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Medicine & Science in Sports & Exercise:
doi: 10.1249/MSS.0b013e3182797637
Basic Sciences

Caffeine Decreases Systemic Urea in Elite Soccer Players during Intermittent Exercise

BASSINI, ADRIANA1,2; MAGALHÃES-NETO, ANÍBAL M.1,2,3; SWEET, ERIC4; BOTTINO, ALTAMIRO5; VEIGA, CARLOS6; TOZZI, MARTA B.7; PICKARD, MEGAN B.8; CAMERON, LUIZ-CLAUDIO1,2

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Abstract

Purpose: We investigated the effects of caffeine on the ammonia and amino acid metabolism of elite soccer players.

Methods: In this double-blind randomized study, athletes (n = 19) received 5 mg·kg−1 caffeine or lactose (LEx, control) and performed 45 min of intermittent exercise followed by an intermittent recovery test (Yo-Yo IR2) until exhaustion. The caffeine-supplemented athletes were divided into two groups (CEx and SCEx) depending on their serum caffeine levels (<900% and >10,000%, respectively). Data were analyzed by ANOVA and Tukey post hoc test (P < 0.05 was considered to be statistically significant).

Results: Caffeine supplementation did not significantly affect the performance (LEx = 12.3 ± 0.3 km·h−1, 1449 ± 378 m; CEx = 12.2 ± 0.5 km·h−1, 1540 ± 630 m; SCEx = 12.3 ± 0.5 km·h−1, 1367 ± 330 m). Exercise changed the blood concentrations of several amino acids and increased the serum concentrations of ammonia, glucose, lactate, and insulin. The LEx group showed an exercise-induced increase in valine (∼29%), which was inhibited by caffeine. Higher serum caffeine levels abolished the exercise-induced increase (∼24%–27%) in glutamine but did not affect the exercise-induced increase in alanine (∼110%–160%) and glutamate (42%–61%). In response to exercise, the SCEx subjects did not exhibit an increase in uremia and showed a significantly lower increase in their serum arginine (15%), citrulline (16%), and ornithine (ND) concentrations.

Conclusions: Our data suggest that caffeine might decrease systemic urea by decreasing the glutamine serum concentration, which decreases the transportation of ammonia to the liver and thus urea synthesis.

©2013The American College of Sports Medicine

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