Folded Knees

[Ayisha]

Often, the frog kick is not intuitive to divers. They try it for a few minutes and then give up because they want to go fast. If I were to give one hint as to how to maximize your thrust and efficiency, it would be to pay attention to your big toe and the bottom of the big toe at that. You tend to use the top of your foot for propulsion when it comes to a flutter kick. The more pressure you feel on the top of your foot on the downstroke, the more thrust you are creating. For the few students who like to bicycle kick, getting them to visualize kicking a soccer ball helps immensely. When it comes to the frog kick though, you should be feeling the pressure on the bottom tips of your toes and especially your big toe. As someone said, you're trying to clap the bottoms of your feet together during the power stroke. Of course during the "cocking stage", you should feel just a tiny bit of pressure on the outer side of your foot if you're feathering your fins correctly. If you're going slow enough, you won't feel pressure anywhere as you get ready for the thrust stroke, but new divers tend to kick way too quickly. Before I get in the water with a student, we sit on a bench side by side and practice each foot so they can get an idea of the mechanics involved. Once they get the individual feet mostly right, we do both together. This way they can see how they keep the fin tips parallel to the bottom during the cocking part, and that you need to turn your calves and ankles during the power portion. I will often use my hands to mimic water pressure on the fins if it appears that they need that tactile feedback on the bench.

All that said, you really have to commit to the frog kick for a while to really get the hang of it, and then you'll never lose it. Even if you feel inept, just keep kicking and trying to figure out how to get woer through the bottom tips of your toes.

I believe that's the best explanation I've ever seen.

Now we need to see you!

 

[Scuba Client]

Some weeks ago, I woke up with a terrible back pain. I never had a back pain before and I am 52. The following night, the pain was so acute that I could not sleep. The next day, I went to see a doctor (in my previous dives, I had been very very far away from risking DCS or any other diving related disease. No deco, not even close to NDL, no rapid ascent, full respect of safet stops,…) who directed me to a physiotherapist. The first session really reduced my back pain and the therapist advised 3 sessions a week for a month. It’s been three weeks now. Just to play safe, I haven’t dived in the ocean since and just practised some exercises in the pool, fully geared. I fixed a submarine camera to film myself and my findings are: what the hell? All the experts and all the videos show divers with their knees folded. I understand that it is a must for tech divers but what about recreational? As a rec diver, my trim is better with my entire body on a straight line, my fins, calfs, thighs, aligned. I am more efficient streamlined doing flutter, frog kick rather folding my knees. And frog kick does not disturb the silt. I even do reverse without folding my knees. What is the point of folding knees as a rec diver?

Does it really matter whether your knees fold or remain straight. I see photographers stretched out with perfect buoyancy. Whatever is natural for you.

 

[John C. Ratliff]

Thanks @boulderjohn but I don't understand. Let me explain my point of view. I find folding my knees unnatural and annoying. To have a good trim, I actually place my cylinder and my weight belt high on my back. This makes sure that my head is lower than my feet. I don't see the benefit of bending my knees. I don't need it for control, it makes my finning less effective and I don't see how it would be better for my trim. When I am over sand or silt, I frog kick and it is enough not to stir the bottom.

This weight distribution could cause or exasterbate your back pain. Try the weight belt around your hips, so that it does not cause bending of your spine.

SeaRat

 

[DaniDives]

When I dive backmount, I sometimes feel a strain in my lower back during a dive. It's because my back is naturally pretty hollow and staying perfectly horizontal instead of ''sea horsing'' through the water makes my back hurt.
What helps, is ever so often, while in horizontal position, I bring my knees to my chest and hug my legs with my arms. I try to make my back round and that usually stretches out the muscles in my back.

Not really a solution but it seems to help.

 

[Ayisha]

When I dive backmount, I sometimes feel a strain in my lower back during a dive. It's because my back is naturally pretty hollow and staying perfectly horizontal instead of ''sea horsing'' through the water makes my back hurt...

That sounds painful. Are you hyperextending or arching your back instead of just stretching out?

 

[MaxTorque]

I prefer the legs pretty bent approach most of the time because i'm tall and lanky! (6.2") so with my XL fins, and perhaps arms out front i'm a pretty "long vehicle" when it comes to diving. Yes, great for low drag, but oh so un-maneouverable

In fact i just measured, stretched out in my glide position i'm 8 feet (2.45m) long. If i were any longer i'd be going "beep, beep beep" everytime i backed up

 

[DaniDives]

That sounds painful. Are you hyperextending or arching your back instead of just stretching out?

Quite painful indeed, probably unknowingly arching my back due to my natural body shape.

 

[Dody]

Ok. After a long break due to my back problems, I resumed diving last week. I purchased my own case for my iPhone and gave it to a friend to film me. The plan was to film my trim and diving positions doing frog kick, flutter kick and static. Unfortunately, it was a bad day. Washing machine at the surface, current and very strong surges pushing you laterally several meters away. So I had to kick more often than usual and doing frog kick was difficult.
Anyway, here is the footage. My own comments are that I did not realize but I fold my knees sometimes even though My resting position is with horizontal legs. And I don’t like my arms position even if I find it very comfortable to see my dive computer without moving.
Now, you can shoot .

 

[Raphus]

not bad. You bend your knees exactly like we discussed in the thread.
First let me tell you, that this is a very good basic you can build on.
After i roasted you on another thread its time to say something positive (completly different topic)
Why dont you like your arm position? Having the arms in front helps with trim. Maybe put them i bit higher, but this is mostly cosmetic

Things you can aprove:
Your trim is leg heavy. Try to move some weigth up, or get a BP/W. You can see in the video, that you start to become legy heavy when u stop finning for a moment.

Your knees hang a bit down. Hard to explain what i mean... i hope you can understand it: your body and your upper legs should be in one line. When you stop finning(between your frog kicks) your upper legs slightly point down. This leads to a leg heavy trim. Maybe fixing this issue is enough to be more in neutral trim.

After watching your video again i saw, that the tank is very low. Maybe moving the tank up for 2-3 cm will help you.
I guess this is a 12l Steel? Is it your own? if you rent them, try a long 12l tank. They give way better trim and overall weigth distribution. Except for small people, they sometimes like to small 12l tanks.

Besides the hanging knees your frog kick is fine. Maybe try to point the fins more together, so you can have more power in your kick. But this depends on the flexability of your ankles. I got problems with that aswell..
For the flutter kick you can use more of your upper legs OR bend the knees and use the modified flutter kick. But since there is current your probably want to do a real, strong flutterkick. If you use more of your upperlegs(which is a huge muscle) you can generate more thrust.

Maybe on this picture you can see what i mean, by saying body and upper legs in a line. Sorry for the bad quality, vis was very bad. Dont have another picture here

 

[Ayisha]

Ok. After a long break due to my back problems, I resumed diving last week. I purchased my own case for my iPhone and gave it to a friend to film me. The plan was to film my trim and diving positions doing frog kick, flutter kick and static. Unfortunately, it was a bad day. Washing machine at the surface, current and very strong surges pushing you laterally several meters away. So I had to kick more often than usual and doing frog kick was difficult.
Anyway, here is the footage. My own comments are that I did not realize but I fold my knees sometimes even though My resting position is with horizontal legs. And I don’t like my arms position even if I find it very comfortable to see my dive computer without moving.
Now, you can shoot .

You do bend your legs, like many of us.

You have classic rocking from top to bottom. Notice how your head to knee position swings up and down during each kick cycle? When you stop kicking, you rotate knees down. This rocking is interfering with developing a stable platform and having control over your fin movements.

The tank looks quite low. Can you reach the valve in that position? If you move some ballast up on your body, like the tank and/or some of your weight or use lighter fins, you should be less foot heavy and avoid the rocking and rotating from top to bottom.

Body positioning can help refine your position in the water as well. Stretch out, put your arms more forward, glutes tight (yup, I said it), and keep your knees up, in line with your chest.

Once you take care of the rotating, everything will become much easier.