Testosterone is known to affect skeletal muscle growth, but the mechanisms by which testosterone affects muscle growth are not known (Bhasin, Woodhouse, and Storer, 2001). Also, women with very high androgen levels—whether it’s due to endogenous or exogenous testosterone—have a 2.5 to 5 percent advantage over women who have androgen levels in the normal range (Berman, 2017). So the difference in performance—between women at least—with high and low levels of testosterone is not too great, though that 2.5 to 5 percent advantage most likely would come into play at the very end of the race.

Also recall that I previously wrote that, per the IOC guidelines, a ‘MtF’ needs to ‘declare herself’ a woman for at least four years while taking HRT for 1-2 years to be able to compete with ‘the gender they think they are’. Well, the testosterone levels that the IOC states is ‘OK’ for ‘MtFs’ is still in the low range of the new testosterone guidelines for men! Testosterone most definitely does give an advantage in sports. Think of sports as a modern day test of survival. Basically, those good at sports—such as football and basketball for instance—would have been better able to form hunting parties in our evolutionary past. So while forming these parties, testosterone rose since testosterone raises while men are in groups as well as preparing for competition (Booth et al, 1989). So since our modern body plans sprang up around 2 mya with the appearance of Homo erectus in the fossil record, we can logically infer that cooperation and testosterone—among other things—were needed to be successful hunters.

So if you look at most sports as just a way for men to have a competitive spirit and simulate fighting/hunting with other men, then it makes it clear that testosterone does infer an advantage in sports. For instance, there is a clear relationship between testosterone and explosive jumping (Cardinale and Stone, 2006). These relationships are very clear, have large effects yet bodies like the IOC disregard these findings, allowing MtFs to compete with real women, even when the data and verbal argumentation against letting them compete are logically sound.

Studies do state, of course, that the relationship between high testosterone and athletic performance hasn’t been proven, they also haven’t been refuted either (Sudai, 2017). In fact, all you need to look at is traits that are influenced by testosterone—height, size of limbs, fat mass, shoulder width/size (the most androgen receptors lie in the shoulders and traps muscles, so to tell if someone is juicing, they will have low levels of body fat but ‘3-D delts’ and large traps) etc. So just by looking at a few simple traits and then comparing anatomy with females who have high testosterone compared to women who do not have high levels of testosterone, we can draw the logical conclusion that testosterone does increase sports performance for both men and women, and we have both anecdotal and experimental evidence for the assertion.

In sum, the anecdotal evidence from Epstein’s book is a good start. However, we will need more than anecdotal evidence to prove that testosterone truly does give individuals an advantage if they do have higher testosterone levels than their competition. As larger studies get done, these effects will begin to get teased out. I am certain that testosterone will be found to give a huge advantage in terms of sports, and since sports are a way for us to compete with each other, impress women, gauge other males’ fighting skills, and began as a way to hone skills used to hunt and fight (Lombardo, 2012). Sports began as a way for us to develop the skills needed to survive and hunt, among other things, and so, to hunt, you need to have high levels of testosterone to give that ‘boost’. So if sports began as a way to gauge potential rivals and allies, and as a way to hone/improve fighting skills, then we can logically state that testosterone does give an advantage in sports competition.