Keeping your center of mass (COM) over your base of support (BOS) is partially a function of your ability to produce the force necessary to do so. To illustrate how, just lay on your back. This is the easiest position in which to keep your balance; you can produce virtually no force and manage to successfully lie on your back. To sit, you need a slightly greater amount of force; there’s some tension in your legs, and some of the muscles of the trunk and back get involved to keep you sitting up. Continue on to standing, walking, running, and finally squatting. Each progressive step is a slightly more challenging one in terms of keeping balance – keeping your COM over your BOS – and each one requires more force production than the one before it.
A note here about balance: it’s interesting to consider this from the point of view of sports practice as opposed to strength training for sports. Not too long ago, it was thought (and still is, by many) that lifting weights while balancing on an unstable surface would increase balance better than lifting heavier weights in a conventional manner. Studies have shown this to be incorrect, so most serious practitioners in the strength and conditioning world have now abandoned the stability ball to the realm of commercial gym personal trainers who are entertaining their clients more than training them.
However, a simple analysis would have led to the same conclusion without waiting for a study to show it. Balancing on a wobble board, Bosu, or stability ball is a skill. It’s improved through practice – stand on a ball every workout for a couple weeks, and you become adept at standing on a ball, just like sports practice. It has nothing to do with strength training for sports. It cannot, except in the case of a completely untrained person, provide enough overload to increase force production, and thus improve the person’s general ability to keep their COM over their BOS in all circumstances. It just makes them better at balancing on the ball.
Similarly, we are not suggesting that training up to a 500-pound squat will automatically make you a master tightrope walker or expert snowboarder. Many high level balance-dependent activities have large skill components, which need to be practiced and honed to achieve competence and then mastery. The ability to produce more force will not, in and of itself, improve your skills at these activities. However, it will allow you to better express the skills you have if you are not already strong.
Most healthy untrained people can produce enough force to perform basic activities of daily living without needing assistance. One of the most important things we can do, however, is give an older person their quality of life back. Training for strength will allow anyone to get up off their chair, or use the bathroom unassisted. It can allow everyone to walk with enough strength to maintain their balance, not fall over, and avoid the broken hips that so often mean the end of an independent existence