Running a marathon can increase cardiac strain in amateur runners, according to a research letter published online Dec. 3 in Circulation.
Beatriz Lara, Ph.D., from Camilo José Cela University in Villafranca del Castillo, Spain, and colleagues selected 63 healthy runners (in triplets) from a group of 322 nonprofessional finishers. Runners were matched for age (mean age, 37 years), anthropometry (66.9 kg), running experience (3.3 years), and 10-year absolute cardiovascular risk (2.8 percent). From each triplet, one runner competed in a 10-km race, a half-marathon race, and a full-marathon race. Blood samples were obtained to measure cardiac biomarkers.
The researchers found that self-reported perceived exertion ratings measured with the Borg scale were similar for all races (P = 0.17). After the races, the serum concentrations of cardiac troponins I and T were significantly higher across running distances. N-terminal pro-B-type natriuretic peptide and creatine kinase-MB concentrations were higher only in marathon runners. Similarly, a correlation for higher serum concentration with running distance was found for serum myoglobin (P < 0.01) and creatine kinase-MM concentrations (P < 0.01).
"These data suggest that the strain imposed on the myocardium by competing in a full marathon is much greater compared with competing in shorter distances such as the half-marathon or 10-km races," the authors write.