I've had mine feel, not numb, but not quite right, maybe _almost_ numb, for several days after my 400k. To avoid it in the future, I had gel pads put under my bar tape, and really, really tried to change hand position a lot- on the hoods, MTB grip, (like pushing a grocery cart) road bike grip, (like car steering wheel) keeping my thumbs on top of the bars and just holding with my fingers with thumbs resting on top, using the aerobars a lot...It helped and I didn't get anywhere near as much tingling on my 600k.