Here you go!

The back pain due to injury is true, but the reason he sat down that way isn’t because of that. Frakes confirmed in an interview that he did it because he thought that would showcase Riker’s cockiness. Nobody stopped him from doing it, so it stuck.

The back injury, however, is the reason behind the “Riker Lean”.

Allowing the rotational periods of the planet to continue and liquid dihydrogen monooxide to immobilize me. Allowing the rotational periods of the planet to continue and liquid dihydrogen monoxide traversing subterranean layers. Into the azure colored atmosphere once more, when the currency has been expended. A single moment in the years that consist of a lifespan and liquid dihydrogen monooxide traversing subterranean layers.