Brain fog — a mentally fuzzy, hazy, and forgetful feeling — isn't just something that happens as you age. Subjective memory impairment (SMI) can happen at any age, and clearing it can help you train for races stronger, longer, and better.

Underlying medical issues can cause persistent brain fog as you age, and smoking, depression, and metabolic issues like diabetes and hypertension can increase those symptoms. In fact, a UCLA study in PLOS One found that 14% of young adults between the ages of 18-39 and 21% of adults between the ages 40-59 reported feeling a decline in both memory and cognitive thinking.

If you’re relatively young, are training regularly, and don’t have underlying health conditions, why are you still experiencing brain fog? Here are two reasons you can’t think or train properly, plus how to clear brain fog quickly.

Why Do You Have Brain Fog, and How Can You Clear It?

1. You Aren’t Focused on One Goal

Are you thinking about your next strength training workout during your weekly long run? Are you cranking out miles on the treadmill while you go over an upcoming work presentation on your lunch break? Thinking about or doing several things at once may seem efficient, but it may also wind up clouding your mind and inhibiting your ability to think clearly. 

Sometimes, less is more. To improve your productivity and clear brain fog, stay focused on the task at hand with your training and your day-to-day work life. Eliminating multitasking allows you to become more present and mindful during workouts, which will allow you to focus on proper form over fast pace and protect your muscles and joints from injury.

Related: The Best Way to "Eat an Elephant"

2. You Are Overtraining

When you're overtrained, your body can’t recover properly to keep up with the physical stress through which you’re putting it. You might experience symptoms like decreased athletic performance while training or racing, chronic injury, extreme fatigue, irritability, insomnia, and an increased perceived effort. If every rep or run feels far more difficult than it should based on your fitness level, you’re probably overtrained.

“Overtraining syndrome can not only derail your progress (and in serious cases cause other health issues), but the brain fog that happens on top of these symptoms will make it that more difficult to train,” Alex Tauberg, DC, CSCS, a board-certified sports chiropractor and owner of The Pittsburgh Chiropractor, says.

Related: Are You Training Too Hard? Here's How to Know (and What to Do About It)

3. How to Clear Brain Fog

There are three things you can do right now to avoid the multitasking and overtraining that lead to brain fog buildup.

First, keep a training log to record not only your workout frequency, but how you felt during and after each workout. This will help monitor your overall performance, and point out any red flags that may mean you need to dial it back a bit.

Next, build in at least one rest day a week depending on the type of event for which you’re training to let your body recover properly. This doesn’t mean you have to lounge on the couch all day, but you do need to switch up your training and focus on stretching and conditioning your muscles.

Finally, evaluate your lifestyle outside of training to pinpoint where you can make mental improvements.

High stress levels, poor sleep, and alcohol or CBD/THC use can all cause various levels of brain fog. Getting enough sleep, hydrating, and focusing on proper nutrition can counteract some of these effects and help clear brain fog.

If you check off all these boxes and still feel like your focus isn’t as razor sharp as it should be, make an appointment with your doctor, Clifford Segil, DO, a neurologist at Providence Saint John's Health Center, says. They'll perform a physical exam and run some blood tests to make sure there isn't a more serious, hidden medical condition behind your brain fog.