The towel grip pull-up video blog is easily the fan-favorite post here at the Bodyweight Files. I started doing that pull-up back in March, 2007. I was anxious to throw up the video blog last February with the arrival of the Perfect Pullup because I knew there was merit of supinating in the pull-up but I didn't see the need to spend $100 to get that training effect. I'm just starting to see it demonstrated in other places but, interestingly, without that supination.
For me, this pull-up is a child of necessity. I travel and good pull-up places can be hard to come by. I thought of it at home but I realized that as long as I had something sturdy above my head to wrap something like a towel around, I could do pull-ups, even if I couldn't get my hands around it. Since I'm crunched on time, this pull-up's difficulty, forearm and grip working qualities covers a lot of ground in a little time.
One thing that I've noticed in my improvisation with this pull-up is that what you're gripping makes a noticeable difference in the ease or difficulty of the pull-up. Here are a few points on the subject:
1. Thickness of the object. The easiest object for this pull-up is the object that is the same thickness of your grip when your thumb overlaps your pointer finger's nail. Anything thicker or thinner than this makes the pull-up more difficult.
2. Does the object have natural spring to it? I've done this pull-up with lifting straps and lay-flat fire hoses. both of these objects want to spring back to their naturally-flat shape so I have to squeeze more intensely to do the pull-up. Along those lines, rope that isn't tightly twisted or braided is more difficult because you have to compress it more to get a good grip on it.
3. Smoothness. Twisted natural rope is far easier material for doing this pull-up than a braided, synthetic. I tried this pull-up with a bunch of braided nylon rope and I was stunned by how difficult that it was (it was also loosely braided, which didn't help either).