13. Gluteus Maximus: Trapezius because the contraction of one doesn't necessarily lengthen the other.
14. Decreased bone mass because strength training adds bone density, keeps the volume, so therefore increases the mass.
15. Not 100% what long/short is, and I'm not 100% sure of the answer. I'm going to say large/small because you already work out the smaller muscles during the working out of the large muscles.
16. The only one that one should stick by 100% is maintaining proper posture, form, and technique. But, this is health, and not bodybuilding. So, maintaining the core tension at all times. You don't need to do that for something that doesn't require the core.
