A Kinematic Comparison of Dive Fins

[Thalassamania]

the point is that no matter what fins you wear or no fins at all, the muscles that you have to drive the fins remain unchanged, exception being if you switch to a frog kick, but I don't anyone is going to argue that a frog kick can create the sustained thrust that a flutter/scissor kick can. The "Trudgen" style uses scissor kick, which is nothing but a wider flutter kick, still the same muscles.

Are some of the same muscles used? Of course, there are only so many muscles in the body, some of the same muscles are used with frog kicks also.

Perhaps the Force Fin is a more efficient fin for flutter kicks, I don't know. Though I agree with you on the toe vs ankle loading issue, I still must point out that terms such as "efficient" must be defined to make any testing of claims meaningful.

Yes, there are some assumptions here, I don't believe they are unwarranted, this is afterall an internet forum not a review panel with subject matter experts, so I am taking certain liberties in argument development, although I am trying to form a whole discussion.

Please deal with our conversation as though it were a peer review, I see no reason to pull our punches and offer up second or third best because it's the internet.

The argument that I am making is that no matter what fins you wear, your legs have muscle groups that only do certain exercises.

I'd point out that the flutter kick motion is a very "unnatural" one, only remotely akin to the actual motions that our limbs evolved to make to facilitate terrestrial locomotion. Thus I would tend to poo-poo the implication that any one fin design is better than another because it permits a "natural" use of the muscles and joints. The only real answers lie in defining "efficiency" and testing to that definition, biomechanical modeling is, to my way of thinking, at best an indicator for hypothesis formation or at worst a red herring.

It is the muscles that define how to best move the legs and the only way to justify that the leg movements should change by placing fins on, is saying that the flutter style kick is faulted and needs to change.

While I see more problems with the analysis than you seem willing to grant, I'm quite willing to profess that there are kick styles superior to flutter kick.

And yes, a dolphin kick uses the same muscle groups in the same fashion as well, although it does utilize a larger planning area, it doesn't change the muscles. in scuba applications, the planning area is limited by the rig to only allow the legs to drive.

That's an unsupported claim that I find patently absurd, watch a competitive swimmer coming off a turn, the wave begins at the outstretched hand and travels down the entire body. Then watch a scuba diver, hands are not out quite as far and there's a more pronounced head bob, but the wave still travels down the body. As far as one's rig limiting the planing area, I don't think that's true. The rig creates additional drag, but it does not prevent spinal flexion from being an integral part of thrust production.

 

[sambolino44]

... an ANOVA is an excellent way to handle each on its own and to pull it out as a block effect that can be separately tested an evaluated you usually wind up with interactive block effect terms that are significant, and all you can do is shrug your shoulders and toss them into the error term, and so it grows, and grows, and grows, and swamps your data...

I think you've hit the nail on the head here, and I don't see any way around it.

 

[Thalassamania]

I suppose you mean except for a robustly designed experiment, such as the one I outlined but with the controls carefully thought out and the ability to increase the sample size if it looked like the interactive terms were getting out of hand?

 

[deco_martini]

I suppose you mean except for a robustly designed experiment, such as the one I outlined but with the controls carefully thought out and the ability to increase the sample size if it looked like the interactive terms were getting out of hand?

There are major problems with controls.

A. if diver knows which fin he is using, he will bias his own results
B. If diver doesn't know which fin he is using (blind), the data becomes junkified (tm) because the diver will kick how he is used to and not get optimal kick cycles

I think perhaps the only thing you can test for certain with fins is which fin style a person most naturally adapts to. You could test that by having non-divers who can swim try a single set of fins and interview them afterwards. Find out how long it took the person to obtain full controlled speed. Sample size large enough, you find out which fin style people take to most quickly. The downside is, perhaps the most "natural" one to adapt to isn't the most optimal for an experienced diver.

I think trying a controlled study of fins at this point just isn't feasible because what you can determine isn't that useful right now. Just my 2 cents.

 

[Thalassamania]

You could easily pull out a block effect due to preference by simply having as an independent variable the fin that each subject normally used. In fact that would be very interesting since if it were significant it would indicate that preference was an important criterion independent of the actual design.

 

[meesier42]

that concept, is in fact the exact starting point that my study a couple years ago used. By testing the person with the fins they were used to as the baseline measurement. The hard part, is acclimatization period for each new fin. As changing fins in reality takes days to weeks to master, as its not just changing form, its training the muscles to perform differently and that takes time. When you do not allow for enough time to adjust to the new fin, and the new fin still manages to outperform the baseline you are really understating the real benefits. I tried to capture some of this by doing multiple test with each fin and examining how much change there was from the first to the second test. Luckily, the differences from one to the next was modest, but then again we didn't do back to back test with the same fin, so basically all of the fins were at an equal disadvantage.

In reality- a completely unbiased review is nearly impossible, if not truly impossible, as its really not possible to find a diver that doesn't know what he/she is wearing on their feet and their bias will be introduced even if it is unconsciously. A serious test would literally take months to years to perform. As each fin would require a minimum of 2 weeks daily conditioning to adapt to, then you would have to reassess the baseline fin for another 2 weeks to ensure that the diver isn't just becoming more fit over the duration of the test. Not an easy thing to perform. So, in a good test, we do our best to find statistically valuable trends, not absolutes.

But even then, we could conclusively prove that a fin was significantly better than the competition and people would still pick and choose the fins they want to use, so what's the point of spending lots of money and time to get conclusive results. To paraphrase a former commander of the Navy Experimental Diving Unit (NEDU), "We no longer have any interest in testing fins for efficiency because in past testing all fins are good enough, so we leave it up to personal preference"

 

[Thalassamania]

That's why you need 10 (maybe more) trails with each fin with the subjects original fin of choice as an independent variable. After each day's trails you run your statistics and eventually you should see the block effect due to original fin of choice drop into insignificance, if you don't, that would be very telling, in and of itself.

 

[meesier42]

10 trials with each fin, plus another 10 with the baseline fin. As I already mentioned, even a basic understanding of exercise theory tells you that could take a month or more to perform. And so many other variables are going to be introduced over that extensive time period that you end up with worthless data again. If you look into any of the studies that have been done, none of them speak in absolutes, they draw conclusions from trends in the data, and even then, they preface it with statements like, "did not follow predictions" and "further study is required to understand" and "can be used to predict... but that would have to be tested empirically" I ask what the hell was the point of the study if it wasn't to collect empirical data.

and of course, many of the studies out there, are biased up front. one done at the UofBuffalo went as far to exclude FF because it violated a simplyfing assumption that they observed to be consistent with other fins. And in their conclusions they identified a series of problems that all fins have and to improve the fins the design should look and act a lot like a ForceFin.

 

[Thalassamania]

No one suggested 10 trials of the baseline fin, unless it happened to be one of the test fins, that would be unnecessary. 10 replications is likely excessive, but exactly how many replications would be needed remains unknown until the actual variances can be calculated at the end each day. Studies that have gone before are quite irrelevant since neither the experimental design that I propose nor the measure of efficiency that I'd use have been featured in the past and which requires no simplifying assumptions of any sort.

Might I recommend to you some hours with Tukey's "Exploratory Data Analysis?"

 

[deco_martini]

In fact that would be very interesting since if it were significant it would indicate that preference was an important criterion independent of the actual design.

If I am reading that the way it appears to be written, I would guess it is already a factor for some without going through the rigors of a controlled study.