I’m going to offer a contrasting opinion to
@Angelo Farina ’s assertion in this thread about the greater efficiency of flutter kicking over frog-kicking.
For me, I find frog kicking allows full and relaxed diaphragmatic expansion thus enabling ideal breathing while maintaining good propulsion. The frog kick isn’t meant for speed, it’s meant for endurance for a sustained period of propulsion and reduced oxygen consumption. When you frog kick, your stable platform is produced by your posterior chain. The contraction of these muscles does not interfere with ideal breathing.
Conversely, flutter kicking puts a much great demand on the abdominal muscles thus interfering with ideal (diaphragmatically-induced) breathing. One MUST engage the external obliques, internal obliques and rectus abdominis muscles to create a stable platform so the legs can hinge up and down at the hips while flutter kicking. When engaging your anterior muscles, you are inhibiting your most efficient breathing. I did not say stopping, just inhibiting.
Roger Williams down in Mexico does 4-5 hour dives in the cenotes. I’m bold enough to bet he doesn’t flutter kick much at all during those long dives.
Again, just get on with some form of exercise and tune in to your body.
That's very interesting. One of the reasons dolphin kick is superior to flutter kick (which is NOT the most efficient kicking style) is that finned swimming athlets synchronize breathing with the cycle of kicking.
As in dolphin kicking all the muscles of the body are involved, such synchronization has two benefits:
1) It allows deeper respiratory cycles with lower effort, hence improving oxygenation and removing CO2.
2) the diaphragm and the other muscles in the chest become active for propulsion, and not just for breathing.
When I have to do a long path, against current, or carrying equipment, I always switch to dolphin kicking, not to flutter kicking.
However it must be said that, while flutter kicking more or less works also if the fins and the kicking style are badly optimized, instead dolphin kicking works only for trained athlets, with perfect fins (or monofin) and perfect kicking style.
On the other side, what you said for frog kicking is also subjected to similar constraints: very few people make the correct leg movement, making a super-wide kick, a strong squeeze of the straight legs after the kick, and rotating the ankles so that the fins are almost vertical, followed by a long pause with legs united, with knees and ankles perfectly straight, arms packed along the body, for travelling by inertia without effort for a couple of meters.
I remember that, at the finned swimming courses, we did manage to teach such an efficient frog kick only to 10-20% of our students.
I must admit that my own frog kick is not so good. My wife instead has an excellent frog kick.
Most divers I see nowadays, instead, cannot kick this way. They keep the knees permanently flexed at 90 degrees, and paddle with their fins moving only the lower part of the legs.
The hips, that is where the correct movement should originate, are kept immobile.
The correct frog kicking is disappearing, most divers watch those videos about cave divers keeping a position totally against hydrodynamicity, and learn just that inefficient "modified" frog kicking style, which is actually much easy to learn for everyone.