If you’ve watched gymnastics in Rio, you’ve probably noticed that the gymnasts are pretty small, and that Simone Biles, the greatest gymnast probably ever, is small even compared to her American teammates. But at 4-foot-8, Biles is actually only slightly smaller than her peers. In fact, over the last 30 years, the average elite female gymnast has shrunk from about 5-foot-3 on average to about 4-foot-9.In the past, the judges gave taller, more elegantly moving young women advantages because they looked better. But that gave an advantage to Eastern European girls raised in the traditions behind the Bolshoi ballet. The Americans have lobbied to make scoring more objective, which gives the advantages to Mary Lou Retton-style muscular human cannonball body types like Biles’.
Why are elite female gymnasts getting smaller? Because the more demanding gymnastics routines have become, the bigger an advantage it is to be small. A smaller gymnast not only has a better power-to-weight ratio. She also has a lower moment of inertia.
You can think of moment of inertia as essentially a measure of a body’s resistance to rotating. The higher the moment of inertia, the harder it is to rotate the object. And larger bodies with more weight far away from the axis of rotation have a higher moment of inertia.
Think about figure skaters. You’ve probably noticed that when figure skaters spin, they start rotating much more rapidly when they bring their arms close in to their chest. By moving their arms in, they’ve decreased the amount of weight that’s far away from the axis of rotation and they’ve decreased their moment of inertia, making it easier for them to spin at high speed.
The smaller a gymnast is, the easier it is for her to rotate in the air.
Over time, the various Olympic sports have become hyper-specialized by body type, so medalists tend to be rather freakish looking.
One interesting question is which sports have the best normal looking athletes: i.e., the winners look like movie stars rather than people selected at an early age for their odd proportions.
Traditionally, men’s pole vaulters — an event that requires both lower body speed and upper body strength — have been good looking guys.
Slate recently ran an article by a woman journalist claiming that Allison Stokke is the most popular lady pole vaulter in the world for a “gross” reason: i.e., people think she’s pretty. (Slate has since memory holed their old headline and replaced it with “Allison Stokke Is the Most Popular Pole Vaulter in the World, and I Wish That Weren’t So Depressing.”)
But Stokke is only the 168th ranked women’s pole vaulter in the world.
My guess is that when pole vaulting was extended to high school girls, the early adapters tended to be rich guy’s daughters who are high-flying cheerleaders during football season. For example, the daughter in the real life family featured in the 2009 Sandra Bullock movie The Blind Side went on to be the Mississippi state pole vaulting champion several times in high school. Her dad had been the U. of Mississippi’s all-time best point guard and her mom the college’s head cheerleader.
But I don’t know whether this pattern has continued.
In general, girly girls tend to be more attracted to the anti-gravity sports like gymnastics, figure skating, and pole vaulting.