Overtraining – What is neural (CNS) fatigue and how to you recover from it?
This will be the first article in a series of articles relating to overtraining. There are many different effects one will experience because of overtraining. Neural fatigue (named more correctly as the Central Fatigue Hypothesis) is a relatively new concept and one used by Powerlifters who use it to explain why one is fatigues after lifting heavy weights. So, what is the Central Fatigue Hypothesis and how do I recover from it?
Initially, it was believed that fatigue after prolonged periods of training was the result of glycogen (energy stores) in the muscle becoming depleted and consequently a low blood sugar level. This thought, however, is not correct because new studies have shown that after intense and long exercise, glycogen stores are at 40% capacity. This led to the development of a new possible cause called the Central Fatigue Hypothesis (CFH).
The CFH suggest that fatigue after any intense exercise (not just strength training) is a result of changes to the central nervous system (brain and spine). The changes are thought to be caused by a relative decrease in Branch Chain Amino Acids relative (BCAAs) to Tryptophan (an essential amino acid) which is initiated by the decrease in glycogen. Low glucose causes BCAAs to be used for fuel which decrease their levels. Tryptophan when high relative to BCAAs will promote higher levels of serotonin in the brain which then results in fatigue and tiredness. However, we cannot be sure whether the high levels of tryptophan are a cause or result of the fatigue since tryptophan increases tolerance to pain and allows an individual to train harder.
Most of this data is still new and is yet to be proved. However, interventions such as consuming any protein (not just BCAAs) before or after a workout will aid in prevent this relative decrease of BCAAs after training intensely. Furthermore, sleep is important, in order to normalise the ratio and recover.
The CFH is a new concept and thought to be perpetuated by an uneven ratio of tryptophan and BCAAs after any intense and prolonged exercise. Prevention includes eating protein around the time of a workout and sleep.