Frog kick efficiency

[Doc Harry]

Go practice in a swimming pool. A few dozen laps has a way of helping you become more efficient out of sheer exhaustion.

The frog is not that great of a kick. It offers no advantages. I never use it. If you want power, speed, and gas efficiency, then the flutter is a much better kick.

However the modified frog is a really useful kick, and one that I use about 95% of the time. Almost all cave divers use the modified frog because it gives you precise control when maneuvering. The modified frog is also a really relaxed kick for just cruising around the reef.

Drag in water is proportional to the square of the speed, so it's pointless to go fast anyway unless you want to use up all of your gas quickly.

 

[The Chairman]

Drag in water is proportional to the square of the speed, so it's pointless to go fast anyway unless you want to use up all of your gas quickly.

Indeed. Trying to go fast never ends well. However, going more efficiently is a noble goal and one worth pursuing. Again, the bottom of the toes are the best feedback sensor you have on that. Especially the big toe. At least for me.

 

[Angelo Farina]

I am a finned swimming instructor.
In my experience just one student over five can get a good frog kick. There are anatomical limitations affecting a significant number of students, which cannot be circumvented teaching the proper technique.
Another group of students simply lack proper body control, as they learned asymetrical gestures which are hard to overcome (this is a typical problem of athlets practicing running, cycling or swimming in free style).
In all these cases (which, as said, are the majority) I was able to teach just some modified frog kicking, which serves just the purpose of avoiding to push water downards, which is simething to avoid inside caves or wrecks.
The resulting propulsion is slow and inefficient, but it avoids silting.
Then, when normal flutter kicking is possible without any silting problem, better to use it if this fits better your anatomy or your alternate movement reflexes.
Of course also the choice of fins does matter: as every anatomy and kicking style is different, one should choose fins which are optimal for him/her. There is not an universal best fin, going well for everyone...

 

[Angelo Farina]

Drag in water is proportional to the square of the speed, so it's pointless to go fast anyway unless you want to use up all of your gas quickly.

Actually it is even worst, the power demand for overcoming drag goes up with the cube of the speed: the drag force is proportional to the square of speed, but the power is force x speed, so going fast will never be energetically efficient, whetever the kicking style.

 

[Doc Harry]

Actually it is even worst

I did somewhat scientific underwater tests with Scubapro jet fins and double tanks where I tracked speed, distance, kick style, and gas usage.

The most gas-efficient kick was a very slow, lazy, flutter kick.
A slow, lazy modified frog came in a close second as a very efficient kick.
A slow frog kick came in a distant 3rd.
Faster speeds were all very gas-inefficient.

"Gas efficient" is defined as greatest distance traveled for least amount of gas used.

 

[Angelo Farina]

I did somewhat scientific underwater tests with Scubapro jet fins and double tanks where I tracked speed, distance, kick style, and gas usage.

The most gas-efficient kick was a very slow, lazy, flutter kick.
A slow, lazy modified frog came in a close second as a very efficient kick.
A slow frog kick came in a distant 3rd.
Faster speeds were all very gas-inefficient.

"Gas efficient" is defined as greatest distance traveled for least amount of gas used.

Nice results.
At the time I was teaching (1989), I made similar experiments but focused on fins, assuming (as you have found) that the most efficient style is a slow and ample flutter kick.
Please note that in my tests the goal was slightly different, as I was training deep free divers, so the test was done measuring the distance traveled with a single breath in a pool.
The first result was that swimming midwater is 20% more efficient than swimming on the surface and 10% more efficient than swimming close to the bottom.
The second result is that nothing can beat a monofin custom made in carbonfiber for an athlet who can use it properly. But this result is of little value for scuba divers, who usually consider a monofin unpractical.
The third result is that long flexible freediving fins are better than short rigid blades. The Beuchat Jetfins (closed heel with additional strap, longer and more flexible, were way better than the Scubapro Jetfin, shorter, more rigid, and with bad coupling between foot and blade).
Last result is that carbon fiber blades, which provide a significant speed advantage in finned swimming competitions, are not significantly better than plastic blades typical of low cost freediving fins such as the Rondine Gara when swimming slowly for getting the maximum distance.
Please note that this test was done 30+ years ago and consequently did not include modern fins designed specifically for high efficiency, such as the Scubapro Seawing Nova, the Mares Plana Avanti 4 or the Hollis F1.

 

[Doc Harry]

I did my kick experiments over a long course because of the wide +/- error in reading the pressure gauge. By using a long course, I got larger changes in gas pressure to minimize the reading error.

I did not correct for fatigue. I started with the slow kicks, and worked my way up to maximal exertion kicks on the same dive. There is a slight chance the faster kicks were less gas efficient because I was more tired. A more rigorous experiment would have a long rest in-between tests.

 

[BlueTrin]

I did somewhat scientific underwater tests with Scubapro jet fins and double tanks where I tracked speed, distance, kick style, and gas usage.

The most gas-efficient kick was a very slow, lazy, flutter kick.
A slow, lazy modified frog came in a close second as a very efficient kick.
A slow frog kick came in a distant 3rd.
Faster speeds were all very gas-inefficient.

"Gas efficient" is defined as greatest distance traveled for least amount of gas used.

It’s interesting that your modified frog kick was more gas efficient than your frog kick.

 

[NW Dive Dawg]

I know that my frog kick needs work and this thread has been helpful.... We have a trip to Bon coming up in a few weeks and will make sure to hand over my video system to my wife so that I can see for myself in clear vis what I may be doing right or wrong and even post the vid back here on SB to get some feedback... Good thread. Thanks!

 

[dmaziuk]

It’s interesting that your modified frog kick was more gas efficient than your frog kick.

I'm not sure what "unmodified" frog kick is in this instance, but in the breaststroke, the foot acts as a propeller blade. So a traditional fin designed to push water with the top of its blade, will not help there.

As an aside, if the goal is to raise your feet up away from the silt, I don't see what's stopping you from doing that and using your fins the way they were designed to be used: doing flutter or dolphin kick with just your ankles.