I've been doing squats for over 20 years and never experienced any of the numbness you guys are talking about. I'm not trying to be an "Alarmist" but as you know, the vertebrae is in the back and many outlying nerves can be affected through the disc and nerve endings in the back. Since you say this happens when doing squats you should be very attentive to this problem. I have for years seen a Chiro who has alleviated what had been re-occuring spasms in the region of the neck to shoulder area. I have a bad disc in my lower neck and the nerves here were causing me to have these spasms. Likewise, maybe your "numbing" experiences are related to a bad disc in your back - pressing against some nerves that create this numbing feeling. If - it's a frequent thing I would seriously have yourself checked out. I know that there's alot of negatism to Chiroprators but I can tell you that I no longer suffer any spasms and can lift freely without having to make any changes in my routine. The key is getting checked out and corrected - early enough - if there is a problem. As for the position of hands and arms, I've tried several hand positions but never had any "numbing". Just saying - be careful - your body may be trying to tell you something isn't quite right.