Sex differences 101 By Mrs Vera West
With all we hear in the media is about how sex differences are a social construction, for a breath of air, consider some basic physiology, neatly summarised here, which is good once I got past a few bits of course language that nowadays seems to fill blogs:
“Men have about 61 percent more muscle mass than women (which is attributed to higher levels of testosterone); most of the muscle mass difference is allocated to the upper body—men have about 75 percent more arm muscle mass than women which accounts for 90 percent greater upper body strength in men. Men also have about 50 percent more muscle mass than women, while this higher percentage of muscle mass is then related to men’s 65 percent greater lower body strength (see references in Lassek and Gaulin, 2009: 322). Men have around 24 pounds of skeletal muscle mass compared to women, though in this study, women were about 40 percent weaker in the upper body and 33 percent weaker in the lower body (Janssen et al, 2000). Miller et al (1993) found that women had a 45 percent smaller cross-section area in the brachii, 45 in the elbow flexion, 30 percent in the vastus lateralis, and 25 percent smaller CSA in the knee extensors, as I wrote in Muscular Strength by Gender and Race, where I concluded:
The cause for less upper-body strength in women is due the distribution of women’s lean tissue being smaller. Men have larger fibers, which in my opinion is a large part of the reason for men’s strength advantage over women. Now, even if women were “discouraged” from physical activity, this would be a problem for their bone density. Our bones are porous, and so, by doing a lot of activity, we can strengthen our bones (see e.g., Fausto-Sterling, 2005). Bishop, Cureton, and Collins (1987) show that the sex difference in strength in close-to-equally-trained men and women “is almost entirely accounted for by the difference in muscle size.” Which lends credence to my claim I made above.
Lindle et al (1997) conclude that:
… the results of this study indicate that Con strength levels begin to decline in the fourth rather than in the fifth decade, as was previously reported. Contrary to previous reports, there is no preservation of Ecc compared with Con strength in men or women with advancing age. Nevertheless, the decline in Ecc strength with age appears to start later in women than in men and later than Con strength did in both sexes. In a small subgroup of subjects, there appears to be a greater ability to store and utilize elastic energy in older women. This finding needs to be confirmed by using a larger sample size. Muscle quality declines with age in both men and women when Con peak torque is used, but declines only in men when Ecc peak torque is used. [“Con” and “Ecc” strength refer to concentric and eccentric actions] Women are shorter than men and have less fat-free muscle mass than men. Women also have a weaker grip (even when matched for height and weight, men had higher levels of lean mass compared to women (92 and 79 percent respectively; Nieves et al, 2009). So men had greater bone mineral density (BMD) and bone mineral content (BMC) compared to women. Now do some quick thinking—do you think that one with weaker bones could be stronger than someone with stronger bones?
If person A had higher levels of BMC and BMD compared to person B, who do you think would be stronger and have the ability to do whatever strength test the best—the one with the weaker or stronger muscles? Quite obviously, the stronger one’s bones are the more weight they can bare on them. So if one has weak bones (low BMC/BMD) and they put a heavy load on their back, while they’re doing the lift their bones could snap.
Alswat (2017) reviewed the literature on bone density between men and women and found that men had higher BMD in the hip and higher BMC in the lower spine. Women also had bone fractures earlier than men. Some of this is no doubt cultural, as explained above. However, even if we had a boy and a girl locked in a room for their whole lives and they did the same exact things, ate the same food, and lifted the same weights, I would bet my freedom that there still would be a large difference between the two, skewing where we know it would skew. Women are more likely to suffer from osteoporosis than are men (Sözen, Özisik, and Basaran 2016). So if women have weaker bones compared to men, then how could they possibly be stronger? Even if men and women had the same kind of physical activity down to the tee, could you imagine women being stronger than men? I couldn’t—but that’s because I have more than a basic understanding of anatomy and physiology and what that means for differences in strength—or running—between men and women.”
There was no bibliography at the end of the article, but I think the original will link, for those writing their thesis on gender differences.
There is a long reply to the article arguing that even though in every ethnic group men are stronger than women, across ethnicities, some groups of women are stronger than men, such as Nordic women being stronger than say, Pakistani men, and many Asian groups. While this is true, it only shows that racial aspects have an impact upon the sex-strength equation as well, and does not show that the central claims are false.