In Starting Strength I read that you should not wrap your thumbs around the bar, do you agree?
yes. you can get your elbows and arms lined up more comfortably under the bar. Though for competitive lifters, some feds like IPF require you to use a regular grip.
I use a regular grip and it’s never been a problem. I have trained with others who don’t. Do what’s comfortable, unless like robo1 said it’s for competition. Then do what rules require to help develope your muscle memory.
Honestly it’s probably more of a personal preference/matter of individual flexibility than a hard and fast rule. I wrap my thumbs around the bar and have never had any discomfort doing so (either on the high rack or low rack position).
Some people I’ve trained/worked with however don’t have the shoulder flexibility that I do and prefer to use a thumbless grip, especially during the low rack position.
And we are talking about back squats right?
If we are talking about front squats, then I completely agree that you should use a thumbless grip. On overhead squats you absolutely need to wrap your thumbs around the bar. So it also depends on what type of squats you are talking about.
My old training partner does the thumbless grip and I can’t understand why anyone would want to do that.
There are a few reasons to grip the bar with a thumbless grip.
First, it emphasizes that the bar is not held in place by the hands but by the shoulders, and second, many people believe it is very difficult to get your elbows in the correct position to accomodate the extreme thoracic extension that will help lock the upper body into one piece, with your thumb around the bar.
I personally could not do these until I changed my stance to a little bit wider, and now it feels great I must say.
I agree with Shadowzz4.
To complement his statement, I see a lot of people that support the bar with their arms when they move to a low bar position. This will kill your elbows and shoulders once the weight starts getting up there. Using a thumbless grip will force you to support the bar with your back.