Science, Art, Litt, Science based Art & Science Communication

Limits of human performance?

Q: What are the limits of human performance?

Krishna: Mental limits or physical limits?

According to sports scientists, the marathon provides an opportunity to test the psychological and physiological factors behind human performance.

Some physiologists suggest (1) that a person’s endurance is restricted by the body’s ability to deliver oxygen to their working muscles. A lack of oxygen leads to a buildup of lactic acid and subsequent muscle fatigue [ recent research says lactic acid buildup is not the real cause of fatigue. Lactate does indeed accumulate in exhausted muscles, but only because we churn it out faster than muscles can use it. (Even so, it’s gone within an hour, not lingering for days.) Fatigue is complex and has many causes (understatement), but it is not caused by muscles drowning in lactate. One reason elite athletes can do more than the rest of us is that their intense training teaches their muscles to use more lactate(3)]. As a result of these and other associated chemical changes, the body is unable to maintain its internal, relatively constant, physiological state of equilibrium known as homeostasis. In response, the body fails “catastrophically” (a term used by sports scientists) and the athlete stops.

If this model is correct, an athlete’s endurance is limited solely by the body’s ability to use oxygen during maximal exercise. These limits are set by people’s physiology, which is impacted by inherited genetic factors, the environment, and training adaptations.

Human performance, defined by mechanical resistance and distance per time, includes human, task and environmental factors, all interrelated. It requires metabolic energy provided by anaerobic and aerobic metabolic energy sources. These sources have specific limitations in the capacity and rate to provide re-phosphorylation energy, which determines individual ratios of aerobic and anaerobic metabolic power and their sustainability. In healthy athletes, limits to provide and utilize metabolic energy are multifactorial, carefully matched and include a safety margin imposed in order to protect the integrity of the human organism under maximal effort (2).

Then there is a impact the work of breathing has on performance. The body, in response to higher intensities, will redistribute oxygenated blood to muscles that need oxygen to produce energy. A lack of oxygen leads fatigue. So while locomotor muscle have to work harder with an increase in effort, respiratory muscles are forced to work at higher lung volumes due to a flow limitation. Thus significantly increasing the work of breathing. Essentially, the respiratory muscles will ‘steal’ oxygenated blood from the locomotor muscles, causing a limit in performance. This in-depth analysis is found in the article “Do your respiratory muscles ‘steal’ blood from your locomotor muscles?”

However, this phenomenon is more complex than just the respiratory muscles stealing oxygenated blood. There is another phenomenon at play called exercise-induced arterial hypoxemia (EIAH). (Definition of hypoxemia; an abnormally low concentration of oxygen in the blood.)

EIAH has been commonly used to describe an increase in the alveolar (lung)-arterial difference in oxygen. Meaning, there is less oxygen being diffused/transported into the blood than normal. This is thought by some to be due to an insufficient hyperventilation response to support increasingly high intensities. Thus resulting in lower arterial oxygen saturation (4).

Other experts suggest that breaking endurance barriers, like the two-hour marathon, is largely a mental obstacle. Despite fatigue, some people will be able to continue to finish it.

Some experts argue a person’s genetic makeup may most strongly influence their endurance capabilities. Research published in the Journal of Physiology in 2011 identified 23 gene variants associated with endurance performance. The genes underpin the maximum amount of oxygen an athlete can consume, the point at which lactic acid is accumulated in the muscles more quickly than it can be removed, and running economy (the energy demanded by the body at a given speed). The likelihood of one individual having the ideal set, all 23 variants, is staggeringly low — as little as 1 in 1 quadrillion. But it’s believed that some people may be gifted with a few or more of the gene variants. (It’s unlikely a person would have more than 16 out of the 23.) (1)

One can overcome limitations using training like athletes and other sports people train their bodies in every possible way to be as efficient as possible, but there is a limit to what they can achieve.

In other fields, human performance limitations are communication, stress, prospective memory and fatigue.

Mental strength is similar to physical strength — some people are born with a genetic advantage while others have illnesses or issues that can be a disadvantage. You can't help it if you are genetically more susceptible to ADHD, anxiety, or depression (5). Some get stronger with bad experiences and lessons they teach. Some can get stronger with knowledge and the right critical thinking abilities. Mental muscles grow with tension — just like the physical ones do. Mentally strong people put time and energy into learning, growing, and challenging themselves. Sky is the limit for these people.

Like they say you don’t know how strong you are until being strong becomes your only choice!

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