drtbear1967
Musclechemistry Board Certified Member
WHAT IS CNS FATIGUE ?
️
There are many myths surrounding CNS fatigue and one is certainly explaining what it is:
In fact feeling tired, sluggish, demotivated is typically misinterpreted as being CNS fatigued, but that's really not what's happening.
In reality, this type of fatigue that occurs within the central nervous system is described as the reduction in the ability of the brain to recruit high threshold motor units that govern high threshold muscle fibers, due to a loss of spinal or CNS excitability.
CNS fatigue is actually measurable: in fact, it can be measured by testing our maximum static contraction in voluntary/involuntary effort by stimulating the muscle electrically, and andcdotally it can be experienced when a weight "moves slower than it should": there's a loss of velocity in bar speed which can be attributed to a decrease in firing motor units/decreased coordination, where the motor control begins to decrease due to fstifue.
Voluntary activation reflects the number of motor units that have been recruited, therefore if the activation is very high most motor units are recruited. If the activation is reduced, some motor units are not being recruited.
Basically, in conditions of non-CNS fatigue, when voluntary activation is high, motor units are recruited in size order (Henneman's size principle explained in a previous post) from the lowest to the highest ones.
If CNS fatigue is present, voluntary activation doesn't recruit high threshold motor units which govern the muscle fibers that grow after strength training.
When the goal is hypertrophy, monitoring training volume frequency and intensity will be crucial when the goal is mitigating fatigue (which can last up to several days if it's induced by muscle damage) and keep making progress.
️
There are many myths surrounding CNS fatigue and one is certainly explaining what it is:
In fact feeling tired, sluggish, demotivated is typically misinterpreted as being CNS fatigued, but that's really not what's happening.
In reality, this type of fatigue that occurs within the central nervous system is described as the reduction in the ability of the brain to recruit high threshold motor units that govern high threshold muscle fibers, due to a loss of spinal or CNS excitability.
CNS fatigue is actually measurable: in fact, it can be measured by testing our maximum static contraction in voluntary/involuntary effort by stimulating the muscle electrically, and andcdotally it can be experienced when a weight "moves slower than it should": there's a loss of velocity in bar speed which can be attributed to a decrease in firing motor units/decreased coordination, where the motor control begins to decrease due to fstifue.
Voluntary activation reflects the number of motor units that have been recruited, therefore if the activation is very high most motor units are recruited. If the activation is reduced, some motor units are not being recruited.
Basically, in conditions of non-CNS fatigue, when voluntary activation is high, motor units are recruited in size order (Henneman's size principle explained in a previous post) from the lowest to the highest ones.
If CNS fatigue is present, voluntary activation doesn't recruit high threshold motor units which govern the muscle fibers that grow after strength training.
When the goal is hypertrophy, monitoring training volume frequency and intensity will be crucial when the goal is mitigating fatigue (which can last up to several days if it's induced by muscle damage) and keep making progress.
