I've tried it once but I've also read that never to do it in one day...So, I'm experimenting a bit, I train table's alternately MWF CO2, TTh O2 and rest on weekends...for 3 weeks or more. I'm having difficulty increasing my CO2 table using this training...Although, I've increase my PB of 1:30 to 2:00 then to 2:15 which is still insignificant...but still steady improvements...
Now, I'm trying M&Th CO2, T&F O2...maybe for another 3 weeks...I'm having easier time at the CO2 table and I feel like increasing it by 5-10secs more...
If I continue feeling better with more rest on a week I may stick to this training for a while since I'm only a beginner...maybe in the future i can train more often when my body adjust to this training...
This is my Co2 @ 45secs Breath hold table:
rest 2:30, 2:15, 2:00, 1:45, 1:30, 1:15, 1:00, 1:00
My O2 table is with 2:00m rest:
@ 20s, 25s, 30s, 40s, 50s, 1:00, 1:10, 1:15
I will not increase my table's till it feels easy for me even though I was able to increase my PB...