The number of marathons athletes who are able to join in a period of three months could be more than hundreds. It looks like there is nothing that can stop them from joining. But how much stress from all these running can the body really take in a month? It turns out that their body is the only obstacle in their way.
A new study is quantifying what seems like an unsurpassable "ceiling" for human endurance, particularly that of athletes, on long-distance biking or running. It shows how much stress the body can take from running a marathon. The study also revealed that the metabolic toll that a woman's body undergoes through pregnancy resembles that of a runner participating in an ultramarathon.
"It is very convincing data that a human's extreme endurance comes with hard limitations," said Daniel Lieberman, an evolutionary biologist from Harvard University.
Athletes and Physiologists have long been interested to find out how far the human body can go. When it pushes itself through physical activities for a few hours, the wealth of data they collected shows that most people or mammals in general max out their endurance when they have reached five times their Basal Metabolic Rate (BMR). this refers to the amount of energy they have when at rest. How humans expend their energy during longer endurance activities is a whole new story, says Herman Pontzer, Duke University evolutionary anthropologist.
Pontzer saw an opportunity for a new study to explore when an endurance athlete by the name Bryce Carlson launched a 4957 kilometer run over the course of 20 weeks. The series of marathons stretches covering the areas of Los Angeles, California to Washington, D.C.
Pontzer's team of researchers measured the BMR of six runners composed of five men and one woman at the beginning of the race. Then, they worked to collect the data on energy expenditure over the course of the race to calculate how many calories they burned in a day. They analyzed this data and plotted it with the other data collected from marathons that were studied in the past.
The team found out that it didn't matter what type of event an athlete enters, their energy expenditure levelled off after twenty days plateauing at roughly 2.5 times as the person's BMR. At this point, the human body is burning more calories that it is absorbing, which basically shows the biological determination of the "ceiling" in human performance. When an athlete hits the ceiling of his endurance, his body dips into the body's fat reserves to help convert them into energy they can use.
"We ended up identifying the very limit of human endurance. This practically envelopes what humans can do when exposed to extreme situations," Brent Ruby said.
