title: Biochemical impact of soccer: an analysis of hormonal, muscle damage, and redox markers during the season.
abstract: This study aimed to analyze changes in performance, muscle function, and stress-related biochemical markers in professional soccer players (n = 14) at 4 timepoints (3 for performance and 4 for stress-related biochemical markers) during the soccer season [Formula: see text] preseason (E1), midseason (E2), end of the season (E3) [Formula: see text] and after the end of the recovery period (E4). Performance in 5- and 30-m sprints, countermovement jump, and agility, and maximal isokinetic knee extension and knee flexion strength were measured (E1 to E3). We observed increased in-season levels of myoglobin (E2 > E1 and E4; p < 0.05), a higher testosterone/cortisol ratio (T/C), and increased levels of creatine kinase (CK), C-reactive protein, superoxide dismutase (SOD), protein sulfhydryls (-SH), and malondialdehyde (E2 and E3 > E1 and E4; p < 0.05). Lower cortisol concentrations (E3 < E1 and E4; p < 0.05) and glutathione reductase activity (E3 < E2 and E4; p < 0.05) were observed at the end of the season. T/C, CK, SOD, -SH, and malondialdehyde decreased during the off-season, and cortisol and glutathione reductase increased (E3 < E4; p < 0.05). Agility increased in E2 and E3 (p < 0.01). Significant correlations were found during the season between hormonal and muscle function parameters (r = 0.56-0.86; p < 0.05). In addition, in E2, significant associations were observed between match-accumulated time (MATE2; minutes played by each player during the competition period), performance, and hormonal and redox parameters (r = 0.456-0.615; p < 0.05). In conclusion, this study shows that soccer players face significant changes in biomarkers of physiologic strain (muscle damage and oxidative stress-related markers) during the season, but values return to normal during the off-season. Additionally, MAT influences physical, hormonal, and oxidative stress-related parameters in professional soccer players.
authors.affiliation: a Center of Research, Education, Innovation and Intervention in Sport (CIFI2D), Rua Dr. Plácido Costa, 91, 4200-450 Porto, Portugal.
authors.forename: João Renato
authors.initials: JR
authors.lastname: Silva
authors.forename: António
authors.initials: A
authors.lastname: Rebelo
authors.forename: Franklim
authors.initials: F
authors.lastname: Marques
authors.forename: Laura
authors.initials: L
authors.lastname: Pereira
authors.forename: André
authors.initials: A
authors.lastname: Seabra
authors.forename: António
authors.initials: A
authors.lastname: Ascensão
authors.forename: José
authors.initials: J
authors.lastname: Magalhães
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D009135:Muscular Diseases / Q000209:etiology / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D012916:Soccer / Q000502:physiology*; D013739:Testosterone / Q000097:blood*
chemical_list: D015415:Biomarkers; D013739:Testosterone; D006854:Hydrocortisone