ETA: reading fail. I don't do pull ups with these. I just use them for lifting. I don't think I could do a pull up even if I tried.
Well, it's technically not quite pull ups (though our teacher said we'd be doing them on Saturday, ;-; I cry). It's swinging your knees up to your elbows, but not even that. I do the modified version where I just dangle in mid-air and sway my torso forward and back. I'm a Crossfit weenie.
The only kind of pull up I do is pulling up a bottle of wine from off the table.