Reciprocal Inhibition - or - why your muscles don't work

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Reciprocal Inhibition. What a title for a post. I can barely say it at this time in the morning, but its quite an important concept for people with tight muscles.

What is it?
Reciprocal Inhibition (RI) is what happens to antagonistic muscles - i.e. muscles that work in opposite directions on the same joint. For ease of imagination/demonstration think about the arm and bending your elbow. When you flex your arm at the elbow joint (your hand travels toward your shoulder) you are contracting your Biceps brachii - at the same time, the Triceps - on the back of the arm - are relaxing. (this isn't EXACTLY what happens by the way - its just a simplified version in order to get the general concept across).

Now, when you extend the arm - (the hand moves away from you) the triceps are
contracting, and at the same time the Biceps are relaxing.
Right. This is simple inhibition. As in the example above, the Biceps contract and the triceps relax. As your brain turns on the neural "path" to the Biceps telling it to contract, at the same time, there is another signal that goes to the Triceps telling it NOT to contract - it must relax - it INHIBITS the triceps. In fact, it reciprocally inhibits the muscle.
In the same way, as the Triceps contracts, there is a neurological signal to the Biceps to NOT contract - it must relax.

This works with all antagonistic muscles - quads/hamstrings, adductors/abductors, internal and external rotators, hip flexors/ hip extensors. You name it, it works.

(Don't worry about the mechanism for the moment, if you really want to know how it does it, drop me a line and I'll see about writing a more in depth post).

So why are you talking about this and how does it affect me?
Ah, well.
Lets talk for a moment about resting muscle tone- which is very pertinent to this issue. Lets take the same example of the biceps and triceps, (we'll expand on it in a moment). Imagine, if you will, that your Biceps is permanently high in tone - it is permanently "switched on". Not to a level that means your hand is constantly by your shoulder, but to the point that your arm is constantly half bent.
Right.
If the biceps is CONSTANTLY switched half on and you find it difficult to relax it, the triceps are always going to be switched off - they will always be Reciprocally Inhibited. Even when you try to use the triceps, because it is used to being switched off, the action that it produces is weakened, and it cannot do everything it is meant to do.

So a high resting tone in one muscle reciprocally inhibits the antagonist - causing it to be in a weakened state at rest. This means that the weakened muscle is going to be weakened in contraction as well - so it is a muscle that is being held weak, and contracts weakly - which obviously can't help you in what you are meant to be doing.

Hope you followed that. If not, tell me and I'll try and explain it better.