Fair eligibility-requirements for intersex and transgender female athletes are sorely needed for Olympic competition. Those designated 46 XY DSD are usually judged to be intersex females at birth with Differences of Sexual Development (DSD), producing testosterone-creating testes instead of ovaries. Men who transition to female are defined as transgender women and have testosterone-creating testes. To quantify the role of testosterone, physics and kinesiology were applied to running, swimming, speed skating and rowing, to evaluate the female/male velocity ratio of Olympic Champions from 1980 through 2020/21 as driven by the relative lean-to-weight ratio of elite athletes. That velocity ratio now equals the relative lean-to-weight ratio of 90%. Since circulating testosterone drives the lean-to-weight ratio, higher testosterone gives men that 10% advantage over women. A definitive paper written when a limit of 10 nmol/L was used, concluded that 5 nmol/L was the lowest reasonable limit to impose, and then it was exceeded against Castor Semenya. Intersex athletes were born that way, suggesting that no limit or a limit of 10 nmol/L would be fair. Since transgender female athletes undergo therapy, 5 nmol/L might be achievable without medical or psychological side effects, instead of requiring transition before male puberty, which happens rarely. Keywords: intersex females, transgender females, testosterone limits, lean-to-weight ratio, gender inclusion