Answer
After the race, a runner needs to get rid of the lactic acid that has built up in his or her muscle cells. This lactic acid goes through a chemical pathway that gets rid of it, but that requires a lot of oxygen.
Work Step by Step
After the race, a runner needs to get rid of the lactic acid that has built up in his or her muscle cells. This lactic acid goes through a chemical pathway that gets rid of it, but that requires a lot of oxygen.