Why do gymnasts use chalk before competing?
Chalk does two important things for gymnasts when they're competing on bars, rings etc, according to the International Federation of Gymnastics. First, it allows a gymnast to swing and turn around the bars without being slowed down by sweaty hands. Second, it helps them maintain good grip and avoid slipping.

How does it work?
Chalk absorbs moisture, helping to avoid sweaty palms that could make them slip on the smooth wooden bars. It also helps decrease friction, allowing a smooth spin and helping to reduce the risk of injury to hands. And it's not just the hands: some female gymnasts apply chalk to their feet before the balance beam for example.
What's it made of?
Gymnastics chalk is typically an inorganic salt, Magnesium carbonate (MgCO3). It can come in a variety of forms, from powder to solid blocks and even liquid.
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However, at the top level, gymnasts will have a form that they feel most comfortable with. The British Gymnastics team for example have taken their own supply to Rio 2016, leaving nothing to chance.
Do gymnasts use anything else other than chalk?
Well yes, actually. In 2012, the Wall Street Journal spoke to US gymnast Jonathan Horton, who squeezes a small amount of honey to his hands before chalking up. Another athletes used a weird concoction of beer and sugar, while US gymnast Trent Wells used melted gummy bears.

Is that legal?
Apparently so. There are no rules governing using extra sticky substances – as long as they don't make a mess.

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A tin of golden syrup from a British training session earlier this March
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