It looks like the ruling Caster Semenya is fighting is about elevated testosterone levels in women. That is definitely testable. According to the ruling, if a woman has above a certain level of testosterone in her blood, the level must be lowered before she can compete. Seeing how testosterone levels are what causes secondary sex characteristics in men, and also the main reason why men are much stronger than women, this makes complete sense to me. When men transition to women, taking medication to lower testosterone levels is one of the main actions (along with raising estrogen) that cause physical changes.
But that's the rub, right? What definition of "men" and "women" are you using?Seeing how testosterone levels are what causes secondary sex characteristics in men, and also the main reason why men are much stronger than women, this makes complete sense to me.
In this context, I meant cisgendered men and women. Cisgendered men are stronger (and faster, and have faster training recovery) than cisgendered women primarily because of higher testosterone levels. So primarily caring about testosterone levels, to me, sidesteps all the gender politics and focuses on what matters for athletic performance. I rather like this method of doing things, because it's just defining a boundary for a competition class. Weight, equipment allowed, supplements allowed, gender, and now testosterone level allowed. It makes sense to me. In a sense it doesn't even matter how the competitors define themselves.
I assume you mean cisgendered in a biological (XY or XX) sense? If so, then it seems that chromosome is a better divisor as testosterone levels aren't consistent in one individual, and as testosterone is just one factor in numerous downstream biological differences due to the sex chromosome difference.