Author(s): JOHN, L., LÜDERS, N.S., WIESING, A., MUNK, M., HENZE, A.S., KIRSTEN, J., SCHULZ, S.V.W., BIZJAK, D.A., Institution: UNIVERSITY HOSPITAL ULM , Country: GERMANY, Abstract-ID: 857

INTRODUCTION:
Marathon participation has increased markedly in recent years, with a growing proportion of novice runners. Marathon running imposes substantial physiological stress, which may differ according to training status and performance level. This study investigated marathon-induced changes in hematological and inflammatory biomarkers across performance groups and evaluated systemic and non-invasive markers of exercise-induced inflammation.
METHODS:
Sixty-two male and female runners participating in the Einstein Marathon 2024 (Ulm, Germany) were recruited; 52 completed post-race testing. Athletes were stratified by finish time into highly trained (G1), trained or developmental (G2), and recreationally active (G3). Blood and saliva samples were collected pre-race and post-race. Blood analyses included red blood cells, leukocytes, lactate dehydrogenase, haptoglobin, creatine kinase, interleukin-6, and kynurenine. Salivary C-reactive protein was assessed. Pre-race body composition was measured via bioimpedance.
RESULTS:
All groups demonstrated significant post-race increases in red blood cells, leukocytes, lactate dehydrogenase, creatine kinase, interleukin-6, and kynurenine, alongside decreased haptoglobin, indicating hemolysis, inflammation, and muscle damage. Creatine kinase differed between performance groups, with smaller increases in faster runners compared to slower groups. Other blood parameters showed no significant between-group differences. Salivary C-reactive protein did not change. Slower finishers tended to exhibit greater markers of cell damage and inflammation, though most group differences were not statistically conclusive. Age and body fat tended to be lower in faster runners, whereas marathon experience and years of training showed no clear association with performance.
CONCLUSION:
Marathon running elicits substantial inflammatory and muscle damage responses, largely independent of performance level. Nevertheless, observed trends toward greater physiological strain in slower runners indicate that prolonged exposure to exercise stress may influence health risk profiles. These findings highlight the importance of considering not only performance but also duration of effort when evaluating marathon related physiological load. Serum kynurenine showed potential as a responsive inflammation marker, whereas salivary C-reactive protein did not reflect exercise induced changes. Although limited by sample size, particularly in the fastest group, the study provides applied field data from a real world marathon setting. Future research incorporating larger cohorts, in-race sampling, and longitudinal recovery monitoring is warranted to further elucidate the interaction between fitness, exposure time, and systemic stress responses.