The Absolute Limit of the Human Body

At least once in our lives, we experience the crushing feeling of hitting rock bottom. We feel the defeat and regret of that first pilates class, or the burning anger and frustration of that screaming match with your older sister. In these moments, you can feel like you have reached your limit and things could not get any worse.

From a scientific perspective however, is it really possible to measure the ‘final breaking point’ of a person’s physical or mental wellbeing? Studies carried out by Hunter (2019), show that the amount of energy burned in many extreme sports such as cycling, swimming, running and rowing is highly dependent on their metabolic rate. A study that took place in 2015 during the ‘Race Across the USA’ event when participants ran 3080 miles in 140 days, along with research into the Tour de France and other extensive sporting events, showed the limit for physical endurance was 2.5 times a person’s resting metabolic rate or around 4,000 calories. (Gallagher 2019) Not even an ultramarathon runner can surpass this ceiling for human endurance. VO2 max (Jewell, 2023) is another important measure of physical ability used by many professionals. It is a scale used to measure your aerobic fitness levels by measuring the maximum volume of O2 your body is able to convert into energy. This depends on a variety of factors such as age, gender and lifestyle. But what about short term exertion? How long can a person really push themselves before their body gives out? 

Every body is shaped differently, due to both genetic and environmental factors, and while unfortunately we all can’t look like Selena Gomez, or run like Usain Bolt, our bodies can still achieve some pretty amazing feats. To determine an overall limit for the average person, we would have to examine different components in their genetic makeup, but also the basic structure of their body and their exercise capacity. For starters, the average human lifespan is 97 years (Koettl 2014), which is only increasing, and the average exercise capacity is 9-11 METS according to Saudi Med (2006) for a healthy functioning human body. However when it comes to a matter of life and death, the rule of three is what needs to be considered. This dictates that any human can survive for three minutes without oxygen, three days without water and three weeks without food. These are the simplest needs of any living human as all of the above are required for metabolism.

Sleep however, has been an intriguing area for many scientists with many different experiments done since the 19th century to test how long animals and humans can survive without sleep. While many animals such as rats or dogs died from severe sleep deprivation in such experiments, it is unsure what the limit is for humans. Many studies, such as the one discussed by Wolchover (2012) and Keating (2018) involved a 1964 high school project by Randy Gardner showing how humans can function for approximately 8-12 days without sleep. Randy and his friend Bruce Mcallister pursued the project to examine the effect of lack of sleep on cognitive ability, and to beat the world record at the time which was 260 hours. Based on a coin flip, Randy was chosen to be the subject of the experiment. They were joined by William Dement, a sleep researcher from Stanford University who recorded their results and monitored their progress. Randy stayed awake for 264 hours without any chemical assistance. His brain waves were monitored immediately after the experiment and it was discovered that during the experiment his brain was taking ‘micro naps’ which meant that certain parts of the brain were asleep while other parts remained awake. This is essentially what prevented him and likely our ancestors from experiencing the more serious consequences of sleep deprivation, such as hallucinations and cognitive impairment. What to really take away from this though, is that the next time you get caught by your parents staying up too late, you can always say it’s for science.

 While there is certainly no doubt that the human body is an intricate machine of finely tuned engineering, the human mind is one of the most fascinating aspects of the body. There is both so much and so little known about the brain and how it works which only adds to the intrigue. Of course, when it comes to intelligence, we are aware of IQ tests which assess cognitive ability based on a person's reasoning and problem solving skills. Currently, one of the highest IQs (Saunders, 2023) recorded is 225-230 by Terence Tao. However, even despite IQ the human brain is one of nature’s most formidable and utterly unpredictable weapons. Some could say that there is no limit to the human mind, it possesses endless possibilities. Arguing that there is a ceiling could also mean there is a theoretical limit to knowledge in itself. Many believe that humans' curious nature and thirst for answers is unstoppable. As more discoveries are made in areas we currently know little about such as space, the human mind itself, and if artificial intelligence could ever outsmart us, it only leads to further questions, ideas and research.

All of us have felt overwhelmed or anxious at some point in our lives. Approaching deadlines, difficult relationships and challenging environments are few of the many factors that push a person towards their breaking point. Psychologists use the term ‘breaking point’ (Miller, 2022) to refer to the point where a person breaks down, can endure no more or where a permanent change is made. This is something that varies on each individual, some people can handle and even excel in stressful and pressuring situations, think army officers and surgeons, while many others have a lower tolerance and become more easily overwhelmed or agitated. This concept of a mental ‘breaking point’ is used in high tension situations such as crime interrogations. Depending on the person, what actually happens at this point could lead to mental illnesses such as depression or anxiety which may require medical attention. What’s surprising is that in some cases, it is the opposite that happens and this ‘snapping’ of a person's mental wellbeing can inspire them to change their lifestyle for the better. Sometimes reaching a breaking point isn’t an instantaneous thing but rather a small realisation that changes your whole world view.

No matter your age, ethnicity, size or abilities it is undeniable that you can achieve almost anything with your body alone. Not all limits are definite and some are made to be tested and broken. Overcoming certain physical limits cannot be done with only one’s body or strength, but also with mental resilience and determination. If our predecessors could see how far we have come today, there is no doubt they would have deemed our discoveries and advancements impossible. As a species, we are encouraged to innovate and explore the limits of what we believe is possible. The future is uncertain and unpredictable, but we have the opportunity to redefine the capabilities of human potential. 

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Neev Kumar is a sixteen year old living on the rainy west coast of Ireland. She is fueled by her infinite curiosity surrounding the mechanisms of the world around her, and her love for STEM. Whether she’s shooting three pointers on the court, laughing with her peers or cooking with her mom, Neev is determined to break limits and seek the thrills of life. She plans on leaving her mark on the world, one fun fact and two dad jokes at a time.

References

1. Hunter S. (21 October 2019) The evolution of human endurance EMBO Reports https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6832006/ 

2. Tim Jewell (15 August 2023) Everything to Know About VO₂ Max Healthline https://www.healthline.com/health/vo2-max

3. Unknown (18 June 2019) Pushing the Limits of Human Endurance The New York Times https://www.nytimes.com/2019/06/12/well/move/pushing-the-limits-of-human-endurance.html

4. Gallagher J. (6 June 2019) Ultimate limit of human endurance found BBC News https://www.bbc.com/news/health-48527798

5. Johannes Koettl (14 December 2014) The physiological limits of life: Will humans one day live to the age of 150 years?  Brookings https://www.brookings.edu/articles/the-physiological-limits-of-life-will-humans-one-day-live-to-the-age-of-150-years/

6. Ann Saudi Med (Jan-Feb 2006) Overview of Exercise Stress Testing PMC https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6078558/#:~:text=Exercise%20capacity%20is%20based%20on,METS%20or%20more%20is%20excellent.

7. Natalie Wolchover (13 August 2012) Limits Of The Human Body: How Much Sleep Deprivation, Radiation & Acceleration Can We Survive? Huffpost https://www.huffpost.com/entry/human-body-limits-survival_n_1773167

8. Sarah Keating (18 January 2018) The boy who stayed awake for 11 days BBC Future https://www.bbc.com/future/article/20180118-the-boy-who-stayed-awake-for-11-days

9. Toby Saunders (27 May 2023) Who has the highest IQ in the world in 2024? BBC Science Focus https://www.sciencefocus.com/science/who-has-the-highest-iq

10. Safir Rifas (29 August 2023) Is There a Limit to Human Knowledge, and If So, What Lies Beyond It? Medium https://medium.com/@safirrifas34/is-there-a-limit-to-human-knowledge-and-if-so-what-lies-beyond-it-f7514bd7dcc0#:~:text=While%20there%20may%20be%20inherent,previously%20hidden%20realms%20of%20knowledge.

11. B. Miller (30 September 2022) Breaking point psychology The Wright Intiative https://thewrightinitiative.com/misc/breaking-point-psychology.html#id-1