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.
And that'll only hold you back in every other lift. You canât do just any moves, though. Performing classic ab moves like crunches and situps at the end of your workout is an exercise in futility. These moves only work the muscles that allow you to flex or round your spine, says Schuler. During heavy lifts like deadlifts and squats, you want to prevent your spine from moving.