So the difference between the Up Kick in the Down Kick in freestyle and Backstroke is its opposite, so the Down Kick is the part of the kick where the heel of the foot is forcefully kicking towards the bottom of the pool, and this is the setup phase, whereas in the Freestyle kick Down Kick is the propulsive phase. So during this setup phase, you’re acquiring help from your glutes, hamstrings, and calves, you should see no more than 120 degrees of knee bend or 60 degrees from the water surface, just depends on how you look at that, but once again the Down Kick portion of Backstroke, is a setup portion, whereas the Up Kick portion is the propulsive portion. This is the phase of the kick where the toes break through the surface, it requires the quads, posterior, plantaris, and hip muscles. You’re going to see 180 degrees of knee extension, which is a straight leg. At the end of this phase, you want to make sure that the leg finishes in front of your body, similar to kicking a soccer ball. As I talked about with the Freestyle kick, you want the foot in front of the body which means that the toes would be kicking through. If it’s not finishing in front of the body, everything would be a straight line under the surface, which is not what we’re looking for. If you kick through the surface of the water, you’re using the firing capacity of your quad, which is super important, in Freestyle and Backstroke kicking.