A recent article published in Circulation by John Del Coso and his team demonstrated that the cardiac stress during a marathon is higher than the cardiac stress produced by competing in shorter-distance events, at least in athletes with lesser experience and lower training background. The manuscript provides evidence of the relatively-high cardiac stress of marathoners, following a competition. Reasons for this high cardiac stress after the marathon arise from the combination of a long distance event and the lack of appropriate training in the study sample. Interestingly, athletes with lower running experience and training backgrounds presented much lower values of cardiac stress, as they decided to compete in shorter distances.
Dr. Coso and his team noted that a high portion of marathoners did not even train longer than 30 km/week during the entire season and also found that most runners commenced preparation for the marathon just a few weeks before the event, while they were inactive for the most part of the year. The investigators found a relationship between the lack of training and the high levels of muscle damage and believed that this “damage” in the skeletal muscle could also occur in the myocardium myofibrils and then designed the current investigation.
[perfectpullquote align=”full” bordertop=”false” cite=”” link=”” color=”” class=”” size=””]”In our experience, we have also found some of this: “new runners” do not usually progress through the endurance distances range (5km, then 10 km, then 21km) because the “true” and “pure” challenge is the 42 KM and shorter distances are considered as incomplete. Thus, marathon races have become mass-events where anyone can register but without any filtering to determine if they are really prepared to run the race. I believe that this does not apply to other sports disciplines (or at least, the magnitude of the problem is smaller) because there is no historical perspective to support 6 hours of consecutive football, or 6 hours of consecutive weightlifting.”- Dr. Beatriz Lara Ph.D.[/perfectpullquote]
A total of 63 healthy runners (in triplets) were selected from a group of 322 nonprofessional finishers because of similarities in age, anthropometry and running experience. The triplets also had similar 10-year absolute cardiovascular risks. Before and 10 minutes after the race, body mass was measured to assess dehydration. Blood samples were obtained to measure cardiac biomarkers, including high-sensitivity cardiac troponins I and T, NT-proBNP (N-terminal pro-B-type natriuretic peptide), and the cardiac (creatine kinase-MB) and skeletal muscle (creatine kinase-MM) isoenzymes of creatine kinase and myoglobin at the end of the races. The time used to complete the races (58±9, 116±16, and 252±35 minutes for the 10-km race, half-marathon, and marathon, respectively; P<0.01) and body mass loss (−1.0±0.4%, −1.7±0.7%, and −2.5±0.7%, respectively; P<0.01) increased with distance. The serum concentrations of cardiac troponins I and T were significantly higher across running distances while the NT-proBNP and creatine kinase-MB concentrations were higher only in marathon runners. Serum myoglobin (median, 82 [interquartile range, 68–107], 199 [154–436], and 636 [436–958] ng/mL, respectively; P<0.01) and creatine kinase-MM concentrations (145 [81–224], 157 [119–213], and 273 [216–654] ng/mL, respectively; P<0.01). were also higher in the groups. Dr. Coso also added, “Because we used healthy participants, I believe that our work has little applicability to the clinical practice, beyond the already available information that endurance exercise can increase cardio-troponins above basal levels, while the cause is different from the rise in cardio-troponins derived from myocardial infarction. The findings are more applicable to the field of exercise physiology and sports science, to suggest that exercise intensity should be prioritized over training volume. And especially for amateur runners, it suggests that running is a very beneficial exercise activity, but training principles should be taken into account (especially progression in volume and intensity).”