Central Fatigue Hypothesis

Proteins we consume in our diet constitute the bigger source of aminoacids.
Aminoacids are the basic units that construct proteins. For the break down of proteins into aminoacids other component are needed (proteolytic enzymes). Aminoacids, then, can be absorbed in the intestine.
Once they are absorbed, they can be used for different purposes.

• To synthesize new proteins (as it happens in muscular growth).

• To be converted into non protein elements, but of great importance in our bodies (as hormones, etc.).

• To obtain energy. Degradation of aminoacids occurs in the liver, what originates ammonium, transformed in urea and then released in urine.

What happens after an intensive training?

Central Fatigue Hypothesis

After an intensive training, a negative balance is produced between the 3 called branched aminoacids (L-Valine, L-Leucine and L-Isoleucine) and the tryptophan (another aminoacid). This happens because during exercise these 3 branched aminoacids are converted into energy by the muscles.

The central fatigue hypothesis explains that the increase of serotonine (produced from tryptophan) can modify the central nervous system, producing the feeling of fatigue.

Tryptophan travels in blood linked to other protein called albumin. Free tryptophan can be transported to the nervous system by a transporter mechanism that transport also the branched aminoacids.

After sustained exercise, as the branched aminoacids are broken down to obtain energy, the balance between Tryptophan and these aminoacids is modified. As there is more tryptophan than branched aminoacids, the carrier protein transports more tryptophan than the other aminoacids. In the brain the tryptophan is transformed into serotonin, producing fatigue.

If we take branched aminoacids after sport we stimulate the protein anabolism, conferring a double function: to protect and build muscles.









What is serotonin?

Serotonin is called the “hormone of happiness”, and it allows us to laugh, to feel full of life and happy.

The transformation is produced by the enzyme trypyophan hydroxylase.
When we run, ride a bike, or we make exercise (not very strong, we have to be able to talk), we produce this hormone, that gives us a well-being feeling that lasts few hours after sport practice.