Today’s episode with Carl Paoli of gymnasticswod.com is about creating a more stable and efficient shoulder (primary engine) position on the pull up rack. The short version is this, opting to not use your thumbs when you might otherwise is potential torque loss at the shoulder and a subsequent force dump. When athletes opt to go without a thumb around the bar, they do so because the bottom (or apex swing/compression momement) is more comfortable than with the thumb over. What is happening in these situations is that using your thumb actually creates a greater potential for torque development at the shoulder, and not using the thumb-over position allows for more internal rotation of the shoulder in the overhead (end range flexion) position. The additional internal rotation slack the athlete “buys” without the thumb creates more room in end range flexion (this is why people love to ben their elbows during kipping pull-ups) but, destabilizes the shoulder as well as it moves the joint into a position of greater capsular slack. Remember, loading at the bottom of a pull up is an all systems go movement. The body is utilizing muscle stretch, fascial loading, and joint capsular loading. You need all the systems to work together to keep that shoulder stable and for optimal force production (read; more pull ups). Creating a less ideal shoulder position overhead without the thumb over the bar potential limits all of these movement co-factors. This is why the movement quality is so important. Good mechanical/physiological movement automatically accounts for all of these pieces. You don’t have to worry, you just have to be in the right position. Clearly you can perform pull ups safely with the thumb over the bar (pull up on a fat bar), but make sure you aren’t compromising your position and potential when you do it.