Having attended the AIDA 1* course I am now suitably armed to undertake some structured practice. One of the things we learned about was apnea tables. These are a series of breathing exercises to help increase either carbon dioxide tolerance, or oxygen capacity. There are CO2 tables, a series of 6 breath holds to about 50% of your maximum time, with a decreasing gap between, or O2 tables, a good rest in between (maybe 2 or 3 minutes) but each hold gets longer. I have an app on my phone which talks me through the tables. They are best explained here https://www.deeperblue.com/iphone-apps-for-freedivers/
I use one called StaticApneaTrainer on Android.
It didn’t take long, a table per day on and off for a couple of weeks to get my breath-hold out of the water up to 4:47, which probably means I could top 5 minutes in the water as the cool water around your face helps lower your heart rate and floating around is more relaxing than laying on a bed. ( I learn’t that on the course too). I supplement this with stretching exercises, taking a full breath and reaching my arms above my head to stretch out my intercostal and back muscles. I don’t know, but I think this A/ helps increase lung capacity (maybe), and B/ means that when you take a deep breath these muscles are nice and loose because they are used to it and aren’t gobbling up valuable oxygen.
I’m convinced all these exercises help with sport in general, and my sport (rowing) in particular because any increased lung capacity, or tolerance to CO2 is going to help, and CO2 means acidic blood, so does it help with lactic acid tolerance too?
UPDATE! You don’t get far into freediving before you realise that there is so much more to it than how long you can hold your breath!….. see the next installment –https://mybluejourney.wordpress.com/2014/06/04/aida-2-star-going-deeper-and-equalisation/