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.
Note that in our dynamic exercise suggestion we did not mention crunches. While many people think that doing a hundred crunches a day will get them rock solid abs, it simply isnât the case. Crunches only target one small abdominal muscle group, and can also place an undue amount of strain on the back and neck.