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.
'Like' https://facebook.com/RussHowePTI Fitness Instructor Russ Howe explains why doing sit-ups and crunches often hurts your neck and explains how to use the correct exercise technique to eliminate this issue altogether.More free info from trainer Russ every week on our new Facebook page.Like' https://facebook.com/RussHowePTI Fitness Instructor Russ Howe explains why doing sit-ups and crunches often hurts your neck and explains how to use the correct exercise technique to eliminate this issue altogether.