A Kinematic Comparison of Dive Fins

[Thalassamania]

For this individual, who may or may not have been using either set of fins properly and who may or may not have gotten the same amount of propulsion per unit of oxygen consumed (which is what would be the really interesting point but was not looked at).

 

[uncleavi]

Point me to one of your posts that are not negative so, I can see that you have another side.

 

[Thalassamania]

Tuna story

 

[simmonsjr]

I've got to say that even with the limited data set (one individual with near perfect swimming mechanics) the hypothesis is thus far proved. Force Fins work as they were designed to do and they do it better than the "other" pair of fins that was involved in the study.

Are there limitations to the study? Absolutely: one subject, two pairs of fins, confined environment. However, that in no way discredits the results. They stand as valid.

I can say that the utmost of care was taken to conduct a scientific study. The cornerstone of making a study truly scientific is the ability for anyone to reproduce your study and achieve the same results.

What is required now is that additional testing be conducted to ensure that the results of this study can be validated. If another study can replicate the results while substituting different variables (swimmers with less than optimal swimming mechanics, different fins, dive gear vs. no dive gear, open water vs. confined water etc) then the experiment is considered to be validated.

That is how the scientific method works. The limited data set of this first experiment was built in to it by design to eliminate a testing variable (swimming mechanics). This actually resulted in an improved experiment not a deficient one.

By the way, I would be happy to volunteer my services for a second round of testing .

Jason

 

[Thalassamania]

What needs to be done is a study with ten people (or more) of varying skill and experience doing five trials each of fins that they've not used before on separate days for ten different pairs of fins using pure oxygen rebreathers over a set distance with the dependent variables being oxygen consumed and time for each trial. Then they should be instructed in the use of each fin an proceed to do five more trial (again each on a separate day). This will tell you what the most efficient fin is (in terms of oxygen consumption) and how much is a matter of fin design as opposed to skill in use. I'm sure that if I think it out a bit more carefully I will make some changes, it alreay occurs to me that the trials should be replicated both pre and post instruction for set speeds through the water. An expensive proposition, ten rebreathers, ten sets of fins, maybe 300 total trials per subect.

 

[simmonsjr]

What needs to be done is a study with ten people (or more) of varying skill and experience doing five trials each of fins that they've not used before on separate days for ten different pairs of fins using pure oxygen rebreathers over a set distance with the dependent variables being oxygen consumed and time for each trial. Then they should be instructed in the use of each fin an proceed to do five more trial (again each on a separate day). This will tell you what the most efficient fin is (in terms of oxygen consumption) and how much is a matter of fin design as opposed to skill in use. I'm sure that if I think it out a bit more carefully I will make some changes, it alreay occurs to me that the trials should be replicated both pre and post instruction for set speeds through the water. An expensive proposition, ten rebreathers, ten sets of fins, maybe 300 total trials per subect.

The only issue with that is that the experiment you have proposed has a different aim than the one that was initially conducted. You propose to test efficiency through oxygen consumption and speed; however, the original experiment was designed solely to examine body mechanics. If you were to proceed with this as the next step you would end up two unvalidated experiments rather than either validating or disproving the original.

That's not to say that the experiment that you have proposed is not without merit; it appears to be well designed to answer another a very worthwhile question - just not the question at hand. I would love to see this issue addressed as well, but in order to answer your original objection, the small size of the data pool, you would have to focus on biomechanics instead of oxygen efficiency.

 

[meesier42]

while I have never attempted to use rebreather, the point of the 1993 UofBuffalo study did basically just that but in a controlled flume tank. They took extreme measures to ensure that each diver had enough acclimatization time that they could learn how to best use each fin. They used about 30 divers and tested 12-15 pairs of fins on all of the divers, some from the Navy's NEDU, some locals. It was a huge study that took over 6 months to collect the data. This study was sponsored by the Navy and from what I understand cost hundreds of thousands dollars (not sure, but >$200k wouldn't surprise me). I really wish that I had a digital copy of it to distribute.

I have conducted a similar concept study, the study (not scientific, but a solid attempt was made) was on a shore dive that myself and the 3 friends that I included in the study conducted on a well known dive site. We executed the same dive 10 times each (2 times with each of 5 fins). We did our absolute best to do the same dive each time (including reviewing depth/time profile on our dive computers). The point was to replicate the dive every time with all 4 divers swimming at speed the entire dive. At the end of the dive we measured PSI consumed and tank size, water temp to calculate SAC for each dive. I was the only Force Fin user at the start of the test.

The fins, were the Force Fin Pro, Force Fin Extra Tan Delta, Apollo Bio-Fin (not sure, but I think the XT) , Jets, and Volo Race. The Divers, included 2 expirienced (500+ dives), 1 intermediate (~50 dives) and 1 new diver (~10-15 at the start). It took us a little over a month to do, but the order that each person used the fins was varied so that we could eliminate patterns. The average swimming speed was high, intentionally too high to allow frog kicking, this also forced the breathing rates up enough that we could more easily observe the difference.

The results- The Force Fin Pro was the most efficient, by a moderate amount (5-8% better for all dives). The Bio-fin was second. Followed by the Force Fin Extra, although it was the best fin for me, it was way too stiff for the other 3 and their SAC suffered. The Volo Race beat the Jets, but not by much. The difference in the bottom 3 was really small, to the point that statistically they were equal.

As a follow on, I should look at repeat at slower speeds to allow frog kicking, although I expect that the results will be really hard to see as the differences will be so small.

 

[Thalassamania]

PSI is not the best measure because divers use the air in their lungs to set their buoyancy as well as to support respiration. Two trials with each of 5 fins with four subjects is likely no robust enough to differentiate at even the .1 level, meaning that differences of 5 to 8 percent are, in reality, down in the noise. I'd be very interested in seeing you raw data as well as the details of your analysis. Did you run an ANOVA? Did you normalize to zeta scores first?

For those interested:

Scientists Debunk Fin Claims

 

[meesier42]

I was aware of the problems, which is why I didn't call it a scientific. I am sure there are hundreds of other problems with the method, but it wasn't meant for publishing, it was because we were interested to see what would happen.

I did not compare diver to diver, I only compared each diver to themself. It was the only thing that I could compare that I believed to be reasonably valid. Then ranked each fin with each diver and assigned a score by inverse rank (best fin gets a 5, worst gets a 1). Then totaled and averaged the sum ranking. To find the gains, I assigned a baseline zero score to the best fin and compared the difference from zero for each fin to the divers 10 dive average.

As it was the same dive profile each time, we assumed that each diver would use approximately the same amount of air to buoyancy etc. As to noise, I was surprised to see how low the variance was when the same diver used the same fin for the repeat, inside of 4%. I know, I didn't believe it either, I was expecting to have to do many more runs to work out the noise, but to be honest none of us wanted to continue with it.

I realize that 2 runs for each diver with each fin is hardly scientific, but it was enough to see a pattern form and with volunteers doing it for fun, it was about all we could take. Too many other good sites to explore, repeating the same dive, day in day out, while living in Hawaii is a real waste

I'm extremely sorry to report that I no longer have the raw data, when I got divorced the other half got the computer that the data was on.

 

[Thalassamania]

Damn, it sounded like a real good start, it's amazing what a normalized data set run through an ANOVA can give you, I was really looking forward to a few evenings of data massage.