If you were a marathon race director, you probably wouldn't

sleep well the night before your big race. You'd worry that the thing wouldn't start on time, or that the leaders might run off course, or that a runner would drop dead at some point in the event. Then the next day's headlines would ignore all the marathon's exciting results and instead scream, as they nearly always do in this situation: "Runner Dies During Marathon Race."But according to a new journal article by esteemed marathon medical director Bill Roberts, M.D., of the Twin Cities Marathon, you should be worried about something even worse than a runner death. Imagine that, while your marathon is taking place, an 8-year-old girl falls down a flight of stairs in her apartment in your city. Imagine she suffers a serious brain injury, and needs immediate medical attention. [Please note: I am making up this fictional account; it does not come from Roberts.] The girl's parents call an ambulance, which comes to their aid.But the ambulance is diverted from several nearby hospitals, because those hospitals are overwhelmed by dehydrated and overheated runners--participants in your marathon. The girl doesn't make it. Now the next day's headline reads: "Local Girl Dies After Being Refused at Hospitals Crowded With Runners."Whether you are a race director or not, I'm pretty sure this isn't a headline you'd want to see the morning after a marathon. Could anything have been done to avert this tragedy? Should something have been done?According to Roberts, the answer might be Yes. If the race-morning temperatures were warm and likely to head higher, the race organizers should have considered canceling the marathon before it started. Even if they had 40,000 runners in town. Especially if they had 40,000 runners in town. The more the runners, the more the cases of dehydration and/or heat illness, and the greater the likelihood of overwhelming local ambulance services and emergency rooms.Roberts' paper, "Determining a 'Do Not Start' Temperature for a Marathon on the Basis of Adverse Outcomes," has just been published by Medicine & Science in Sports & Exercise." It's available here as a free, full-text PDF Over the years, I've read about a million papers on running in hot weather. I've written detailed stories about high school cross-country runners who died of heatstroke. Last spring I ran in the University of Connecticut's heat chambers with too-many nasty electrodes and probes attached to my body. None of these experiences scared me as much as Roberts's paper.Much of the paper rests on Roberts's 20+ years as marathon medical director at the Twin Cities Marathon. He notes that most years, the early-October marathon enjoys a start temperature in the mid-40s to mid-50s, and has only a modest number of medical problems among runners. The 2007 race was another matter, however. (As it was for other fall marathons that year.) The 8 a.m. start temperature at Twin Cities in 2007 was 72 degrees. Result: so many runners suffered from heat or dehydration or other medical issues that they effectively shut down six local hospitals, turning the marathon into a Mass Casualty Incident. When this happens, others needing emergency care must be taken to more-distant facilities, meaning that it will take longer for them to get the help they need.After this 2007 wake-up call, Roberts decided to look back at Twin Cities Marathons dating to 1997, when computer chips first gave him an accurate count of race starters. He already knew the temps for each race, the number of DNFs (runners who Did Not Finish), and the number of runners treated in medical tents. With this data, he was able to plot a sort of "medical stress test" for each race with start temps on one axis and "unsuccessful starters" (DNFs, plus runners who ended up in a medical tent) on the other. The resulting curve clearly showed the runners loved races that started in a range from 41 to 54 degrees F. At about 55F, the number of unsuccessful starters began to increase. In two Twin Cities races that started at about 67F, there were enough medical cases to close down several local hospitals, but not to cause a Mass Casualty Incident. [The actual temperatures used in Roberts's paper were expressed as Wet Bulb Global Temperatures, which account for humidity and sun exposure. See far bottom of blog post for more explanation.]Roberts has now determined that Twin Cities has a potential "Do Not Start" temperature of 69F, especially if the weather forecast calls for rising temperatures during the marathon. To allow the race to begin under this scenario, he writes, "would pose a danger to the runners and the community members-at-large, as emergency response vehicles become unavailable and emergency facilities are stretched beyond their capacity to care for the overall patient load."Roberts believes that other big marathons also have "Do Not Start" temperatures. These temps will be higher than 69F in places like Honolulu and Miami, and lower than 69F in marathons like London and Rotterdam, where runners are not accustomed to racing in the heat. In the 2007 Rotterdam Marathon, which started at about 69F, approximately 3600 runners among 7800 starters did not finish. At the same year's London Marathon (65F start temp), the finish line medical tent was overwhelmed to the point that some stricken runners had to wait an hour for an ambulance. One of these runners subsequently died, though it's impossible to say if the slow-responding ambulance was a causative factor.Below, Roberts answers several questions that I asked him. But, first, what do you think: Should marathon race directors cancel events in conditions that could overwhelm local medical facilities? Or is there another, better approach? Use the "Comments" link to post your thoughts. ------------------------------------------------------ Here, Roberts answers several questions about his paper.A: It puts regular runners into the equation. It's based on what actually happens to them at the races, and not on lab studies. It will allow individual races to set specific cancellation parameters that reflect the size of the race, the medical assets of the community, and the type of runners involved.A: Yes, there have been cases of hospital overload and lack of ambulance support with delayed response times in several of our Twin Cities races, and at Boston, Chicago, and London.A: At Twin Cities, the decision is in the hands of the race executive committee with input from the medical operations group.A: That's the million dollar question. You're damned if you do, and damned if you don't. However, the safety of the community and the runners should trump the marathon's "reputation". Brian Mastel, our race director, did cancel a race in Montana. He took a lot of heat for it, but he's glad he did.A: I've heard everything from "We don't think this is valid for us" to "This is really interesting. We're going to study it some more." The idea has been discussed at the World Marathon Majors, but no action has been taken. Several of the races are interested, several seem less so.The idea is for every race to determine its own temperature where runner medical problems could begin to overstress local ambulance and medical response. It won't be the same for all races. It will be higher at Honolulu and maybe even a little higher at Marine Corps. It will be lower in London where the runners aren't as accustomed to warm weather. For Chicago, New York, and Boston, it will probably be quite close to what we found at Twin Cities.In part, this is about the safety of the runners in our own races. That's very important to us of course. But we also have a responsibility to the communities where we live. I wouldn't mind if this idea is fully debated, and then discarded because medical experts decide it's wrong. I just think it's important that we have the discussion.The formula is WBGT = 0.7 x Wet bulb temperature + 0.2 x Black Globe temperature + 0.1 x Ambient or Dry Bulb temperature. The key point is that ambient temperature contributes little to the calculation and the water content of the air or humidity is the main factor. 69 WBGT would be the equivalent of 69 degrees at 100% relative humidity with no sun.So like you mother says, it is not the heat it is the humidity.Also the utility of this method is that it takes into account the regional differences in acclimatization to heat so the Texas races would have a different curve and different cut off than the northern latitude races.

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