Leg fins imprint the correct kicks on your muscle memory, the more you swim with them. You position the fins on your legs to face your kick direction and match your kick. This works for freestyle, backstroke and fly.
Regular foot fins work with a very different kick to your natural kick. You can feel the difference. For example, they cause you to slope your thighs down, bend your knees too much and strain your calf muscles too much. Foot flippers imprint the wrong muscle memory for your legs and arms, as well as for your stomach and torso muscles too. This incorrect muscle memory imprint happens because the different foot flipper kick style also changes your arm pulls and your entire body balance. So alternating between foot flippers and barefoot swimming confuses your muscle memory.
So regular foot fins imprint their own, different kick on your muscle memory. You feel this when you take them off and swim without them. It often takes a number of laps to reduce the muscle memory of their different kick, to get back to your natural good kick. Many competitive swimmers know this. So you can see for yourself why foot flippers do not improve your natural swimming kick. They may even be making it worse.
Leg fins overcome these problems because they attach to your legs. You position them to match your natural kick direction and kick action. This lets them match your natural kicks. So they imprint natural, correct kicks on your muscle memory. So they guide and strengthen your natural kick technique, speed and endurance. You notice ongoing improvements each time you swim. A useful trick is to swim a bit more just after you take them off. This helps to imprint correct kicks on your muscle memory that stay with you in the long term .
Now you can have fins that give you extra speed and imprint correct kicks on your muscle memory!
See related FAQ about correct timing of your hip and knee joints.
See all FAQ about why hip power fins are the best for swimming.