Why is it implausible? Standing still requires muscle. There is some minimum standard of fitness required to stand for a fairly long time. Being thin or having

Why is it implausible? Standing still requires muscle. There is some minimum standard of fitness required to stand for a fairly long time. Being thin or having a normal BMI doesn't mean you're fit. It's just a useful statistical measure to find out the general fitness of a population. Youth won't help you either.