Red Blood Cell Variables in Young and Mature High-Trained Football Players
Authors: Grudeva Janet G. , Boyadjiev Nickolay , Taralov Zdravko , Batashki Ilia 
Published: April 2020

Abstract
A suboptimal values of the haematological variables has often been recorded in young athletes involved in intense physical activity. There have even been reports of “sports anemia” associated with intensive physical training. There are profound studies describing the haematological changes of the soccer players after training or 90 min match. Our previous studies demonstrated lower values of red blood cell count (RBC), packed cell volume (HCT), haemoglobin concentration (HGB) in highly trained football players than in untrained controls of the same pubescent age.
THE AIM: It was a matter of interest to evaluate the haematological status of 2314 football players (15.11±2.89 yrs old) and to compare the results for pre-pubescent, pubescent and mature boys recruited in the study and also to relate the values obtained to the individulal aerobic functional capacity.
MATERIAS: A total of 2314 highly trained football players were included in the study. Their mean±SD age, weight, and BMI were: 15.11±2.89 yrs, 56.33±13.28 kg, and 19.62±2.58 kg/m2. The sportsmen were divided into three groups in accordance with their age: pre-pubescent (9–14 years) group A (n=1178) − 13.22±1.05 yrs (158.6±12.6 months); pubescent (15–19 years) group B (n=1029) − 16.57±1.04 yrs (198.9±12.6 months); and mature (20–35 years) group C (n=107) − 24.30±3.78 yrs (291.6±45.3 months) old. Profound clinical examination of all sportsmen was performed at the day before obtaining the blood samples. Haematological variables including RBC, HCT, HGB, mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin content (MCHC), white blood cell count (WBC) and platelet count (PLT) were analysed on a Sysmex K800 (Japan) analyser. Each football player passed also PWC170-test for assessment the working capacity on AT-104 Spiro-Ergo equipment (Schiller, Switzerland).
RESULTS: All haematological variables in the groups were found in normal ranges, but the RBC was highest in group B (5.17±0.28 *1012/l vs. 5.03±0.28 *1012/l for group A, and 5.08±0.41 *1012/l for group C). Group A demonstrated not only lowest values for the RBC, but also for the HGB (144.7±6.4 g/l vs. 149.1±6.0 g/l for group B, and 151.8±7.5 g/l for group C, P&lt;0.001), and for HCT (0.437±0.02 vs. 0.451±0.02 for group B, and 0.451±0.03 for group C, P&lt;0.001). Group A demonstrated similar values for the above basic red blood cell parameters to these measured for great male group of same age. The pre-pubescent football players (group A) had lower MCV (87.1±2.8 fl), than the players of group B (87.5±2.9 fl) and than the players from group C (88.1±3.0 fl). No evidences for blood dilution as a result of long-term training had been found in groups B and C. There was not difference in the WBC and PLT between pre-pubescent, pubescent and mature footballers. The mature players (C-group) demonstrated higher PWC/kg than pre-pubescent (20.6±2.3 vs. 19.2±2.3 kgm/min/kg), and than pubescent boys (19.8±2.7 kgm/min/kg). Significant correlations were obtained between the age and HGB, and between the age and HCT in groups A (0.19 and 0.19 respectively) and B (0.24 and 0.15 respectively). Good correlations were found between RBC and PWC170/kg in all groups investigated.
CONCLUSIONS: Pre-pubescent highly trained football players have lower values of the red blood cell variables than pubescent and mature footballers, which correlates with lower aerobic working capacity.