A new study has been created to examine the endurance levels of athletes. Some of the toughest sporting events like the Ironman triathlon to the Tour de France were used for research analysis The team of researchers from the Scotland’s University of Aberdeen and the Chinese Academy of Sciences found that all humans have the same metabolic limit, a maximum level which humans can sustain in the long term. Experts confirm that even the world’s fastest marathoners cannot manage to surpass this limit.
The research confirmed that through physical activities which lasted for days, months and weeks, humans can burn only 2.5 times the calories to their resting metabolic rate, beyond which the human body starts to break down its tissues in order to make up for the caloric deficit. Experts suggest that this limit is because of the human digestive track’s ability to break down food.
“There’s just a limit to how many calories our guts can effectively absorb per day,” says co-author Herman Pontzer.
For the study which is published in the journal Science Advances, the team measured daily calories burned by athletes who participated in six marathons in a week for a period of five months as a part of the 2015 Race Across the USA. Moreover, the team also considered other feats of human endurance, which included punishing 100-mile trace races and pregnancy.
The results of the study concluded that the athletes started out with relatively high performance in the beginning and then flattened out 2.5 times to their basic metabolic rate towards the end of the event.
Urine samples were tested as a part of the research during the first and final legs of the Race. This shed light on the fact that the marathoners burned 600 fewer calories a day than expected after twenty weeks of running back to back marathons. This revealed that the human body can “downshift” metabolism to maintain sustainable levels.
This L-shaped curved was observed by all endurance events, be it running or cycling. “It’s a great example of constrained energy expenditure, where the body is limited in its ability to maintain extremely high levels of energy expenditure for an extended period of time,” says Co-author Caitlin Thurber in a statement.
However, experts found that sustainable energy expenditure was slightly higher among endurance athletes than metabolic rates among women during pregnancy. Shortcomings were observed in the digestive process, the ability to process food and absorb calories and nutrients.
In conclusion, experts suggests that, no one’s ever sustained levels beyond a certain limit. “So I guess it’s a challenge to elite endurance athletes,” reports Pontzer. “Science works when you’re proven wrong. Maybe someone will break through that ceiling some day and show us what we’re missing.”