4 Common Causes of Unexplained Fatigue and How to Troubleshoot Them

If you've been a runner for long enough, you've inevitably suffered through some miserably tired runs—runs where your legs are dead, your breathing is labored and you feel like each mile takes an eternity to complete. As they say, you have to experience the bad runs to appreciate the good ones, right? But what happens when one bad run turns into a string of miserable ones? 

Unexplained fatigue can strike even the most disciplined among us. Once it hits, it can create a snowball effect—ultimately burying you so deep that it may seem you will never get out of your funk. But there's hope in doing your own detective work and troubleshooting the cause of your sluggishness. 

Before you jump to diagnose yourself, keep in mind that a runner's first line of defense is rest. If you've given yourself a minimum of two weeks rest, it may be time for further exploration. Below are some potential culprits for unexplained fatigue, as well as some suggested next steps. 


While its name may suggest otherwise, overtraining syndrome is not always about your actual training but rather the volume and how that fits in with your life and current stressors. It doesn't necessarily occur during the heaviest periods of training but instead when your training simply outpaces your ability to recover due to everything else you have going on (your job stress, home life, mental health). If you're experiencing fatigue after taking two weeks of relative rest, it's time to investigate further. 

Diagnosing Overtraining

Unlike most disorders that cause fatigue, there's no blood test for overtraining. Over-trained athletes may experience a suppressed immune system and suffer from colds or illness more frequently. They may also experience psychological effects of low level depression and be trapped in a cycle of low mood, lack of sleep and too much stress (both physical and mental). Performance in training and races often drops as well, as runners are exhausted yet continue to push their bodies harder to try and improve their performance. Without intervention, it can turn into a vicious cycle. 

Treating Overtraining

Depending on how deep of a hole you've gotten yourself into, it may take weeks or even months to fully rebound from overtraining. But you can help yourself along the way by incorporating these suggestions: 

  • Adjust your training schedule. Decrease training time by 50 to 70 percent or more, if necessary. Immediately cease speed work and competition. 
  • Walking can be incorporated after an initial period of rest to gently stimulate circulation and muscle fibers and provide psychological benefits as well.
  • Decrease or eliminate caffeine consumption by avoiding coffee, tea and soda. Caffeine increases cortisol in the body and can interfere with recovery. 

Diet and nutrition should be examined with the focus on eliminating high-glycemic foods (especially sugars and refined flours), insuring adequate caloric intake and concentrating on consuming quality carbohydrates, moderate amounts of protein and healthy fats. 

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