Troy Aikman: INSANE PHYSIQUE ... Check Out My 8-Pack!!!

How 'bout that Cowboy???

Here's 49-year-old Troy Aikman ... showing off his ripped physique during a shirtless jog out in Hawaii this week ... looking more like a ripped linebacker than a retired QB.

FYI, Aikman is a workout-aholic -- he's raved about his obsession with FlyWheel spin classes.

Clearly, it does a body good.