title: Effect of caffeine supplementation on haematological and biochemical variables in elite soccer players under physical stress conditions.
abstract: OBJECTIVE
  To evaluate the effect of caffeine on white cell distribution and muscle injury markers in professional soccer players during exercise.
  
  
  METHODS
  22 male athletes completed a placebo controlled double blind test protocol to simulate a soccer match, followed by a Yo-Yo intermittent recovery test.
  
  
  RESULTS
  Exercise caused an increase in packed cell volume that was enhanced by caffeine. Caffeine and exercise had a synergistic effect on the blood lymphocyte count, which increased by about 38% after exercise, and by an additional 35% when combined with caffeine. Caffeine promoted an exercise independent rise in circulating monocytes, and a synergistic action of exercise and caffeine was observed on segmented neutrophils. Caffeine promoted thrombocytosis. Plasma adenosine deaminase, aspartate aminotransferase, and lactate dehydrogenase concentrations were enhanced by exercise, and alanine transaminase concentration was enhanced in both groups, with a synergistic effect of caffeine.
  
  
  CONCLUSIONS
  The pronounced increase in the white cell count in the group receiving caffeine appeared to be caused by greater muscle stress and consequently more intense endothelial and muscle cell injury. The use of caffeine may augment the risk of muscle damage in athletes.
authors.affiliation: Laboratory of Protein Biochemistry, Federal University of State of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Adriana
authors.initials: A
authors.lastname: Bassini-Cameron
authors.forename: Eric
authors.initials: E
authors.lastname: Sweet
authors.forename: Altamiro
authors.initials: A
authors.lastname: Bottino
authors.forename: Christina
authors.initials: C
authors.lastname: Bittar
authors.forename: Carlos
authors.initials: C
authors.lastname: Veiga
authors.forename: Luiz-Claudio
authors.initials: LC
authors.lastname: Cameron
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D000886:Anthropometry; D015415:Biomarkers / Q000097:blood; D001774:Blood Chemical Analysis; D002110:Caffeine / Q000008:administration & dosage*; D003402:Creatine Kinase / Q000097:blood*; D004311:Double-Blind Method; D005080:Exercise Test / Q000379:methods; D006801:Humans; D019344:Lactic Acid / Q000097:blood* / Q000378:metabolism; D007958:Leukocyte Count; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology*; D010976:Platelet Count; D011336:Probability; D020127:Recovery of Function; D012016:Reference Values; D012680:Sensitivity and Specificity; D012916:Soccer / Q000502:physiology*
chemical_list: D015415:Biomarkers; D019344:Lactic Acid; D002110:Caffeine; D003402:Creatine Kinase