The author compares this to cross fit, an approach to fitness where routine is the enemy! So, on top of all the other advantages of speaking more than one language - it can keep you fitter, for longer! I like that thought!
When you think about it, only a few countries have only one language, so being at least bilingual is the norm for most.
Check out some more advantages here.
New York Times article on bilingualism from 2012