Athletes and Fatigue

In order to achieve peak performance, athletes need to be able to maintain energy levels and prevent fatigue when in training and during competition. To clarify, fatigue, from an exercise-science standpoint, is a temporary reduction in your ability to physically perform a task or activity. What many athletes are unaware of is that there are two aspects of fatigue: peripheral (in the muscles) and central (in the brain/nervous system).

Peripheral Fatigue

Overall, most athletes are quite familiar with peripheral fatigue. This is often experienced in a weight training session when an exercise is used to bring a specific muscle into failure or during an endurance event when one muscle fatigues before others. In short, peripheral fatigue occurs within the muscle itself and in specific parts of the body. For example, you may feel peripheral fatigue in the upper body from lifting weights, but still, be able to go for a run.  Peripheral fatigue is most often the result of the accumulation of metabolic byproducts (e.g., lactic acid) or the depletion of fuel stores.

Central Fatigue

The other form of fatigue, central fatigue, results from alterations in the central nervous system. In addition, the central fatigue hypothesis suggests that biochemical changes in the brain cause a person to stop exercising or reduce exercise intensity under certain circumstances. So, in essence, you can think of this as your brain telling your body to slow down, when in fact your muscles can still push harder or go further.

Preventing central fatigue is critical to exercise performance since the lack of adequate central nervous system drive to the working muscles is the most likely explanation of fatigue for most people during exercise. In fact, research has shown that central fatigue can reduce performance by as much as 15%. In practical terms, that means your competitors have a 15%  advantage if they avoid it and you don’t.

How Do You Prevent Central Fatigue?

Adequate recovery with training is the biggest influencing factor. However, you can also mitigate the risk with a key diet modification - supplementing with BCAAs (branched chain amino acids).

What Are BCAAs

Amino acids are the building blocks of protein. And, of the nine essential amino acids, 3 are grouped together as BCAAs: leucine, isoleucine, and valine. BCAAs are called such because of their structure, which includes a “side chain” of one carbon atom and three hydrogen atoms. BCAAs provide the basis for protein synthesis and energy production and can comprise up to one-third of muscle protein. That being said, BCAAs have gained a great deal of attention in research with regards to athletic performance and have been theorized to delay the onset of central fatigue.

Central Fatigue Hypothesis

Central fatigue can occur from prolonged exercise and is associated with neurochemical changes in the brain, primarily involving serotonin (5-hydroxytryptamine or 5-HT). As we know, serotonin is the neurotransmitter that makes us feel calm and relaxed. In other words, the central fatigue hypothesis suggests that increased concentrations of brain serotonin can impair central nervous system function, creating increased physical and mental fatigue, leading to reduced intensity or interruption of physical exercises, resulting in a deterioration in sport and exercise performance.

The Role of BCAAs in Preventing Central Fatigue

To understand central fatigue it’s important to understand what happens in the brain with serotonin. The amino acid tryptophan (TRP) is a precursor to serotonin. Increased brain serotonin synthesis occurs in response to an increased delivery to the brain of blood-borne tryptophan. Also, most of the tryptophan in blood plasma circulates loosely bound to albumin, but it is the unbound or free tryptophan (f-TRP) that is transported across the blood/brain barrier. This transport occurs via a specific mechanism that tryptophan shares with other large neutral amino acids, most notably BCAAs. Thus, brain serotonin synthesis will increase when there is an increase in the ratio of the concentration of f-TRP in blood plasma to the total plasma concentration of BCAAs, (i.e., when f-TRP/BCAAs rises).

It has been proposed that this would occur during prolonged exercise. As BCAAs are taken up from the blood and oxidized for energy in contracting skeletal muscles and plasma free fatty acids increase in the blood, this causes a parallel increase in plasma free tryptophan as free fatty acids to displace tryptophan from its usual binding sites on plasma albumin molecule. Thus, allowing more tryptophan to be available to the brain. Moreover, this is when the ratio of tryptophan to BCAAs increases, more serotonin is produced, and an individual experiences central fatigue.

Benefits of BCAAs

So, where does BCAAs supplementation come into this? In short, by ingesting BCAA's, the ratio of serotonin precursors to BCAAs is reduced while still providing substrate needed for muscle contraction. Altering this ratio by increasing BCAAs allows less tryptophan into the brain, resulting in less or delayed fatigue.

See: 4 Reasons To Supplement With Amino Acids


In conclusion, introduce the use of BCAAs with your more quality-based training sessions to determine if they do provide benefit for you in reducing your central fatigue. Since adequate carbohydrate intake is essential for peak athletic performance, it is recommended that a high-carbohydrate diet is maintained (50-65% carbohydrate) and that a light carbohydrate-protein meal (30-50g carbohydrate and 5-10g protein) be consumed ~60 min prior to exercise to ensure adequate glycogen and amino acids levels. Research has shown that the addition of BCAAs (2-10g/hr) to a glucose solution during prolonged exercise bouts may help to decrease the fTryp/BCAA ratio and muscle protein breakdown, therefore decreasing fatigue and increasing recovery.

First, for a pre-workout supplement, try Fast Charge 45 to 60 minutes before activity. Made with plant-based amino acids (BCAAs, Arginine, Glutamine) + B Vitamins, Fast Charge is designed to boost natural muscular energy and fight fatigue during your workout.

Secondly, for increased stamina and performance, drink Action while you work out. Made with plant-based amino acids (BCAAs, Arginine, Glutamine) + electrolytes, Action provides healthy hydration, energy, and focus.


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