This observational study was designed to determine whether football players with a history of
heat cramps have elevated fluid and
sodium losses during training. During a "two-a-day" training camp, five Division I collegiate football players (20.2 +/- 1.6 y, 113 +/- 20 kg) with history of
heat cramps (C) were matched (weight, age, race and position) with a cohort of teammates (19.6 +/- 0.6 y, 110 +/- 20 kg) who had never cramped (NC). Change in
body weight (adjusted by fluid intake) determined gross sweat loss. Sweat samples (forearm patch) were analyzed for
sodium and
potassium concentrations. Ad libitum fluid intake was measured by recording pre- and post-practice bottle weights. Average sweat
sodium loss for a 2.5-h practice was projected at 5.1 +/- 2.3 g (C) vs. 2.2 +/- 1.7 g (NC). When averaged across two practices within the day, fluid intake was similar between groups (C: 2.6 +/- 0.8 L vs. NC: 2.8 +/- 0.7 L), as was gross sweat loss (C: 4.0 +/- 1.1 L vs. NC: 3.5 +/- 1.6 L). There was wide variability in the fluid deficit incurred for both C and NC (1.3 +/- 0.9 vs. 0.7 +/- 1.2%) due to fluid intake. Sweat
potassium was similar between groups, but sweat
sodium was two times higher in C versus NC (54.6 +/- 16.2 vs. 25.3 +/- 10.0 mmol/L). These data indicate that sweat
sodium losses were comparatively larger in
cramp-prone football players than in NC. Although both groups consumed
sodium-containing fluids (on-field) and food (off-field), both appeared to experience an acute
sodium deficit at the end of practices based on sweat
sodium losses. Large acute
sodium and fluid losses (in sweat) may be characteristic of football players with a history of heat cramping.