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Heat Stress in Atlanta: Preparing for the Olympic Worst

Robert Roos


The weather might provide the toughest competition for endurance athletes at the Summer Olympic Games in Atlanta next month. The heat stress is likely to be higher than in any of the last several summer games. Here's a report on the expected conditions and how medical officials for the games are preparing.

Every summer for the past 4 years, physiologist David E. Martin, PhD, has collected weather data in Atlanta, site of the 1996 Summer Olympic Games (1). On each of the 17 days corresponding to the Olympic dates-July 19 through August 4-Martin has set up shop at a stadium construction site and taken temperature and humidity readings every 5 minutes over 4-hour periods in the morning, midday, and early evening.

In 1993, the hottest of the four summers, Martin recorded nearly infernal conditions: Temperatures reached 100°F (37.7°C) or more on 6 days and hovered in the 90s every other day but one. Such weather may be excellent for swimming, but running a hilly marathon or playing soccer in it would be much like taking an endurance test in a sauna. Endurance athletes competing in these conditions could run a high risk of heat exhaustion or heatstroke.

Indeed, the possibility of excessive heat stress much occupies the minds of the people charged with medical coverage of the 1996 Summer Olympic Games. One of them is Joe Wilson, MD, medical director of the men's and women's marathons. Despite careful preparation and thorough medical coverage at the marathons, "Every runner who finishes the race in this type of climate will have a body temperature above what most people would consider acceptable," says Wilson, a cardiologist at St Joseph's Hospital in Atlanta.

Concern about heat was the main reason the time of the men's marathon, the culminating event of the games, was recently changed from 6:30 pm to 7:00 am. The same concern has prompted the development of a new strategy for medical monitoring and care of the marathon runners (see "Inside the Olympic Medical Tent). And even with these precautions, Wilson expects a high dropout rate.

The worries about heat illness focus primarily on the men's and women's marathons, but other outdoor sports and events may incur risks as well: race walking, middle-distance running, soccer, and field hockey, to name a few. And some observers worry that the Olympic fans will come to Atlanta unprepared for the heat and suffer more than the athletes.

Climatic Events

Though there is good reason for concern, no one is flatly predicting that Atlanta will be a giant sauna during the games. "If there's one thing that defines Atlanta's weather in the summer, it's unpredictability," says Martin, regents professor of health sciences at Georgia State University in Atlanta and a member of the Olympic Medical Support Group of the Atlanta Committee for the Olympic Games (ACOG). "Some summers are quite warm, sunny, and dry; some are quite cloudy and wet, and some summers have a mixture."

The average high temperature for the Olympic period over the past 30 years has been a warm but not sizzling 88°F (31°C), according to Michael Ross of the National Weather Service in Atlanta. Average humidity in July varies from 88% at 7 am down to 60% at 1 pm, when the warmer midday air can hold more water vapor, Ross reports.

Martin says his data for the past 4 years illustrate the variability of Atlanta weather. Midsummer of 1993 was a scorcher, but the same period in 1994 brought highs mostly in the 80s, and one of only 75° (23.8°C). Lows over the 4 years were mostly in the low 70s. As major southern cities go, Atlanta is probably the coolest, Martin says. Because the city sits at an elevation of 1,010 ft on the edge of the Appalachian Mountains, he says, "We don't have quite the humidity and oppressive nighttime heat the seacoast cities have." He adds that high heat and high humidity "don't seem to go hand in hand here."

So how does Atlanta's weather compare with that of other recent summer Olympic sites? Phillip B. Sparling, EdD, a physiologist at Georgia Institute of Technology in Atlanta, ventured an answer in a recent article (2) in the Clinical Journal of Sport Medicine. After reviewing official temperature and humidity data for 1993 and 1994, Sparling wrote that the overall heat stress at the Atlanta games is expected to be "slightly greater than conditions reported for the 1992 Barcelona Olympic Games."

Sparling's data showed that heat stress at 1 pm reached the "hazardous" level about half the days of the 17-day Olympic period in 1993. ("Hazardous" means the wet bulb globe temperature [WBGT] exceeds 82°F (27.7°C), the level at which the American College of Sports Medicine [ACSM] recommends canceling endurance events (3). WBGT reflects humidity, radiant, wind, heat, and air temperature.) The average WBGT at 7 am, the time of the marathon, was 72.2°F (22.3°C) in 1993. In 1994, both the 7 am and 1 pm WBGT readings were lower (71.2°F [21.7°C] and 77.0°F [25°C]). However, Sparling recently published a correction (4) that places the average WBGT readings 2.0°F to 4.0°F higher. That puts the 7 am averages for both 1993 and 1994 in the "high risk" range, which starts at 73.0°F (22.7°C).

Temperatures during the Barcelona games in 1992 reached the low 90s, but the humidity was lower than it typically is in Atlanta, according to John D. Cantwell, MD, chief medical officer of the Atlanta games. "I don't think [the weather] will be a dramatic difference from Barcelona, but the heat stress index will be a little higher," says Cantwell, a cardiologist who directs the preventive medicine program at Georgia Baptist Hospital in Atlanta.

Martin agrees that Atlanta is likely to be warmer than Barcelona, which was warmer than other recent Olympic sites. Looking as far back as Mexico City in 1968, "None of these games had as much climatic heat stress as the Atlanta games will have," he says. "I think the average high and low will be higher than those, unless we have an unusually cool summer."

On the other hand, Martin doesn't think the fairly high heat stress will be dangerous for athletes because, hot, humid weather is nothing new to athletes in international endurance events. For example, the World Track and Field Championships took place in sweltering weather in Tokyo in 1991, he observes. "There were no deaths. There were quite a few dropouts, but that's true in lots of these competitions."

Bob Kempainen, a member of the US Olympic marathon team, expects that with start-time temperatures in the 70s and humidity at 90%, the heat stress in Atlanta will be higher than he has faced before. "I've never run a marathon in those conditions," he says. "You only see that in world championships or Olympic years, because otherwise, marathons are in the fall or spring, for that reason [heat]."

Kempainen, a Minneapolis medical student, says it was about 83°F (28.3°C) and 60% humidity when he ran the Olympic marathon in Barcelona in 1992. "The humidity wasn't too bad," he recalls. "It wasn't comfortable by any stretch, but I don't think there were dozens of people being treated for heat exhaustion."

Timing the Marathon

The focal point for worries about heat stress has been the men's marathon. Originally the race was scheduled for 6:30 pm Sunday, August 4, the last day of the games. That time was picked so that the finish of the race would bring the games to a dramatic end and segue directly to the closing ceremonies in a packed stadium. Use of the men's marathon as part of the grand finale has been a tradition since the 120214 Summer Games in Los Angeles. The women's marathon was originally and still is set for 7:00 am.

Medical people and athletes were concerned from the beginning that running the men's race in the evening would pose too great a risk of heat injury for the runners. Prolonged efforts to change the time finally triggered a decision in late March to switch the start to 7:00 am. The move was made by Primo Nebiolo, president of the International Amateur Athletic Foundation (IAAF), in concert with the IAAF Council, according to Martin.

Wilson says he and other ACOG medical personnel had been seeking the change for about 2 years. He adds that the weather data collected by Martin helped precipitate the decision by showing that heat stress would be less severe in the morning than in the evening.

Some temperature data from the summer of 1995 made a schedule change look even more critical, according to Martin. Daily temperatures in midsummer usually peak at about 2 pm, but last year they peaked around 4 pm, "which meant that it never got very cool at night," he reports. "On four occasions last year, even at 10 at night, we had temperatures around 90." Thus, running a race in the evening could mean running at temperatures in the mid 90s.

Martin says the IAAF Medical Committee, led by Swedish physician Arne Ljungqvist, lobbied vigorously for changing the time of the race. Ljungqvist was particularly concerned after he reviewed Martin's weather data at a meeting in Atlanta last fall, according to Martin.

Others spoke up as well. One was famed hurdler Edwin Moses, a member of the Medical Commission of the International Olympic Committee (IOC). He expressed concern that in addition to a high air temperature and humidity, runners could be dealing with pavement temperatures exceeding 130°F (54.4°C). "From the athlete's point of view, I felt that [holding the marathon just before the closing ceremonies] was not as important as the risk of someone getting seriously hurt running in an event in the heat of the day," says Moses, an Atlanta resident. "So we went on the record as being on the side of safety."

Other groups that lobbied for the change included the ACSM and the International Marathon Medical Directors Association, according to William O. Roberts, MD, White Bear Lake, Minnesota. Roberts serves as medical director of the Twin Cities Marathon, and is a board member of the ACSM and an editorial board member of The Physician and Sportsmedicine.

Despite all this concern, heat worries weren't the only motive for the schedule change, according to Wilson. Thunderstorms and television coverage also played a part. Atlanta has thunderstorms often in the afternoon but rarely in the morning, and thunderstorms would both endanger the runners and hinder TV crews, Wilson says. Also, a morning race works well for TV because it means that Europeans can watch the race in midafternoon and Asians can see it in the evening.

Mobile Marathon Medicine

Of course, a 7 am start for the marathon is no guarantee that runners will have a nice, cool time of it. For one thing, as mentioned above, Atlanta humidity at 7 am in July averages 88%. And it could already be hot. Says Moses, "I go to work at 7:30 in the morning, and I can remember days when it was 91, 92 degrees at that point in the morning. You walk outside and it just hits you right in the face."

In fact, Joe Douglas, who coaches US marathon team member Jenny Spangler, thinks the race should start even earlier to minimize heat stress. "I think it should start at 6 o'clock. The earlier the better," says Douglas, distance running coach for the Santa Monica (California) Track Club. He adds that getting up so early is also hard on athletes, "but you're trying to pull the best out of a bad situation."

In any case, postponement of the race due to hot weather is not in the cards. Cantwell says an electrical storm could delay the race, "but I don't think an event like the marathon will be canceled because of heat and humidity. It'll be run at that time, when we have pretty good data that it'll be a reasonable heat stress index."

Since cancellation is unlikely, Wilson and his medical team hope that a new approach to marathon medical coverage will prepare them for the worst. Wilson heads the medical team at the Peachtree Road Race, a 10K event that attracts up to 50,000 runners to Atlanta each July 4. "Our experience at the Peachtree Road Race has convinced us that immediate treatment for a collapsed runner with heat problems is important. So instead of taking the runner to the treatment, we're attempting during this race to take the treatment to the runners."

The medical team hopes to do this by monitoring the runners carefully and stationing seven medical vans and five ambulances along the marathon course, Wilson explains. At aid stations set up every 2.5 km, nurses equipped with radios will watch the runners and track their 2.5-km times. If a runner starts slowing up, the medical team can watch him or her and be ready to help immediately if the runner stops or collapses.

The medical vans will take the place of a central medical tent. Each van will be staffed by a multilingual physician and a nurse who can provide cooling and fluid replacement. Also, an ambulance will be nearby in case someone needs immediate hospitalization.

"We don't feel that most of the runners at this level are having much damage when they're running; the damage occurs when they stop," says Wilson. "If we can be there the moment they stop, and prevent that damage, we can go a long way to prevent a lot of the problems related to heat."

The mobile-monitoring treatment approach will debut at the women's marathon, a week before the men's. "It's never really been attempted to provide this kind of care before," Wilson says. "We hope the women's race, with fewer runners, will give us a bit of a learning curve before the men's situation." He expects 60 to 70 in the women's race and roughly 120 in the men's.

The aid stations will offer wet sponges as well as cold drinks, Wilson reports. Alternate aid stations will have the runners' selected drinks, and the rest will have "generic" drinks. Sponges will be offered instead of cooling sprays, whose efficacy as a cooling aid is in doubt.

Help Along the Course

Even with plenty of precautions, Wilson predicts that the heat will take a toll. "We expect at least a third of the people here in Atlanta not to finish the race, and all those who stop will need to be treated medically or at least evaluated for the need for treatment. And we expect everybody at the finish line to need some assistance with cooling."

Runners who stop during the race can be medically assessed without being disqualified, Wilson reports. The rules on this have changed slightly since 120214, when overheated Swiss marathoner Gabriele Andersen-Schiess staggered into a Los Angeles stadium and around the track as medical personnel watched, prohibited from touching her because it would have meant instant disqualification. Now, runners are disqualified only if they receive actual medical assistance. Physicians can do such things as talk to a runner and take a pulse without triggering disqualification, Wilson says.

Wilson's bottom-line prediction is that the marathons will be safe events. "We're attempting to prepare for the worst scenario, and if we don't get it, then we'll all be very happy with the boredom we suffer through during the race," he says. "I think with the changes ACOG has made in the treatment of these situations, we can run the race safely and tell the athletes, 'If you get in trouble, that's OK, because we'll be there to take care of you.'"

Preparing to Cook

Of course, endurance athletes can increase their safety margin somewhat by training to deal more efficiently with heat. The consensus seems to be that athletes should allow 2 weeks for acclimatization to heat but should not train hard in hot, humid conditions.

"Some studies have shown that after 2 to 3 weeks, 90 to 95 percent of the heat acclimatization will have occurred," so most athletes probably will go to Atlanta no more than 2 to 3 weeks early, says Martin. He adds that they will do their real "quality training" at home and then taper off in Atlanta so that they won't be acclimatizing under "undue stress."

Kempainen plans to go to Atlanta no more than 2 weeks early, and Douglas says Spangler will do the same. In fact, Douglas believes hard training in heat is harmful. "We're not going to train hard (in Atlanta), so we're not going to have all the negative effects of training in the heat. If you do that, it causes a lot of problems with your blood chemistry," he says. "You pay a heavy price."

Beyond the Marathon

The Olympic medical experts seem far more concerned about the marathons than any other event, but they acknowledge that some of the others could make athletes very warm as well. Competitors in the 50K race-walk, for example, circle a 2,000-m outdoor track for 4 hours or longer, says Martin. The race will take place in the morning. Drinking while on the move isn't as hard for race-walkers as it is for runners, but they are "under considerable thermal stress for a fairly long period," he says.

He also says entrants in the pentathlon could have some trouble with the 4,000-m cross-country run, since the multiple nature of their event means they usually aren't as well trained for endurance as habitual distance runners are.

Though soccer is a demanding running sport, Cantwell doesn't expect a lot of heat problems in that area. Games will be played at the University of Georgia football stadium in Athens, where the medical people are used to dealing with heat, he says. "It isn't going to be any hotter than guys out there in full football gear playing in August and September."

Other events that could cause heat problems include the 10- and 5K runs, long-distance cycling, and the equestrian events, according to Martin. But all of these events combined account for only a small minority of the 10,000 Olympians expected for the games, he says. And, he adds, many athletes will compete only in air-conditioned indoor venues.

Flaming the Fans

The endurance tests at the Summer Games won't all be on the athletic fields. Thousands of fans will face their own ordeals, sitting in the sun for hours and walking miles to various venues. That's why people like Moses and Martin are more worried about the fans than the athletes.

"I think the heat is going to be terrible for the spectators, more than the athletes," says Moses. "There's really no escape if you're outside. If you go in the shade you're still in the heat and humidity.

"The athletes are probably more prepared for it, because they're highly conditioned. But there are going to be a lot of people who may not be as healthy who are trying to go up and down hills or walk 2 or 3 miles or wait for transportation in non-air-conditioned areas." Conditions could be especially tough for people with heart problems, diabetes, or excess weight, he adds.

Martin shares this view. In fact, he says fans who plan to attend the Olympics should train for the experience. "I really fear that unless these people think of themselves as Olympians in their own right and get out and start training themselves, they're going to set themselves up for potential health casualties," he says.


  1. Martin DE: Climactic heat stress at the Atlanta 1996 Olympic stadium venues, 1992-1995. Sports Med Training and Rehab, in press
  2. Sparling PB: Expected environmental conditions for the 1996 Summer Olympic Games in Atlanta (editorial). Clin J Sports Med 1995;5(4):220-222
  3. American College of Sports Medicine: The prevention of thermal injuries during distance running. Med Sci Sports Exerc 120217;19(5):529-533
  4. Sparling, PB: The risk of heat stress in Atlanta '96 (author's reply to letter). Clin J Sports Med 1996;6(2):142-143

Robert Roos is senior editor of The Physician and Sportsmedicine.