In the race to the finish line, nearly all marathon runners will experience small bumps along the way — blisters, stomach cramps, even bloody nipples.
But this weekend, the Chicago Marathon shut down early after an unusually hot Midwest day appeared to catch organizers, and runners, off guard.
Some experts now wonder whether a more critical look should be taken of the runners, who in the face of the brutal conditions, may have lacked a little "common sense." Others wonder whether races this size should require participants to prove they are fit enough to run a marathon.
During Sunday's race, when temperatures soared to the high 80s, about 50 people were taken to hospitals. Hundreds more were treated on the course for heat-related illnesses. Many runners complained about a lack of water and said race officials were not prepared for the heat.
At least five people remained hospitalized Monday evening, The Associated Press reported.
Chicago marathon officials insisted they saw the heat wave coming and added extra water, ice and misting stations. But one official told the AP that perhaps they should have placed more water earlier on the course and that they did not anticipate so many would use water to douse themselves.
"It is very easy to blame the organizers," Jeffrey Sankoff, an emergency room attending physician and an experienced triathlete, told ABCNews.com. "What happens in a lot of these races [is that] people get focused on their time. It's often more of a problem for the experienced athletes than the novice runners."
According to Sankoff, who was also the assistant medical director at last year's Colfax Marathon in Denver, runners often spend so much time training for a marathon that they may not want to stop — even when they're told to, by their bodies or by the race organizers.
"It's very easy to spend time shooting for a goal and when you get to the race you may not pay attention to the kinds of signals that your body is giving you when it's telling you to stop. … It's tough," he said.
That's what happened to Mark Roberts, a 37-year-old engineer in Memphis, Tenn., when organizers announced that the race was over and that he should stop running — he still had 6.2 miles left to the finish line.
"At the end — mile 20, they said the course is closed, make sure you stop at the next aid station. It might be the last time you can get water or Gatorade," Roberts told ABC News. "After training for three months … when you get that close to the end, you want to finish your race."
Roberts kept going and crossed the finish line in four hours and 45 minutes — 45 minutes longer than he was expecting. He says he found plenty of water aid stations along the way.
"The aid stations were all open … [but were] starting to shut down after I went through," Roberts said.
Other runners were not so lucky.
Sunday's marathon was marred by reports of water shortages, which Roberts said that he experienced during the first six miles.
At the first aid station, there was no water or Gatorade and at the second, there was no Gatorade, according to Roberts.
"Some of the spectators were handing out bottles of water. I definitely drank bottles of water from people that were just standing on the side," he said. "Without those, I would have slowed down a whole lot."
But a lot of people didn't get the hydration they needed or may not have listened to their bodies.
"When you step onto the field of battle, whether it's football or a marathon, there's an inherent risk of the sport and you accept that as a participant and it's up to each individual to be ready to go," said C.T. Moorman III, the director of sports medicine at Duke University.
Moorman says that in a situation like the Chicago Marathon, runners have to use "common sense."
"It's a really hot day. Make sure electrolyte balance is good. A lot of good sports drinks can do that," Moorman said. "Go slow and hydrate and if you're not in shape don't do it."
Experts agree that if you feel nauseous, lightheaded or if you have stopped sweating during a race, you should seek medical attention.
But there's also another potential element to the marathon-gone-wrong equation: running novices, who may not as easily recognize warning signs that could indicate dehydration or heat exhaustion.
Other critics point out that the Chicago Marathon, at 35,000 runners, is one of the largest in the country that does not require runners to qualify.
The Chicago race is renowned for having a less challenging, flat course, one that attracts eager beginners hoping for a relatively easy run.
"That's exactly what you're going to hear. I think novice runners definitely listen to that kind of advice," said Christopher Ingersoll, editor in chief of the Journal of Athletic Training and a professor of sports medicine at the University of Virginia.
"On one hand, it would be a shame to exclude someone who is not an elite athlete, but is in adequate condition. … Medical professionals and race organizations need to put their heads together … to think about inclusions criterion for entrance" to races, Ingersoll said.
Moorman, a one-time marathoner, agreed that more limits on who enters marathons might help alleviate race-day problems.
"Events that don't require qualifying time are going to have more novice runners than others and that are perceived as less difficult are going to draw more novice runners," he said.
A few marathons, including the Boston Marathon, have minimum requirements for runners wanting entry into the race.
Over the years, however, some charities have actively targeted those novices to train for marathons and other arduous racing events, including Iron Man competitions.
One of the most well-known is Team in Training, a part of the Leukemia and Lymphoma Society. The group leads would-be marathoners, including many who have never done any running before, through a six-month training program that is meant only to get them across the finish line, while raising money for the charity in the process.
"My first answer is … if they [Chicago runners] had only been with Team in Training," said Tommy Owens, Team in Training's national training coordinator and head coach of a Georgia-based group. "We prepare them for those eventualities. I tell my people they're better prepared than most people at the start line."
But some, more serious athletes have criticized groups like Team in Training for putting nonathletes into what some believe is an extreme sport.
While Sankoff, a Team in Training alum, has witnessed the criticism and understands it, he doesn't agree with it.
"I don't look at those programs as being negative on the whole. They probably do engender that feeling that you can do anything and make it seem to people that it's not such a big deal," Sankoff said. "We're in a society that doesn't emphasize fitness enough. Anything that's going to make people participate is a good thing."
Despite criticism that these organizations might face, however, Sankoff maintains that it's the more middle-of-the-road competitors that are more likely to find themselves passed out with heat exhaustion.
"It's not the amateurs, the newbies that get in trouble. It's the people that are sort of in that middle ground," he said. "It's that middle ground who are trying for personal best, who are clearly out of their element when you get into those conditions that you don't recognize. … You always need to pay attention. You need to be completely in tune with your body."
Mark and Elisa Dennis, a Chicago-based husband-and-wife team, also ran Sunday; it was his first and her second. Although hot, they felt good while running. But when saw more experienced runners passed out on the route, they decided it was time to take it easy.
"At first you see people -- maybe people who aren't in the best physical condition starting to slow down and you see elderly people slow down, but when we saw people in our own age group, more experienced runners, passed out, we knew we needed to take it easy," Elisa Dennis, a 27-year-old architect, said.
Between mile 19 and 20, the couple realized from the bullhorns of both race officials and police that the race was over. Runners, according to Dennis, were advised to get on a bus that would take them to the finish line. Despite the warnings, however, the couple, like thousands of runners, continued to the finish line, walking most of the way.
"Honestly, I thought it was a joke," Dennis said. "From there on out we walked the rest of the race and if we felt good, we jogged a little. ... We were bound and determined to go 6 more miles and finish even if we had to walk. .. The majority of people kept going."
The couple ran across the finish line with a time of five hours, 50 minutes.