One of the best surface-training methods is so-called walking apnea, which involves holding your breath and walking over a soft surface (in case you pass out) for extended distances. The idea is that the oxygen your muscles use when you’re walking slowly is about the same amount of oxygen muscles use during a freedive. You start by holding your breath while standing still for about thirty seconds until you feel your heart rate decrease, then you walk slowly in a straight line, turn around when you feel you’ve reached your halfway point, and walk back to your starting place. The distance you
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