I'm sure many of you have tried to see how long you can hold your breath. I'm not sure of any of the real science behind it, but you know when you take deep breaths before you attempt, it makes it much easier to hold your breathe longer.
Would doing this same deep breathing that you use before holding your breathe yield any benefit (although minor) before a race, specifically a mid distance race?
If it did, then everyone would be doing it wouldn't they?
Hyperventilating as you described causes levels of CO2 to increase in the blood. This would reduce race performance.
actually it lowers CO2 levels, which kills freedivers occasionally when they pass out from hypoxia since high CO2 levels control breathing.
It's still bad for racing because CO2 also controls vasodilation, without which oxygen delivery to working muscle can't increase. Maybe ok for 400m but I doubt for 800 or beyond. It's kind of like undoing your warmup.
Yes I've made a mistake there. Funny since I knew about swimmers hyperventilating before diving under water then passing out and drowning.