So, the freestyle kick really has two main aspects, you have the up kick and the down kick.
The up kick is what we’re really seeing in this picture you can see here on this guy’s toes, and basically his entire bottom of his foot is kicked out of the water and the down kick is obviously when the foot is going towards the bottom.
So going more deeper into both of those. The Up-Kick kick is the part of the kick where the heel comes back up towards the surface of the water and knee flexion is seen. As far as muscle groups required you need your glutes, hamstrings and your calves to fire. There’s also some lower back muscles there obviously to get that whole posterior chain to fire but it’s really a posterior chain driven kick. So it’s everything on the back line of the body as making that Up-Kick happen.
In general, there should be no more than 120 degrees of Knee Bend, which is the same amount of Knee Bend that you have when you walk. I always use that analogy with my swimmers, because saying 120 degrees and get them trying to think about what that looks like comparatively to a straight line is never very accurate but if you have someone walk around naturally you’ll see that they’re bending their knees, but they’re not bending their knees to an excessive amount, like a 90 degree knee bend or what it would be like to sit in a chair.
During this part of the kick, you do want to keep your toes plantar flexed, you don’t need them to be like ultra plantar flex. But the best part of that is if you keep them plantar flex you’ll be ready for the down kick portion, which is directly what follows each up kick.