KOW March 9, 2020

Continuing our analogy with stand up paddle boarding we find the basic forces of propulsion between the two are nearly identical. The key to creating powerful propulsive forces in both swimming and paddleboarding is keeping your hands or oars in one place as you push against the water to move your body or board forward pass those anchor points.

The process is very clear in stand up paddle boarding but not as visible in swimming. 
We're going to take a look at three examples of how the hand stays still in the water and the body moves past that point.

Let's start by looking at a side view of freestyle.

We want to watch how far her hips move forward from frame number 4, where her right hand begins putting pressure on the water, to where that same hand releases pressure in frame number 10. Counting the colored floats that are 4 inches wide, we see that her hips have advanced about 11 floats, for a total gain of nearly four feet. 

This next view shows a swimmer with lights on her right hand, right foot and lower back and was filmed underwater, from the side, doing butterfly. This view provides a great demonstration of how the hands stay virtually in one place while the body lose past.  We can see three different light traces. 
In the middle of the frame the clear, nearly horizontal wave are the hips undulating from left to right. 
The larger amplitude, less visible trail in the background is from the foot creating bubbles and turbulence while kicking. 

The vertical lights that go almost straight down and back up is the light on her right hand. The outstanding takeaway here is to notice that the hand enters, goes to it's deepest point and then returns back up to finish it exit at nearly the exact point at which it entered. 

This swimmer was also filmed with lights on his wrist, elbow, shoulder and hip. It was observed that hip velocity changes within the duration of each individual arm pull.

In this one still from the video we see on the top graph that the hip velocity is at its greatest level, whereas at the exact same moment on the bottom graph the wrist velocity is at its lowest or stationary point. Combining these results clearly reinforces the fact that when your hand stays still in the water your body moves forward.