Of course nothing illegal, only natural, a disadvantage if you don’t utilize it for you.
There are beetroot parties at almost any Triathlon event for the runners, apnea divers also get a huge natural and healthy boost.
I use it for long runs I don’t really feel the difference every time, but stats and data speak their own language.
Give it a try, timing is a bit tricky depending on your feast.
But caution: don’t overdo it due to oxalate as potential risk.
And mustn’t be the juice, the beetroot itself already does the job.