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.
Ice it. Ice effectively numbs pain and decreases inflammation. Put crushed ice in a plastic bag and cover the bag with a pillowcase (a terry towel is too thick to effectively transmit the cold). Apply the icepack to your painful neck for 15 minutes at a time.