Here's Why You Feel So Tired After Completing a Major Project

Math problems and marathons have a similar effect on our brains.

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Photo by Courtney Keating/Getty Images

If a stressful or confusing problem has left you feeling like you just spent hours running the track, you might be on to something. Research from Texas A&M Health Science Center School of Public Health showed that we activate the same area of our brains during physically and mentally exhaustive tasksmeaning a tough problem can leave you feeling as tired as an intense workout.

Researchers looked at the prefrontal cortex (PFC), which controls fatigue, and found the brain was most tired after attempting tough mental and physical tasks simultaneously. Did you know your brain can become fatigued, just like other muscles? The findings, published in Human Factors: The Journal of the Human Factors and Ergonomics Society, showed lower blood oxygen levels in the brain following tasks that combined physical and mental effort, as compared to those just involving physical effort.

“Not a lot of people see the value in looking at both the brain and the body together,” study leader Ranjana Mehta, Ph.D. said in a statement. “However, no one does purely physical or mental work; they always do both.”

To prevent fatigue, consider whether or not you've dealt with a lot of cognitive stress at work before heading out on a run. If you're still feeling tired, and can't figure out why, see these eight susprising causes of exhaustion.