Three: Step Strategies:
Last, but most certainly not least, is the step strategy! This is our last line of defense against a fall. This strategy is a last resort, and only kicks in when the perturbation is so large that the ankle or the hip cannot help. The only option is the take a step, broadening our base of support, to correct this kind of perturbation. This is the first and only of the strategies that modifies the base of support, and the strategy that kicks in once we fall outside of the cone of stability.