Fin Tests- Techniques and conditioning

[Thalassamania]

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A ScubaBoard Staff Message...

Split off from The Kinematic Comparison of dive fin thread.

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Dear Thalassamania, what a diving bio you have and still using jet fins. You must have had fun working with Captain Billy Deans. I made the Excellator fin for him.

Actually I use different fins, depending on the demands of the dive, Jet Fins are a resonable all around compromise, sort of second best at most everything.

I was not working with Billy for fun, we were WORKING. You know ... combining our efforts to enhance both of our paychecks.

In all honesty, I have nothing either for or against your fin, I tried them and they were not to my taste, but I'm the first to admit (see below) that there's a learning curve to any fin and I only used them on one dive. I was left with the feeling you have when biking up hill in too low a gear and having to spin faster than you want to.

I fail to see how measured "data" can be "anecdotal" , the terms are by definition in opposition.

the conclusions drawn in the paper have a particularly small data set (1 diver) so the stastical validity may be drawn into question, but the scientific method and collected evidence is quantified data, not anecdotal. The conclusions drawn from the data follow the evidence collected to date and matches up with the current understanding of exercise theory.

So until you put up the money to expand the data set and prove the data wrong, or gain a PhD in Sports Medicine and Physiology to interpert the existing data differently you are in no position to discredit the data or the interpretation of it.

When a study has N=1 then it is anecdotal regardless of how "scientific" it appears. That is to say, "based on casual observations or indications rather than rigorous or scientific analysis," which requires a sufficiently large sample size to pull the signal out of the noise.

One reason I thought Ryan's study was so interesting

Form my original post-
Ryan used a biomechanical analysis software program called Peak5® to digitize video footage of a swimmer moving past a viewing window in a pool kicking conventional fins and when kicking Force Fins. The software translated the range of motion, acceleration and velocity the hip, knee and ankle joints into data points that show the differences in that range of motion to reveal the strain put on those joints of the leg when kicking the fins.

Ryan was getting real information on the different effects of using different fin designs in the water, a comparison with no room for human interpretation. With the Peak5® software he could translate video footage of a diver’s leg in motion into percentages of range of motions on joints of the body, interpret forces acting on legs using known bio-mechanic norms and limitations of the human leg.

I think it is a very promissing approach and I hope to see it pursed as a way to compare a number of different fins.

Many, many years ago we tested five different fins (sorry, the Force Fin was not in test group). We used ten subjects and a highly robust experimental design that controlled for many variables, including training effect, that is to say our dependent variable was oxygen cumsumption, measured by weighing the oxygen bottle from an oxygen rebreather before and after each test, over a defined course. The independent variables included fin model, subject's number, subject's initial fin preference, time to swim a mile, number of previous trials, number of previous trials with a give fin, etc. Subjects were divided into two groups, on succeeding days one group of five swam five different fins in rotation until they had five trials on each fin, the other group of five swam one fin design five times (each trial on a succeeding day) and then switched to the next, and so on. The data was normalized and run though an ANOVA. As I recall the most significant item was the block effect due to trial number in the group that swam one design fin five times in a row and then changed design. The conclusion was that within normal boundaries (we intentionally used one fin design that we all agreed was the worst possible ... the Fara-Fin with the ankle brace). Guess what? There was a more significant reduction in oxygen consumption in the second group's fifth trail with a given fin than there was between the fin types with the exception of the the Fara-Fin, which was the worst in every possible way. I love to see a similar experiment replicated with Peak5®.

 

[Thalassamania]

...

The subject for this study was a competitive lever swimmer chosen for his near perfect swimming mechanics. This was done so that poor swimming mechanics could be eliminated from contaminating the collected data.

When I originally conceived this study I did not set out to prove anything other than there was some difference in swimming mechanics (kinematics) when you swim different styles of dive fins...

That's one of those things that any crusty diver could tell you, but it is always nice to have it confirmed. I'd suggest that a resonable interpretation of both our studies is that they agree with each other. What do you think of applying the program as a tool with the sort of experimental design that we used?

 

[*Floater*]

Ryan Lindsey, his daughter Charisse and Bob Evans all with their new favorite Force Fin.

Charisse's favorite fin looks a bit huge for her...

Personally, I'd like to see a fin designed to optimize frog kicking efficiency... and then tested against divers flutter kicking with force fins or biofins in terms of air consumption at moderate speeds when pushing the type of loads that rec and tech divers carry, respectively.

 

[Thalassamania]

Good suggestion.

 

[meesier42]

Charisse's favorite fin looks a bit huge for her...

Personally, I'd like to see a fin designed to optimize frog kicking efficiency... and then tested against divers flutter kicking with force fins or biofins in terms of air consumption at moderate speeds when pushing the type of loads that rec and tech divers carry, respectively.

such a fin has been designed already, Bob is holding in that picture. The Excellerating Force is a great fin for Frog kicking. It is the only ForceFin in the collection that is not flexed forward, in fact it is actually flexed back slightly, and progressively so towards the tips. While performing a frog kick this fin is fantastic. It will outperform Jets for Frog Kick ability as it will at least match the power stroke of the Frog Kick, but you can also use the Whiskers, Batwings, or SharksTeeth to add fine tune control while gliding.

As for pushing the loads that Tech and rec divers carry, Yes, I have tested them, If you know my background I have been a Navy diver for 6 years now and pushing twins, drysuits, pneumatic tools, cameras, lights, etc... has all been done with ForceFins. And for a long time I used the Extra Force TanDelta, but I have converted to the Excellerating Force TanDelta as it provides a more balanced kick and has better performance for fine control.

I have never really attempted to do a comparison of air consumption with a frog kick, as I can only imagine that it would be only slightly above the base metabolic rate when properly performed. When I worked with the Seals who were pushing Navigation sleds, ammo, firearms, and SDVs about, it was very common for them to to use ForceFins, most using the FF Pro, with some picking the FF TanDelta and although I personnally have not seen it, I understand that the SD-1 Military is becoming more and more popular with them as well. The Smoke Black TanDelta material was made by special request of the Seals, and Bob was more than happy to comply. What I noticed was interesting, none of these guys use a frog kick, its too slow and doesn't provide enough thrust to do anything, so they master the flutter kick and perform it properly, something nearly all of us would do well to accomplish. Sure the frog kick has its place in tech diving but it doesn't help you when you have to get somewhere.

With the Batwings you can get forward thrust on the recovery (outward kick) as well, to some extent the Whiskers do this as well, but to a much lower extent. There are lots of other tricks that the ForceWings can do, but they have already been discussed at length, see the ForceWings Thread.

 

[*Floater*]

such a fin has been designed already, Bob is holding in that picture. The Excellerating Force is a great fin for Frog kicking.

I've heard good things about the Excellerating force fins, but I can't justify spending $400 (regular, no extras) to $800 (Tan Delta with all extras) on a pair of fins, especially when I don't know if I'd even really like them...

I have never really attempted to do a comparison of air consumption with a frog kick, as I can only imagine that it would be only slightly above the base metabolic rate when properly performed. When I worked with the Seals who were pushing Navigation sleds, ammo, firearms, and SDVs about, it was very common for them to to use ForceFins, most using the FF Pro, with some picking the FF TanDelta and although I personnally have not seen it, I understand that the SD-1 Military is becoming more and more popular with them as well. The Smoke Black TanDelta material was made by special request of the Seals, and Bob was more than happy to comply. What I noticed was interesting, none of these guys use a frog kick, its too slow and doesn't provide enough thrust to do anything, so they master the flutter kick and perform it properly, something nearly all of us would do well to accomplish. Sure the frog kick has its place in tech diving but it doesn't help you when you have to get somewhere.

I'm guessing the Seals swim faster than average divers and are less concerned with air consumption, so for their needs the flutter is probably better. In my own experience, the frog kick tends to be more efficient in terms of air consumption for covering distance at moderate speeds. Even when swimming in a pool, I find the breaststroke better suited for long distances than the front crawl.

 

[meesier42]

I'm guessing the Seals swim faster than average divers and are less concerned with air consumption, so for their needs the flutter is probably better. In my own experience, the frog kick tends to be more efficient in terms of air consumption for covering distance at moderate speeds. Even when swimming in a pool, I find the breaststroke better suited for long distances than the front crawl.

To the Seals air consumption is critical, as they have to complete a mission on the air that they can carry. Not like you and I that if we run low we can surface, for them surfacing anywhere other than the planned location will be their end. This is one of the reasons that FF's are so common. They have found that they can cover significantly more distance at greater speeds while maintaining their air consumption low. Although they don't normally use open circuit scuba either, they use a specialized rebreather, but with any rebreather you have to maintain a workload and not allow your breathing loop to get out of whack.

If you have found that breaststroke is better suited for covering long distances than a crawl then you need some swimming lessons. As a competitive swimmer for some 18 years, reaching a very high level, I can promise you, there is no stroke more efficient to cover distance than the crawl/free style. For kick only swimming, at least while in scuba gear, were you can't use a dolphin kick, there is no kick better than the flutter. If you have had other findings then there is something else going on. Such as poor technique, poorly designed fins , poor fitness, etc... Talk to any competitive level swimmer and they'll tell you the same. In all of my years of diving, I have seen never seen a diver properly perform a flutter kick, with 2 exceptions
1) they were also competitive swimmers
2) they were wearing ForceFins or Apollo/Atomic splits

please don't interpret that to mean that frog kicking doesn't have its place, but its a specialty kick and should primarily stay in its specialty market. I think it has creaped into general recreational diving due to poorly designed fins that cause cramps and are uncomfortable to really perform a flutter kick for extended periods of time.

with rare exceptions for average divers, conventional paddle fins force the knee to bend too much to maintain optimum power tranfer from the quads, hip flexors, gluts and abs where the real power is generated. Convential paddle fin use the hamstrings and calves (also primary muscles for frog kicking, coincidence, maybe not) which are comparitively very weak muscles and will tire faster. Thus increasing the heartrate and O2 requirement to remove and metabolize the lactic acid. Compared to a properly performed flutter, where using very large muscles at very low loads nearly prevents lactic acid production all together. This combines to mean that you end up meaning that you have a lower HR to maintain the same speeds and ulitmately lower your air consumption. This probably supports your conclusion that with most convential fins a frog kick is better, and to be honest, its probably true. But, ForceFins are not conventional paddle fins and I doubt anyone will argue that.

quick note- lactic acid is produced by the muscles when operating with decreased O2, if you maintain true aerobic exercise and keep the loads low you minimize lactic acid production to levels such that it never builds up in the muscles.

To comment on splits, although they have proven time and time again that they can go very fast it is nearly impossible to maintain the kick frequency that they require to do. So sure you can make headway into a current, but your not going to get very far. The beautiful thing about ForceFins is that while they still use a fairly high kick rate the kick rate is low enough that you can actually maintain it for an extended period of time.

 

[*Floater*]

messier42, you make a good case above for the flutter kick.

that said, my understanding is that the frog kick was adopted as the main propulsion technique by early cave divers (pre-scooters, etc.), which suggests that they likely found it to be the most efficient way to cover distance on thirds. of course, it's also an anti-silting kick, but in many caves that's not an issue, and for these cave explorers, being able to go as far as possible with limited gas was the main often the goal.

i'm also reminded of a particular fin comparison article I read some time ago. the author noted that force fins didn't stand out in the test, but he found a very experienced FF user who did best on those fins, and was also very close to the top of all testers across all fins. the part I found interesting was this observation (emphasis mine):

I tracked down two such divers, but one was traveling in Alaska and unavailable at the time. Thus, I was only able to get one (identified as diver "z" in the speed data, an instructor with over 2,700 dives, mostly with FFs) to run the tests to date. He did excellent with the FFs (using the Tan Delta model). When moving at normal diving speeds, he used a kick style, sort of a modified frog kick with a twist at the end (which I've also observed among a couple of dive masters in the tropics) that appeared very efficient and required only about one kick to five or six of my normal flutter kicks. I was unable to duplicate that kick even after watching and trying it for much of one of our dives together.

My personal belief is that the most efficient propulsion techniques in diving involve optimizing the kick-to-glide ratio, and that fins which maximize the amount of glide per each large kick, and minimize the effort required for such kicks, tend be most the efficient for normal dive speeds.

Links:
Fins -- Main Page (for overall)
Fins -- In depth (2002) (for quote)

 

[*Floater*]

If you have found that breaststroke is better suited for covering long distances than a crawl then you need some swimming lessons. As a competitive swimmer for some 18 years, reaching a very high level, I can promise you, there is no stroke more efficient to cover distance than the crawl/free style. For kick only swimming, at least while in scuba gear, were you can't use a dolphin kick, there is no kick better than the flutter. If you have had other findings then there is something else going on. Such as poor technique, poorly designed fins , poor fitness, etc... Talk to any competitive level swimmer and they'll tell you the same. In all of my years of diving, I have seen never seen a diver properly perform a flutter kick, with 2 exceptions
1) they were also competitive swimmers
2) they were wearing ForceFins or Apollo/Atomic splits

For me the breaststroke at relaxed speeds is like walking, in that it feels fairly effortless, whereas the forward crawl exhausts me more even at similar speeds. I try to use the Total Immersion style, but my lack of finesse in the technique is probably to blame for why the breaststroke feels easier.

In any case, surface swimming is perhaps a poor example since air consumption is not constrained, so let's look at dynamic apnea swimmers. Here's a clip of the old no fins record breathe-hold swim (166m): YouTube - dynamic apnea without fins old record 166m

The guy in the clip uses the breaststroke kick, and there's the kick-and-glide thing I was talking about before. Do you know if dynamic apnea divers compete using 2 separate fins of their choice? I've only seen clips of the mono-fin apnea divers using the dolphin technique (obviously not well suited to scuba), but I'd be interested to know whether they can cover more distance using the frog or the flutter using their choice of a pair of fins.

 

[meesier42]

I have found many of his observations to be true. ForceFins have a significant learning curve and they take time to acclimate to, but I have been saying that from day 1. With someone who knows how to use them well, they are going to move extremely well, someone that does not know them will generally do poorly. I just verified this in a recent test I was involved with for Spearing Magazine. But I noticed something somewhat odd and unexpected in those test. 1) That the FF Pro did very well with divers new to them. 2) even though my times were progressively faster with the higher end FF's, the divers new to them did progressively worse. 3) Even with that being the case, every single method of data analysis that I could run, showed that the 3 FF's (Pro, Excellertor TanDelta, Extra TanDelta) were still best scuba fins in the test, I don't want to name names until the study is published. In the testing that you found (thanks by the way), diver Z was one of the fastest divers in the test no matter what fin he used, which shows that he was a highly proficent swimmer and sure enough, the fins that he produces the top results with were ForceFins.

Your belief about kick to glide is probably right, if all you care about is air consumption. But again, this is where the unique design of ForceFins tops the charts. With the premium materials and time consuming production process, Bob was able to produce a fin that is able to continue providing thrust AFTER you stop your kick. The ForceFin blade will rebound with significant force and continue pushing you forward at the end of your power stroke, similar to loading and releasing a spring. All fins have the loading part of the spring, but the low cost TPU's and natural rubber that they are made from absorb it and do not return it to the diver. If you look at the Aqualung Slingshot, you can see that someone else has realized this spring effect as well and has made a vain attempt at replicating it at a low cost, but failed to realize that this spring must exist throughout the blade to allow it to work for you, as speed is generated at the blade tips, not at the toes.

for Dynamic apnea- although I have only done some of this, assuming I rule out the dives with monofins
Fins- flutter is the kick of choice, using a large efficent blade at low kick rates. I used to use Cressi Garas, but have switched to ForceFins, normally going for the Excellerator TanDelta and sometimes the Pro, TanDelta, or ExtraForce. I have found no difference in single effort distances, but I can repeat the distances in the ForceFin Excellerator, while I am blown for 20-30 minutes with the Cressi's