Try Deepl:
Reindeer length is an old unit of measurement of length used when moving reindeer. Reindeer length is the distance a reindeer can travel between (reindeer) urination breaks. Reindeer cannot urinate while running, and running too long can cause them to become paralysed. The maximum distance a reindeer can run is up to 7.5 kilometres.

Re: Try Deepl:
Nobody said they couldn't urinate while flying. That's why I stay inside on Christmas Eve.