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.
Relevance. Rating Newest Oldest. Best Answer: Make sure you are not placing your hand behind your neck...that is common and is NOT a correct way to do crunches. That makes your hands push on your neck for support. Place your hands across your chest when doing the crunches, so that only your abs are working.