Blood Biomarkers Variations across the Pre-Season and Interactions with Training Load: A Study in Professional Soccer Players

Filipe Manuel Clemente; Francisco Tomás González-Fernández; Halil Ibrahim Ceylan; Rui Silva; Saeid Younesi; Yung-Sheng Chen; Georgian Badicu; Paweł Wolański; Eugenia Murawska-Ciałowicz

doi:10.3390/jcm10235576

Blood Biomarkers Variations across the Pre-Season and Interactions with Training Load: A Study in Professional Soccer Players

J Clin Med. 2021 Nov 27;10(23):5576. doi: 10.3390/jcm10235576.

Authors

Affiliations

¹ Escola Superior Desporto e Lazer, Instituto Politécnico de Viana do Castelo, Rua Escola Industrial e Comercial de Nun'Álvares, 4900-347 Viana do Castelo, Portugal.
² Instituto de Telecomunicações, Delegação da Covilhã, 1049-001 Lisboa, Portugal.
³ Department of Physical Activity and Sport Sciences, Pontifical University of Comillas, 07013 Palma, Spain.
⁴ SER Research Group, Pontifical University of Comillas, 07013 Palma, Spain.
⁵ Physical Education and Sports Teaching Department, Kazim Karabekir Faculty of Education, Ataturk University, Erzurum 25240, Turkey.
⁶ Research Unit for Sport and Physical Activity, Faculty of Sport Sciences and Physical Education, University of Coimbra, 3004-531 Coimbra, Portugal.
⁷ Department of Exercise and Health Sciences, University of Taipei, Taipei 11153, Taiwan.
⁸ Department of Physical Education and Special Motricity, University Transilvania of Brasov, 500068 Brasov, Romania.
⁹ Department of Physiology, Gdansk University of Physical Education and Sport, 80-336 Gdansk, Poland.
¹⁰ Department of Physiology and Biochemistry, University School of Physical Education, 51-612 Wrocław, Poland.

Abstract

Background: Pre-season training in soccer can induce changes in biological markers in the circulation. However, relationships between chosen hematological and biochemical blood parameters and training load have not been measured. Objective: Analyze the blood measures changes and their relationships with training loads changes after pre-season training. Methodology: Twenty-five professional soccer players were assessed by training load measures (derived from rate of perceived exertion- known as RPE) during the pre-season period. Additionally, blood samples were collected for hematological and biochemical analyses. Results: For hematological parameters, significant increases were found for platelets (PLT) (dif: 6.42; p = 0.006; d = -0.36), while significant decreases were found for absolute neutrophils count (ANC) (dif: -3.98; p = 0.006; d = 0.11), and absolute monocytes count (AMC) (dif: -16.98; p = 0.001; d = 0.78) after the pre-season period. For biochemical parameters, there were significant increases in creatinine (dif: 5.15; p = 0.001; d = -0.46), alkaline phosphatase (ALP) (dif: 12.55; p = 0.001; d = -0.84), C-reactive protein (CRP) (dif: 15.15; p = 0.001; d = -0.67), cortisol (dif: 2.85; p = 0.001; d = -0.28), and testosterone (dif: 5.38; p = 0.001; d = -0.52), whereas there were significant decreases in calcium (dif: -1.31; p = 0.007; d =0.49) and calcium corrected (dif: -2.18; p = 0.015; d = 0.82) after the pre-season period. Moreover, the Hooper Index (dif: 13.22; p = 0.01; d = 0.78), and all derived RPE measures increased after pre-season period. Moderate-to-very large positive and negative correlations (r range: 0.50-0.73) were found between the training load and hematological measures percentage of changes. Moderate-to-large positive and negative correlations (r range: 0.50-0.60) were found between training load and biochemical measures percentage of changes. Conclusions: The results indicated heavy physical loads during the pre-season, leading to a decrease in immune functions. Given the significant relationships between blood and training load measures, monitoring hematological and biochemical measures allow coaches to minimize injury risk, overreaching, and overtraining.

Keywords: biology; performance; soccer; workload.