Central Nervous System Fatigue: Real or Fake?
You’ve heard the claims from many athletes, those in sports performance and in Olympic weightlifting. “My CNS is fried!”
This statement is thrown around with minimal regard to what this actually even means. The majority of athletes don’t fully comprehend the actual definition, let alone have a full comprehension of what it may mean for their physical state. Frying the CNS can be difficult to accomplish and it can also have very negative long lasting implications if it is not handled accordingly! Let’s find out what this phrase even means.
To understand neural fatigue and a fatigued response from central drive, we have to understand neurotransmitters to a point. Neurotransmitters are chemicals that enable neural transmission from the corticospinal tract to the motor neurons. They carry a neural message from the synapse from one neuron to the muscle cell (not always the muscle cell but for our case, we will use the muscle cell). Neurotransmitters are a crucial signaling aspect between various organs.
When excitation is maintained for a long period of time, cortisol tends to rise significantly to manage adrenaline saturation in the bloodstream. Cortisol is not the devil hormone it is frequently portrayed to be but it is important to acknowledge that when cortisol levels are elevated for very long periods of time, glycogen storage can be depleted which will impact recovery and the next day’s training in a negative manner. Elevated cortisol for a longer period can also increase myostatin, a myokine that inhibits muscular growth.
Adrenaline and Dopamine
Excitation is managed by adrenaline and dopamine. Glutamate can contribute to excitation to an extent but it does not play as close of a relationship as adrenaline and dopamine. When analyzing the fatigue element of a session of training, we have to recognize that duration of the training, the intensity of the training AND the total volume of the session can all lead to a heightened aspect of excitation. This is important to comprehend to ensure that the coach and athlete manage excitation accordingly.
If a session is maintained for a longer duration or a higher intensity, the athlete will deplete dopamine over time. Most individuals will read that sentence and lose their mind but the human body is built to adapt to these factors...AS LONG AS RECOVERY IS OPTIMIZED! Because adrenaline can stay connected to receptors for a long period of time AFTER an intense or long workout, the depletion of dopamine becomes a factor if poorly managed.
Neural fatigue or “CNS” fatigue is no more than two things. Dopamine depletion is one aspect of CNS fatigue, based around poor recovery from longer workouts, intense workouts. The second part of CNS fatigue is based around adrenergic receptor desensitization otherwise known as adrenaline resistance. By CONSTANTLY having high levels of adrenaline, our body struggles to recover and struggles to coordinate effectively.
Signs of CNS Fatigue
CNS Fatigue has multiple signs, in most cases there are simply small acute cases of neural fatigue, rarely is this type of fatigue chronic unless there is a genetic factor involved. By recognizing how dopamine and adrenaline interact with recovery is important to fully comprehending this topic.
Understanding that SLEEP IS VITAL FOR RECOVERY and that proper usage of nutrients is key for overall recovery enables us to know what signs of neural fatigue generally are. When dopamine is elevated for a long period of time, our serotonin is generally lower. IF an athlete works out closer to bedtime and also uses caffeine within 3-5 hours of their sleep period, it can be understood that serotonin levels will be disrupted which will have a negative impact on sleep. Let’s dive into a few glaring symptoms of neural fatigue.
1. Falling asleep, then waking up during the sleep period and not being able to fall back asleep.
Oftentimes, athletes can calm down enough prior to sleep that they fall asleep but struggle to maintain that sleep pattern. This is due to heightened levels of dopamine and adrenaline and lower levels of serotonin. This also can be related to a reverse cortisol profile. When cortisol is elevated prior to bed, it will have a negative impact on sleep. Ideally, we should fall asleep and elevated cortisol should occur during the last few hours of sleep and reach its peak right at the waking period. The elevated cortisol is the main reason athletes will wake up in the middle of the night, thus impeding recovery.
2. Poor coordination.
When I first got diagnosed with Lyme disease, I was certain that I was struggling with CNS fatigue caused by training, not caused by Lyme. After studying my coordination and my sleep patterns for a few weeks, I realized there was certainly something deeper at play and it wasn’t just “CNS fatigue.” Be aware that poor coordination is an issue with neural fatigue but it is not overly prominent as an issue.
3. Struggling to fall asleep.
Many athletes may struggle to fall asleep when dealing with CNS fatigue. To be clear, most cases of this are related to using caffeine too close to the sleep period. However, if an individual regularly struggles to fall asleep, their serotonin/dopamine ratio could be a complete disaster and this needs to be addressed!
Some of the simplest aspects behind recovery are immediately based around training time and usage of caffeine. Ideally, an athlete will only use caffeine 2-4 times a week. By picking 2 or 3 of the most important training sessions each week to use caffeine, the body will handle the heightened levels of dopamine and adrenaline a bit more effectively. They will be able to adapt quicker and the receptors will not become desensitized.
Simple aspects of recovery like proper nutrition also play a very important role. Using creatine consistently will help not only with power output but also with recovery on a daily basis. I highly recommend using .1g of creatine per kilo of bodyweight on a daily basis.
Athletes consistently struggle with the concept of sleep preparation. By engaging with blue lights, television, podcasts and videos before sleep, the body is continuously being flooded with high levels of dopamine. Instead of engaging with media prior to sleep, establish a protocol.
1. Establish a hard stop on using electronics 1.5 hours before bed.
2. Use red lights or candles for 1 hour before bed instead of blue light. TRUST ME, this works.
3. Meditate or pray before heading to bed and initiating your rest period.
4. Go to bed 6 hours or more AFTER ingesting the last of your caffeine. This will aid in improving your sleep patterns.
5. Use Zinc and Magnesium (forty winks) to help with calming the nervous system and mind before bed!
CNS Fatigue is real but in most cases, it is a poorly understood excuse used to define regular fatigue caused by physical training. It is important to understand fatigue, the various aspects that do cause fatigue and learn how to appropriately manage these points on a consistent basis. Be aware of general feeling on a regular basis and consistently establish recovery protocols to optimize the effects of training!
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