Indirect markers of muscle damage in military physical training session with neuromuscular and aerobic exercises in circuit (Cross operational): acute effects and recoverability

The Brazilian army recently developed the military physical training “Cross Operational” (CO), composed of four different difficulty levels. The moderate/high intensity character of CO can damage the muscle fibers, characterized by alterations at the cellular level, which can be evaluated indirectly by intramuscular proteins showing up in the bloodstream. In this context, the analysis of muscle damage biomarkers can be used as part of an initial injury prevention tool and in the evaluation of training progression and post-exercise recovery. This study aimed to observe the acute effect of CO on indirect markers of muscle damage in military personnel of the Brazilian army. Twenty-four male recruits aged between 18 and 26 years participated in the study. The four sessions corresponding to the CO levels were performed in cross-design, with a seven-day washout period, and blood samples were collected at rest, immediately after, 24 and 48 hours after each training session. The measured markers were creatine kinase (CK), myoglobin (Mb) and lactate dehydrogenase (LDH). In all CO levels, CK had a significant increase 24 hours after CO, whereas Mb and LDH incresead immediately after CO. Regarding recovery time, LDH returned to baseline values within 48 hours in all levels, whereas CK and Mb, after 48 hours of recovery, reduced but did not return to baseline in level 4. The serum elevations of the biomarkers studied, like those found in studies with other consolidated physical training methods, suggest that CO can contribute to the improvement of the physical training of military personnel.