Fluid Turnover During Two-a-day Practices In College Football

Abstract

PURPOSE To determine 24-h fluid turnover (FT) during a 7-d period of two-a-day football practices. METHODS We tested nine training players (T) and five active references (R) by having each ingest a deuterium oxide (D2O) dose equivalent to 1 g/kg body weight in 100 mL of sports drink starting their first day of two-a-day practices. R were active (strength/conditioning drills in full uniform), but not participating in on-field team drills, and one R was walking the sidelines. A three-site skinfold (SF) equation was used to estimate body composition before and after the 7-d to determine change in fat and fat-free mass. During a representative practice (∼2.3 h, day 2, WBGT 24.6°C), sweat loss and fluid intake were measured. Change in body weight, corrected for fluid intake and urine loss, was used to estimate gross sweat loss (GSL). Voluntary fluid intake (water and sports drinks) was measured by recording pre- and post-practice bottle weights. RESULTS Average FT was 10.3 ± 2.2 L/d (T) compared to 6.8 ± 1.2 L/d (R) (P<0.05). At baseline, characteristics of T were 118.3 ± 20.2 kg, 22.2 ± 7.8% fat (via SF), with TBW (total body water via D2O) of 77.2 ± 9.0 L. Those of R were 100.7 ± 10.7 kg, 19.3 ± 9.0% and 68.2 ± 8.0 L TBW. During the representative practice, the volume of fluid consumed was 2.2 ± 0.7 L (T) versus 1.4 ± 0.7 L (R). Sweat rates were 1.4 ± 0.7 L/h (T) and 0.7 ± 0.6 L/h (R), resulting in GSL of 3.4 ± 1.5 L (T) and 1.7 ± 1.3 (R) (P>0.05). Fat-free mass appeared to decrease significantly by 2.4 ± 2.1 kg (P<0.05) over 7d in T, but not for R (0.22 ± 1.6 kg) and may actually reflect a loss of TBW. CONCLUSIONS These data suggest that during two-a-day training, football players have FT that greatly exceeds sedentary values (2–3 L/d). Even R, who were active on the sidelines, had large FT compared to literature values for sedentary. The observed FT rate and apparent loss of TBW emphasize the importance of fluid intake during and after football training.