molecule. 1  Chemistry, Physics. the smallest physical unit of an element or compound, consisting of one or more like atoms in an element and two or more different atoms in a compound. 2  Chemistry. a quantity of a substance, the weight of which, measured in any chosen unit, is numerically equal to the molecular weight; gram molecule.
When I do crunches my neck starts to tighten up and it makes me have to rest before doing another set of crunches.
Besides headaches, sensitivity and a sore jaw, bruxism can also loosen the teeth's position in your gums. The solution is a night guard that you can get specially made for you by a dentist. Insurance usually covers part of it, and it will keep your sleeping self from crunching through the night.