In honor of a lot of topics discussed in the Endure book, the article I found was on the idea of endurance and testing to see how far the body could endure gruesome physical activities on a metabolic scale. In endurance challenges such as the Ironman triathlon or the Tour de France bicycle race, everyone has the same maximum level of exertion that they can maintain throughout the physical challenge. They concluded that in grueling physical activities that last for days, weeks and months, humans can only burn calories at 2.5 times their resting metabolic rate and not even the fastest ultra-marathoners can best that limit. One of the main reasons why is because above the limit of 2.5 times a person’s resting metabolic rate, the body begins to feed on itself to obtain the additional calories needed to function. In addition the limit may have to do with digestive capability of the gut. There’s a limit to how many calories our guts can effectively absorb per day and it’s why just eating more won’t improve endurance right away. From these findings from previous studies, these are some of the factors that up until now,  defined what exactly is possible for humans in regards to endurance. In this study, the researchers measured daily calories burned by athletes who ran six marathons a week for five months as part of the 2015 Race Across the USA, which stretched 3,000 miles from California to Washington, D.C. They also looked at other ways to measure endurance through 100-mile trail races and pregnancy. What they found was that the mega marathon runners burned 600 fewer calories a day than expected suggesting that the body can lower down metabolism to keep the body going and prevent you from burning up all of your fuel sources. In addition, they also found that the maximum sustainable energy expenditure in endurance athletes was only slightly more than women’s metabolic rates during pregnancy suggesting that there the limits that prevent Ironaman triathletes from breaking speed records could be related to the same that keeps babies from growing too big in wombs. I thought this article was interesting as it gave another example of just how limiting the human body is across varying groups of people. Something I wish they spoke about was the manner at which the study was conducted. They could have looked at the effect that competitive drive played a role in the endurance. Perhaps another group could have compared how going head to head with other individuals affected endurance compared to doing the trial by yourself.  I would have liked to see more of this because although there are physiological limits stopping us from reaching certain records, there are also neurological factors that can cause us to either break these limits or hinder our ability by telling us we are tired when the body may still have a little bit more energy to continue on. These topics are discussed in the Endure book such as in the section regarding belief and ones ability to believe they can surpass someone in a race as opposed to just running against yourself.