Abstract
Twelve healthy young adults participated in 50 min basketball game and 120 min resting without cooling-down exercise or 90 min resting with 30 min cooling-down exercise. When these subjects took 120 min rest alone, blood lactate decreased gradually, but urinary bicarbonate and pH began to increase extensively during resting period. When cooling-down exercise was introduced immediately after exercise, blood lactate decreased rapidly to normal levels within 30 minutes, and no increase of urinary bicarbonate and pH was observed for resting period. Such drastic changes in blood lactate and urinary bicarbonate could be explained by the facts that cooling-down exercise enhanced both the oxidative metabolism of lactate and the respiratory rate, resulting in quick discharge of carbon dioxide into expired air from the blood, and finally causing the reduced discharge of bicarbonate into the urine. Without cooling-down exercise, intracellular pH of the circulating erythrocytes was postulated to be acidified, because urinary bicarbonate increased drastically during the resting period. Drastic increase of urinary bicarbonate was explained by the facts that carbon dioxide was metabolized to bicarbonate and hydrogen ion by erythrocytic carbonic anhydrase, and then bicarbonate was discharged from the blood to the urine, resulting the leftover of hydrogen ion in the cells and increased erythrocytic Bohr effects. [J Physiol Sci. 2007;57 Suppl:S188]
