Sidemount Tanks with Top Mounted Stages interfering with frog kick

[JamesK]

Thanks is for the tip. I will try bottom first!

 

[Karl_H]

Two reasons. First, using the hips means you are using larger muscles. Larger muscles require more oxygen when used so you increase your RMV. My RMV is .35-.4 because I don't use my hips. Second, when you use the hips you spread your legs out farther. This creates drag in the water and slows your movement down. Using just your calves and ankles minimizes drag and allows you to cover more distance. Just using my calves and ankles I can swim at a pace of about 65 fpm and against strong flow. With the right fins, swimming with just the calves and ankles can be quite powerful.

Hi Rob,

It good to get your take on and I don't want to say you're wrong but I don't know if the facts add up on this one?

Normal RMV rates are mainly controlled by CO2 and lung volume, not O2 requirements - in fact any kind of diving (unless you're using some kind of hypoxic shallow trimix) will leave you in a state of internal hypoxia due to the increased partial pressure of O2 in the breathing gas? Larger muscles tend to work more efficiently, hence less CO2 per unit power - so this actually works in reverse?

A well done frog kick has the power stroke as the diver is almost stationary (or moving very slow) at the point of the power 'hit' so the additional drag from the hips (which are pretty much covered by the tank slipstream anyway?) shouldn't have much impact - the only way I can see drag becoming an issue is if someone is finning too regularly due to lower power strokes? Although thats more an inefficiency in technique than because the hips are used?

I'm all in favor of modified frog kicks (as you described in the original post) but full frog kicks can be required and do use the hips. Almost all the drag comes from the fins being out of position?

Just my thoughts (in peace!) :-/

Karl

 

[Dive-aholic]

While CO2 and lung volume are big factors in breathing rate, muscle use is also a factor. It's not as much of a factor, but it does play a role.It may only mean the difference a .1 RMV, but that can add up over an hour long dive at 3 ata.

You're right, your hips are covered by the tanks, but your fins aren't, and the added movement of your fins when using your hips will create more drag that the smaller fin movements created by doing a modified frog kick.

I've done both regular frog kicks and modified frog kicks. I can actually get much more distance from modified frog kicks even in high flow caves. The drag takes a lot more out of your forward moment than you might think.