Muscle, Neuromuscular, and Cardiac Damage in Trail Running: A Systematic Review

<b>Background</b>: Trail running (TR) is an endurance discipline characterized by prolonged exercise, irregular terrain, and marked elevation changes, which increase eccentric muscular load and may induce muscular, neuromuscular, and cardiac damage. <b>Objective</b>: This study aimed to systematically review the evidence on muscular, neuromuscular, and cardiac damage associated with TR participation. <b>Methods</b>: This systematic review followed PRISMA 2020 guidelines and was registered in PROSPERO (CRD420251135043). Five databases (PubMed, Web of Science, Scopus, SportDiscus, and ScienceDirect) were searched up to 31 August 2025. Observational, longitudinal, prospective, and case studies involving healthy adolescent or adult trail runners were included. Outcomes comprised muscle damage biomarkers (e.g., creatine kinase, alanine aminotransferase), neuromuscular function (e.g., squat jump performance, maximal voluntary isometric contraction), and cardiac biomarkers (e.g., CK-MB, cardiac troponins, NT-proBNP). Methodological quality was assessed using the National Heart, Lung, and Blood Institute Study Quality Assessment Tool. Results were synthesized qualitatively. <b>Results</b>: Fifteen studies met the inclusion criteria, including a total of 247 participants. Post-race analyses consistently showed marked increases in muscle damage biomarkers and significant reductions in neuromuscular performance. Transient elevations in cardiac biomarkers were also observed, suggesting acute but reversible cardiac stress following TR events. <b>Limitations</b>: Evidence was limited by methodological heterogeneity, small sample sizes, and underrepresentation of female athletes. <b>Conclusions</b>: It was found that trail running induces substantial acute muscular, neuromuscular, and cardiac stress, particularly in events with high eccentric loading. Monitoring biochemical and neuromuscular markers may support training load optimization, recovery strategies, and injury prevention.