Hi again "dinghar"!
There was one glaring omission from the drills I commented on, and I had a sleepless night thinking about it. Felt like the old famous composer who used to have his specs and music manuscript by his bedside in case he had any bright ideas in the night, and needed to get them down on paper quickly while the ideas were still fresh! I nearly got up and switched my PC on to rectify the omission!
I was busy in my first post thinking about the drills on the DVD I mentioned, but before coming across that, my main source was Maglischo's "Swimming Fastest" (now a bit "dated") and I avidly read much of the stuff on technique and tried to put it into practice - well as far as I could anyway! This "omission" of mine was the first real fly drill that I ever used and is basically fundamental to swimming the full stroke, and helps comprehend the part that body undulation plays.
"SolarEnergy" calls it the "0-arm" fly drill, but that name suggests the arms play no part in the action - which is not strictly true because they do still have a minor role to perform! I just think of it as practice for the major kick of the full stroke. ...
( The minor kick comprises the leg upbeat done as the arms recover over the water, and its downbeat as the arms enter the water so as to offset the pushing drag of the arms which have just entered. There is very little place for any body undulation in this minor kick - it would badly destroy body balance. By contrast, the major kick, is of much bigger amplitude and is the kick where undulation plays a principal part, it follows smoothly on from the downbeat of that first minor kick done after the arms entered the water following recovery. )
... It starts by getting into a prone position on the surface (i.e. on the tum!), with legs together and arms outstretched ahead shoulder width apart. (As an aside I need to tell you that whatever part of the body is foremost - head or arms - that is the part which must be used to start an undulation, by pressing down slightly into the water to get a very "temporary anchor", to help "lever" the next following part of the body upwards!) Press the arms and head as one unit down slightly - I often say this is a bit like "nodding" ones head into the water as if "heading" a soft ball. You then proceed to effectively "hump the back" starting from the shoulders or shoulder blades area, progressively working down the spine in a rolling action (you don't need to do it fast!). Your head which should have been kept level with the arms so far, should as your hips reach the highest point of the action, be raised slightly to look ahead - i will say a bit more about this later!!!! You should find the head and arms have descended to a lower level and your back, then legs, have "curled" upwards a bit, so that your feet end up near the surface - this is the upbeat! Don't let the lower legs curl back more than the tiniest bit (sometimes called "displaying the dolphin's fluke!"), otherwise they will cause drag! (if you were doing the full stroke, your upper arms would be at 10 o'clock and 2 o'clock, with the forearms dangling downwards. Your body position would be similar to that of a scorpion - so I call this the "scorpion position"). You should have noticed the floor tiles move past quite a bit as the result of this upbeat - the more deliberate and "fish-like" you make the rolling action of the back - the more distance forward the upbeat should provide. Don't "do your back in" by putting too much muscular effort into the action - take care of the back and you could still be doing this sort of stuff at my age!
You are now ready to do the powerful downbeat if doing the full stroke, but for the drill just make it a steady action. (You can actually get away with doing it slowly and see how far you move!) With the feet up near the surface you throw your thighs forward at a moderate angle (if you overdo it, you create too much drag!), and follow that by beginning to flick the lower legs down. As the lower legs flick down the upper legs (thighs) move upwards - all done in a flowing smooth "re-bounding" action. That downbeat (which can almost be thought of as starting with a quick tensing of the abs if you want to add a bit of power to things) should bring the upper part of your body up to the surface again, and at that point you should do a quick little sideways scull of the hands to create another "momentary anchor", enabling your arms to help in getting your mouth above the water for inhalation. At all other times, as SS advise, you should be exhaling into the water when your face is in the water! Well that's it - I hope it makes sense to you -its much easier to do than describe!
If you refer back to my earlier post in which I commented on the "Reverse body dolphin done on the surface with arms at the sides", I mentioned there, that as the lower part of the body undulated and the lower legs flicked up towards the ceiling - your head would break the surface and you should be able to see a small surface wave coming towards your head - Maglischo's "reverse body wave" possibly helping propulsion. Well that same business applies in this drill, and is the reason you need to raise your head slightly as the hips reach the highest point in the upward undulation that is the upbeat. I reckon that at that stage you have created a sort of rolling wedge of water - an underwater "reverse body wave" - that is pushing towards the front of your body! Well and good! - give the wave something to push against - the back of your head!!! So, that should help forward propulsion!
If you're interested in doing a bit more, then by adding a bit of the full stroke action using just one arm while holding the other outstretched ahead, you can get a lot of pleasure. ("SolarEnergy" calls it the 1-arm fly drill!) It is probable easier doing almost a front crawl arm action for that - don't hurry the downsweep, do an almost semi-circular pull with forearm pointing to the bottom, to bring the upper arm close to the ribs, then tilt your body away from the stroking arm as you do the upsweep mainly with the forearm - inhale with your head turned to the side during the strong upsweep! (I prefer to look more towards the front with my head tilted a bit, 'cos that is closer to the front breathing position of the full stroke. The arm upsweep will bring your head sufficiently high to permit doing that.)I've included below an extract from one of "SolarEnergy"'s old posts, with 2 clips of him showing how to do his 0-arm drill (+ a bit of 1-arm) : -
... On the first clip, you see a slow execution [OF 0-ARM] ending with the integration of one-arm. On the second clip, you see a fast execution of the [0-ARM] drill that resulted in a 50m kick done in 41sec flat....http://www.youtube.com/watch?v=-p15jmC95ZIhttp://www.youtube.com/watch?v=pnxvdnu3Bn0
Whatever you do in the fly drills, or in the full stroke if you try that - aim to make all movements as "fish-like" as possible - then you won't go far wrong!
Best wishes! _Bye / Don