What term means to tighten when it comes to muscles?

Which of the follow is good way to gauge musculature endurance?

Answer in a couple of paragraphs, 1 or 2 at the most if anything! 20 points + brainliest--> explain what all the systems in your body do to work together < --list of systems needed: circulatory systemrespiratory systemdigestive systemexcretory systemnervous system

Which of these example of a hereditary risk factor? smoking, eating junk food everyday, being a couch potato, having fair skin that is prone to sunburn