Going beyond the sex “grip strength” binary

Jesse Singal brought this piece in Deadspin, She’s Got The Strength, But Who Has The Power?, to my attention.

Some very interesting sections:

When we shove the concept of athletic ability—strength, for instance—into the same black-and-white binary that we try to put gender into, we’re wrong. There is no stark line separating what men can do athletically and what women can. Some women, in fact, are bigger, faster, and stronger than some men. A large data set analyzed for a 2018 study looked at the body composition and endocrine profiles of 689 elite cisgender athletes in various sports. When it came to physical attributes there was complete overlap between the men and women analyzed, McKinnon pointed out. For instance, the shortest person in the data set was male, not female. The lightest male weighed the same as the lightest female. There were men athletes and women athletes who had testosterone levels that hit the top of the chart and the bottom. Simply put, the range of any physical characteristic within a sex, (like, for instance, the six feet of difference between the shortest man in the world and the tallest man) is far greater than the average difference in height between the average man and the average woman (five inches). And elite athletes tend to live at the far ends of these spectra anyway.

USA Powerlifting’s response to transgender athletes is head-spinning. The thing about all this talk equating hormone replacement therapy to doping, and the threat to “biological females,” and the “unfair advantages” of “male puberty,” is that it’s based entirely on social perceptions of gender.

“There’s absolutely no scientific evidence at all that supports their position,” said Rachel McKinnon, an expert on athletes’ rights and a professor of philosophy at the College of Charleston, and a world champion track cyclist to boot.

Recently a very successful person told me that mathematical intelligence is probably overrated in comparison to verbal intelligence. It is true that some women are bigger, faster, and stronger than some men, and therefore a lot of social policy follows from this truth? Well, empirically that seems to be the case today.

Despite the irrefutable sophistication of words, I decided to pull some data from the National Center for Health Statistics. These data are useful because they separate by sex and age (and in some cases race/ethnicity). Rather than focusing on ranges, I was curious about the distributions for two characteristics:

  • Height in males and females of a range of ages and between the sexes
  • Dominant hand grip strength in a range of ages and between the sexes

In some cases, there were age intervals, so I simply took the midpoint (e.g., 25-29 becomes 27). Also, they had an 80 and over category. I just left that as 80.

First, let’s look at the age. The figure below shows the distribution of height for males and females over the years, with intervals along with two standard deviations for each age.

Let’s zoom in on puberty.

None of the results should be surprising. I assume many of you remember age 12 when the girls were taller than the boys?

Now let’s look at the distribution at age 25.

You probably want to know the overlap. The shaded area is 51% of the total area under the union of the two curves.

Not a great surprise. Men are taller than women, on average. But there are many women taller than many men.

But what about grip strength? This is one of those standard metrics that’s used to measure health. People with illnesses tend to weak. So they measure this in many people to get epidemiological data.

Here is the plot by age and sex. Again, two standard deviations. Notice that the two curves are more distinct during adulthood than height. Men have stronger grips than women to a greater extent than their simple size difference.

Let’s zoom in on puberty. Here we can see a very large difference between males and females. The difference is more striking than with height. Between the ages of 12 and 13, males start to zoom away from females in grip strength. There’s basically no difference in grip strength for children of elementary school age, on average.

Now let’s look at the distribution at age 25. Again, it is more striking than that for height.

So finally, what’s the overlap? ~21% of the area under the curves overlaps. This means that are a substantial number of women who could pummel a substantial number of men. But, in these cases, it is the strongest of women and the weakest of men. I would say that that’s not sporting, to be frank.

In media, there is often a depiction of rather petite women taking on larger men in physical fights. Because film and television is fantasy, of course, the women, if they are on the “good” side, will come out victorious (just like the hobbits in Peter Jackson’s films). But reality would not be as pretty.

On the other hand, a large woman and a very small man seem like it would be a reasonably “fair” fight from these data. But I’m certainly glad that Red Sonja was not written and filmed in a more realistic manner, with the towering Brigitte Neilsen avoiding Arnold Schwarzenegger’s Lord Kalidor to only slay smaller fry.

You may have noticed that males are stronger than females when you correct for body size. Why? The average body fat percentage of a male (not overweight or obese, though not fit) is in the low 20s. The average body fat percentage of a similar woman is in the high 20s. In contrast, men have 40% more muscle mass in the upper body, and 33% in the lower body.

I’m just a simple geneticist. I don’t really know much biology. I don’t know what goes on physiologically and structurally beyond what I learned in high school and what I know from being a human being who went through puberty. But something happens that makes males and females quite distinct in their athletic abilities from what I can see in the data.

11 thoughts on “Going beyond the sex “grip strength” binary

  1. Kind of wonder how much this hand grip strength dimorphism is mediated by hand size – men have larger hands on average, which should be due both to the later cessation of growth in height and overall larger size (male height advantage), and due to testosterone in concert with environmental stressors during teens and early adulthood thickening and increasing hand size relative to height directly (e.g. increase in hand grip continues up to age 30 after height increase stops).

    (Decline in older people would be separate from this and reflect general health efficiency?)

    Transgender people are on various hormone therapies and this does seem to have an effect on skeletal muscle and fat distribution overall, but not really on bone size at all (certainly not under M->F therapy, not sure about the inverse). So maybe worth thinking about how much handgrip strength is sensitive to t responsive muscle, or just a product of bone size differences that are fixed at puberty and insensitive thereafter? (When thinking about handgrip strength as index of overall M:F differences).

    This is not to imply that this same issue (products of bone structure differences don’t go away under hormone therapies and will continue barring some future therapies that can reverse skeletal dimorphism) not a concern in terms of other measures of strength and transgender athletes though, as still quite likely to be.

  2. Rachel McKinnon is most emphatically not an “expert” on athletes rights. He is a man who wants to destroy women in women only events and will use any argument no matter how specious or absurd to defend his victories over natal females. If forced to compete on a level playing field against natal males he would be so thoroughly trounced that no one would ever pay any attention to him.

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  3. What sort of krazee thing are you going to assert next? That it was not long ago mathematically proved that Unregulated Free Markets and Totalized Gun Totin’ in tandem will necessarily produce The Best Possible Societal End-Result?

  4. Without thinking too much about the subject, here’s a view I have formulated. It might come across as a bit inflammatory but I couldn’t think of a better example off the top of my head. Arguments are welcome.

    Test various relevant attributes of all professional biologically female athletes. Test all trans women athletes similarly. Let only the ones who aren’t beyond something like ~3sd of the biologically female average results compete. This will likely exclude a decent percentage of trans women who go beyond that, which is one of the arguments, though trans women will still be overrepresented at the top relative to absolute numbers in the general population.

    If not, why not? Jews, for example, have similar advantages in other fields due to their biology but I don’t see many people making the argument that certain intellectual competitions should be gentile-only since Jews have an unfair biological advnatage. What’s the argument left in this case, other than something about “the essential reality of sex”? Without discounting the more fundamental differences in sex vs race, reality also tells us that blacks and whites belong in very different broad population groups with different competitive advantages in sports. Should we also segregate in that case? Don’t gentiles also potentially feel bad when they see Jews being so overrepresented in various areas? Should gentile feelings be taken into consideration in that case or not?

  5. The obvious fact that eludes advocates of the propositions refuted by Razib, is that competitive athletes are not in the middle of the distributions. They are in the right tails, areas where there is no overlap. Further, by the time you get to major college level sports, you have left the 2nd sigma behind. There are no XX-women who could compete at the highest level of any athletic competition.*

    *I know about Danica Patrick, but the automobile does most of the work in that game.

  6. In 1976, Jenner (then Bruce, now Caitlyn) was the greatest athlete alive winning the men’s decathlon at the Olympics. Jenner’s scores would have won gold medals in 4 women’s events (100M, 400M, Long Jump and High Jump.) Men and women use different weights in the javelin, discus and shot put but Jenner’s was clearly stronger than all the women competitors. Jenner would have been able to win the 200M and heptathlon and possibly the 800M. If Jenner had competed with women, Jenner would have been able to win 9 or 10 individual gold medals plus two relays for a total of 11 or 12 golds.

    To put that in perspective, I believe that Betty Cuthbert is the only woman to ever win three gold medals in track and field in one Olympics (2 individual and 1 relay).

  7. Grip strength is a nice example because it comes up in everyday life: women ask men to open jars.

    @Matt:
    the muscles are more in the arms than the hands. I have tiny hands, smaller than most women, but still I can open jars.

  8. Hmm: “Test various relevant attributes of all professional biologically female athletes. Test all trans women athletes similarly. Let only the ones who aren’t beyond something like ~3sd of the biologically female average results compete.”

    How intersex individuals with external female anatomy (like appears to be the case of Caster Semaya) will be treated in this system? Like trans women or like biological woman?

    Can be argued that this is a very rare case, but I am not much sure – I will not be suprised if, in the real world, there was more intersex than trans people.

  9. The grip strength differences are pretty striking. Looks like the mean for men is about at mean + 3-sigma for women — so maybe 0.5% of women reach or exceed the grip strength of the average man. (I find this a bit more intuitive than the degree of overlap between the distributions.)

  10. @ Walter

    > There are no XX-women who could compete at the highest level of any athletic competition.

    There are several women among the world’s top rock climbers – say, top hundred or so. Of course this might reflect the relative immaturity of rock climbing as an athletic discipline, where the limits of human physical potential aren’t being reached yet.

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