In this video, we are going to talk about the fifth and final torque involved in running. This torque is produced by muscles around the spinal column that rotate the torso in one direction or the other. And because it doesn’t involve any of the extremities, it is not as obvious as the previous four torques.
Now the easiest way for us identify which direction the torso would rotate, if there were no other forces acting on it, would be to look at the torques involving both shoulders. See Figure 1.
Figure 1. Left and right shoulders producing a counterclockwise torque around spinal column.
You will recall in the previous video that both shoulders produced a CCW torque around the spinal column. In order for this to take place the torso would also have to rotate in the same direction to assist this movement, much like it does when you are performing oblique sit-ups. See Figure 2.
Figure 2. Torso rotates in same direction as shoulders during oblique sit-up.
The muscles involved in rotating the torso in this CCW direction are known as the lateral spine rotators and their names are the external abdominal oblique, multifidus spinae and rotatores spinae muscles. See Figure 3.
Figure 3. Lateral Rotators of the Spine Muscles.
The one thing that is worth mentioning here is that these lateral spine rotator muscles exist on both sides of the body. Therefore the ones located on your right side contract to turn the front of your body to the left as seen in Figure 4.
Figure 4. Right lateral spine rotators contract to turn front side of body to the left.
The lateral rotators of the spine on the left side contract to turn the front of your body to the right as seen in Figure 5.
Figure 5. Left lateral spine rotators contract to turn front side of body to the right.
So now we know that it is the lateral spine rotators on the right side of this athlete’s body that are contracting to help produce this CCW torque. See Figure 6.
Figure 6. Lateral rotators of the spine contracting in this image.
That completes the identification of all 5 torques that are produced around the spinal column when you run and here they are for you to see all at once as well as the final torque equation that must be balanced so that you are able to run in a straight path. See Figure 7.
Figure 7. Final torque equation for the running process.
Now I am going to conclude this series of videos with one more final video where I will point out some unique details regarding these torques, such as what it means to your running speed, running stride and turnover rate if your hip flexors are weak, what would happen to your top end speed if your shoulders are weak as well as some other interesting relationships regarding all of these forces in the body.