Athletic Advantage before Birth

Boys normally get huge athletic advantages over girls at puberty, so many assume that puberty defines the difference. According to this post, the differences start before birth:

Male athletic advantage begins in utero.

Late first-trimester male foetuses already have uniformly higher concentrations of type IIa and IIb muscie fibers across skeletal muscles. This differential in IIa and IIb concentration continues throughout all of life and is one of the major reasons for greater male performance in speed/power (IIb) and speed-endurance (IIa) events.

It’s pretty well documented that elite men’s track records are on average about 10% faster than elite women’s, across essentially all the contested distances. What most people don’t know—but certainly should—is that essentially the same 10% differential obtains between boys’ and girls’ track records, ALL the way down the age groups.

The fastest boys are still faster than the fastest girls, by the same 10ish %, all the way down to the 8-and-under age group. https://www.usatf.org/resources/statistics/records/championship-meet-records/usatf-national-junior-olympic-track-field-champion

(All the boys’ records are clustered in the first half of the page, followed by all the girls’ records in the second half. The easiest way to compare them is to open the same page in two tabs, shrink each tab to half-screen height, stack the two tabs on top of each other and then navigate to N year old boys’ records in one tab and N year old girls’ records in the other.)

Moreover.
Almost all joint angles differ on average between the sexes, with these differences already being well established between male and female foetuses (relevant papers will appear under the area of forensic fetal osteology

One of the most consequential differences is in the “Q angle” or “quadriceps angle” between each femur and the pelvis. The Q angle in women and girls averages about 2x as far from the vertical as in men—so that female legs in standard gait are angled inwards from the hips, with female footfalls from both feet almost in single file. Male hips are narrower on average, with male legs closer to vertical and male footprints generally in two easily distinguishable, left and right, tracks. (Please understand “on average” to be attached to each observation in this paragraph.)

The Q-angle differences are hugely significant to athletic performance. Jumping, pushoff and leg pressing power are developed only as vectors perpendicular to the ground, so women’s wider Q-angles reduce their potential jump height, sprint speed and maximum performance in any “closed chain” weight lift (squat, deadlift, clean/jerk/snatch etc). Furthermore, the stresses exerted along the residual (parallel to ground) component of female legs place women and girls at far greater risk of ACL tears and related injuries

Another example many readers may at least have noticed—if not considered here—is that women’s elbows typically hyperextend a few degrees beyond straight (https://musculoskeletalkey.com/wp-content/uploads/2016/06/F000067f006-014-9781455709779.jpg) and are deflected a few degrees laterally (https://musculoskeletalkey.com/wp-content/uploads/2016/06/F000067f006-002-9781455709779.jpg).

These two types of deflection of women’s arms away from straight—as opposed to male arms, which are quite close to perfectly straight at full extension—is the most important reason by far behind the almost unfathomable sex differences in punching power (men punch 263% as hard as women of similar size and height). The same female hyperextension and deflection is the reason why girls and women hold and bow violins differently, with different types of chin rests needed even by very young girls and boys.

ALL of the differences mentioned in this post exist systemically between the sexes not “from puberty”, not even “from birth”, but from long, long BEFORE birth. Every single one of them is already a statistically significant distinction between male and female foetuses by the end of the FIRST TRIMESTER of pregnancy.

Sports and other pursuits of physical performance just need to be sex-segregated, at all ages, period. This is not complicated, nor is it an issue with two sides or with ‘nuances’ or ‘subtleties’—let alone a ‘human rights’ issue (a phrase that in the 2020s is guaranteed NOT to have anything to do with actual human rights).

This is for those who say that sports can be made more fair by controlling for sex differences. I am not arguing for that. Sex-segregated sports would make sense even if there were no sex-based advantages.