Routine blood parameters in elite soccer players

Area of Science:

• Sports Medicine
• Clinical Biochemistry
• Exercise Physiology

Background:

• Elite athletes often undergo repeated blood screening, but normal ranges for highly active individuals are not well-established.
• Training and competition can significantly influence blood test results, complicating interpretation.

Purpose of the Study:

• To establish reference data for routine laboratory parameters in professional soccer players.
• To investigate the impact of elite soccer training and competition on blood screening results over a season.

Main Methods:

• Longitudinal study of 467 male professional soccer players from the top two German leagues over one season.
• Standardized venous blood sampling conducted four times to analyze complete blood count, liver enzymes (AST, ALT), creatine kinase (CK), kidney function markers (creatinine, urea), uric acid, cholesterol, electrolytes, ferritin, CRP, and TSH.
• Statistical analysis to identify significant changes and assess intraindividual variability.

Main Results:

• Significant seasonal changes observed in hematocrit, creatinine, uric acid, CK, AST, urea, sodium, potassium, magnesium, and TSH.
• Hematocrit and CK levels showed changes substantial enough to potentially influence clinical decisions.
• Upper limits of 95% confidence intervals for AST, urea, creatinine, and potassium slightly exceeded general population reference ranges.
• Intraindividual coefficient of variation was below 10% for most complete blood count parameters (excluding leukocytes), creatinine, uric acid, total cholesterol, and electrolytes.

Conclusions:

• Elite soccer training and competition profoundly affect hematocrit (plasma volume) and creatine kinase (CK) levels.
• The spontaneous variability of most tested blood parameters is too low to justify repeated sampling for routine screening in this population.
• Reference data for elite soccer players is crucial for accurate interpretation of blood screening results.