Are you sleeping through your morning alarm or dozing off at work, despite getting a full night's sleep? That persistent fatigue is your body's way of telling you to take it easy so it can heal. Poor sleep is also a symptom of too much hard running.
Vigorous physical activity stimulates the body's sympathetic nervous system, which increases your heart rate and gets you revved-up to run. To meet that demand, the body releases cortisol. When stress is constant, the sympathetic system goes into overdrive, and your cortisol levels remain elevated.
"The sympathetic system in overdrive is like taking shots of Red Bull," says Dr. Fieseler. "The longer this chronic stress occurs, the longer the sleep disturbance persists."
Remedy: Rest--not just an easy run day, but an actual rest day. Ongoing fatigue and sleep disturbances should be taken seriously.
"Take a few extra days off each week and stop racing and running hard for at least three weeks," says Heather North, a physiotherapist at Red Hammer Rehab and running coach with Revolution Running, both in Louisville, Colorado. "Even if someone experiencing fatigue runs a mile a day several times a week, the habit is preserved and this is important."
She also recommends getting your blood tested to make sure you aren't suffering from low iron levels or other conditions that can cause fatigue. In extreme cases of exhaustion, Fieseler says you might need to completely stop running and exercising for an extended period until you regain your energy. Lastly, it's also important to evaluate your diet and hydration and make improvements if necessary.