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.
do you suck in your stomach or maybe the better question is do you know anyone who doesn t many people mistakenly believe that holding their stomach muscles tight not only makes them look more trim and fit but also helps them stand straight and tall but sucking in your stomach muscles makes it impossible to breathe correctly which in turn prevents you from having good posture poor posture leads to a host of other problems including a sore neck and shoulder muscles poor balance arthritis and injuries