Longitudinal Training-related Hematological Changes in Boys and Girls from Ages 12 to 15 yr

Purpose Natural growth and maturation cause hemoglobin mass (Hbmass) and blood volume (BV) to increase during childhood and adolescence. Whether endurance training during the same period can cause further increases in these variables is not clear. Also, body composition develops differently in girls and boys during puberty, and the effect of these differences on hematological variables has not been previously studied. Methods Forty-two endurance athletes (End group; 24 boys) and 34 athletes from other sports (non-End group; 23 boys) were tested at ages 12, 13, and 15 yr for Hbmass, BV, plasma volume (PV), red cell volume (RCV), hematological variables, and anthropometrics. Results At age 12 yr, Hbmass and BV showed no difference between sexes and training groups in absolute values or relative to fat-free mass (FFM). Relative to FFM, Hbmass and BV averaged 11.7 (0.8) g·kg−1 and 95 (6.8) mL·kg−1. Increases in FFM from ages 12 to 15 yr primarily determined the increased Hbmass and BV for both sexes with no differences between training groups. At age 15 yr, Hbmass relative to FFM was higher in boys than girls, 13.1 (0.8) g·kg−1 and 12.1 (0.9) g·kg−1 (P
Source: Medicine and Science in Sports and Exercise - Category: Sports Medicine Tags: APPLIED SCIENCES Source Type: research