Back in 1998, I had spoken with several divers who had competed in Sardinia. I was asking about deep equalizing techniques. Several divers used a 'mouthfill' method which involved filling the mouth up each time you tried to equalize. Among those divers was Australian Tony Heugh, who explained to me how he would fill his mouth up with air each time he tried to equalize.
I was doing a chi-gong standing meditation around October of '98 when an idea popped in my mind. All of my ideas come to me during chi-gong standing meditation (the fluid goggle idea came during such a meditation).
It occurred to me that one might benefit by filling the mouth only ONCE, at the maximum depth which one could fill the cheeks completely. When this idea came to me, it was not at all obvious that a single mouthfill method would have any advantage over current techniques, including the 'repeated mouthfill' method. I tried to do many calculations but at the time I didn't understand enough about the various airspaces to conclusively decide whether or not the technique would be helpful.
Further, I was uncertain if it was even possible to trap air in the mouth and equalize with the throat still closed (epiglottis closed). I didn't understand enough about the anatomy of the nose and throat to figure that out.
Eventually I began doing experiments, and at first it seemed that it was impossible to do the standard frenzel with the throat closed. However, after many hours of practice, I found that it was in fact possible, but it was simply a reflex to raise the soft palate whenever you close your epiglottis. Eventually I 'de-trained' that reflex after many hours of practice. At the time I had never heard of anyone else spending 3+ hours a day on the couch trying to detrain a throat reflex, so I began to wonder if anyone had done this before. I thought that if this technique really did offer an advantage, then surely someone must have thought of it before. The fact that I had never heard of anyone doing a single mouthfill made me think that the technique could not possibly offer any advantage over existing techniques.
Mayol himself described the extreme effort it would take to 'force' air into his ears while trying to equalize head-down on his 80m+ dives. This alone told me that he had not used a single-mouthfill technique.
Anyway, it was not until early 1999 that I took a trip to Alouette lake to test out the technique for real. At first I tried filling my mouth at the surface and then doing negatives. I quickly found out that performing the technique in the water, with so many other things to think about, was not easy, and I kept losing my mouthfill or my soft palate would lock up. Eventually I managed to do it on negative dives.
Then I tried a dive where I filled my mouth up at about 10m and continued down to 22m. I was amazed that when I got to the bottom, my mouth was still full of air. I sensed that the technique might actually have some merit after all. This confused me even more, because by now (several months later) I had spoken to many more divers about equalizing techniques and still none had ever mentioned a 'single-mouthfill' technique although many had spoken about repeated mouthfills or reverse packing, diaphragmatic frenzel, continuous valsalva, saline equalizing, etc...
I competed in Nice, France in 2000 and did several 67m dives, but I didn't feel the need to do the mouthfill and instead relied on the diaphragmatic frenzel, which I found I could still do with little difficulty at 65m+. After the competition was over I had a long talk with Herbert Nitsch about equalizing techniques. I explained my 'single-mouthfill' technique to him, even though I didn't actually use it at the competition. He told me that he had tried the repeated mouthfill and reverse packing methods before, but he had not heard of the single mouthfill -- and like most people, the idea that a single mouthfill at 30m could last you until 100m+ seemed ridiculous.
It was not until I was training for the CW record in 2001 that I found out how much energy I saved by filling my mouth at 30m and then never doing any effort until the bottom. It allowed me to sleep during the descent, and I saved a ton of energy. The descent became a joke. The ascent was the whole dive.
It was during that time, June 2001, that Herbert was training for the CW record in the Austrian lake. I had been chatting over e-mail about how much energy I was saving by doing the single-mouthfill. Unfortunately it is so hard to learn that Herbert hadn't been able to do it yet. Equalizing was his limit and although he was aiming for 82m, he ended up with a 72m record.
Two months later I did my personal best of 88m and found that even after equalizing at the bottom I found that my mouth still had air left for more equalizations, ultimate proof, for me, that this technique did offer an advantage.
I did the 82m record and then eventually decided not to go to Ibiza. However, when Herbert congratulated me on my 82m record I spent some more time chatting with him about the single-mouthfill method, and I told Herbert not to give up. During training in Ibiza he finally figured it out and did 89m, followed by 86m during the competition, breaking my short-lived 82m dive which had only passed 'official' ratification the night before.
At that point I had some mixed emotions. I wondered about my philosophy of sharing techniques. The selfish part of me said that if I never shared techniques, perhaps I would still hold the record! Then, I figured that I would get good karma by sharing and good things would happen eventually.
I had also been chatting with Patrick Musimu. Early the next year (2002) he was trying for the CW record with the IAFD. He had a personal best of 79m and was limited by equalizing. Pipin was trying to teach Patrick the sinus flooding technique, which Patrick tried, but he found he got very dizzy and disoriented, since he was not on a sled. I kept e-mailing Patrick during the days before the record, offering more detailed explanations than are given in the document on my website. Patrick then did his 87m record with ease, and told me that three days before, he had gone out into shallow water with Isabel and finally figured out how to do the single-mouthfill.
So, when faced with the question, was anyone doing the single-mouthfill technique before 1998? I suppose we can never say for sure. Unfortunately when people say 'mouthfill' technique, almost everyone thinks of the 'repeated mouthfill' technique, and people like Dieter Baumann say 'oh, I've been filling my mouth since the 70's.' Unfortunately it isn't the same technique. Dieter was Herbert's coach during his 72m lake record where Herbert missed his target of 82m due to equalizing. I felt like asking Dieter why he didn't teach Herbert the 'mouthfill' technique back then.
What I can say is that so far, of the people who are currently doing the single-mouthfill technique, none are doing it very efficiently. Herbert still broke his eardrum in Cyprus despite the mouthfill technique. Musimu himself said he thought he could maybe make 95m with the mouthfill. However, if done properly it will get you far, far deeper.
Currently my personal best for a negative dive, filling my mouth at the surface, using a sphera mask, is 32.8m. With a full pack, I can get a full mouthfill at 35m with great effort.
Doing the math:
0m to 32.8m = 1atm to 4.28m = 4.28x
Mouthfill @ 35m = 4.5atm
4.5atm * 4.28 = 19.26atm = 182.6m
So, if I were to fill my mouth at 35m with the same efficiency as I did on the 32.8m negative dive, using the sphera mask, I would reach 182.6m, head-down, equalizing with a mask. Now THAT is an example of an efficient mouthfill.
If someone like Hubert Maier with 14L lungs did it that efficiently, he could probably get to 200m+ with a mask!