"My toenails turning black happened before," said Jessica Horne, 26, an amateur athlete who will be running for the second time in the ING New York City Marathon this Sunday.
"But it wasn't until this intense, long-distance marathon running that I discovered everything else," Horne said.
Horne is just one of thousands of non-elite athletes joining the marathon boom in the United States. And as more amateur athletes take up the sport, more people like Horne are discovering the "everything else" side effects that come from pushing their bodies literally to the limits -- black toenails, missing toenails, stomach problems and bloody appendages.
In 1970, the New York Marathon only had 127 runners. By 1976 it was 2,090. Last year, 39,265 people started and 38,607 finished.
"This sport is exponentially increasing," said Dr. Lewis Maharam, medical director for the ING New York City Marathon and a columnist at runnersworld.com.
As an athlete during high school, Horne had already experienced the infamous "black toe" before she started training for a marathon.
Black Toes and Other Problems
Black toe, technically called subungual hematoma, is just a simple bruise from repeated impact that turns into a pool of blood under the nail.
Bruce Williams, president of the American Academy of Podiatric Sports Medicine, ran in six marathons and treated hundreds of marathoners in his career.
"We've seen lots of things from lots of blisters, black toenails, in-grown toenails, stress fractures," said Williams. "Just about everybody is going to get a blister."
Unlike many other sports where athletes tear ACLs or break bones, the majority of injuries in marathons tend to be overuse injuries, said Riann Palmieri-Smith, a certified athletic trainer at the Bone and Joint Injury Prevention and Rehabilitation Center at the University of Michigan in Ann Arbor.
"One of the biggest things that happen when people injure themselves is they're really running too far at a low intensity, or they are rapidly increasing their intensity," said Palmieri-Smith.
Marathoners Rubbed Raw
All that rubbing and pounding can cause tendons to rub over joints (called ITB or illiotibital band syndrome), inflamed muscles in the foot, foot stress fractures, skin chaffing on skin and nipples rubbed so raw from moving shirts that they bleed.
"You want to have as little on the body as possible," said Horne.
To help with chaffing, she uses a product called 'glide' on her skin. Luckily, Horne said, she doesn't have a problem with bleeding nipples.
"That makes me just shiver," said Horne. "It mainly happens to men because women have sports bras. A lot of the guys that I train with on my team wear Band-Aids to help."
Horne runs with the Team for Kids, which has raised millions of dollars to improve the lives of children in the United States, as well as in the Cape Town region of South Africa.
As for her black toe, Horne said she never lets it slow her down.
"It never really bothers me; it hurts in the beginning when my toenails turn black and blue," said Horne. "Another toenail grows underneath and the black and blue one falls off."
Black toe can also happen to mountaineers, hikers, and other athletes.
A great documentation of a black toe experience can be found on the Starling Fitness Blog.
In Williams' experience, most marathoners run through the worst of the problems.
"Some of them can be pretty hardcore, and nothing is going to stop them from race day, and they're just going to fight through the pain," he said.
Unfortunately for Horne, another problem faced by serious runners kept her from reaching her finishing time goal. Last year, Horne finished in 4 hours and 53 minutes.
"Runners' stomachs can be ... sensitive," said Horne.
The runner's runs is a common term for it, and many serious long-distance runners face the problem. Although doctors do not necessarily understand the cause, one hypothesis is the blood flows so much to the legs during a run that the intestines react and cannot function properly, according to the Mayo Foundation for Medical Education and Research (MFMER).
Champions Run Through Pain, Trouble
Horne said her stomach problems seemed connected to the high-carbohydrate gels and health bars marketed to runners.
"I tried those, and they did not work for me; they really destroyed my stomach," said Horne.
A trip to the nutritionist to help her find other foods, and careful training to ease her knee pain has made Horne much more hopeful this year.
But some elite marathoners have ignored this problem and kept running through stomach problems to win a race.
Elite long-distance runner Uta Pippig came from behind to win the 1996 Boston Marathon, despite showing visible signs of menstrual problems and diarrhea while she ran, according to reporting by the Boston Globe.
But, for all the unpleasant side effects, marathoners say they are happy to live through the accomplishment and feel the better for it.
More Health Than Hurt?
"The benefit of running has all the health benefits -- decrease in blood pressure, stronger heart, decreased risk of diabetes," said Maharam, who will be in charge of all medical teams attending this year's ING New York City Marathon.
Despite the images of extreme pain, sweating, and breathing, Maharam says running a marathon is relatively safe if the runner has prepared properly.
But, Maharam said, one thing marathoners should do to make race day even safer is to be wary of drinking a lot of water. Consuming too much water on race day could lead to something called hyponatremia, or water intoxication.
"If you walk or run a race more than 10 miles, it could be an issue," said Maharam.
According to Maharam, when runners exercise in long distances, a lot of blood flows to the muscles and away from the internal organs like the stomach or kidneys.
"That's why if you try to feed a runner when they finish, they throw up," said Maharam.
The effect on the kidney is to reverse its normal functioning. Instead of ridding itself of excess water, the kidney keeps it.
"You pee out salt to retain free water. Even if you drink Gatorade, you pee out salt to retain free water," said Maharam.
Running Strategy Is Key
"It's very easily fixed, just by education," said Maharam. "You need to only need to drink for thirst."
Although water intoxication can cause death, the last death at the New York City Marathon was caused by a genetic abnormality.
"We had Ryan Shay last year," said Maharam. "Before that, the last death was in 1994."
Ryan Shay collapsed and died in 2007 during the Olympic trials race, one day before the ING New York City Marathon. Doctors had previously diagnosed him with an enlarged heart, but he was cleared to compete in the race.
Maharam insisted the odds of death are pretty low, about 1 in 60,000 people during a marathon.
Yet, the city will have more than 25,000 medical volunteers with medical stations at every mile and eight triage areas to help people along the way.
"You know, 26.2 miles is not a walk around the block," said Maharam.