Water planning is an important logistical and risk management concern for event organizers of road races. Until now event organizers have relied upon experience to estimate water needs on race day.
PURPOSE: To compare estimated water needs using a commercial water planning tool against both 1) empirical group water losses of runners and 2) documented event water usage.
METHODS: Group sweating rates (L/h) from 14 published studies were compared to a weighted composite average using the Road Race Water Planner© app (RRWP). Estimated water (gallons) and cup (#) needs were compared to documented usage at a large marathon event. RRWP inputs were air temperature (°C), race distance (km), numbers of runners and numbers of water stations; outputs were gallons of water, numbers of cups, and both gallons and cups per fluid station. An a priori constant error (y-intercept) of less than ± 0.250 L/h per runner was used as an acceptance threshold and evaluated using Deming Regression.
RESULTS: Published studies provided 14 group mean sweating rates from 321 runners for comparison to composite RRWP estimates. Air temperatures ranged from 13.4 to 28.5°C and running distance from 11.7 to 42.2 km. Constant error was 0.203 L/h with one outlier and 0.053 L/h with outlier removed. The 2017 Boston marathon hosted 27,222 runners on a day averaging 21.5°C. Water and cup usage was 31,740 gallons and 1,036,003 cups (51.8 cases), respectively. RRWP estimates were 33,505 gallons and 1,072,160 cups (53.6 cases), respectively. The difference in gallons expressed as liters was 0.246 L per person. For a ~4 h marathon, the difference as a rate was 0.062 L/h. The difference in cups was 1.8 cases (3.5% error).
CONCLUSIONS: The results of the RRWP analysis indicate acceptably small error, thus RRWP provides event organizers with a quantitative way to narrow the uncertainties of water planning related to changes in weather, participant numbers, and race distance.
Travel support for Dr. Sollanek provided by Sports Science Synergy, LLC.