Impact of weather on marathon-running performance

ELY, M. R., S. N. CHEUVRONT, W. O. ROBERTS, and S. J. MONTAIN. Impact of Weather on Marathon-Running Performance. Med. Sci. Sports Exerc., Vol. 39, No. 3, pp. 487-493, 2007. Marathon running performance slows in warm weather conditions, but the quantitative impact of weather has not been established. Purpose: To quantify the impact of weather on marathon performance for different populations of runners. Methods: Marathon results and weather data were obtained for the Boston, New York, Twin Cities, Grandma's, Richmond, Hartford, and Vancouver Marathons for 36, 29, 24, 23, 6, 12, and 10 yr, respectively. The race results were broken into quartiles based on the wet-bulb globe temperature (Q(1) 5.1-10 degrees C, Q(2) 10.1-1 degrees C, Q(3) 15.1-20 degrees C, and Q(4) 20.1-25 degrees C). Analysis of the top three male and female finishers as well as the 25th-, 50th-, 100th-, and 300th-place finishes were compared with the course record and then contrasted with weather. Results: Marathon performances of top males were slower than the course record by 1.7 +/- 1.5, 2.5 +/- 2.1, 3.3 +/- 2.0, and 4.5 +/- 2.3% (mean +/- SD) for Q(1)-Q(4), respectively. Differences between Q(4) and Q(1), Q(2), and between Q(3), and Q(1) were statistically different (P < 0.05). The top women followed a similar trend (Q(1) 3.2 +/- 4.9, Q(2) 3.2 +/- 2.9, Q(3) 3.8 +/- 3.2, and Q(4) 5.4 +/- 4.1% (mean +/- SD)), but the differences among quartiles were not statistically significant. The 25th-, 50th-, 100th-, and 300th-place finishers slowed more than faster runners as WBGT increased. For all runners, equivalence testing around a 1% indifference threshold suggests potentially important changes among quartiles independently of statistical significance. Conclusion: There is a progressive slowing of marathon performance as the WBGT increases from 5 to 25 degrees C. This seems true for men and women of wide ranging abilities, but performance is more negatively affected for slower populations of runners.