Folded Knees

[Dody]

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?

 

[Vitesse2l]

Helicopter turns with straight legs?

Personally I find I have more control with bent knees, letting my ankles do the fine positioning work.

Especially so in tight spaces like gullies.

 

[Dody]

Helicopter turns with straight legs?

Personally I find I have more control with bent knees, letting my ankles do the fine positioning work.

Especially so in tight spaces like gullies.

Yes, you can do helicopter with (almost) straight legs. Maybe not the conventional way but for me, it has always been natural (unlike back kicking). I will try to post a video. My point is not to say that bent knees is wrong but to question the "always bend your knees" approach. Bending your knees equals to poor streamline and additional effort as it is not natural. We should do it when needed but certainly not systematically.

 

[boulderjohn]

It's not just kicking. It's trim.

The effectiveness of weight increases with its distance from the center of gravity. WIth your knees bent, the weight of your feet is the same, but it is effectively less. Couple that with your arms out in front of you, and you can adjust your trim by adjusting the position of your arms and legs.

 

[Dody]

It's not just kicking. It's trim.

The effectiveness of weight increases with its distance from the center of gravity. WIth your knees bent, the weight of your feet is the same, but it is effectively less. Couple that with your arms out in front of you, and you can adjust your trim by adjusting the position of your arms and legs.

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.

 

[lowwall]

Straight legs are fine as long as you aren't disturbing the bottom. In fact the fastest and most efficient (meters per unit of gas consumption) finning method is a fairly straight flutter kick.

But that's not saying it's the right kick for every occasion. Often we want greater precision or lower effort or to avoid disturbing sediment or kicking stuff. It's good to have several tools in the toolbox.

 

[Dody]

But I am 100% a recreational diver. Not a tech one. I don't penetrate wreck, I don't enter caves. And I avoid low vis.

 

[boulderjohn]

But I am 100% a recreational diver. Not a tech one. I don't penetrate wreck, I don't enter caves. And I avoid low vis.

Then stick your legs back and kick.

If you are actively kicking, that active kicking will compensate for trim issues.

 

[lowwall]

But I am 100% a recreational diver. Not a tech one. I don't penetrate wreck, I don't enter caves. And I avoid low vis.

Alternate kicking styles are useful for purely recreational divers. Sometimes you want to swim along the bottom to look at something, or move very slowly but still have directional control, or fit through a swimthrough with a sandy bottom.

 

[Dody]

Then stick your legs back and kick.

If you are actively kicking, that active kicking will compensate for trim issues.

I hope I don’t have trim issues . The only things that could outbalance me are my SPG, my knife dive on the inside of my right calf, my LPI, my reg and octo, but unless I am watching or during safety stop when I am upright and doing 360’s without moving my legs, I always dive horizontal.