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.
A simple and effective way to ease neck pain from a cold or flu virus is to use an ice pack or heating pad. Heat can relax tense muscles in the neck, while ice can reduce inflammation. There are no clear-cut guidelines on which (hot or cold) is most effective, so you may need to experiment.