24. Trans Athletes: No Opinions, Just Science!

Rare or surprisingly common to have a sex chromosome disorder, here are the numbers, you decide!https://www.uptodate.com/contents/sex-chromosome-abnormalities/abstract/1 Use these links to check out where you stack up, height-wise, compared with males and females across the world.https://www.medicinenet.com/height_men/article.htmhttps://www.medicinenet.com/height_women/article.htm Bone density in trans females appears to stay at the higher biological male levels seen pre-transition.https://onlinelibrary.wiley.com/doi/10.1046/j.1365-2265.1998.00396.x Adult males typically have larger hearts than adult females but only because, typically, they’re larger!https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2148100/ What’s the most important factor causing biological males to have more hemoglobin than biological females? It’s that lovely testosterone!https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4022090/ You might be surprised to know that scientists don’t fully understand why biological males typically have more muscle mass than biological females – testosterone is one part of the answer but doesn’t explain everything.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2148100/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2148100/  Biological males typically have more type 2 fibers, advantageous for explosive, strength-based eventshttps://journals.physiology.org/doi/full/10.1152/ajpendo.00098.2004than their biological females counterparts who instead have more type 1 (fatigue resistant) fibers throughout their muscles.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4285578/ Elite endurance runners and cyclists appear to naturally have a lot of type 1 fibers whereas power athletes appear to have a much higher proportion of the various type 2 fibers.www.ncbi.nlm.nih.gov/pmc/articles/PMC8473039/pdf/sports-09-00127.pdfhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC4469925/#:~:text=The%20world%2Dclass%20sprinter's%20leg,%C2%B1%200.1%20W%2Fl).  And switching of muscle fibers appears to be very limited, so what your parents gave you seems to be pretty much what you’ll have throughout your life!https://onlinelibrary.wiley.com/doi/full/10.1111/sms.13675 If you’ve already listened to the episode, you’ll know that the USA airforce carried out a fascinating study on 46 trans female recruits, click here to check out that work:https://bjsm.bmj.com/content/55/11/577.abstract For a ton of interesting research and to see why World rugby currently says no to trans female players in the women’s game, check out their thoughts here.https://www.world.rugby/the-game/player-welfare/guidelines/transgender And see here why USA rugby decided upon the opposite approach.https://usa.rugby/transgender-policy