It's not quite the same thing as when a muscle gets tired.
Jaw tension shows up in some folks as soon as they start to sing, so fatigue doesn't cause it, per se.
Fatigue-induced shaking is an example of tremoring - when one muscle loses strength and fights with another one for dominance.
Fatigue causes the body to allocate effort to a second muscle (ie: the biceps try to give over to the triceps or other less prominent muscles nearby). Since the second muscle isn't designed to handle the things the first muscle does, it tries to pass the stress back over to the first muscle. This battle recurs, causing a shaking. It's like being stuck in between gears. (That is a supper simplified explanation)
This is not what we see in the jaw.
(Edit - text added after)
I have to admit though, that I'm not well-versed in termoring and the muscular system...so please feel free to take contension with this or educate us all if any of you know more about this subject. Thanks!
Updated On: 7/3/08 at 05:26 PM