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Mental vs. Physical Fatigue

Mental vs. Physical Fatigue

Whether it’s that drowsy sensation right after you wake up or the drained feeling you get after a long day’s work, we know mental fatigue when it hits us. In these moments, it can be difficult to stir up enough energy to become physically active. Personally, I’ve struggled with overcoming this laziness in the past. That is until one day, someone once asked me “Do you feel tired because of your body or because of your brain, because if your body feels tired then you should rest for the day, but if your brain feels tired than you should try to work out.” Her question still sticks with me every time I debate a workout after a long day.

            There are two important types of fatigue that should be distinguished from each other before a workout. We often confuse mental fatigue with physical fatigue, leading us toward the mistake of skipping a workout for the day. Nonetheless, rest days are very important. The key is to know when to take these rest days. 

Mental fatigue occurs when the brain becomes overactive, typically caused by prolonged cognitive activity and a lack of sleep. Symptoms include mental block, lack of motivation, irritability, stress eating, and insomnia. Often times, these symptoms can lead to long term effects, such as anxiety and burnout. Interestingly though, one of the best remedies for mental fatigue is physical activity. This means hitting the gym for a workout, meditating, or even taking a brisk walk outside can help in lessening the effects of mental fatigue. Studies have shown that physical exercise can improve cognitive functioning and even aid in memory retention. This is due to the increased blood flow around the body and increased release of both endorphins and anti-inflammatory cytokines during exercise.

            Physical fatigue, on the other hand, should be taken seriously in considering a workout. Physical fatigue occurs when the body is physically overworked. For example, pain and soreness can be associated with fatigue and can negatively affect your workout, ultimately leading to an increased likelihood of injury or immunodeficiency. There is a thin line, though, when determining the extent of physical fatigue. Delayed onset muscle soreness (DOMS) is common after an intense exercise bout, but surprisingly further light exercise can decrease this soreness. In the case that the soreness is so intense that it causes pain, then it is preferable to take a rest day and let your body recover.

            Fatigue varies in intensity and characterization, making knowledge of the difference important for an exercise routine. Work hard, push your limits, but know when it’s time to take a break and recover.



 Taylor Donald

B.S. Biochemistry, Exercise Physiology

University of Miami