Sodium balance during U. S. football training in the heat: cramp-prone vs. reference players.
U. S. football players with a history of heat cramps were evaluated for the effect of physical training, sodium intake, and loss of sweat sodium on whole blood sodium concentration (BNa). Athletes (n=14 males, 24+/-1 y) were recruited and studied based on medical history, age, and position. The reference group (R, n=8 without a cramping history) and cramp-prone group (C, n=6, history of whole-body cramps associated with extensive sweat loss during exercise in the heat) were measured for body mass and BNa (ISTAT) before and after team training of 2.2 h in hot conditions (WBGT=29-32 degrees C). Intake and loss of fluid and sodium were also measured to determine respective acute balance. In R, BNa was stable pre- to post-training (138.9+/-1.8 to 139.0+/-2.0 mmol/L) while it tended to decline in C (137.8+/-2.3 to 135.7+/-4.9 mmol/L), and three subjects in C had BNa values below 135 mmol/L (131.7+/-2.9 mmol/L). C consumed a greater percentage of total fluid as water (p<0.05). Mean sweat sodium concentration was (52.6+/-29.2 mmol/L for C and 38.3+/-18.3 mmol/L for R (p>0.05). Compared to R, C tended to experience a decline in BNa and greater acute sodium imbalance. These changes may place cramp-prone players at greater risks for developing acute sodium deficits during training.
Horswill
C A
CA
Gatorade Sports Science Institute, Pepsico R & D, Barrington, IL, United States. craig.horswill@gatorade.com
Stofan
J R
JR
Lacambra
M
M
Toriscelli
T A
TA
Eichner
E R
ER
Murray
R
R
D000328:Adult; D016022:Case-Control Studies; D003681:Dehydration; D004326:Drinking; D005538:Football / Q000502:physiology*; D018882:Heat Stress Disorders / Q000209:etiology* / Q000378:metabolism; D006801:Humans; D008297:Male; D009120:Muscle Cramp / Q000209:etiology* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D013542:Sweat / Q000737:chemistry; D013546:Sweating / Q000502:physiology; D014481:United States; D014882:Water-Electrolyte Balance / Q000502:physiology; D055815:Young Adult
D012964:Sodium