During aerobic exercise, lactic acid is released into the bloodstream as a result of glycolysis. Homeostasis causes lactic acid to come to chemical equilibrium with lactate and hydrogen ions, which accumulate in the blood as a result of exercising. A "good runner" is defined as an individual with a high lactate concentration threshold, and who therefore produces less lactate and hydrogen in the bloodstream. A "bad runner" is defined by a lower lactate threshold and faster acidosis, which can potentially cause higher rates of respiration, nausea and vomiting. Red blood cells are used to visualize the varying concentrations of lactate in the two runners.