Frog Kick Blues

[danvolker]

If the frog kick is the most efficient kick, how come most free-divers use the flutter kick?

Plenty of freedivers will frog kick do a huge glide, then frog kick again, on the bottom phase of a drop as they are lazing along a 60 to 80 foot reef. It is an excellent kick for conserving blood oxygen, and still maintaining a good forward motion.

However, going back to the surface is going to call for a higher speed sometimes, as the seconds you have left before your blood is depleted of O2 are rapidly diminishing....flutter kick, or dolphin kick tend to be more effective when high speed with good efficiency is desired over PURE efficiency. Freedive fins without rails on the side of the blades, will frog kick extremely well...the models with rails are created for divers that need help keeping the blade tracking straight--I never needed or liked the rails--and they cause too much articulation drag for your ankles when you rotate the fins for the frog kick--making this annoying.
DiveR Freedive fins are amazing frog kick machines!!!

 

[Foxfish]

Plenty of freedivers will frog kick do a huge glide, then frog kick again, on the bottom phase of a drop as they are lazing along a 60 to 80 foot reef. It is an excellent kick for conserving blood oxygen, and still maintaining a good forward motion.

However, going back to the surface is going to call for a higher speed sometimes, as the seconds you have left before your blood is depleted of O2 are rapidly diminishing....flutter kick, or dolphin kick tend to be more effective when high speed with good efficiency is desired over PURE efficiency. Freedive fins without rails on the side of the blades, will frog kick extremely well...the models with rails are created for divers that need help keeping the blade tracking straight--I never needed or liked the rails--and they cause too much articulation drag for your ankles when you rotate the fins for the frog kick--making this annoying.
DiveR Freedive fins are amazing frog kick machines!!!

I've never seen a freediver doing frog kick with the long freediving fins. I'd agree the long blades aren't particularly suited. The frog kick is often used by freedivers when swimming without fins but the arms are used in that case which makes it a very different stroke than frog kicking with fins.

I'd argue that the most efficient way to fin is to maintain relatively constant, smooth propulsion and be streamlined with your fins trailing directly behind and moving within the envelope of your body. When frog kicking you are decelerating and accelerating and the kicking motion is relatively wide and outside the envelope of your body. A similar debate rages in swimming circles regarding the merit of a glide phase at the end of the freestyle stroke. I'd agree the flutter kick is also faster than frog kick but if you traveled at the same speed doing both strokes you'd use less energy than using the frog kick.

That said I've had to fin quite hard using the flutter kick to keep up with scuba divers with a strong frog kick.

Kicking and gliding can be a convenient and comfortable way to fin when ambling along on a scuba dive. I disagree you cannot do this with the flutter kick. I do it often.

 

[Dive-aholic]

Freedivers also use a very different fin from most scuba divers. Doing a frog kick with fins that are three feet long would be pretty frustrating, I think.



I found out this is almost completely solvable! I had noticed for years that I was braking with the reset on my frog kick. The first insight was that it was due in part to stiff ankles -- if I totally relaxed my ankles during the reload phase, the fins would orient themselves to provide minimum resistance to the water, and the braking was greatly decreased. But the big insight was having Natalie Gibb take my frog kick apart during my sidemount class. She wanted me to kick with my knees all but tied together. It changes the mechanics of the kick into an almost circular motion, and reduces the braking to almost nothing. I'll warn you, though -- if you have a well-established frog kick and you start working on this, you're going to feel like an absolute buffoon for a while. I couldn't keep my balance in the water at the beginning, and I was cursing Natalie with each breath!

I've threatened a few of my students with tying their knees together...

 

[danvolker]

I've never seen a freediver doing frog kick with the long freediving fins. I'd agree the long blades aren't particularly suited. The frog kick is often used by freedivers when swimming without fins but the arms are used in that case which makes it a very different stroke than frog kicking with fins.

I'd argue that the most efficient way to fin is to maintain relatively constant, smooth propulsion and be streamlined with your fins trailing directly behind and moving within the envelope of your body. When frog kicking you are decelerating and accelerating and the kicking motion is relatively wide and outside the envelope of your body. A similar debate rages in swimming circles regarding the merit of a glide phase at the end of the freestyle stroke. I'd agree the flutter kick is also faster than frog kick but if you traveled at the same speed doing both strokes you'd use less energy than using the frog kick.

That said I've had to fin quite hard using the flutter kick to keep up with scuba divers with a strong frog kick.

Kicking and gliding can be a convenient and comfortable way to fin when ambling along on a scuba dive. I disagree you cannot do this with the flutter kick. I do it often.

I think you need to see what I am talking about....and it is NOT swimming with your hands.....As to the efficient swimming, you can see dolphin or Cuda kick once and then glide for a huge distance.....a free diver can actually glide a long way also--at least when compared to the scuba divers that are not geared to be slick.

 

[Foxfish]

I think you need to see what I am talking about....and it is NOT swimming with your hands.....As to the efficient swimming, you can see dolphin or Cuda kick once and then glide for a huge distance.....a free diver can actually glide a long way also--at least when compared to the scuba divers that are not geared to be slick.

So how do you pedal a push bike? One cycle of the pedal and then roll or pedal at a constant speed. If you glide your speed reduces and the next kick you use energy accelerating back up to speed. Newton's first law of motion. When you maintain a constant speed you only have to overcome drag or water resistance. Underwater you can minimise your resistance by going slow and being streamlined. If you cover a given distance in a given time, the total resistance will be less if you maintain a constant speed. If you know high school physics this should be self evident. If not, trust me.

Definitions:

The thrust from a fin is a force.
Efficiency is the ratio of the theoretical energy required to travel a given distance in a given time and the actual energy used to travel the distance.
Energy is the work done in traveling from point A to B. It is the area under the force distance graph or the average force multiplied by the distance traveled.
When you move forward underwater the main resistances are drag or water resistance and accelerating the inertia or mass.

 

[danvolker]

So how do you pedal a push bike? One cycle of the pedal and then roll or pedal at a constant speed. If you glide your speed reduces and the next kick you use energy accelerating back up to speed. Newton's first law of motion. When you maintain a constant speed you only have to overcome drag or water resistance. Underwater you can minimise your resistance by going slow and being streamlined. If you cover a given distance in a given time, the total resistance will be less if you maintain a constant speed. If you know high school physics this should be self evident. If not, trust me.

Definitions:

The thrust from a fin is a force.
Efficiency is the ratio of the theoretical energy required to travel a given distance in a given time and the actual energy used to travel the distance.
Energy is the work done in traveling from point A to B. It is the area under the force distance graph or the average force multiplied by the distance traveled.
When you move forward underwater the main resistances are drag or water resistance and accelerating the inertia or mass.

Good luck trying to intellectualize this without actually experiencing all the factors you are not including in your "equation".
For one thing, remember you are walking a tightrope where you are trying to keep your hear rate at it's lowest possible level--say at 55 bpm....AND cover as much ground as you can-----you are actually capable of one big PUSH with the freedive fins in a frog kick, that gets you up to a pretty good speed, without stimulating higher heart rate....particularly IF you then coast for the next 5 seconds...what happens is then speed is sustained at a useful average over your bottom time, and with the ultra low heart rate, your breathing rate is as low as it is possible to be at. If this is not "FAST ENOUGH", then you will need to do the flutter kick, or the dolphin kick, but your heart rate will climb, and so will your breathing rate. So while you can swim considerably faster with your average pace during bottom time--you WILL HAVE LESS BOTTOM-TIME....so you need to determine what is more important....speed or bottom time.....and of course, factor in not silting please if you are near the bottom for some important reason


Different fins perform good or badly with this pig push and glide going on...the best are the DiveR and similar type of Freedive fin, huge composite blades that are effortlessly swung into position, and loaded by the bent leg--and then PUSHED OFF WITH....and then glided with.....Try this with the worst fins, like the splits...and from the PUSH, very little speed results, so no real glide occurs, so no rest occurs, and another kick cycle must occur immediately.... high cadence results, and heart rate and breathing goes up.....Jet fins, long embraced as THE fin for grog kicking, give a nice PUSH to allow a good glide( though not as big as is possible with freedive fins) ....on the other hand, with an overhead ceiling, the freedive fin can hit or silt the ceiling, so for cave and many wreck penetrations, it is the wrong tool for this frog kicking job.
Extra Force Fins are what I have found to be the best compromise for penetration AND reef.....a blade big enough to allow a big push and glide, but small enough to be great in a low overhead penetration, and with a control surface that allows very precise positioning in an exploration level penetration when hovering is key....and is awesome for reverse kick and helicopter---The Extra Force are dramatically better than the jets for ease in a high speed reverse kick ( or in learning this kick), and they are dramatically better at emergency pace flutter kick--due to technology never imagined many decades ago when jets got their technology( and where they have remained with no more development of note).

 

[nimoh]

So how do you pedal a push bike? One cycle of the pedal and then roll or pedal at a constant speed. If you glide your speed reduces and the next kick you use energy accelerating back up to speed. Newton's first law of motion. When you maintain a constant speed you only have to overcome drag or water resistance. Underwater you can minimise your resistance by going slow and being streamlined. If you cover a given distance in a given time, the total resistance will be less if you maintain a constant speed. If you know high school physics this should be self evident. If not, trust me.

Definitions:

The thrust from a fin is a force.
Efficiency is the ratio of the theoretical energy required to travel a given distance in a given time and the actual energy used to travel the distance.
Energy is the work done in traveling from point A to B. It is the area under the force distance graph or the average force multiplied by the distance traveled.
When you move forward underwater the main resistances are drag or water resistance and accelerating the inertia or mass.

Newton's first law of motion is simply that a body in motion will stay in motion at a constant velocity unless acted upon by an external force and suggests nothing about a body at a constant velocity incurring less resistance, so I'm not sure what your intention was with that reference.

You also seem to make a big leap by drawing a conclusion that constant speed minimizes resistance because going slow and being streamlined minimizes resistance.

I am not discounting what you are claiming, I use both frog kick and flutter kick (among other kicks) in various situations. I am only suggesting that your wording isn't very convincing.

 

[Foxfish]

Good luck trying to intellectualize this without actually experiencing all the factors you are not including in your "equation".

Seems that most of what I said went whistling overhead. Anyway, feel free to post links to freedivers setting bi fin records in the way you describe. All the ones I've seen fin in the way I described. I assume that in their experience, this is the most efficient way to dive.

 

[danvolker]

Seems that most of what I said went whistling overhead. Anyway, feel free to post links to freedivers setting bi fin records in the way you describe. All the ones I've seen fin in the way I described. I assume that in their experience, this is the most efficient way to dive.

I think the whistling noise is coming from inside your head
Since you apparently don't understand how a freedive record drop is different than a cruise over a reef..let me explain.....and you can try this yourself....

In the record attempt, the freediver will be falling most of the way down, once they get started downward from the surface...they go into a freefall, and have their body positioned to allow maximum speed in this freefall...they want to cover the largest distance possible in the next minute or 2 as they drop--and they want to do this with the lowest resting heart rate they are capable of attaining.

When they get to the bottom, after grabbing the marker or whatever proves they reached the depth.....and they begin to swim up toward the surface, they will be swimming as fast as they can, with the lowest heart rate they can use for this....they will need it to stay very low....probably 50's or 60's or even well below this for some ( 40's ), and the need to breathe again very soon ( since they have been down several minutes already) demands that speed is more important than absolute efficiency ( which would be the slower frogkick) ...So here they are using flutter or dolphin kick..my choice would be dolphin on the ascent to the surface....


However, same guy or girl, freedives down to a 60 foot reef bottom....and they have 1 or 2 minutes they can easily dawdle along the bottom, looking at the sights, or maybe hunting for lobster...whatever....they "CAN" go slow, and things can be coming to them to a degree....and like many scuba divers, this is a time when high speed is NOT really your friend--this is a time when slow and seeing everything, is more in the mission parameter....so the Frog kick with huge glide, is the ticket for this--allowing the lowest possible heart rate other than just lying still on the bottom...and still allowing the freediver to move pretty well over the reef--to extend what they can see and come in contact with for the longest duration possible. When they decide it is time to head to the surface, they will in all likelihood, switch from frog kick back to flutter or dolphin kick--because now the speed is their friend.

All freedivers do not use the frog kick...it is a subset that learned it ( it is not as intuitive as is flutter) -- and all freedive fins are not made to do frog kick with...many models of freedive fins have rails on the edges of the blades, and this will be enough to discourage the diver using this fin, to experiment with frog kick. Fins like DiveR, or Specialfins.com , and many others ( Omer among these.....I'd have to do a search) do NOT have rails, and are easy to frog kick with.

If you ever watch a class of new student divers, all swimming along with their version of a flutter kick...you will see "some" that can't keep the kick stroke straight....their down-kick curves, they may hit their other fin--basically they are not getting optimal thrust because the fin path is not the optimal path...rails help divers that for some reason, can't easily keep the ideal kick path without the rail...( could be coordination, could be flexibility issues, could be postural from knock knees or being bow legged....could be weak ankles....could be the instructor never told them what to do, and they don't know any better)...this is the "why" of the rails. Personally, I don't like them.

 

[nimoh]

If you ever watch a class of new student divers, all swimming along with their version of a flutter kick...you will see "some" that can't keep the kick stroke straight....their down-kick curves, they may hit their other fin--basically they are not getting optimal thrust because the fin path is not the optimal path...rails help divers that for some reason, can't easily keep the ideal kick path without the rail...( could be coordination, could be flexibility issues, could be postural from knock knees or being bow legged....could be weak ankles....could be the instructor never told them what to do, and they don't know any better)...this is the "why" of the rails. Personally, I don't like them.

Side rails seem very analogous to the center groove on downhill skis, although it has been a while since I was into skiing...things may have changed.

Recreational skis have a center groove down the base presumably to help it track straighter, while racing skis don't have a center groove, presumably resulting in greater speed...assuming you are able to make the ski track straight and not wobble side to side.