ABSTRACT
This chapter examines blood chemistry of the players in high-school soccer tournaments at Japan in mid-summer and compared them to those in mid-winter. Soccer played in a hot and humid environment may pose a potential problem for the player's health. Players were allowed to have fluid intake during matches. Body mass was determined and venous blood and urine samples were collected from the same individuals in a medical office immediately after and the morning after a soccer match. Data are presented as mean ± standard deviation (SD). The significance of difference between groups was calculated using Student's paired and/or unpaired t-test. The greatest potential problem for the player's health in the summer soccer tournaments is dehydration caused by high temperatures. It shows that dehydration leads to increments of plasma Anti-Diuretic Hormone (ADH), Plasma Renin Activity (PRA), and plasma angiotensin II (Ang II) levels and also has a potential risk of acute renal failure.
