How Exhale and FRC dives can boost your physical and mental preparation for depth
If you exhale instead of taking a full breath before diving you can fake your depth.
In freediving we prepare our body and mind for longer dives by simply exhaling.
A passive exhale at the surface means diving with 50% of your full lung capacity, which equals double the pressure or 2 bar (10 m).
Picture showing how pressure normally affect your lungs with a full breath at the surface - a passive exhale (called FRC - Functional Residual Volume) equals starting the 50% of the lungs capacity i.e. 2 bar. Source: DeepBlu
What is Functional Residual Volume (FRC) ?
FRC is the volume of air that remains in the lungs after a passive exhale
FRC = ERV + RV
Source: Freediving UAE
How 30 m equals 70 m
Taking 50% of your full lung capacity to 4 bar (30 m) therefore means 8 bar (70 m) pressure wise (2 bar x 4 bar = 8 bar / 70 m)
This means that you you can practice deeper dives, both physically and mentally, by just breathing out.
Be aware of that exhale and FRC dives are very demanding on your body, where you should never go from exhale and FRC dives to full lung and deeper dives since you increase the risk of squeezes (ruptures on your lungs and trachea)