John O'Brien '08

Hydration status and heat acclimation in division III collegiate offensive linesmen during summer practice

Eleven heat related deaths occurred between 2001 and 2004 in addition to one of the more publicized deaths, Korey Stringer of the Minnesota Vikings.  Football linemen are at an increased risk for heat related illness due to a low surface area relative to body mass reducing the ability to dissipate heat.  Individuals exercising in heat acclimate to the environment, which includes increasing sweat rate and increasing cardiac output.  Football linemen in particular need to properly heat acclimate to reduce the risk of heat related illnesses. 

Purpose: To assess the hydration status and measure the extent of heat acclimation in Division III offensive linemen. 

Methods: The study was approved by the institutional review board.  Thirteen healthy collegiate Division III offensive linemen (mean ± SD, age 20±2 yr, height 188±6 cm, mass 100±12 kg, BMI 33±3.5 kg/m²) volunteered to participate in the study during the first ten days of preseason practice.  Subjects' HR, water consumption, and RPE were recorded during practice.  Subjects were weighed and provided urine samples before and after practice to determine sweat rate and change in hydration status.  Subjects' diet was analyzed for the first five days of the study. 

Results: Sweat rate increased by 0.50 L/hr between day 1 and day 5 with little change after day 5 (Day 1= 0.65 L/hr, Day 5= 1.15 L/hr).  Urine specific gravity increased during practice (Pre-Practice= 1.016, Post-Practice= 1.021). 

Conclusion: No significant changes were detected in HR or RPE.  Sweat rates increased modestly over the first five days of the study but were more dependent on unseasonable, cool ambient temperatures, moderate practice intensity, and players acclimated to heat prior to summer practice.  Players came to practice dehydrated and did not consume adequate fluid throughout practice to offset fluid loss through sweat.  Subjects' pre and post practice urine specific gravities improved due to more awareness of individuals' hydration status; however, the subjects never became well hydrated, which would have been a concern if the temperature was hotter.

John O'Brien presenting his research at the Northland Chapter of the American College of Sports Medicine, March 28, 2008, St. Cloud, MN

To view Poster, click on link below:
Hydration status and heat acclimation in division III collegiate offensive linesmen during summer practice

Research advisor: Amy Olson, PhD, RDN, LD