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.
How To Do Ab Crunches. Starting position: Begin lying on the floor with your knees bent and your hands behind your head. Form: Exhale and curl your body forward, and lift your shoulder blades off the floor.Hold for 1 second at the top and slowly return to the floor.hen your spine moves, your stomach muscles work. Lying on the floor, limits the amount that your spine can move, and this also limits how much your core muscles can work. A simple remedy for this con is to do crunches on an exercise ball. Con #2 If you only use your body weight, your strength will plateau.