Hyperammonaemia is related to both central and peripheral fatigue during exercise. Hyperammonaemia in response to exercise can be reduced through supplementation with either amino acids or combined keto analogues and amino acids (KAAA). In the present study, we determined the effect of short-term KAAA supplementation on ammonia production in subjects eating a low-carbohydrate diet who exercise. A total of thirteen male cyclists eating a ketogenic diet for 3 d were divided into two groups receiving either KAAA (KEx) or lactose (control group; LEx) supplements. Athletes cycled indoors for 2 h, and blood samples were obtained at rest, during exercise and over the course of 1 h during the recovery period. Exercise-induced ammonaemia increased to a maximum of 35 % in the control group, but no significant increase was observed in the supplemented group. Both groups had a significant increase (approximately 35 %) in uraemia in response to exercise. The resting urate levels of the two groups were equivalent and remained statistically unchanged in the KEx group after 90 min of exercise; an earlier increase was observed in the LEx group. Glucose levels did not change, either during the trial time or between the groups. An increase in lactate levels was observed during the first 30 min of exercise in both groups, but there was no difference between the groups. The present results suggest that the acute use of KAAA diminishes exercise-induced hyperammonaemia.

During exercise, ammonia levels are related to the appearance of both central and peripheral fatigue. Therefore, controlling the increase in ammonia levels is an important strategy in ameliorating the metabolic response to exercise and in improving athletic performance. Free amino acids can be used as substrates for ATP synthesis that produces ammonia as a side product. Keto analogues act in an opposite way, being used to synthesise amino acids whilst decreasing free ammonia in the blood. Adult male rats were divided into four groups based on receiving either keto analogues associated with amino acids (KAAA) or a placebo and resistance exercise or no exercise. There was an approximately 40 % increase in ammonaemia due to KAAA supplementation in resting animals. Exercise increased ammonia levels twofold with respect to the control, with a smaller increase (about 20 %) in ammonia levels due to exercise. Exercise itself causes a significant increase in blood urea levels (17 %). However, KAAA reduced blood urea levels to 75 % of the pre-exercise values. Blood urate levels increased 28 % in the KAAA group, independent of exercise. Supplementation increased glucose levels by 10 % compared with control animals. Exercise did not change glucose levels in either the control or supplemented groups. Exercise promoted a 57 % increase in lactate levels in the control group. Supplementation promoted a twofold exercise-induced increase in blood lactate levels. The present results suggest that an acute supplementation of KAAA can decrease hyperammonaemia induced by exercise.

O objetivo desse estudo foi avaliar o estado de hidratação e desempenho cognitivo-motor em atletas durante uma prova de fast triathlon no calor. Doze triatletas (34 ± 2,7 anos) participaram do trabalho. O estado de hidratação foi mensurado pela perda de massa corporal (MC), coloração e gravidade específica (GE) urinárias. O desempenho cognitivo-motor foi verificado pela coordenação motora (CM) e tempo de reação simples (TRS). Após a prova houve uma diminuição significativa da MC (1,8 %; P < 0,001). Um aumento significativo entre pré e pós-competição foi observado para o índice de coloração da urina (P < 0,001) e GE (P < 0,001), respectivamente. O TRS foi melhor após a prova. Porém, demonstraram dismetria, prejudicando sua CM. Conclui-se que níveis de desidratação foram observados entre os atletas após a prova. Alterações opostas foram encontradas quanto ao desempenho cognitivo-motor. Atletas demonstraram uma maior descoordenação motora, mas melhoraram seu tempo de reação. Palavras-chave: Desempenho atlético. Desidratação. Tempo de reação.