Sports Medicine and Fitness

Stock car drivers are exposed to high ambient temperatures prior to-, and during competition, further complicated by the fact that they are encapsulated in protective clothing; however, the hydration status of these drivers has not been determined. Purpose: To quantify the degree of fluid losses during a competitive event in hot conditions.

 

Methods: Nine male stock car drivers (30 ± 9 yr, 178 ± 3 cm, 83 ± 19 kg) were studied during a Pro Series Division NASCAR race. Sweat rate (SR) and dehydration was determined via nude body weights (BW) pre- and postrace. SR calculations included ~40 min of pre-race activity and ~20 min or racing.

 

Results: Urine loss was considered fluid loss and BW was corrected for fluid and food intake. Pre-race BW was 81.5 ± 18.5 kg and decreased to 81.1 ± 18.5 kg post-race (p=0.001). BW loss post-race was 0.77 ± 0.3% and average sweat rate was 0.63 ± 0.4 L/h. Intestinal core increased from 38.0 ± 0.4°C to 38.5 ± 0.4°C post-race (p=0.001). Skin temperature increased from 35.8 ± 0.8°C 36.9 ± 0.8°C post-race (p=0.001), whereas the core-to-skin temperature gradient narrowed from 2.2 ± 0.9°C to 1.6 ± 0.9°C, pre to post-race (p=0.001). Heart rates (HR) post-race were 89 ± 0.0% of the drivers’ age-predicted maximum HR. Conclusion: Fluid losses during competitive racing can be significant, particularly when SR is extrapolated to longer duration events. Without a fluid replacement strategy, fluid losses for these drivers may exceed 3% BW and could negatively impact driving performance.