I'm growing increasingly convinced that Larry King's body has grooves that hold his suspenders in place. I mean, look at him.
One obvious candidate is callouses, but this seems to me unlikely. The callouses would likely accumulate where the greatest amount of friction exists — that is, under the suspenders, such that you'd have the opposite of a groove. You'd instead have a raised, solid "track" over which the suspenders would be perched, rather than nested. Let's discuss other possibilities:
Muscle development could well be in play here. Consider what a bulge in the trapezius could accomplish, if it arose just between the shoulder and the spot where Mr. King customarily lodges his suspenders. The muscle-bulge would act like a notch — you slip the suspender over it and it can't possibly slide off laterally over the shoulder. Now consider that a second, smaller bulge might crop up between neck and suspender, to preclude lateral movement of the suspender in a neckward direction. It seems to me that Mr. King's forward-leaning "lunge" posture could well accomplish these two results, in a bilateral presentation — especially as from all appearances he is straining against the suspenders themselves. All it would take to develop these bulges would be a gradual tightening — if not as well a reduction in the elasticity — of the suspenders over time.
Third and finally, I suggest bone spurs. This hypothesis speaks for itself, I think, and I don't really see much to be gained from elaborating it.