The second torque your body must produce in order for you to run your best will come from the leg that is off the ground, and in our example here, it is the left leg. See Figure 1
Now, looking at it on our female athlete I want you to once again, imagine it is the only force acting on her body. We see then that because it has been thrust out in front of her, which is a function of the hip flexor muscles shown in Figure 2 below,
it will exert not a pushing force this time, but rather, a pulling force on the left hip, forward, in this direction as depicted by the white horizontal arrow. See Figure 3.
And yes, just like there was a vertical component to the force produced by the glutes/hams, quads and calves there is a similar one to this force as well, shown by the red arrow. See Figure 4.
But to remain consistent, and to make things easier for you to follow, I am going to show the net result of these two components with just one simple horizontal white arrow as before. See Figure 5.
Now, again, if this was the only force acting on the body, do you think the effect of it would be to simply pull her straight forward, or, do you think there might also be some additional reaction? Well, the only way this force causes her to move straight ahead, and in no other direction, would be if it were acting along her midline, over here in Figure 6 shown below,
but that’s not the case. So, since it’s displaced away from it, again seen in Figure 7, below,
It would not only pull her forward, but would also cause her body to twist, or, rotate. Again, it would have to because it does not fall along her midline where her center of gravity lies. So, if she does rotate, the question then, is, which direction would it be? Clockwise, or, counterclockwise? To help you see this better, let’s look at this from above on our male athlete.
The same force on our female athlete pulling her left hip forward can also be shown pulling on our male athlete’s left hip shown in Figure 8 below.
So, as the force pulls forward on this vertical line that represents the level of his hips, we can see where it will try and rotate it in the… what direction? Care to take a guess? If you said the clockwise direction, then good job, you are correct and let’s show it by the direction of this yellow arrow. See Figure 9.
And now let’s go ahead and place the corresponding clockwise arrow showing this torque, or, rotational force on our female athlete and perhaps now you can envision this one taking place a little better. See Figure 10.
So, this is the second torque your body must generate in order to run its best.