I was watching one particular match where one of my dojomates was executing a beautiful combination from Uchimata into Tani Otoshi. I have seen Jimmy Pedro actually demonstrate this in a video made to teach the American audience about Judo for the Olympics, and this guy was great at it, he must've hit it several times yesterday. Watching him got me thinking, not just about the combination itself, but the concept of Combinations in General as well as the concept of reflexes.
Any one will tell you that the key to performing effortless Judo is all in the timing. If you do not agree with me, or don't believe me, try executing De-Ashi-(H)Barai in Randori or Shiai. Hard isn't it? Of course your answer to that question is proportionate to the amount of time you've spent in Judo, and how much time you have devoted to practicing foot sweeps. In reality we are not talking about dance-move style timing, but rather reaction time - or in another word - reflexes.
Essentially a reflex is an action triggered by a stimulus - just like the little kick we give when the Doctor hits our knee with that little rubber hammer, or how our pupils dilate when we walk into bright light. For the most part, these are unlearned and involuntary - or are they? None of us were born walking, yet once we start (assuming we don't have other impediments) we ultimately get the hang of it and it becomes second nature. None of us are born talking either, yet again, barring any other impediments, we learn and ultimately are able to talk as if we did it straight out of the womb. So clearly, reflexes can be learned. Depending on your level in Judo, you may already be noticing this in yourself or have noticed it in your dojomates.
Another interesting thing about reflexes is that the more you practice the quicker they become. Why is this? In theory you aren't able to detect the action any quicker, nor is your body becoming faster, so why does response time improve? The answer of course is in the brain.
You see our brain is really one massive computer network. When we want to raise our hand, a message from the part of the brain which we think with travels from our brain to the necessary muscles to get them to move in the right direction. These paths that the impulses traverse are known as neural networks. But unlike computer networks that have fixed bandwidth, the speed at which the impulse travels is increased with the frequency of a particular action - In other words the more often you do something, the quicker you will be able to do it because the frequency will prepare your body to boost its execution priority. Obviously, we will hit a wall with speed at some point, but by continuously practicing something over and over again, both as a motion on its own, and as a reaction to uke's action, we will improve our reflexes and lower our response time.
I am sure that this is evident the first time any of us learns a new technique. We go slow the first 10, 20, 50, 100 times and then ultimately as we get the motion down pat we start to pick up speed. This why Uchikomi are important, and even more important are combinations - why you might ask? It's very simple. If you just study simple Uchikomi, your attacks will be single-faceted. But as we all know humans take multiple reactions to the same action, therefore, one move is not enough. By practicing combos you are further training your mind to deal with what steps lie further ahead.
Ultimately, by putting together various combinations from a specific starting move, your body and brain will learn the appropriate action to take in response to a specific reaction from uke. Obviously, the possibilities are endless, which is why practice in Judo is so very important.
The bottom line: keep practicing, and you will even begin to amaze yourself.