Hyperammonemia During Physical Exertion

Accumulation of Nitrogen Metabolic Products During Intense and Prolonged Workouts

The problem of the increasing accumulation of nitrogen metabolic products (NMP) in the blood, brain, and muscles during intense physical exertion has been the subject of close attention since the early 1960s. The accumulation of ammonia is considered one of the significant causes of neurogenic fatigue in sports. These biochemical changes are combined with such factors of fatigue development as the accumulation of lactate, a decrease in pH, and an imbalance of electrolytes.

According to the „ammonia theory of fatigue development“, the excessive ammonia formed in the body during metabolism must be removed as quickly as possible, as it is a natural „waste“ product of metabolism. Fatigue is a synonym for a wide range of well-known physiological manifestations in high-performance sports and the usual high-intensity training process, which are based on the following mechanisms:

• Accumulation of peripheral toxins/metabolic by-products;
• Central (neurogenic) self-regulation – an adaptive protective reaction;
• Production of inflammatory cytokines;
• Disruption of neurotransmitter mechanisms;
• Peripheral regulatory control of the metabolism of organs and tissues.

The Role of BCAA in the Accumulation of Nitrogen Metabolic Products During Intense and Prolonged Workouts

It has long been known that BCAA during prolonged training can provide up to 10% of the total energy consumed by the athlete. The long-chain essential amino acids with a branched chain – BCAA – leucine, isoleucine, and valine – make up about 40% of the essential amino acids (EAA) coming from food and play an important role in the structure of globular and membrane proteins, especially in muscle tissue.

In the mitochondria of skeletal muscles, BCAA undergo metabolic changes due to two enzymes: 1) branched-chain amino acid (BCAT) aminotransferase and 2) branched-chain α-keto acid dehydrogenase (BCKDH). As a result, compounds with coenzyme A are formed, which can be utilized in the tricarboxylic acid (TCA) cycle to generate energy through oxidation. However, with an increase in the intensity of muscular movements and their duration, the biochemical reactions shift towards the excessive formation of ammonia.

Clinical Studies of Hyperammonemia in Elite Athletes

In a study by W.S. Coelho et al., the metabolic response of elite canoeists (participants in world championships, Olympic and Pan American Games) was investigated during a combined training session. The training protocol consisted of several sprint runs at different distances and intensities with three-minute intervals between them, followed by strength training. During the study, a significant increase in aspartate aminotransferase (AST), myoglobin, indicators of muscle damage, leukocytes, and platelets was observed. Extremely indicative was the change in the plasma concentration of BCAA, which decreased significantly during both types of physical activity and continued to decline during the rest period.

Conclusion

The accumulation of ammonia plays a significant role in the development of fatigue in high-performance sports and high-intensity training. Increased ammonia concentrations in the brain impair the function of astrocytes and neurons, disrupt neurotransmitter mechanisms, and weaken the regulation of motor functions. The determination of the ammonia threshold during laboratory tests can be a useful tool for sports doctors and coaches in the practical application of training loads.