Why female gymnasts are so short They defy gravity, spinning through the air at an improbable rate. They do somersaults on beams we’d fall off if […]

They defy gravity, spinning through the air at an improbable rate. They do somersaults on beams we’d fall off if we were sitting down. They show superhuman-seeming strength. And they’re all about five feet tall.

Simone Biles, the multiple world champion and favourite to win the Olympic gold tomorrow night, is 4’9″. Amy Tinkler, the British gymnast who excelled on the floor in qualifying, is about a quarter of an inch taller. So why do the tiny trounce the tall in gymnastics?

People who mature later stay in the sport longer

The first reason is to do with self-selection. The author Malcolm Gladwell refers to a phenomenon whereby ice hockey players born earlier in the year are much more likely to make it to the pros – because they’re more likely to be bigger, and thus at an advantage, the whole way through the junior ranks.

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Something like the inverse is the case with gymnasts. “Particularly in women’s gymnastics, those who are late matures are more likely to stay in the sport,” says Dr Michael Hiley, senior lecturer in sports biomechanics and motor control at Loughborough University.

It’s natural selection, not stunted growth

Rumours have it that intensive training at a young age keeps gymnasts short, and a 2004 Greek study showed that skeletal maturation was delayed especially among females. But the data doesn’t show that this is caused by training, according to more recent research by Professor Adam Baxter-Jones of the University of Saskatchewan.

For the most part, female gymnasts are short because it’s harder to be good at a lower level if you’re tall – for reasons we’ll go into below – so the tall ones weed themselves out early and we don’t see them on TV at the Olympics.

It’s easier to flip if there’s less of you

Hard work and perseverance will go a long way for an athlete, but everybody has to obey the same laws of physics. Dr Hiley says:

“In terms of mechanics, the larger you are the larger your moments of inertia will be (i.e. the harder you find it to rotate, and therefore the larger turning forces required to generate the same number of somersaults). The taller you are, the larger your moments of inertia (about the somersault axis).”

In layman’s terms, short people flip faster than tall people, and in a sport with a strong emphasis on flips, that puts the short people at an advantage. There are benefits to have short legs on apparatus like the beam – you’re less likely to run out of space – and the floor – there’s more room to run and jump if there’s less of you. Dr Hiley points out that female gymnasts must swing between the uneven bars and that “if you are suitably short you may not need to change your technique”.

The smaller you are, the less muscle you need

Only muscle can move your frame, and the more of you there is, the more muscle you’re going to need. The more muscle you have, the heavier you are. The heavier you are, the more difficult it’s going to be to swing yourself around and tumble through the air. Dr Hiley says:

Muscle strength is related to cross sectional area, and therefore total volume (and mass). In other words, the bigger you are the more muscle you need, and since gymnasts work by moving their bodyweight, it is an advantage to be lighter.

Men’s gymnastics is different, so their bodies are different

Okay, so female gymnasts are short. But Lewis Smith’s 5’10” – bang on the average for a British man. His teammate Kristian Thomas is 5’9″. Why the discrepancy?

Men and women have differing apparatus in gymnastics. The rings, for example, require very powerful upper-body muscles. So the advantage to being slight is lessened.

In addition, if being a late bloomer helps female gymnasts stay short and light, serious training in men’s gymnastics only begins once post-pubescent muscle growth begins – it’s less clear that a teenager is going to excel at everything he needs to excel at before he has developed the physical tools to do so.

American gymnastics coach Brian Powell explained in a letter to parents of his students: