The Dark Side of Fitness

Inside the often unfortunate, sometimes weird, and occasionally gruesome drawbacks of fitness fanaticism.

April 2016

—Photography by Tom Speruto

Because a lot of scary medical stuff can go down during an endurance race. 

Dr. John Hill, director of CU’s primary care sports medicine fellowship, has not only overseen Leadville 100 biking and running events as a medical director—he’s also experienced them as an athlete. Below, he helps us break down eight serious ways the human body can react to the stress of competition.


If your blood-sugar level drops too low, your brain—which feasts on glycogen from the liver—can begin to starve. When that happens, Looney Tunes–style delusions set in: Boulders morph into giant Chipotle burritos and purple gorillas begin chasing you in the dark. “Being confused and seeing things, especially at night, happens to most long-distance endurance athletes,” Hill says.


This is a system-wide collapse caused by depleted fuel stores. Athletes will feel weak, fatigued, and disoriented because they are low on glucose and/or glycogen, which the muscles and brain need to function. “Once someone gets to this point,” Hill says, “it’s difficult to save their race because they need nutrition but can’t eat. We can give them anti-nausea drugs and salty snacks. It doesn’t always work.”

Exercise-induced Asthma

Dust, cold temperatures, dry air, extreme exertion, and high elevation can provoke asthma symptoms like coughing, wheezing, shortness of breath, chest tightness, and excess mucous. Sometimes the symptoms
are serious enough that physical activity must
be stopped immediately.


Drinking too much fluid can cause the concentration of sodium in athletes’ blood to drop to dangerous levels. Sodium helps regulate the amount of water in and around cells; when there’s not enough sodium relative to the H20, the body’s water levels rise and cells swell. Weakness, brain herniation, seizures, and coma can result. “The medical consensus is if you trust your thirst,” Hill says, “you’ll be OK.”


During hyperthermia the body is unable to regulate its internal temperature and becomes overheated. Most people have heard the term “heat stroke” but may not know it’s a medical emergency. If the body’s temp gets as high as 105, internal organs can be damaged, and without treatment, you can die. “We sometimes have to use immersion tubs to rapidly cool these athletes,” Hill says.

High-altitude Pulmonary Edema

A condition that usually occurs above 8,000 feet in elevation, high-altitude pulmonary edema (HAPE) happens when fluid—instead of oxygen—floods the alveoli in the lungs, causing extreme breathlessness. Without medical treatment (at a lower elevation), HAPE can be fatal.


When muscle tissue breaks down, which can occur when athletes overstrain their bodies, muscle fibers are released into the bloodstream. These fibers can cause renal failure—and sometimes death, particularly when an athlete takes ibuprofen, which can accelerate kidney deterioration. “Some of these disorders are hard to diagnose,” Hill says. “I mean, who feels good 70 miles into a race? My advice: Go to the medical tent if you feel bad.”

Sports-related Sudden Cardiac Death

Undiagnosed heart conditions—like coronary artery disease or hypertrophic cardiomyopathy (thick ventricles)—can be irreversibly aggravated during endurance events. With participation in endurance sports increasing over the past 15 years, sudden deaths from previously undiagnosed heart conditions have made headlines in publications from USA Today to Men’s Journal to Scientific American.

Because death is an honest-to-God possibility. 

1 in 76,000 

The approximate fatality rate for athletes participating in a triathlon, according to a study released by USA Triathlon in 2012.

1 in 114,000 

The approximate fatality rate for athletes participating in a marathon, according to a 2010 study focusing on 30 years’ worth of races in the United States, Britain, and the Netherlands.


The estimated number of sports-related sudden cardiac deaths in the United States each year, according to a 2011 study circulated by the American Heart Association.

At least 10 

Athletes—from long-distance mountain bikers to triathletes to ultrarunners—who have died competing (or shortly after competing) in Colorado events since 1992.