Kinetics of Serum Myoglobin and Creatine Kinase Related to Exercise-Induced Muscle Damage and ACTN3 Polymorphism in Military Paratroopers Under Intense Exercise

<b>Background</b>: Physical conditioning is essential to meet the operational demands of military environments. However, high-intensity exercise provokes muscle microinjuries resulting in exercise-induced muscle damage. This condition is typically monitored using serum biomarkers such as creatine kinase (CK), myoglobin (MYO), and lactate dehydrogenase (LDH). Nevertheless, individual variability and genetic factors complicate the interpretation. In this context, the rs1815739 variant (<i>ACTN3</i>), the most common variant related to exercise phenotypes, hypothetically could interfere with the muscle physiological response. This study aimed to evaluate the kinetics of serum biomarkers during a high-intensity activity and their potential association with rs1815739 polymorphism. <b>Materials and Methods</b>: 32 male cadets were selected during the Army Paratrooper Course. Serum was obtained at six distinct moments while they performed regular course tests and recovery time. Borg scale was assessed in 2 moments (~11 and ~17). <b>Results</b>: Serum levels of CK, CK-MB, MYO, and LDH significantly increase after exercise, proportionally to Borg's level, following the applicability of longitudinal studies to understand biomarker levels in response to exercise. R allele carriers (<i>ACTN3</i>) were only slightly associated with greater levels of MYO and CK, mainly in relative kinetic levels, and especially at moments of greater physical demand/recovery. Although the <i>ACTN3</i> was slightly related to different biomarker levels in our investigation, the success or healthiness in military activities is multifactorial and does not depend only on interindividual variability or physical capacity. <b>Conclusions</b>: Monitoring biomarkers and multiple genomic regions can generate more efficient exercise-related phenotype interventions.