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.
Variations of the crunch workout different parts of the abdominal muscles, but any toned muscle you build above the belly button will not be visible if you do not lose any layers of fat.trength Training. Crunches and their variations give a highly effective abdominal workout. To do a standard crunch, lie on your back with your knees bent and feet flat on the ground. Place your hands at either side of your neck, lightly touching.