NATICK, Mass. — As runners get ready for the Boston Marathon, many no doubt partake in training programs aimed at helping them to be optimally prepared, whether it be helping them achieve their best time and reduce physical injuries or simply to finish. With all this preparation, many may be surprised to find out about the wild card that April brings — the weather.
In 1967, snow squalls accompanied the runners through the first five miles. In 2004, temperatures reached midsummer levels topping out at 86 degrees. In 2012, as many as 2,100 runners were treated at medical tents along the 26.2-mile course for dehydration, heat exhaustion and other ailments as temperatures soared into the upper 80s, smashing records.
“April is a very volatile month in Massachusetts in terms of weather,” said Samuel Cheuvront, a research physiologist with the U.S. Army Research Institute of Environmental Medicine, or USARIEM. “Conditions can vary greatly from extreme cold to extreme heat. Extreme heat can be challenging for marathon runners who have been training in the cold for months. This can lead to excessive heat injuries.”
Since 2012, USARIEM has been an official course weather monitoring authority for the Boston Athletic Association, or BAA. Collaborative research between USARIEM and the BAA is focused on determining how many locations are required for monitoring along the 26.2 mile route, as well as to determine if a 72-hour forecast would give accurate results for race day planning.
According to Cheuvront, USARIEM provides real-time, hourly WetBulb Globe Temperature, or WBGT, measures on the course for race officials.
“Since last year our researchers have been stationed at three places along the marathon route with portable WetBulb Globe Temperature devices that provide real time readings of the conditions as racers go by,” Cheuvront said. “We have also done and will continue this testing through September to give us more data to help us achieve long term accurate readings.”
Cheuvront said the BAA chose USARIEM for this task partly because of their long standing partnership since the 1970s, when Soldier medics would volunteer in caring for runners in medical tents while simultaneously conducting light weather monitoring. The other and more scientific reason is the military’s expertise in the use of the WetBulb Globe Temperature Index and its important use in sports medicine.
The WBGT measures heat stress in direct sunlight which takes into account, humidity, temperature, wind speed, sun angle and cloud cover (solar radiation). Cheuvront said it is a more sophisticated measurement than a simpler heat index, which accounts for air temperature and humidity only and was not designed with heavy activity in mind.
“Military agencies, the American College of Sports Medicine and many nations use the WBGT as a guide to managing heat stress,” Cheuvront said. “The majority of the heat gained by runners comes from muscle contraction. The WBGT informs us of how easy or difficult it will be for runners to balance that heat gain with heat loss.”
Since the 1950s, U.S. military installations have displayed flags to indicate the heat category based on WBGT. White, green, amber, red and black flags represent conditions ranging from WBGT readings of 79.9 degrees (white) to over 90 degrees (black). Each flag serves as an indicator for guidelines for water intake and physical activity level for individuals based on the heat category. The sports medicine community uses WBGT flag categories also, though the absolute values used for guidance are different.
“Our hope is that by measuring the WBGT on the course we can provide more accurate information than airport weather given many miles away, Cheuvront said. “We also hope that accurate 72-hour forecasting may be possible.
“If the WBGT can be accurately forecasted and we know that race day’s flag will be red, for example, then the organizers can plan for more water stations, more ambulances and more signage to alert runners that they may have to take it easier on the course.”
This research is not just going to benefit marathon runners. It will also be used to update the guidance that USARIEM provides to service members through the doctrine they publish for heat injury management.
“The information we learn here will be taken to update the guidance we push out to the field to help protect the Soldier from heat injury. That is always a huge priority for us,” Cheuvront said.