Fatigue happens after all difficult exercises. Running a mile gets harder after you’ve already run two. Powerlifting becomes more challenging after multiple reps. Recognizing this fatigue is how we continue pushing ourselves to run further distances and lift heavier weights, growing faster and stronger with every workout.
However, consistently overtraining to the point of exhaustion can cause the brain to become chronically tired. Known as central nervous system (CNS) fatigue, this condition is marked by decreased functioning in the part of the brain responsible for voluntary movement.
While some people debate what causes it (and others deny its existence altogether), many athletes and active individuals have struggled with the long-term side effects of CNS fatigue. Read on to learn what CNS fatigue is, how to spot the symptoms, and when it’s time to step back and recover.
Understanding the Central Nervous System
Most mental and bodily functions are controlled by the central nervous system (CNS), which is comprised of the brain and spinal cord. The brain interprets everything we see, hear, feel, smell, and taste. The spinal cord is responsible for sending messages about these experiences into the body to elicit a reaction. Speech, memory, movement, and general awareness are all a direct result of a properly functioning nervous system.
The CNS also enables us to engage in physical activity — it’s what helps us run, squat, and lift on command. Specifically, the motor cortex is the area of the brain responsible for helping us plan and execute voluntary movements. Located in the brain’s frontal lobe, the motor cortex is divided into multiple sections that govern different movements and responses.
One important area of the motor cortex is the primary motor cortex, which helps us control different parts of the body on queue. The primary motor cortex helps us learn new athletic skills and complete them faster and more efficiently through repetition.
Central Nervous System Fatigue
The brain and spinal cord are designed to give us freedom of movement, but chronic overtraining can fatigue the central nervous system to the point of inefficiency. This is called central nervous system fatigue, or CNS fatigue.
Extending oneself during workouts is one of the leading causes of CNS fatigue, though it can also be caused by poor sleep and nutrition. CNS fatigue is thought to be most common among weight lifting and strength training athletes, but it can happen to anyone engaging in high intensity exercise. Plus, everyone has a different work capacity, meaning that some people may be able to endure more strenuous exercise before experiencing CNS fatigue.
Overtraining and CNS fatigue are sometimes put into the same category, but one is more serious than the other. Overtraining is a common side effect of trying a new and rigorous exercise routine, and it can usually be overcome with a few days of adequate rest and nutrition. In contrast, CNS fatigue results from chronic muscle fatigue and is more difficult to overcome.
What Causes CNS Fatigue?
According to the late Olympic coach Charlie Francis, CNS fatigue is caused when high-intensity work occurs too often during training or when high-intensity exercise persists even in the presence of fatigue from a previous workout. When the motor neurons responsible for voluntary movement are forced to fire very quickly and very often, they get tired.
This results in CNS fatigue — where a person’s neurons don’t fire as quickly as they should. When the brain doesn’t send messages to the body to move quickly, a person isn’t able to exercise at the same rate as before.
CNS fatigue also inhibits muscle regrowth, which reduces exercise performance. For example, lifters may start to notice that they’re not building muscle as quickly as before or that their training program has become less effective.
Unlike peripheral fatigue, the normal muscle tiredness that occurs after lactic acid buildup from a workout, chronic CNS fatigue causes persistent symptoms that interfere with a normal workout regimen.
One of the first symptoms of CNS fatigue is irritability and emotional changes. It also disrupts sleep patterns and can cause either food cravings or loss of appetite, all of which can exacerbate a heightened emotional state.
Another core sign of CNS fatigue is a weakened immune system. If you find yourself feeling sluggish throughout the day and you’re getting sick more often than normal, it could be a sign your body is struggling to fight off everyday pathogens.
Overcoming CNS Fatigue
Rest is the first and most important way to overcome CNS fatigue. Sleep helps your body recover and promotes muscle growth, which ensures your workouts remain effective. In addition to getting enough sleep each night, you’ll also want to schedule adequate down time between workout sessions.
Workouts that require more muscle activation, such as heavy weight lifting or spinning, should be balanced with more rest, and you should have a post-workout recovery plan that includes proper nutrition.
Similarly, meditation can help reduce the mental and bodily stress associated with CNS fatigue. Whether you’re already experiencing fatigue or you’re working to prevent it, a regular meditation practice can clear your mind and help you get back in the game.
Change Your Workouts
Your workouts are also going to need to change if you want to overcome CNS fatigue. Studies show that muscular fatigue occurs more with endurance exercises like long-distance running or bicycling.
Rather than decreasing your training volume and working out less, you can simply change what you’re doing so that you’re still increasing your heart rate without enduring prolonged exercise.
Coach and bodybuilder Jason Ferruggia suggests using straps and deadlift variations when lifting weights. This reduces the need to grip the bars tightly, which can ease CNS stress. Similarly, switching to fat bars when lifting weights can reduce stress on the nervous system.
Training sessions that alternate muscle groups on different days are a great place to start. You may also consider turning to low-intensity exercises like swimming or cycling for short periods of time.
Alter Your Lifestyle
Many people who suffer from CNS fatigue also have busy, stressful lives. Learning to say no to tasks, events, and outings that don’t serve you can help you create more space for rest and relaxation.
Being more mindful about what you do and how you spend your time can retrain the brain to act normally, rather than overfiring. Reducing daily stress is an important aspect of overcoming CNS fatigue, as it’s a result of chronic stress on the mind and body.
Additionally, neurotransmitter imbalances are associated with CNS fatigue. Changing your diet can help you rebalance serotonin and dopamine to get back to feeling your best. In addition to eating a diet low in refined sugars and processed foods, you can boost your body’s stress response by supplementing with fish oil, curcumin (found in turmeric), glutamine and amino acids like tyrosine.
Strengthen the Motor Cortex
Strengthening the brain (and the motor cortex in particular) can also help you overcome CNS fatigue so you can return to your normal workouts.
“A strong electrical signal from the motor cortex of the brain coordinates the individual fibers to work as a team, helping you produce maximum force and hit new PRs (personal records). Without coordination from the brain, it would be impossible for athletes to get stronger,” says engineer and record-holding powerlifter Emily Hu.
Repeating the same low-intensity workouts on alternating days can retrain the brain to work out without getting excessively fatigued. It can also help you create muscle memory in new areas of the body.
Overcoming CNS Fatigue for Health and Prosperity
Fatigue is a normal side effect of exercise. But if you’re feeling chronically irritable, tired, and like you can’t exercise to your fullest capacity, you may be experiencing CNS fatigue.
CNS fatigue is when the motor neurons in the brain don’t function as efficiently as they should, which takes a major toll on your ability to perform at your best. Fortunately, getting enough rest and taking care of your body can help you overcome this challenging, yet common condition so you can achieve optimal health.