The link between mental and physical fatigue

link between mental and physical fatigueWhen we have been physically active, we can experience fatigue afterwards – this is a no-brainer. In other words, it stands to reason that our muscles become weaker; we are tired and perhaps even irritable. However, mental activity can also have a big impact on our level of fatigue.

While physical fatigue and mental fatigue are two different states, they are interconnected. This is why we often feel physically exhausted and have difficulty performing physical tasks after worrying about something all day. We also now know that being physical and stressing our minds can make us feel exhausted quicker.

How we know mental and physical fatigue are related


A study conducted at Texas A&M Health Science Center School of Public Health showed that when we attempt mental and physical tasks at the same time, we trigger areas in our brain called the prefrontal cortex. This can cause our body to experience fatigue much sooner than if we were only taking part in physical activity.

Assistant professor, Ranjana Mehta, was leading the study and reported that there were lower blood oxygen levels in the prefrontal cortex following combined physical fatigue and mental fatigue compared to just physical fatigue conditions. She could see through examination of both muscle and brain function that taking part in complex mental tasks cause brain resources to divide, which may explain why physical fatigue then increases.

7 medical reasons for fatigue

Most people face mental fatigue or physical fatigue by just overdoing it, but some people can have fatigue for reasons that are a little harder to pinpoint. Many biological and psychosocial factors could be the cause of someone’s fatigue. Below we explain seven different mechanism/modifiers of fatigue:

  • Skeletal muscle changes: skeletal muscle is a reserve of energy so reduction in muscle mass can influence our level of energy and therefore feelings of fatigue.
  • Mitochondria: is often referred to as “powerhouses” of cells. They generate energy for the cells in our body. Mitochondrial dysfunction can lead to fatigue.
  • Neuromuscular mechanisms: largely associated with old age, neuromuscular fatigue is best defined as a decline in skeletal muscle function with repeated effort. It can include decreased muscle strength and size, as well as an increase in fat deposits outside the muscle cell.
  • Dehydration and electrolyte disturbances: bodies need water to work well and stay cool. We also need electrolytes to help retain fluid, control our muscles, as well as our blood ph and transmission of nerve impulses. Dehydration and electrolyte issues increase with age.
  • Inflammatory mediators: chronic inflammation has been known to influence fatigue.
  • Psychoneuroimmunologic mechanisms: a person’s state of mind can have an influence on disease and therefore impact the level of fatigue. For example, immune function can be affected by chronic stress and depression.
  • Psychosocial influences: the interaction between social and psychological factors can have an impact on fatigue. Studies have shown that some people with chronic pain or diseases experience less fatigue during social interaction, but more fatigue the following day.

Fatigue is a common problem that shouldn’t set off any alarms. Most people know why they are fatigued, but if they experience unexplained exhaustion they should seek medical attention. To avoid both mental fatigue and physical fatigue the best defense is to get plenty of rest, drink lots of water, eat nutritious meals, and exercise regularly.

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