I have a similar problem w/ my entire left arm going numb while running. I just take my arm, put it behind my back for about 30 secs, and bring it back in front and I can feel blood going back into it and it goes away. Yeah, it's weird and often wondered what the hell is going on w/ my left arm.....but then I forget about it after my run. Not that this helps you, but at least you know you're not the only one.....be interested to see other replies to this........