Weather Roulette, Page 2


This chart shows that, on average, May 18th is not a terrible day for a marathon. The usual heat index through the middle part of the day is 67F, which is not ideal but is workable. Unfortunately, May 18th, 1986, was 16F warmer than average, and the results were dismal. (May 18th, 1986, had the second highest temperatures for that date in 25 years.) To determine the actual risk of high temperatures for May 18th, 10 am to 3 pm, hourly heat index distribution frequency can be determined from the SAMSON database:

Pittsburgh, PA-May 18th-heat index frequency distribution-10 am to 3 pm-1961-1990.gif (7293 bytes)

For the 30-year standard period 1961-1990, the May 18th, 10 am - 3 pm period shows 15% of hourly heat index values to be greater than 80F. A 1-in-6.5 chance that conditions will be highly unfavorable is not desirable, especially with such a large and heterogeneous field.

The quality of the field must also be considered. Since the Pittsburgh Marathon was only in its second year in 1986, it is safe to say that it was not well-established. This is borne out by the fact that 970 runners, about one-third of the field, had never run a marathon before. These novice marathoners, and most of the rest of the field, very likely hailed from the northeastern US. This set the stage for the second part of the weather catastrophe: Inadequate heat acclimatization.

Acclimatization is a critical part of the athlete's preparation for competition in hot weather. It must be remembered that highly-trained, elite athletes have already acquired some degree of heat tolerance by virtue of their high degree of fitness. Even those athletes benefit from an additional 10 to 14 days of exposure to training in heat, however. In the process of acclimatization, the athlete's total plasma volume increases, sweating starts earlier in exercise, sweating is more copious and the sodium concentration of sweat decreases. Here is Pittsburgh's May, 1986 temperature pattern:

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