Fluid-Electrolyte Balance Associated with Tennis Match Play in a Hot Environment

Twenty (12 male and 8 female) tennis players from two Division I university tennis teams performed three days of round-robin tournament play (i.e., two singles tennis matches followed by one doubles match per day) in a hot environment (32.2 ±and 53.9 ± 2.4% rh at 1200 hr), so that fluid-electrolyte balance could be evaluated. During singles play, body weight percentage changes were minimal and were similar for males and females (males -1.3 ± 0.8%, females -0.7 ± 0.8%). Estimated daily losses (mmol ·) of sweat sodium (Na+) and potassium (K+) (males,158.7,31.3; females,86.5,18.9) were met by the players' daily dietary intakes (mmol ·) of these electrolytes (males,279.1 ± 109.4,173.5 ± 57.7; females,178.9 ± 68.9,116.1 ± 37.5). Daily plasma volume and electrolyte (Na+,) levels were generally conserved, although, plasma [Na+] was lower (p< .05) on the morning of Day 4. This study indicated that these athletes generally maintained overall fluid-electrolyte balance, in response to playing multiple tennis matches on 3 successive days in a hot environment, without the occurrence of heat illness