Fin vs. no-fin = +25% ???

[baiyoke]

Maybe it's and old topic, if so could you please post links to other threads, but:

It seems like there's only a 25% gain in distance/efficiancy when using huge fins compared to no fins.

If looking at the mens WR:

Constant Weight Apnea (CWT) Men 124 / Constant Weight Apnea Without Fins (CNF) Men 101 = 1,23


Dynamic Apnea With Fins (DYN) Men 273 / Dynamic Apnea Without Fins (DNF) Men 218 = 1,25

Now that is to me a bit surprising. And I wonder why that is???

The main factor I guess at that level must be O2 limit. So even if the fin is a lot more powerful, it is not a lot more efficient... Right? Going twice as fast through water increases the resistance 4 times, so that's probably the main reason right?

In that case, normal svimming with relatively small hands and feet is to me surprisingly effevtive!! 80% compared to putting on a huge monofin..! At least in apnea.

Have I got these factors right, or have I missed a lot of other contributing factors to the small difference???

But then again I'm thinking, these WR holders are the elite. For me on the other hand there might be a bigger gain in distance, when putting on fins... Because it's easier to pick up decent speed with big fins, but getting the rigth swimming technique in DNF is probably difficult for people of many differen shapes an sizes.. I'm short, stocky, muscular, small feet... That does not sound like a WR in DNF, so I'm thinking that for most/ordinary people, the difference in distance will be greater than those 25%...

So a) What are your thoughts on the factors that limit the difference in DYN and DNF?

And b) Do you think non-elite divers will show a bigger difference between DYN and DNF?

Thomas - Nuuk - Greenland

 

[efattah]

For me the difference is much bigger, I get twice the depth/distance with a monofin compared to no-fins.

 

[Mullins]

Compare biggest comp performances and the DYN/DNF ratio is even smaller - 1.18

 

[trux]

Yes, this topic was discussed frequently on DB, so you may want to check out for example this thread: http://forums.deeperblue.com/general-freediving/89498-relationship-between-dynamic-apnea-depth.html. Unlike what the title tells, the fins/nofins correlation is discussed there too. However, there are many other similar threads here on DB - just try the search function, and you'll find plenty of interesting comments.

Or have a look at the statistical correlation between the CWT/CNF and DYN/DNF disciplines directly at Apnea.cz - they are based on PB's of some 5 thousands of competitors:

APNEA.cz - Blog
APNEA.cz - Blog

​

 

[baiyoke]

Thanks for replies...

trux, nice stats in your link. Very interesting... Thats tells me that, roughly speeking, the ratio is pretty much established as a trend, from 1,18 (Mullins vs. Gorans record dives) to a mean of 1,36 from thousands of results, but with possibly bigger differences in the individual diver (efattah fx).

And from the statistics, my second question is answered: It indicates that the ratio is smaller for record divers, than for others it seems.

My first question however relates more to the factors that seem to limit dive-length in DYN. Why is the difference so surprisingly small, compared to the huge monofin.

Or in other words: Why is the monofin only a little more effective, when it comes to oxygen preservation...??? (about 36 %)

Looking at it, I would espect it to be much more effective than all that flapping and moving water in different directions with arms and legs in DNF.

A monofin resembles natures own solution in dolphins and whales to effective propulsion it seems. Or perhaps not: Maybe its the answer to speed, not effectiveness/oxygen preservation!?? Speed for hunting and moving with full lungs??

A can think of speed as the main limiting factor. Since resistance increases exponentially as a function of speed, and therefore oxygen consumption increases exponentially as well. Is that it? Is that the answer? Or are there other major factors?

Even so, it seems strange to me, that the efficiancy is only 36% better compared to flapping arms and legs... I wander if I have missed another major factor?

I've looked for related threads in the search function, but couldn't find anything. I'll try some more...

 

[Mullins]

A person using a mono is only superficially similar to 'nature's own solution' in dolphins etc. The fin looks much the same but it's being driven by a body totally unsuited for the purpose. All the joints positions, muscle connections etc are wrong.

You're right about speed though. The pace at which a mono really comes into its own is well above the optimum for freediving (unless you happen to be called Fed). The streamlining benefit it brings (constant arms-up posture) is also negligible at slow pace. That said, ~20% improvement is still significant.

 

[trux]

Yes, there are mutliple factors playing a role. Additional drag of the monofin (or bifins), possibility to gain more from push-off at DNF, more natural and relaxing movements at DNF, the lower velocity (and hence lower drag force) at DNF, but I'd tell a very important factor is also that you use more muscle groups at DNF. Once the vasonstriction kicks in, they work practically without taking away any oxygen needed the core. And since there are more muscles used, you spare more oxygen.

 

[Goran Colak]

And since there are more muscles used, you spare more oxygen.

I don't really understand this part Ivo...?

 

[trux]

I don't really understand this part Ivo...?

I meant that when you use more muscles in anaerobic mode, they can generate more power without using oxygen. So the more muscles you use, the more power is available for the propulsion.

 

[Goran Colak]

I meant that when you use more muscles in anaerobic mode, they can generate more power without using oxygen. So the more muscles you use, the more power is available for the propulsion.

That I agree

 

[Kars]

Hi Goran, just a question for Branko, about the bi-fin - mono-fin ratio, how far can you get using bi-fins?

 

[baiyoke]

Great info guys... There's a lot of factors I had'nt thought of.. I think my initial questions are more or less answered now.. Thanks!

About the vasoconstriction and using both arms and legs: If it is one of the major limiting factors i DYN (the use of only the lower body), wouldn't it make sense to start using the arms at some point, after the vasoconstriction has kicked in... fx if a DYN 273 meter diver started with armstrokes at fx 240 or similiar? Then perhaps he could reach... 300? Perhaps using arms and legs alternate...

About the monofin, speed and resistance/drag: I think it would be interesting to have a discipline where divers are allowed to use gear for better hydrodynamic properties... Likea dolphin-like tail, and submarine-like front or whatever... A sort of No-Limit dependent on only body-propulsion... "How far and deep can a diver go using only muscles and hydrodynamic gear..?" Has anyone ever done stuff like that?

 

[trux]

Hi Goran, just a question for Branko, about the bi-fin - mono-fin ratio, how far can you get using bi-fins?

Tom Sietas used to do 250m in training with bifins many years ago, and I believe that bi-fin divers can still beat monofinners today. I believe 300m and perhaps more should be possible.

If it is one of the major limiting factors i DYN (the use of only the lower body), wouldn't it make sense to start using the arms at some point, after the vasoconstriction has kicked in...

Definitely. This is the way I do DYN in competitions. I combine bi-fin kick with glide, arm strokes and dolphin kicks. Works fine for me. And for exemple Eric van Riet Paap increased his DYN PB from some 150m to +200m after switching from the classical monofin kick to alternate kick and armstroke style. I believe this is the way to reach 400m.

 

[Simos]

Tom Sietas used to do 250m in training with bifins many years ago, and I believe that bi-fin divers can still beat monofinners today. I believe 300m and perhaps more should be possible.


Definitely. This is the way I do DYN in competitions. I combine bi-fin kick with glide, arm strokes and dolphin kicks. Works fine for me. And for exemple Eric van Riet Paap increased his DYN PB from some 150m to +200m after switching from the classical monofin kick to alternate kick and armstroke style. I believe this is the way to reach 400m.

Do you think there's any benefit in starting to throw arm strokes in etc if you are not in any way limited by lactic accumulation?

 

[efattah]

the classical monofin kick to alternate kick and armstroke style. I believe this is the way to reach 400m.

At Vertical Blue 2011 I tried this in constant weight.
Dive 1: 40m FRC ordinary monofin kick
Dive 2: 40m FRC, alternating kick-glide-armstroke
Dive 3: 40m FRC ordinary monofin kick
Dive 4: 40m FRC, alternating kick-glide-armstroke
Dive 5: 40m FRC ordinary monofin kick
Dive 6: 40m FRC, alternating kick-glide-armstroke

Each time, the dive with the kick-glide-armstroke was far more difficult, in fact I almost had a samba one of them. The dives with the ordinary monofin kick were very easy. The strange thing is that ascending from 40m with the kick-glide-armstroke took an incredibly few number of strokes, only 6 !! But still I had way less air at the end. It really didn't make sense, I expected it to be better.

My DNF armstroke is pretty good. My frog-kick sucks. But frog-kick was not used in this experiment. So I would not attribute the results to bad technique.

 

[Kars]

Eric I think this is because in FRC CWT one is negative all the time, so the arm movement takes too long time allowing the diver to come to a full stop, after which one needs to overcome the inert and constant negative buoyancy. With just monofin kicks one has a much more of a continuous speed.

 

[Simos]

Eric I think this is because in FRC CWT one is negative all the time, so the arm movement takes too long time allowing the diver to come to a full stop, after which one needs to overcome the inert and constant negative buoyancy. With just monofin kicks one has a much more of a continuous speed.

I was thinking the same - monofin starts from rest seem to need a fair bit of energy whereas once you get into a rhythm things are easier.

Also if we really practiced the armstroke/monofin stroke for years like we do with the more conventional ones it might get reasonably efficient as there is a natural undulation that happens when swimming breastroke anyway.

 

[baiyoke]

I would personally make a big theoretical distinction between the pool and the deepth disciplines... Because that gravity-force is a bit of a joker...

Nonetheless the distances covered does seem to be all in the same range DYN 273, CWT 248 return & DNF 232, CNF 202 return, deepth distances a little shorter.

And looking at the ratio:
Constant Weight Apnea (CWT) Men 124 / Constant Weight Apnea Without Fins (CNF) Men 101 = 1,23

Dynamic Apnea With Fins (DYN) Men 273 / Dynamic Apnea Without Fins (DNF) Men 232 = 1,18

It seems to me that gravity and armestrokes does not make a bad combination, since the ratio is roughly the same in horisontal and vertical performances...

So when talking about monofin vs. armstrokes and the experience Eric has, it seems to me that perhaps incividual differences is more likely to account for the experience, since Eric earlier wrote:

For me the difference is much bigger, I get twice the depth/distance with a monofin compared to no-fins.

But that said, I agree that gravity is a difficult factor to work with, since it is the time spend in the negative zone that will decide how much force will be aplied to the body... And that again also depends on the depth, the deeper the bigger, so it's a depth X time = "gravity force" wich on the other hand has to be balanced with ascent speed, since speed also creates an exponentialle growing resistance... Too slow, and you'll spend too much time in negative zone, too fast and resistance is too big and energy costfull.

So it's a Time X Deepth X Speed equations that makes it really complicated to hit the optimal speed.

In dynamic it's more a time X speed equation, although difficult, it's a factor less to consider, and the gliding phase is easier to work with...

And since the monofin works best above a certain minimum speed like you guys mention above this post,that's also a factor, but a shared factor in both deepth and dynamic as I see it: In depth disciplines, that just means that you have to kick shortly after the armstroke...

Hope it makes sense...

 

[baiyoke]

My DNF armstroke is pretty good. My frog-kick sucks. But frog-kick was not used in this experiment. So I would not attribute the results to bad technique.

I forgot to take this into account... That confuses the picture a bit...

Could it be, that your arms are just not used to the work load after vasoconstriction has kicked in... That it is something you don't train a lot??

 

[efattah]

I thought maybe it had something to do with my arms not used to working, but on my first ever attempt at a deep free immersion dive I did 84m in 3'33" with enough air for 100m+. So I still don't get it...