In my e-coaching program I prescribe exercises similar to that, with the idea of creating as much vasoconstriction FIRST, then exercising the muscles.
In fact, the evidence is mounting that doing a static on the bottom of the pool (Murat style), before even starting your dynamic swim, may increase the maximum distance you can swim. In the future, the dynamic world record might be done this way.
We do similar exercises every week ie static followed by DYN and I'm always surprised that the DYN distance after a short STA is comparable to just the DYN distance. Questions relating to this though:
1. I've always assumed the above effect has to do with the relaxation, lower HR and vasoconstriction from the STA. (not myoglobin)
2. Even if training this way does increase myoglobin, why would it help for the actual competition attempt? (obviously you won't increase myoglobin on the spot right?)
3. Is myoglobin in the muscles used for all breatholding (eg during a static) or does it come into play when your muscles work unaerobically for a long time and are close to 'failure'. In other words, would it help all STA/DYN dives or just the max DYN.