The human thorax rotates. As bipeds, this is especially helpful when we run. The rotation helps moves our hips.
One major key to all human motion, including running, is the iliofemoral ligament. That ligament extends from the ilium to the femur in front of the joints. If you didn’t know, the iliofemoral has a tensile strength exceeding 772 pounds. It’s the strongest ligament in the human body.
In many quadrupeds (picture a horse, for instance) there’s no such rotation. The whole running motion looks different.
If the upper body of humans didn’t rotate, our running motion would not look so smooth.
We hope you’re familiar with the great Minister of Silly Walks sketch from Monty Python.
Well, check this video for a companion silly run as demonstrated by Anatomy in Clay® Learning System founder Jon Zahourek—showing us how our running motion might appear if we lacked thoracic rotation and showing us, also, how we developed this capability as we evolved. (No spoilers here!)
.
.
.
.
.