Hey SBer's,
My last two dives I spent working on DIR style kicking and found that, yes, they do reduce silt kick up significantly. I was able to reduce my silt to zero even when cruising inches from the ground.
I am curious on a few things though:
1) Why do people use the frog kick even when traversing open water well above the bottom? As a former competitive swimmer, frog kick is the most inefficient kick of all three because of the repeated fast acceleration and fast deceleration. Even the DIR style flutter kick with 90* bent knees is much more efficient.
Not just in open water but through kelp forests too. I watched as both of my experienced buddies this weekend frog kick through kelp forests and couldn't help but notice that if for instance kelp snagged on their tanks, the fast acceleration from frog kick would pull them upwards, or otherwise worsen things by pulling tighter. Whereas when I switched to DIR flutter, if something snagged, it would be gradual and I could quickly untangle without as much thrashing around as frog produces.
I can see frog kick's utility when maneuvering in smaller areas but not for longer distance travel or even cruising at depth.
2) Again, as a competitive swimmer, frog kick is really hard on the knees. Those of us who used to race the stroke can attest that long workouts of breaststroke did not leave us with happy knees. While I don't have bad knees yet, I'm expecting some in a couple of years due to rowing injuries. Does DIR actually address this or is it just a HTFU issue for them?
If you do have bad knees, how do deal with frog kick? Or do you just not do it?
In the end, I just don't see the heavy emphasis on DIR frog kick being correct or necessary. Yes, it is a kick that has uses and should be used should the situation call for it. But to use it as a primary mode of movement? It seems impractical.
I have similar issues to you; I often see videos of DIR-trained local divers using frog kicks to the exclusion of all others, when silting isn't an issue. The use of regular type kicks wasn't really discussed in Fundies class (it apparently being assumed that you already know them), and the whole emphasis of Fundies was to learn the bent-knee kicks. I had a considerable discussion with my Fundies instructor about the use of them, and whether in fact bent knee kicks (frog and flutter) as taught in DIR classes are a more _efficient_ propulsion method than the ones we were taught as swimmers. I suggested that you were raising your feet/legs out of the lower drag 'V' formed by your head/body when doing kicks bent leg, thus increasing drag. Of course, if you're routinely using doubles with/without a stage, your streamlining sucks regardless. My DIR-style kicks are still quite poor so I'm withholding final judgement, but my current attitude is that until I see/hear of free divers or Navy Seals using 90 deg. bent knee kicks because they're more efficient, I'll continue to use my regular swimming flutter kicks for transits. Note that this requires you to have better aerobic condition and leg strength than the typical diver, but I imagine both of us do.
Many of the technical dives done locally (Monterey/Carmel) are done from boats where the 'transit' involves dropping down the anchor/drop line, so being efficient while transiting isn't much of an issue. Many DIR divers use scooters when they have to transit any distance, something which I'm not interested in. Where I think the DIR-type kicks are very useful is in maneuvering in tight areas, especially if you're a photographer who needs to hold position sans hands. Most of these kicks require use of a stiff paddle fin to do well (or in some cases, at all). They are very useful kicks, but the average diver doesn't _need_ to know how to do them to dive successfully. While the class mentions that the DIR-style kicks are tools to use when called for, I suspect that many divers who take Fundies don't have good enough swimming skills to evaluate when the use of these kicks is/is not more efficient. From my observation many DIR divers (and divers in general) are relatively poor swimmers, who don't know or aren't very good at the standard swimming strokes; just look at the number of divers who bicycle kick while trying to do a standard flutter.
For me, I still prefer to use my split fins/flutter kick for a dive that involves a long transit (most shore dives I do locally), as opposed to a boat dive where transit is irrelevant but maneuverability more important, where my jet fins come into their own as I amble around. This sort of situational fin choice isn't DIR, but works best for me. Not silting up the bottom in open water locally while doing a standard flutter kick is just a matter of staying far enough off it; when I need/want to drop down close I use a more appropriate, slower kick.
Many divers, photographers especially, prefer to cruise slowly over a smaller area, looking at every macro aspect - most of the time that isn't for me, as part of the enjoyment I derive from diving is due to the sheer pleasure of exercising while swimming. While having a good SAC rate is important, I'm not trying to extend my gas to the exclusion of everything else. And although swimming slowly/using DIR frog/flutter kicks gives you a low SAC rate because you're not using the big leg muscles as much, so does any kick involving small leg movements.
Having the lowest possible SAC rate is important when you're piddling around in a small area, but having a higher SAC rate while moving considerably faster may well be more efficient while transiting. For instance, swimming out to the Barge at the Breakwater on two consecutive dives, on the first (while taking our time owing to one of my buddies hauling a large video camera) I used 700 PSI in the 14 minute transit, for an average DAC rate of 50 PSI/min.
On the next dive done solo (exactly the same route, same tank size), I swam out to the Barge much faster, taking only 7 minutes and using 500 PSI, for a DAC rate of just over 71 PSI/min. So even though my SAC/DAC was worse on this second dive my efficiency was better, as I had 200 more PSI available at the barge to spend piddling around there (actually 400 PSI, assuming the same advantage going back, and not exceeding min gas limits). It's the difference between best endurance and best range, which (perhaps) many newer DIR divers don't understand. After all, your car uses the least amount of fuel idling while sitting still, but your MPG is zero.
On your other point about knees and the like, I don't have that problem but I do have a bad hip and old groin muscle tear, and doing a standard frog kick for more than 5 minutes or so now is painful. I was pleasantly surprised during Fundies class to find that doing DIR-style frog and modified frog kicks didn't cause me any pain. Whether that would hold true for your knees I couldn't say, but there does seem to be a considerable difference in which parts of your body are being stressed.
Bottom, line, do take a Fundies class when you're ready, but maintain your skepticism about DIR frog/flutter kicks being the answer to Life, the Universe and Everything until you've determined for yourself if they're the most _efficient_ kicks, as well as having the lowest SAC. To me, that's what being a 'thinking diver' is all about.
Guy
