I am guessing that the science of breathold increase is your body adapts and gets better at dealing with breathhold situations. Sort of like getting used to living in a cold climate, and being able to handle the cold better than someone who visits from a hot climate. Everyone has a different body, and different sized lungs so how do I go about finding when its a good time for me to head surface? I have heard its a great idea to surface on the first contraction. How would you guys suggest I determin on dry land, doing breath hold attemps, my maximum breath time? Right now I can hold my breath for a max of 3 mins on a giant breath. But contractions start at 1 minute 45 seconds. Also, is it a good idea to free dive on the biggest breath I can take, or should I be taking in only 80% breath or something?