Modified Flutter versus Frog Kick (from a different point of view)

[Doctor Rig]

This has been discussed in part before but those discussions didn’t answer my related questions.

Frog Kick VS Modified Flutter

I have been diving for just over a yr now, and I find I am having a hell of a time, performing a Frog Kick. I have been guilty of leaving the silt trail behind me as I flutter kick along. I have gone diving with some local GUE divers, one of whom, his feet seem to be the only thing moving in...

scubaboard.com

I dive a pair of Deep 6 Eddy fins and my finning preference is the Modified Flutter, the majority of the time. I’ve found this stroke takes very little energy and my feet off stay off the bottom. (I do a lot of lap swimming where I swim with the Frog Kick, so I’m quite familiar with the stoke.)

Diving with the Modified Flutter versus the Frog Kick…. For me (using the Eddy fin) the Modified Flutter takes much less energy (more efficient) than the Frog kick. My legs have to move very little for the Modified Flutter so that is logical to me. I don’t get the glide of the Frog Kick, but the total energy (for me) is less.

Cave diving kicks every diver should know

The “standard” flutter kick taught in Open Water Diver courses is one cave divers simply don’t use. Instead, they have a repertoire of propulsion techniques that allows them to choose the right technique for each situation.

cavediving.com

However, my observation is….I seem to be in the minority with my assessment. Most divers prefer the Frog Kick for its ease and efficiency, if I understand correctly.

Does anyone else feel this way, or have worked through this learning curve, if that is the case?

I haven’t extensively tried other fins, so I’m wondering if my stroke preference could driven by my fin, technique or body mechanics issues.

 

[rongoodman]

The Eddys work great for frog kicks, back kick, and helicopter turns, so I doubt they’re the problem. My understanding is that the frog kick used when diving is quite different than that used for swimming, so I’m guessing it’s a technique issue.

 

[tbone1004]

I think you are confusing ease of kick with efficiency.
When we talk about "work" as an engineering unit it is the area under a curve that is generated by amount of effort expended and duration of that effort. In this case the Y-axis is thrust generated which correlates to the exertion of the kick and the X-axis is duration of the exertion. When frog kicking you have what essentially looks like a heart rate monitor with a fairly high spike when you kick and then you glide and are not expending any effort. Area under the curve is fairly small but the thrust generated is quite high. When you do a shuffle kick the exertion level is considerably lower *easy*, but because there is never any gliding involved in a shuffle kick it is a constant exertion so the total amount of exertion is considerably higher.
You are likely not doing a modified frog kick properly though, most divers engage their upper legs far too much *like you would when swimming breast stroke*, but the reality is that for most cruising around you can do it almost exclusively from the ankles and go shockingly quick if you are kicking properly. This is where some time with an instructor that really understands propulsion techniques goes a LONG way as most people think they're frog kicking properly but they usually are not.

Hint, there is a "flick" of the ankle that has to happen at the right time during the kick cycle and it gets you insane amounts of power for almost no effort but it has to occur at the right time during the stroke.

 

[Robert H. Diver]

 

[lowwall]

When we talk about "work" as an engineering unit it is the area under a curve that is generated by amount of effort expended and duration of that effort. In this case the Y-axis is thrust generated which correlates to the exertion of the kick and the X-axis is duration of the exertion.

True as far as it goes, but translating work to forward movement requires examination of additional factors. I'll list the most important.

First is drag. Due to increased frontal area from both the leg movement and fin path, the frog kick causes substantially more drag than the flutter kick. This isn't a huge issue at very low speeds, but the energy that must be expended to overcome drag is squared as the speed doubles. So if you need to move fast or overcome a fast current, you should switch to flutter.

Second is diver physiology. Amount and type of muscles (fast or slow twitch) and leg length all influence which kicks are more efficient (thrust per calories expended) for each diver.

Another factor is fin type. If everyone is using basic paddle fins this won't matter, but many fins are optimized for flutter kick and will be much less efficient if used for frog kicks. Original Force Fins and freediving fins are extreme examples of this.

 

[tursiops]

Another factor is fin type. If everyone is using basic paddle fins this won't matter, but many fins are optimized for flutter kick and will be much less efficient if used for frog kicks. Original Force Fins and freediving fins are extreme examples of this.

...and split fins are also examples of a fin optimized for a fast, small-amplitude flutter kick.

 

[tbone1004]

@lowwall
I'll have to disagree on drag. The frontal area should not be any different during the "glide" portion of a frog kick as that position has the legs extended and the fins in the most streamlined position possible. When you have to kick in strong currents you create some drag as you "load" your legs for a big power kick but the thrust generated from that kick is immense. I will say that if I have to move for long distances at high rates of speed I do tend to use a flutter kick but that is more to do with the muscles that are being engaged vs. the kick itself. Big slow twitch muscles in the upper legs and glutes can hold their own for a lot longer than your calves tend to.

Agreed on the fin design though but since it started with the Eddy fin I figured I'd remove that variable from the equation.

 

[lowwall]

@lowwall
I'll have to disagree on drag. The frontal area should not be any different during the "glide" portion of a frog kick as that position has the legs extended and the fins in the most streamlined position possible. When you have to kick in strong currents you create some drag as you "load" your legs for a big power kick but the thrust generated from that kick is immense.

Wishful thinking on drag. Yes, there is no drag penalty during the phase of a frog kick when you aren't kicking

But to move, you will have to kick at some point. And when you do, the frontal area increase is substantial. It's not just the legs coming out of the slipstream, it's the path that the fin follows. Look at the image in the first video a couple of posts up. Talk about flat plate area.

I want to be clear, I prefer frog kicking myself for most of my low to moderate speed diving. I'm just trying to make the point that it's not always the best answer. Like most things in life, the absolutist position is going to be suboptimal in certain situations.

 

[tbone1004]

Wishful thinking on drag. Yes, there is no drag penalty during the phase of a frog kick when you aren't kicking

But to move, you will have to kick at some point. And when you do, the frontal area increase is substantial. It's not just the legs coming out of the slipstream, it's the path that the fin follows. Look at the image in the first video a couple of posts up. Talk about flat plate area.

I want to be clear, I prefer frog kicking myself for most of my low to moderate speed diving. I'm just trying to make the point that it's not always the best answer. Like most things in life, the absolutist position is going to be suboptimal in certain situations.

yeah I mean it's definitely more obvious in sidemount but the tank is blocking a good bit of it but if you are doing it correctly it's a "surge" kick vs. a continuous movement so by the time you reload you shouldn't be moving very fast at all. I do agree though with the continuous rapid movement and I usually shift to a dolphin or flutter kick for those scenarios but the reality is if I'm doing stuff where I'm in that kind of flow or have to make that kind of speed I use a DPV because I'm not about moving that fast under my own power

 

[lowwall]

yeah I mean it's definitely more obvious in sidemount but the tank is blocking a good bit of it but if you are doing it correctly it's a "surge" kick vs. a continuous movement so by the time you reload you shouldn't be moving very fast at all. I do agree though with the continuous rapid movement and I usually shift to a dolphin or flutter kick for those scenarios

Dolphin is fun. I've been playing with Force Fin Pros and you can really fly with dolphin. Not something you'd want to do near the bottom though as it moves a lot of water. I wonder if I could come up with a modified dolphin for silty areas. Hmmm....

edit: found this - Shuffle and mod-dolphin kicks? and this: