I also do these one-breath CO2 tables because they are a better use of my time than the regular CO2 tables. I always try to do about 30 minutes so my buddy can use the other part of a one hour static session.
My holds this way were up to three minutes in a pyramidical scheme. The longest session I did took one hour. see:
YouTube -One hour static freediving (successive apnea)
Never had headaches from this and not using Bandhas. I just try keeping my throat, neck and backmuscles relaxed. I am quite sure this is not training my low O2 tolerancy. At the end of the session contractions for me start almost straight after the inhale. The (slow) exhale+inhale take me about 30 seconds.
My holds this way were up to three minutes in a pyramidical scheme. The longest session I did took one hour. see:
YouTube -One hour static freediving (successive apnea)
Never had headaches from this and not using Bandhas. I just try keeping my throat, neck and backmuscles relaxed. I am quite sure this is not training my low O2 tolerancy. At the end of the session contractions for me start almost straight after the inhale. The (slow) exhale+inhale take me about 30 seconds.