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.
You core is weaker, but take caution with the crunches 6 of 10. It may seem like crunches are a great idea for targeting post-pregnancy girth, but not so fast. Many women (a third of first time moms, and many more second time moms) find they have a gap between their stomach muscles after pregnancy.