Many individuals face difficulties completing even a mile of running, while some effortlessly conquer 10 kilometers. Rarely, individuals embark on ultramarathons, races over 26.2 miles (42.2 kilometers).
But what is the ultimate distance a human can run without stopping?
To address this question, it is crucial to determine the meaning of "stopping." Dean Karnazes unofficially holds the record for the longest run without sleeping, covering 350 miles (563 km) in three and a half days back in 2005. In 2023, ultrarunner Harvey Lewis set a new record in the form of a backyard ultra race.
This competition entails runners completing a 4.17-mile (6.7 km) loop hourly until only one runner remains. Lewis completed 108 loops within as many hours (equivalent to 4.5 days), totaling 450 miles (724 km), with brief rests at the end of each hour.
Despite ultramarathon runners usually taking short breaks for various reasons, such as walking, eating, or sleeping, there is no official record for the longest continuous run. The need to answer nature's call would likely serve as the primary limitation.
The Human Advantage
Physicist Jenny Hoffman, an ultrarunner herself, remarked on the possible constraint of bathroom breaks for extended runs. She holds the world record for the fastest U.S. coast-to-coast run by a woman.
Humans possess certain characteristics advantageous for endurance running. Guillaume Millet, an exercise physiologist, highlighted traits such as robust glute muscles for propulsion, energy storage in tendons and muscles, and strong neck ligaments for stability during running. Sweating allows humans to regulate body temperature efficiently, aiding endurance in hot conditions.
Although humans exhibit these adaptations for running, they did not specifically evolve for ultra-long distances. According to evolutionary biologist Daniel Lieberman, humans historically underwent intense physical labor for survival, emphasizing efficient running and endurance, although extreme distances were not the norm.
Physical and Mental Limits
Numerous physical factors, like injury and fatigue, can halt a runner's progress. Mental determination also influences endurance running, necessitating the ability to push through discomfort and weariness.
Endurance runners need extensive training to prevent injuries. Before Hoffman’s transcontinental run, she gradually increased running distances to build aerobic capacity and skeletal strength to endure prolonged periods of exercise.
Ultramarathon participation has surged by 1,676% between 1996 and 2020, indicating a growing interest; new athletes may challenge existing records, continually pushing the boundaries of human endurance.
Hoffman anticipates that these limits will persistently be pushed further as more individuals venture into the sport.
As human endurance continues to be tested, the limits of long-distance running remain elusive. While physical constraints such as injury, fatigue, and the need for rest play a role, mental resilience and training advancements enable athletes to push further than ever before.
The growing popularity of ultrarunning suggests that records will continue to be broken, challenging our understanding of human capability. Whether the ultimate limit will ever be reached is uncertain, but one thing is clear—human endurance is as much about determination as it is about physiology.
What's the Longest Distance a Human Can Run? The Science of Running
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