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.
Since the muscles are not designed to be under constant stress, it is extremely essential that the stress or load is taken off as the muscles relax in the passive mode. If any activity acts as a trigger and causes the neck muscles to stay under constant tension, one is most likely to develop tension knots. Though some practitioners cite the accumulation of abnormal protein deposits within the muscle tissue as the triggering factor behind the development of muscle knots in the neck area, this theory has not been corroborated by medical research.