Frozen Foot - Gear and Technique?

[KoiWatcher]

I have found a few threads that deal with drop foot and they didn't provide the answers I'm searching for - Thus this post.

If a foot is frozen at a 90 degree angle for walking (currently with a prosthetic brace, there is a chance of needing ankle fusion surgery in the future), and the advice in some of the other drop foot threads of placing the foot into a 45 degree angled foot brace for use in the water is not possible, then:

1) Has anyone had to adjust their finning technique to account for the improper angle of the foot? If so how?

I am wondering how to balance obtaining a finning form that provides adequate propulsion with the need to not further injure the leg/foot.

2) Has anyone tested different types of fins to see if one type works better than another given the parameter of keeping one foot inflexible and frozen at a 90 degree (walking) angle? The boards of full of heated "the best fin is" threads, but none seem to apply here.

Thanks!

 

[Kilili]

What little I know...
In Fiji, I've seen fins rebuilt with aluminum struts and push rivets. Not much work involved. Perhaps you could cut a fin beneath the foot pocket and re-rivet at the angle you wish. You could find an old fin, rebuild it, and experiment in a swimming pool to determine effectiveness. The angle could be easily "fine-tuned" with a hammer.

 

[pasley]

Adopt a modified cave or wreck diver kick. They kick with knees bent to get the fins away from the bottom and use a frog kick. Heres is one example. There may be others. The Frog kick may not work, but the other might.
[video=youtube;U5wliityRuU]http://www.youtube.com/watch?v=U5wliityRuU[/video]

Getting the wetsuit on over the foot will be aided by the instatlation of a zipper to the knee.

 

[nimoh]

my first thought was...get a scooter

seriously though, I agree with pasley that bending your knee 90 degrees should put your fin in the correct orientation, and then moving your upper leg up and down should get the fin moving to generate thrust.

However, you may also want to consider bent fins such as the Tusa Imprex TRI-EX (link below). They are bent at 20 degrees, so you could straighten your legs slightly, probably making for a more efficient kick. I think a 90 degree leg bend works well for a frog kick or modified flutter kick, when your ankle can bend, but in your case, I think extending your leg slightly will make a more efficient kick since the upper leg motion will generate a larger range of motion at the fin tip.

Tusa

 

[KoiWatcher]

Thank you all for your ideas!

I am not sure if pictures will help this discussion. I am posting these in case they do:

:tmi2:

Prosthetic Brace designed to prevent the ankle from moving to much. It is made from leather, plastic, and metal. It is only removed when sleeping. If this does not work out then surgery to fuse the foot is the next step. The foot issue is the result of nerve damage below the right knee caused by losing about one third of the right leg on the vertical (i.e not much calf muscle left, etc.).

These are the Mares Volo fins that I currently use.

I would prefer not to modify the brace since if I mess up it would be about a $2K(US) error. Prosthetics is the most expensive part of my kit...

Although I do not have easy access to a pool to provide immediate feedback I intend to test all your suggestions so please keep them coming!

- Manny

 

[John C. Ratliff]

Manny,

First, I would not try to test out the proposals above. The frog kick mentioned needs a twist of the ankle to work, as the flat part of the fin's blade must be at 90 degrees to the thrust to work. The other technique with the legs high probably won't work either, as you still need to get the fins oriented so that they "push" against the water. I developed a "scoop fin" concept, but I would not recommend that either as I don't think you should be putting pressure on the ankle at all. Wait until later, when and if the brace is not needed. You haven't said whether your brace can go in the water, but I assume it can.

There was a device called the Aqueon which was available in the 1970s, and would be perfect in your situation. I think it is still available, as The Innerspace Corporation still exists, and Dr. Gongwer may be still alive, and if so is probably in his 90s now. Here is information on the company, and contact info:

Innerspace Corporation.Thrusters,Hydraulic Motors,Screens

Innerspace Corporation.Thrusters,Hydraulic Motors,Screens

Innerspace Corporation.Thrusters,Hydraulic Motors,Screens

What is the Aqueon? It is a device that is operated my the lower legs, not the feet, for underwater propulsion:

Aqueon 1 - YouTube

Aqueon 2 - YouTube

Aqueon Sea Trials - YouTube

I believe that there is a similar concept which was recently tested by DARPA, and I'll do a search on that and post it below if I find it.

Navy SEALs Could Turn Superhuman with Pentagon's PowerSwim - Popular Mechanics
This, to me, is a copy of the Aqueon and is not that new. I have an Aqueon, and have used it. I found it somewhat cumbersome, but it does work.

http://www.youtube.com/watch?v=u5SHn0SdXjw

The DARPA PowerSwim apparently does exist.

http://en.wikipedia.org/wiki/PowerSwim

SeaRat

 

[pasley]

... The other technique with the legs high probably won't work either, as you still need to get the fins oriented so that they "push" against the water..

In the cave/wreck diver flutter kick, as I see it, the foot is used in the position in which the brace holds it (not discussing if it is a good idea medically, that subject is between the OP and his doctor). With the line from the shoulder to hip to knee forming a straight line, the legs are bent at the knee approximatly 90 degrees. The foot is held in the normal standing position, or 90 degrees to the shinn so the bottom of the foot is above and parallel to the line from the sholder to knee. This would put the fin into the proper position for swimming. Proposion is obtained by simply moving the legs at the hips a short stroke moving the foot (and fins) up and down while maintaing the knees and ankles locked at 90 degrees. I suspect this would not work well in strong currents, but SCUBA is not a speed event anyway. You just need to move the fins a little bit, a small modest flutter kick or even a side to side wiggle to move you through the water at a slow speed to facilitate SCUBA diving (go slow and see what is there, scuba is not a sprint).

 

[John C. Ratliff]

Force Vector Analysis of Frozen Foot Finning

Melvin, I'm not trying to put anything down on the finning technique for cave, wreck or other diving. But I've spent a lot of time analyzing fins, and what I see from the technique is not what you see. I see the diver using a lot of ankle flexion in order to achieve a fin blade that can push the water.

If you look at the fins in the video, and watch closely, you'll see that the angle between the foot and the leg is very low (about 10 degrees). This allows a force vector to effectively push water straight back. But if you look at the other foot, this is about the angle that the foot would be in a "frozen foot" position. In this position, the force vector straight back is very small, and it decreases as the foot descends in the kick. So I really don't think this will work well in this instance.

I am curious what you think of the Aqueon for this application. I have used the Aqueon, and it does work. There were certain aspects of it that I did not like. I still have mine, and have used components of it for a new underwater swimming technique I have developed. But that technique would not work for Manny either. The Aqueon seems to be an almost ideal solution to the frozen foot problem, as it does not rely at all on the foot, but instead on lower leg and thigh muscles. Here's the brochure for the Aqueon:

http://www.innerspacethrusters.com/Aqueon.htm

SeaRat

 

[pasley]

.... I see the diver using a lot of ankle flexion in order to achieve a fin blade that can push the water.
If you look at the fins in the video, and watch closely, you'll see that the angle between the foot and the leg is very low (about 10 degrees). This allows a force vector to effectively push water straight back. But if you look at the other foot, this is about the angle that the foot would be in a "frozen foot" position. In this position, the force vector straight back is very small, and it decreases as the foot descends in the kick. So I really don't think this will work well in this instance.

I think a very small flutter kick will move the diver just fine. The type of SCUBA I do is not about distance covered or speed, it is about the journey. I often move about my more or less wiggling my fins a bit. Moves me about the pace of a normal cruising speed fish which encourages them not to run away from me. So just moveing the fin up about 2 inches and down 2 inches would do. Actually I would suggest he forget the whole thing and just use the one fin for now or use his arms. Many of my dive buddies use only their arms and move about the reef just fine.

.... I am curious what you think of the Aqueon for this application.

SeaRat

Well, it would work I suppose. But I would not recommend it. My concerns/reservations are as follows:
1. Looks like it does a great job of moving you at a good fast speed (5.5 knots) through the water. Unfortunalty what I am looking for is to move slowly (0.1 knot or less) through the water to conserve energy and not scare away the fish. Things moving fast in the ocean are often looking for dinner. Result, the fish tend to flee from fast moving fish or divers. Slow and stealthy gets you more fish to see and you can see the small stuff too. Octopus, nudibranc, eels, Giant Kelp fish etc, stuff fast swimmiers fly right past. Example, beautiful girl swimming past a wreck in Bimini,[video=youtube;FyBiw0-jgAo]http://www.youtube.com/watch?v=FyBiw0-jgAo&feature=related[/video] but not a single fish in view. I would argue that a slow approach would have resulted in plenty of fish at this site. I also watched another video shot by a SCUBA diver at the same site in Bimini and there were plenty of fish (sorry, can't edit to add the other video ,
2. Too Bulky - We have beautiful kelp forrest here. So for my local water it would not be practicale, but may work in other areas with sandy bottoms.
3. Requires the purchase of additonal equipment when adequate propulsion can be obtained using what the OP already has, 2 fins or 1 fin or his arms or a combination there of.

I will agree that if you need to get to a dive destination and just need to cover the distance quickly (such as in a rescue or a distant dive site) then product is I imagine cheaper than a quality scooter.

 

[John C. Ratliff]

Melvin, you and I have much the same philosophy on diving. I am currently diving in a small river section of the Clackamas River called High Rocks. I look at the small things, as much of my interest is in the zoology of the river. Here are a few photographs I've taken there:

Small sculpins are very interesting, and aggressive fish. Even though small, they are very territorial. I've had them "attack" my finger when I presented it.

Sometimes I see smallmouth bass in this area. These are introduced fish, and therefore an invasive species that consumes native trout and salmon smolt.

There is a SUV on the bottom of the river where I dive, and here a sculpin has "posed" for my camera on the metal edge of the wrecked car.

I often use a new device called the SeawiscopeEY, developed by an optometrist in Hong Kong. It allows me to observe very small life close-up (and in 3-D too!).

I proposed the Aqueon as an alternative because it appears to be available, and Manny wanted to know the options. It is an option, albeit an expensive one. My evaluation of the Aqueon years ago are that it is clumsy in the water, and you have to get used to it with a number of dives. It does work, and quite well for going straight ahead. It will tangle in kelp, and at the bottom it is not so effective as you must be off the bottom for it to work. So it rather depends on the style of diving you do. Some blue water divers and free divers have taken it up, and are using it but again it needs a lot of time to get used to.

Manny, I like Melvin's thought of simply using one fin. That is the easiest, and most cost-effective means of getting wet. Your use of Mares Velo fins may be an advantage too, as they appear to bend more readily than others. You can try it on the "frozen" foot and see whether it over-taxes the foot, and whether it is effective underwater with the angles you will be using on that foot.

I have also done work on fin design, and in the 1970s developed what I call the "scoop" fin design. It is best shown rather than described:

These are rather easy to make, and can improve the angle of attack of the blade of a "frozen" foot. I will try it out today when I dive in the river. I tried to patent it in the 1980s, but it was already patented. Mares tries to use this concept, but to this day still hasn't made a fin that fully utilizes the design. The flexible inner portion of the fin provides a much better "scoop" action than any fin currently on the market. The old Mares Plana or Power Plana fins are usually available at a dive shop, used and can be then cut up to make the scoop fin. I'll post again after my dive today.

John