After a full day of classes, lunch dates, and club meetings, it can be quite tempting to proclaim, “I feel like I’ve been running around all day!” Of course, the majority of our waking hours are usually spent sitting down–whether studying or on Facebook–while the majority of our exercise comes from madly dashing across campus. To say we’ve been running around “all day” is certainly an overstatement for most of us–but not for all.

Enter a small group of elite athletes known as ‘ultrarunners.’ Ultrarunners push themselves to their physical and mental limits by competing in footraces (aptly named ‘ultramarathons’) that exceed the 26.2 miles of a typical marathon. Ultramarathons often involve extreme conditions and terrain, and can span over 24 hours. While many people shake their heads at the notion of running 26.2 miles through city streets, ultrarunners regularly tackle 100 miles through the Sierra Nevada Mountains (Western States Endurance Run); 135 miles through the scorching desert hills of Death Valley (Badwater Ultramarathon); and 153 miles from Athens to Sparta (Spartathlon). To say that these athletes are dedicated to their sport would be an understatement. Yet, what exactly is the cost of this dedication for their bodies?

An average runner lands on each foot approximately 5,000 times per hour throughout the duration of a race, though this varies significantly for ultramarathons when taking into account the extreme terrain. With the athlete’s feet absorbing up to three times their body weight with each step forward, they can exert over one million pounds of pure force during any given hour. Over 24 hours, such an amount of strain on the lower extremities becomes tremendous; feet can swell up to three sizes, and injuries related to the soft tissues of the lower extremities become the most commonly cited reason for dropping out of a race.

Rhabdomyolysis—dissolution of skeletal muscle is especially prevalent among ultrarunners. Rhabdomyolysis results from buildup of creatine phosphokinase (also known as CPK, an enzyme found inside muscle cells) after strenuous exercise. High CPK levels also indicate the release of myoglobin, a protein that crystallizes within the kidney tubules. In extreme cases (such as when the individual is dehydrated, taking Ibuprofen, or under severe heat stress, as often happens during ultramarathons), excessive myoglobin buildup can result in renal failure.

Violent spasms of hiccups, seizures from inadequate blood flow to the brain, gastrointestinal bleeding–all are relatively common physical side effects of participating in an ultra. Arguably the greatest physical challenge, however, is maintaining a sufficient energy balance to allow satisfactory performance.

It is not uncommon for ultrarunners to burn over 10,000 calories during a race, especially when spanning multiple days. Prolonged endurance-based activity is known to significantly suppress an athlete’s hunger drive, as do high temperatures and chronic dehydration. In short, the very nature of ultramarathons makes eating solid food extremely undesirable, if not impossible. In order to cool the body down and maintain motion, blood flow is diverted from the digestive system towards the outer extremities, causing nausea and possible vomiting (which results in even greater dehydration). Yet, it is during these events of extreme athletic endurance when solid foods, as opposed to more digestible specialty products like ‘GU’ and energy drinks, are ultimately required to keep up an adequate balance of calories.

Running for such extended periods of time with a continuous caloric deficit–unfortunately, a common occurrence—–s only one factor contributing to the enormous psychological impact incurred during an ultramarathon. With athletes moving for extended lengths of time through extreme conditions while maintaining a negative energy balance, losing 4-6 liters of water per hour, and depriving themselves of sleep to meet a time goal, it should not be shocking that many experience some sort of hallucination mid-race. A 2003 study done on Death Valley’s Badwater Ultramarathon (particularly notorious for its incidences of hallucinations) found that at least 30% of runners hallucinated at some point. Of these reported cases, most occurred during the race’s second night, when sleep deprivation was high, physical exhaustion was near its peak, and the silent darkness of the desert was so absolute. These conditions have the potential to send the brain into ‘survival mode,’ weakening its ability to discern what is real. One participant reported seeing rotting corpses cluttering the road in front of her; another felt a bat constantly flapping its wings against his shoulder. Marshall Ulrich, a ten-time Badwater participant, once experienced an auditory hallucination so intense that he believed an airplane was landing right next to him.

Foot injures. Renal failure. Seizures. Hallucinations. Is the satisfaction of completing an ultra truly worth the tremendous physical and psychological traumas incurred? Why do athletes subject themselves to such suffering? What do they possibly stand to gain, apart from bragging rights? Scott Jurek, two-time winner of the Badwater Ultramarathon and seven-time winner of the Western States Endurance Run, said it best in his memoir, Eat and Run: “the longer and further I ran, the more I realized that what I was often chasing was a state of mind […] where worries that seemed monumental melted away, where the beauty and timelessness of the universe, of the present moment, came into sharp focus.” A moment of serenity, a state of near-transcendence, a time in which only your mind, body, and the road beneath your feet seem to exist–a runner’s high of epic proportions.