why slow movement builds coordination

"There are several excellent reasons to use slow and gentle movement as a means to develop coordination. Probably the most interesting reason (I’ll start with that one) is based on an obscure principle called the Weber Fechner rule. The Weber Fechner rule describes the relationship between the magnitude of a particular stimulus and the brain’s ability to sense differences in the amount of the stimulus. The basic rule is that as you increase the stimulus, the ability to tell a difference in the amount of the stimulus decreases. This is a very common sense idea. Imagine you are in a dark room with only one candle lit. It will be very easy to sense the difference when one additional candle is lit. But if you are in a room with two hundred candles, you will have no idea when an extra candle comes on.

This rule works for all varieties of sensory perception, including sensations of muscular effort. So, imagine you are holding a one pound potato in your hand while blindfolded. If a fly landed on the weight you would not know the difference, but if a little bird landed you would know. Now imagine holding a fifty pound potato. You wouldn’t be able to feel the little bird landing. It would have to be an eagle. The point is that when you increase the weight from one pound to fifty pounds, you become about fifty times less sensitive to changes in the amount of muscular force you are using to lift the weight.

Why do we care? Because if you want to make your movement more efficient, you have to be aware of when you are working too hard. If you slow down and thereby increase your ability to sense differences in muscular effort level, you increase the brain’s ability to sense and correct any potential excess and unnecessary effort. Imagine that every time you try to extend the hip, you are at the same time slightly contracting the hip flexors instead of relaxing them. This means that your muscles are cross-motivated – the flexors are fighting the extensors a little in their effort to extend the leg, making them work harder. You will be much better able to sense and inhibit this inefficient co-contraction by moving very slowly and easily. By contrast, if you move fast and hard, you will never be able to sense and correct the problem."

--Todd Hargrove (extract from a blog post, read the rest on his very informative blog here)