This isn't that kind of double negative. This kind of double negative crops up even in the most formal English as it introduces a subtle difference in meaning.
For instance, take the sentence, 'it wasn't uncommon'. That means almost the same thing as 'it was common', but isn't as strong a statement.
The same thing is happening here.
Does that mean that "All kinds of athletes sleep"? If so it's such a roundabout way to say it.