Improving air use in currents

[Iralub]

Just a question. But what currents? Where? For example I dive the St Lawrence seaway alot. I crawl on the bottom never use my legs. Very stron currents.

Anything more than a very mild current really. I won't dive in very strong currents (at least not until I'm able to deal with them), but even a moderate current raises my air consumption to an extent that I lose my ability to sip air, making it harder to use smaller tanks than others.

Best way? Buy a DPV

Lol. Yep, that would solve the problem Unfortunately, pretty much all the diving I do requires air travel.

I'd offer one addendum however, which is that focusing on your breathing is a well-known meditation/centering technique which reduces nervous system activation and therefore, demand from the muscles. Used that way, it is certainly a way to reduce consumption.

I think that's probably the one thing that I am doing right - focusing on breathing so that my breathing is slow and deep with very long exhales. I think it keeps me quite relaxed. Yoga training helps there. I think I lose some of that with greater physical exertion if swimming quickly or against a current. May be part of what's contributing to air use spike.

 

[TSandM]

Since you say your gas consumption is very good when diving quietly, I will assume that you have already got a pretty nice, rhythmic breathing pattern.

That said, the amount you have to breathe is set by the CO2 you generate. CO2 production is increased by any increase in metabolism, so muscle activity will mandate moving more volume through the lungs. Swimming into resistance (current or flow) requires the diver to work harder than just floating or swimming slowly, so it will ALWAYS increase gas consumption -- if it doesn't, you are at risk for CO2 retention, with the consequence headaches, nausea, and worse.

So, how can one minimize the amount of increased muscle activity when swimming against current? Bob nailed a big one, which is trim. The smaller the cross-section you present to the water, the less resistance against which you must swim. Proper trim is a combination of body posture and static weighting, and with a single tank, it is almost always possible to adjust the two to gain horizontal trim. HERE is a good article on achieving good trim.

In addition, using a propulsion technique appropriate for the situation is important. Several people above have recommended the frog kick; although it is the primary kick I use, it is NOT ideal for battling current, because it incorporates a glide phase, which is a period where you are not driving forward and are therefore losing momentum (or even moving backwards!). Much better in current is a kick technique that provides continuous forward force, which is some sort of flutter kick. Flutter, done with a long leg and from the hip, is a difficult kick to do with much force, because it is generated by short muscles with little mechanical advantage across the joints you are moving. Modified flutter, done with a. flat body and bent knees, is much better, using long muscles with good mechanical advantage, and furthermore, muscles most of us use a lot, which are therefore fairly strong to begin with. HERE is a good vide of the modified flutter kick -- note the long, flat body, and minimal movement of the knees.

Finally, it may be necessary to look at the equipment you are using. Soft fins, although they minimize the muscle effort needed to move them, also do not transmit much of the force from your muscles to the water. Therefore, they tend to require a rapid kick cycle, which ends up being a lot of work in total. (Much like pedaling a bicycle in very low gear.) Very stiff fins efficiently transfer force, but require significant strength to use. Finding a fin that works for you can be quite individual, but in general, you probably want something that has some stiffness (paddle rather than split) but isn't tech diver stiff.

And remember, too, that you DID manage bigger tanks, even if they were more work, so that is always an option.

 

[Eric Sedletzky]

No, it is an anecdote. Similarly it is also anecdotal that I know divers who smoke like chimneys who sip air and can outlast anyone else I know on any given cylinder size.

---------- Post added November 10th, 2014 at 12:48 PM ----------



Try frog kicking, there are lots of video guides on doing it, here's just one;

[video=youtube;DoJ2BhS6Bis]https://www.youtube.com/watch?v=DoJ2BhS6Bis[/video]

This is a true frog kick. Pulling your legs up, flaring your legs and fins out sideways, then turning your fins inward and pushing back and together so that when your are finished with the cycle your legs are straight back behind you, this is a frog kick. Reload and repeat. I use this exact kick a lot.
The kick that the some call a frog kick where your feet are bent up at a 45 to 90 degree angle and your feet are sculling is not a frog kick.
They need to term it an anti silting kick or a cave kick or something else, but it's not a frog kick. Newbies may get confused.

 

[flots am]

Because my diving experience is so much more pleasant with the small tanks, I'd like to use smaller tanks in the future when they are available, however I am worried about limiting the group's bottom time if I am the first to get to the turn around air point. In normal conditions it doesn't seem to be an issue, but as soon as there is a current, my air use goes up pretty dramatically.

The best way would be to avoid diving into the current. Humans are terrible at it.

Buy a scooter or do a drift dive or whatever it takes so that you aren't fining against a lot of current.

If you have to swim against the current, you're going to use more air. That's just how it is.

There are things you can to to make it "less bad" but nothing that will make it "good".

flots

 

[kr2y5]

During my first trip to Cozumel, I noticed that certain folks were particularly better at dealing with current on drift dives. In this case, it was moving more slowly, while I was being blown forward with current all the time, and struggling to stay back with the group, but I suspect it works both ways. As far as I could tell, this had something to do with their ability to take advantage of the topography of the bottom, the fact that the speed of the current is not the same in all places, or at least that's the only explanation I could think of. I'm sure someone here can explain this better.

 

[jdg]

If you are less than 130 feet and not in a protected area crawl arms are smaller than legs, They use less o2. If ocean diving stay as close to the wall as you can go with the flow. Drift diving should pick you up near the end of your dive. You need to do a river dive. and crawl on the bottom

---------- Post added November 17th, 2014 at 12:32 AM ----------

crazy when you have a dive in 3-4 knots you don't want a snorkel on your face. Feels like a wall coming at you. You need to get almost neutral.then leap frog on the bottom/ use the fins to kick in.

 

[Iralub]

So, how can one minimize the amount of increased muscle activity when swimming against current? Bob nailed a big one, which is trim. The smaller the cross-section you present to the water, the less resistance against which you must swim. Proper trim is a combination of body posture and static weighting, and with a single tank, it is almost always possible to adjust the two to gain horizontal trim. HERE is a good article on achieving good trim.

What an excellent article! Thank you. I can see that I'm doing about three quarters of that wrong, which is great as it gives me things to work on! The dropping knees and head are things that I do constantly. It also looks like my positioning of the arms, crossed on my chest, may be contributing to the issue - it does the opposite of the raising of upper back/head that the article talks about and instead brings them forward.

Lots of things to work on there

Flutter, done with a long leg and from the hip, is a difficult kick to do with much force, because it is generated by short muscles with little mechanical advantage across the joints you are moving. Modified flutter, done with a. flat body and bent knees, is much better, using long muscles with good mechanical advantage, and furthermore, muscles most of us use a lot, which are therefore fairly strong to begin with. HERE is a good video of the modified flutter kick -- note the long, flat body, and minimal movement of the knees.

Aha! I've been using the flutter kick with long leg. I'll work on the modified version. Thank you very much

Finally, it may be necessary to look at the equipment you are using. Soft fins, although they minimize the muscle effort needed to move them, also do not transmit much of the force from your muscles to the water. Therefore, they tend to require a rapid kick cycle, which ends up being a lot of work in total. (Much like pedaling a bicycle in very low gear.) Very stiff fins efficiently transfer force, but require significant strength to use. Finding a fin that works for you can be quite individual, but in general, you probably want something that has some stiffness (paddle rather than split) but isn't tech diver stiff.

Fins have been quite problematic for me. I've been diving with hire fins which, in my size (I'm about women's 4.5), have been pretty crappy plastic children's fins. Or fins a couple of sizes too big. I wasn't able to find decent open heel fins that work for my size, so I'm getting full foot seawing novas that I'll wear with dive boots (full foot with boot is the only option I have been able to find to get a decent fin to fit). With a bit of luck, it may help.


Thanks so much for the advice. It's extremely useful and heaps of things for me to work on, which was the point of asking for advice

 

[Iralub]

OK, so after the last diving trip:

1. Getting better fins definitely helped a lot. I was using seawing novas and could kick against currents that previously will have been impossible for me. I still had trouble with strong currents, but they were the same ones that many others had trouble with, so not feeling too bad about that. I'm still getting used to the fins for frog kicks (they seem to require slightly different movement to normal paddles), but I was getting excellent thrust with flutter kick, even with my short, underpowered legs. Win!

2. I was diving on a smaller 10L tank, with everyone else on 12L and was outlasting most people, even though they were on bigger tanks. My air use was never a limitation to anyone else in the group, which was great. That's not to say that there's not room for improvement.

3. My trim however was not great and requires much more work. I had a strong tendency towards a head up position and dropping my knees (although fins are slightly positive). I have always used (hire) jacket type bcds but for some reason found the particular one I was using especially uncomfortable and hard to get used to. May have to start thinking about getting my own bcd so at least it will respond consistently as I try to improve my trim.

 

[dumpsterDiver]

If you are really worried about getting your trim worked out, i think it is super important to buy your own BC, configure it the way you want and then practice with it. Also, to get really good trim, you are going to want to TRY to use the same tank. if you are constantly switching tank size and maybe steel or aluminum, then you will constantly be playing with your ballast- adding- subtracting and moving it around. Eventually you would become a great diver, but it would probably not be much fun for the first 100 or 200 dives while you figure it out.

 

[Iralub]

If you are really worried about getting your trim worked out, i think it is super important to buy your own BC, configure it the way you want and then practice with it. Also, to get really good trim, you are going to want to TRY to use the same tank...

Thanks DumpsterDiver. Yeah, I think I'll need to start looking for my own bc, although it will probably take a while as it will need to fit a very small person and be light enough for travel. I'm "worried" about the trim in the sense that I'm hoping to make a natural disadvantage (small size and lack of power) into either an advantage in terms of air use or at least offset it by improving my motion in the water.

Tanks is a bit harder because all the diving I do requires air travel, so I can't carry my own tank. A 10L Al tank seems to work best for me - enough air and much easier to deal with than 12L, but it seems most ops carry the AL80 and don't always have 10L.