title: Red blood cell variables in highly trained pubescent athletes: a comparative analysis.
abstract: BACKGROUND
  A suboptimal haematological status has often been recorded in athletes involved in intensive physical activity. There have even been reports of "sports anaemia" associated with intensive physical exercise. However, studies on the effect of different types of exercise practiced over a long period of time on the red blood cell variables in pubescent athletes are very few.
  
  
  OBJECTIVE
  To assess the basic red blood cell variables in highly trained pubescent athletes from different sports and to compare the results with those for a control untrained group. Sex related differences in these variables were also assessed.
  
  
  METHODS
  876 highly trained athletes (559 boys and 317 girls) were included in the study. Their mean (SEM) age, weight, and duration of training were: 14.01 (0.06) years, 56.24 (0.52) kg, and 3.52 (0.07) years respectively. The control group consisted of 357 untrained subjects (171 boys and 186 girls) with mean (SEM) age and weight of 14.58 (0.09) years and 57.75 (0.67) kg. The group of athletes was divided into seven subgroups according to the sport practiced: athletics (105), swimming (107), rowing (230), wrestling (225), weight lifting (47), various team sports (92), and other sports (67). Venous blood samples were drawn from the cubital vein, and the red blood cell count, packed cell volume, haemoglobin concentration, and mean corpuscular volume were measured. Statistical indices were computed for each group and for each variable, and analysis of variance factorial analysis was performed to evaluate the statistical significance of the differences detected.
  
  
  RESULTS
  The highly trained group was found to have lower red blood cell count, packed cell volume, and haemoglobin concentration (p<0.001) than the control untrained group (4.61 (0.01) x 10(12)/l v 4.75 (0.02) x 10(12)/l, 0.389 (0.001) v 0.404 (0.002) l/l, and 133.01 (0.38) v 139.9 (0.62) g/l respectively). These variables were lower for the boys of the trained group than for the boys of the control group (p<0.001), and similarly for the girls (p<0.001). The lowest red blood cell count, packed cell volume, and haemoglobin concentration were measured in blood samples from the boys of the swimming subgroup (4.54 (0.06) x 10(12)/l, 0.386 (0.006) l/l, and 129.38 (1.80) g/l respectively) and the rowing subgroup (4.66 (0.03) x 10(12)/l, 0.400 (0.003) l/l, and 136.21 (0.94) respectively). The same distribution was found for the girls: lowest in the rowing subgroup (4.32 (0.04) x 10(12)/l, 0.314 (0.003) l/l, and 124.27 (0.93) g/l) and the swimming subgroup (4.40 (0.05) x 10(12)/l, 0.375 (0.005) l/l, and 125.90 (1.30) g/l). No differences were found in the mean corpuscular volume.
  
  
  CONCLUSIONS
  Continuous (more than one year) high intensity sports training (twice a day/five days a week) results in a decrease in the basic red blood cell variables in pubescent boys and girls, this being most pronounced in the submaximal sports.
authors.affiliation: Department of Physiology, Faculty of Medicine, Higher Medical Institute, Plovdiv, Bulgaria.
authors.forename: N
authors.initials: N
authors.lastname: Boyadjiev
authors.forename: Z
authors.initials: Z
authors.lastname: Taralov
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D001790:Blood Physiological Phenomena; D004906:Erythrocyte Count; D004909:Erythrocyte Indices; D005163:Factor Analysis, Statistical; D005260:Female; D006400:Hematocrit; D006801:Humans; D008297:Male; D011627:Puberty / Q000502:physiology; D012737:Sex Factors; D013177:Sports / Q000502:physiology*; D013550:Swimming / Q000502:physiology; D014142:Track and Field / Q000502:physiology; D014891:Weight Lifting / Q000502:physiology; D014952:Wrestling / Q000502:physiology