Abstract and Introduction
Abstract: 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 (Q1 5.1-10°C, Q2 10.1-15°C, Q3 15.1-20°C, and Q4 20.1-25°C). Analysis of the top three male and female finishers as well as the 25th-, 50th-, 100th-, and 300th-place finishers 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 Q1-Q4, respectively. Differences between Q4 and Q1, Q2, and between Q3, and Q1 were statistically different (P < 0.05). The top women followed a similar trend (Q1 3.2 ± 4.9, Q2 3.2 ± 2.9, Q3 3.8 ± 3.2, and Q4 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°C. This seems true for men and women of wide ranging abilities, but performance is more negatively affected for slower populations of runners.
A 42-km marathon footrace is among the most physiologically demanding endurance events in the world. Competitive runners typically maintain a pace corresponding to 70-90% of their maximal aerobic capacity [3,15,20] for more than 2 h. At maximal mechanical efficiency, more than 80% of the energy required for this task is transferred as heat to the body core . Moreover, the rate of endogenous heat production associated with a 2-h 10-min marathon estimated from ordinary heat-balance equations  is approximately 1400 kcal·h-1. This metabolic heat must be dissipated to the surrounding environment, or body temperature will rise to physiologically dangerous levels.
Lind  has demonstrated that core temperature is independent of climate over a temperature range he has termed the "prescriptive zone." It has been demonstrated that the width of the prescriptive zone progressively narrows as metabolic rate increases. Thus, climate begins to affect physiological responses to exercise at relatively cooler temperatures during activities that elicit high metabolic rate compared with those eliciting lower metabolic rates. More recently, it has been demonstrated that endurance performance is indeed impaired when exercising in warm versus more temperate laboratory conditions and that air temperatures of approximately 10°C seem optimal for endurance exercise . One criticism of these and other laboratory findings is that typical airflows used for indoor testing situations are well below those encountered when running or cycling outdoors over the ground. The lack of appropriate airflow substantially reduces the combined heat transfer coefficient  and may overestimate physiological strain .
Few field studies have examined the effect of weather conditions on endurance running performance [16,17,22]. Although it is generally observed that race performances worsen as weather warms, there are currently no data quantifying the magnitude of performance reduction. In addition, these studies relied only on data from elite male runners; thus, the implications for slower competitors or women runners are only speculative.
The purpose of this study was to analyze marathon running performance from multiple mass participation marathons to 1) quantify the impact of weather on performance, and 2) determine whether the weather differentially affects performance of runners of varying abilities or between genders.
Med Sci Sports Exerc. 2007;39(3):487-493. © 2007 American College of Sports Medicine
Cite this: Impact of Weather on Marathon Running Performance - Medscape - Mar 01, 2007.