cmufieldhockey8
Contributor
I get sooo much more power out of the extension that I do it whenever I have the space in the cave.
Frog kick mechanics
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parabuzzle
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I do an extension usually just because it seems more efficient. The less work you do (less exertion) the less air you will use usually. I find the smallest amount of extension will increase the glide time a lot as long as your trim is good and drag is to a minimum. This will reduce your kick cycle and I find this equals a drop in total exertion required to cover the same ground as the non extended kicks. Thus reducing gas consumption and giving you more time to putz around in the cave. And let's face it, the more time to look at the wet rocks, the better 
Now, I agree that if you want to use the extension you really need to make sure your watching where your fin tips are going through the cycle and ensure your water turbulence goes straight back and maybe slightly up. But once you get it right and get the feel for it, its a great skill to have.
One more side note, I am an NACD/CDS guy and the philosophy is more of a "Whatever Works" in my opinion. These guys essentially invented the sport and rules around it (Sheck Exley, Lamar Hires, Wes Skiles, Forrest Wilson, etc). They invented the basics and even the gear (Hires and Wilson, etc). The impression I get is really that of the WW concept and I think that's really born out of the innovative things that they HAD to do back in the 60's and 70's. Rigid basics are good but as a technical diver, it is really your responsibility (in the spirit of these guys) to keep evaluating yourself and your techniques as well innovating and trying new things to attempt to better yourself as a technical diver and, perhaps, the community. Who knows you may be the person that comes up with a style of kick that reduces exertion by 50% and helps extend that unmapped section of a cave because of it!
Now, I agree that if you want to use the extension you really need to make sure your watching where your fin tips are going through the cycle and ensure your water turbulence goes straight back and maybe slightly up. But once you get it right and get the feel for it, its a great skill to have.
One more side note, I am an NACD/CDS guy and the philosophy is more of a "Whatever Works" in my opinion. These guys essentially invented the sport and rules around it (Sheck Exley, Lamar Hires, Wes Skiles, Forrest Wilson, etc). They invented the basics and even the gear (Hires and Wilson, etc). The impression I get is really that of the WW concept and I think that's really born out of the innovative things that they HAD to do back in the 60's and 70's. Rigid basics are good but as a technical diver, it is really your responsibility (in the spirit of these guys) to keep evaluating yourself and your techniques as well innovating and trying new things to attempt to better yourself as a technical diver and, perhaps, the community. Who knows you may be the person that comes up with a style of kick that reduces exertion by 50% and helps extend that unmapped section of a cave because of it!
You need to remember that the kicks learned during your GUE Fundamentals class were exactly that - fundamental. All of those kicks may be modified or extended in some way for power, speed, or finesse.
There is no such thing as a one-size-fits-all perfect kick. Take a look at the members of a gym on any given day and you will see a wide range of anthropometrical characteristics. When starting out as cave divers, lithe endurance athletes will generally prefer a quick light fin stroke while powerfully built divers often will prefer a more open push which will allow greater advance with less finning.
With experience, cave divers will improve hydrodynamics and velocity while conserving energy by balancing the choice of stroke, the amplitude or width of the stroke, with the rhythm or frequency of the stroke. Experience will place the diver in environments in which a perfect modified frog kick will create vortex after vortex along the ceiling which may find their way to the floor or the perfect frog kick for open water will stir up silt 25 feet behind the diver. Efficiency and modifications for all kicks and athletic abilities are learned over time.
The most efficient technique for each stroke is determined by:
1) Characteristics of the fin
2) Technical ability of the diver
3) Anthropometrical characteristics of the diver
4) Quality of training
5) Quality of the water (fresh or salt)
6) Characteristics of the environment
Fin design determines what strokes will give us the most power. A loose foot pocket is one of the greatest causes of lack of efficiency. This is due to a loss of power through reduced transmission of energy from foot to blade. The softness or hardness of the foot pocket and fin also come into play. The softer the foot pocket, the more dispersion of energy due to elastic deformation. A lack of lateral railing or strengthening spars that only run partially down the blade of the fin can be responsible for as much as 10% to 20% reduction in efficiency due to the dispersion of displaced water. When performing flutter or modified flutter kicks the lack of lateral rails could cause a lateral skid and a valgus foot position as blades turn inward.
The technical ability of the diver to execute the kick is usually the focus of training. In cave diving, the best technique usually will create the least amount of motion and will be the most streamlined. For example, that may mean that a diver's knees are together for a modified flutter kick with little up and down movement of the thighs. For the frog kick, it is often best to isolate thigh movement scissoring back and forth which may create an up and down disturbance of the water as the thighs move together. Eliminating an extension during the frog kick reduces superfluous motion that may create a vortex on the floor or ceiling. The ideal frog kick will send water back, but not high and back or low and back. Generally speaking, high is better than low, but low flow caves with precious ceiling decorations and bacterial sediments on the ceilings and walls are best not disturbed.
When it comes to power kicks or speed kicks in caves, divers tend to discover what kick works best for them based upon their size, strength, endurance, leg length and the strength of their ankles. This comes from experience and is not always discovered during class. You may also have the same speed and power in a flutter or frog kick, but you may have a better consumption rate with one vs. the other.
The quality of training and the attention paid to stroke technique and understanding the mechanics of swimming that are best for you is also important. Not all scuba instructors are educated in the fine points of swimming. Those with swim team coaching, competitive swimming, or swimming instructor backgrounds often are a wealth of information and know what to look for in divers to help them improve their abilities.
Fresh and salt water have different densities which not only affect buoyancy, but different resistance to hydrostatic force. You may notice an incredibly subtle, but different "feel" to your kicks.
Lastly, the environment will determine how powerfully or carefully you may fin.
Personally, I try just to scull with my ankles most of the time when cave diving so I'm either using a powerful or gentle modified frog kick. In very high flow, I will add an extension into my frog kick or do a cave flutter kick for power and speed. I tend to be able to do this better by putting my knees together locking my thighs pointing my toes and kicking hard. I find that the quality of the kick decreased for me if my knees aren't together. Diving in the Bahamas really taught me to make flutter kicks and shuffle kicks part of my arsenal.
There is no such thing as a one-size-fits-all perfect kick. Take a look at the members of a gym on any given day and you will see a wide range of anthropometrical characteristics. When starting out as cave divers, lithe endurance athletes will generally prefer a quick light fin stroke while powerfully built divers often will prefer a more open push which will allow greater advance with less finning.
With experience, cave divers will improve hydrodynamics and velocity while conserving energy by balancing the choice of stroke, the amplitude or width of the stroke, with the rhythm or frequency of the stroke. Experience will place the diver in environments in which a perfect modified frog kick will create vortex after vortex along the ceiling which may find their way to the floor or the perfect frog kick for open water will stir up silt 25 feet behind the diver. Efficiency and modifications for all kicks and athletic abilities are learned over time.
The most efficient technique for each stroke is determined by:
1) Characteristics of the fin
2) Technical ability of the diver
3) Anthropometrical characteristics of the diver
4) Quality of training
5) Quality of the water (fresh or salt)
6) Characteristics of the environment
Fin design determines what strokes will give us the most power. A loose foot pocket is one of the greatest causes of lack of efficiency. This is due to a loss of power through reduced transmission of energy from foot to blade. The softness or hardness of the foot pocket and fin also come into play. The softer the foot pocket, the more dispersion of energy due to elastic deformation. A lack of lateral railing or strengthening spars that only run partially down the blade of the fin can be responsible for as much as 10% to 20% reduction in efficiency due to the dispersion of displaced water. When performing flutter or modified flutter kicks the lack of lateral rails could cause a lateral skid and a valgus foot position as blades turn inward.
The technical ability of the diver to execute the kick is usually the focus of training. In cave diving, the best technique usually will create the least amount of motion and will be the most streamlined. For example, that may mean that a diver's knees are together for a modified flutter kick with little up and down movement of the thighs. For the frog kick, it is often best to isolate thigh movement scissoring back and forth which may create an up and down disturbance of the water as the thighs move together. Eliminating an extension during the frog kick reduces superfluous motion that may create a vortex on the floor or ceiling. The ideal frog kick will send water back, but not high and back or low and back. Generally speaking, high is better than low, but low flow caves with precious ceiling decorations and bacterial sediments on the ceilings and walls are best not disturbed.
When it comes to power kicks or speed kicks in caves, divers tend to discover what kick works best for them based upon their size, strength, endurance, leg length and the strength of their ankles. This comes from experience and is not always discovered during class. You may also have the same speed and power in a flutter or frog kick, but you may have a better consumption rate with one vs. the other.
The quality of training and the attention paid to stroke technique and understanding the mechanics of swimming that are best for you is also important. Not all scuba instructors are educated in the fine points of swimming. Those with swim team coaching, competitive swimming, or swimming instructor backgrounds often are a wealth of information and know what to look for in divers to help them improve their abilities.
Fresh and salt water have different densities which not only affect buoyancy, but different resistance to hydrostatic force. You may notice an incredibly subtle, but different "feel" to your kicks.
Lastly, the environment will determine how powerfully or carefully you may fin.
Personally, I try just to scull with my ankles most of the time when cave diving so I'm either using a powerful or gentle modified frog kick. In very high flow, I will add an extension into my frog kick or do a cave flutter kick for power and speed. I tend to be able to do this better by putting my knees together locking my thighs pointing my toes and kicking hard. I find that the quality of the kick decreased for me if my knees aren't together. Diving in the Bahamas really taught me to make flutter kicks and shuffle kicks part of my arsenal.
OP
Oh, I certainly agree about the foot pocket issue! It's just plain maddening if your fins aren't solidly attached to your feet -- the lost energy is extremely clear. I find the same thing with fins that are overly flexible.
I've also found that a good cave flutter for me depends on eliminating thigh motion. Man, do my butt muscles get sore doing that!
I have, since the class in August, found myself using the flutter more and more, and I have noticed that I easily outswim my husband in flow that way.
I've also found that a good cave flutter for me depends on eliminating thigh motion. Man, do my butt muscles get sore doing that!
I have, since the class in August, found myself using the flutter more and more, and I have noticed that I easily outswim my husband in flow that way.
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