Central Nervous System Fatigue & Its Effects on Athletes
by Melinda Burris

An intense discussion has been waging around the topic of central nervous system fatigue for several years now, especially within the athletic community as the condition directly affects the body’s ability to perform at optimal levels. While questions still abound over the specific mechanism of central nervous system fatigue, research and observation have uncovered some valuable information about its causes, effects, and the best methods for preventing and treating it.
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Why the Central Nervous System Is Key

The central nervous system (CNS) includes the brain and spinal cord, and because the brain sends neurons throughout the body telling it what to do and the spinal cord makes it possible for the body to coordinate these movements, the CNS is frequently referred to as the body’s “control system”. An intricate organ with many different facets, for the purposes of sports performance, two regions of the brain—the cerebellum and the diencephalon—are of primary significance.¹

The cerebellum is the primary structure of the hindbrain and is found behind the brain stem. The cerebellum sends out neurons that direct the coordination of voluntary movements. It is this part of the brain that controls motor skills.

The diencephalon is known as the messaging center because this is where the hypothalamus processes sensory messages and relays them to other areas of the brain. This part of the brain is known as the interbrain, and it controls much of the autonomic function performed by the peripheral nervous system. It is therefore responsible for letting your brain know what’s happening outside your body. The hypothalamus is essential in maintaining bodily stasis as it lets us know when we are hungry or thirsty and it regulates the release of bodily hormones and maintains a regular body temperature.¹

How the Body Interprets Messages from the Brain

Sensory organs such as the eyes, ears, tongue, and nose carry messages from the brain to receptor organs including glands and muscles. This means the CNS has a direct impact on how your muscles are told to work. If the brain can’t send the proper message or the body is too exhausted to interpret it and respond accordingly, CNS fatigue has set in.

Overtraining Versus CNS Fatigue

Overtraining is often misdiagnosed as CNS fatigue. The two terms are often used interchangeably, and it is incorrect to do so. While overtraining should be avoided, it frequently occurs whenever a demanding new workout regimen is undertaken. Recovery from overtraining can be successfully achieved by simply listening to your body and giving it the rest and nutrition it needs to restore itself.² In contrast, CNS fatigue is the result of long-term overuse of the same muscle groups and requires changes in your fitness routine and lifestyle.

Risk factors for CNS fatigue are believed to include lack of proper sleep, poor diet, and pushing yourself too far too fast during training. The condition has been observed most often in athletes who participate in weightlifting and strength training, but it is important to note that anyone who engages in high-intensity workouts can be at risk for developing CNS fatigue.²

Causes and Symptoms of CNS Fatigue

Coach Charlie Francis, a legendary Olympic sprinter in his own right, was an expert on CNS fatigue and determined it happens when training sessions include too much high-intensity work or when fatigue is present but is ignored and the athlete continues the high-intensity exercise despite receiving the body’s message that it is being pushed too far. The body signals it needs a break; the message from the CNS system is ignored as the athlete attempts to “power through” and at some point, the brain loses its ability to relay the motor neurons that signal the body to perform the requested voluntary movement. The motor neurons simply fail to fire because they can no longer keep up with the requested output speed and frequency and as a result, the body can no longer maintain its previous level of exercise.²

Early symptoms of CNS fatigue can include impatience, annoyance, and moodiness. You may experience unusual food cravings or a decrease in appetite. Emotional upset, an irregular diet, and fatigue often combine to compromise the immune system—a primary symptom of CNS fatigue.²

Why Hurdlers Need to be Particularly Cautious

Hurdlers require explosive power to reach the speeds necessary to clear obstacles and make their best times. This puts more pressure on the CNS to perform at a high level.³ This is why making sure you give yourself adequate warm-up and recovery times is vital to enable your body to handle the stress you put upon it with each workout and competition.

Combating CNS Fatigue

First and foremost, get an adequate amount of rest. This gives the body the time it needs to recover and lets the small tears in your muscles heal while your neurons reset. Be sure to give your body adequate cool-down time so it can revitalize between workout sessions as well!²

Eat right! Your body needs the proper fuel to perform at its best and to recover from strenuous training sessions.²

Consider mindful living practices such as meditation to alleviate stress and anxiety that take a toll on your body and mind and can contribute to CNS fatigue.²

It is important to change up your training exercises! When you overwork certain muscle groups you begin to plateau or worse yet, do more damage than good. The same is true when you continue to make the same demands on your body by doing repetitive, high-endurance voluntary movements again and again.² Change it up! Your mind and body will thank you!

While coaches, athletes, and researchers agree there is a phenomenon that appears linked to the CNS and how it interprets and reacts to fatigue or “burnout”. There is also consensus among these groups that more investigation is needed so we can properly understand precisely how the CNS adapts to prolonged physical stress, how that is impacted by individual factors such as stamina and recovery time, how best to avoid CNS fatigue and its negative impact on all aspects of training from speed work to weight training and beyond, and finally, how to properly diagnose the condition when it does develop so the athlete receives proper and timely treatment.

As is the case when most training challenges arise, a plethora of CNS fatigue “recovery supplements” have flooded the fitness and nutrition market. The findings from a 2018 scientific study indicate the recovery time for general fatigue produced by high-energy exercise is usually 72 hours.⁴ While it does take longer for the body to heal from the more serious condition that is CNS fatigue, research shows that as with most things, given time and proper care, the human body does a good job of healing itself!

References:

1. Hamilton, A. (2022). Brain Over Brawn — CNS Training for Enhanced Performance.
2. (2022). What Is CNS Fatigue? Overcoming the Side Effects of Overtraining.
3. Bott, C. (2017). Central Nervous System Fatigue: Effects on Speed, Power Athletes.
4. Thomas, K., et. al., (December 2018). Neuromuscular Fatigue and Recovery after Heavy Resistance, Jump, and Sprint Training.

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