Daniel, the swimmer with the fastest time on the college swim team, routinely hyperventilates before a meet, as he says "to sock some more oxygen into my lungs so I can swim longer without having to...

Daniel, the swimmer with the fastest time on the college swim team, routinely hyperventilates before a meet, as he says "to sock some more oxygen into my lungs so I can swim longer without having to breathe." "Furthermore, my heart won't have to adjust it's output".

Which organ(s) would actually require more oxygen that Daniel may not be realizing? Why so?