When a social media influencer from New York City boasted of completing the Brooklyn Half Marathon recently, she did not receive the reaction she had hoped for. Instead, she was chastised for admitting she completed the race without signing up. The same happened with a runner in the Miami Half Marathon who said she had first made a fake bib number so she run the race – and then said she ran using someone else's entry.

Either way, she also sparked anger and frustration from other runners. These are two cases of so-called 'race banditing' – so why does it happen, and why is it so controversial? Race banditing is when runners take part in a race unregistered. They might do the entire race without officially entering, run some of the race without signing up, or use the bib of someone else who has entered when the race rules do not allow this to happen.

There are a number of reasons why runners become race bandits, whether it is a deliberate or unintentional act. There are many more running races than there used to be, even a decade ago, and some runners might find the cost of entering events too expensive. The cost of an event should not be an excuse to become a race bandit, but there are runners who see their banditing as a protest against high entry fees.

There are also some runners who might not be familiar enough with race rules to know they are race banditing. There are runners who take the bib of someone else, perhaps because the runner who entered can't run. Some swaps.