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Myocardial strain increases with longer races for amateur runners
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Amateur runners competing in full marathons had more strain on the myocardium compared with those who ran half marathons and 10-km races, according to a study published in Circulation.
“We typically assume that marathon runners are healthy individuals without risk factors that might predispose them to a cardiac event during or after a race,” Juan Del Coso, PhD, director of the exercise physiology laboratory at Camilo José Cela University in Madrid, said in a press release. “With the growing popularity of long-endurance races, the exponential increase in the number of participants and the lack of appropriate training in some cohorts of amateur runners, our findings suggest that running shorter endurance races might reduce the strain imposed on the myocardium during running competition.”
Runners with similar characteristics
Del Coso, along with Beatriz Lara, PhD, of the exercise physiology laboratory at Camilo José Cela University, and colleagues analyzed data from 63 participants (mean age, 37 years; 39 women) who had similar running experience (3 years), anthropometry (66.9 kg) and 10-year absolute CV risk (2.8%). Participants were placed into 21 groups of three runners each, in which one ran a 10-km race, another ran a half-marathon race and the last one ran a full marathon.
Body mass was measured before the race and 10 minutes after the race to assess dehydration. Blood samples were also taken at the end of the race to measure cardiac biomarkers, including N-terminal pro-B-type natriuretic peptide, high-sensitivity cardiac troponin I and troponin T, and the skeletal and cardiac muscle isoenzymes of myoglobin and creatine kinase.
The time to complete the races was 58 minutes for the 10-km race, 116 minutes for the half marathon and 252 minutes for the full marathon (P < .01), according to the study. Body mass loss increased with distance, with –1% lost for the 10-km race, –1.7% lost for the half marathon and –2.5% lost for the full marathon (P < .01).
All races had similar self-report perceived exertion ratings, which was measured with the Borg scale, the researchers wrote.
Serum measurements
Serum concentrations of cardiac troponin I and troponin T after the races were significantly higher for all running distances. Participants who ran marathons had higher concentrations of NT-proBNP and cardiac muscle isoenzymes of creatine kinase compared with the other distances.
Serum myoglobin increased with running distance in participants who ran 10-km races (median, 82 ng/mL; P < .01), half marathons (median, 199 ng/mL; P < .01) and full marathons (median, 636 ng/mL; P < .01). This was also seen for skeletal muscle isoenzymes of creatine kinase (10-km race: 145 ng/mL; half marathon: 157 ng/mL; full marathon: 273 ng/mL; P < .01 for all).
“To assess the clinical significance of these findings, future studies should examine both the mechanism of cardiac troponin release with long-distance running and its potential impact on long-term clinical outcomes,” Lara and colleagues wrote. “Regardless, the findings from the present study demonstrate how running distance affects the cardiac stress induced by an endurance running competition in athletes with low experience and low training background.” – by Darlene Dobkowski
Disclosures: The authors report no relevant financial disclosures.
Perspective
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Michael S. Emery, MD, MS, FACC
There have been multiple observational studies showing elevated cardiac markers after longer endurance events. I am not sure this adds much to our current knowledge base.
The studies following up on athletes who have died after marathons, etc. show that the athlete had an underlying cardiac disease that may have been unknown and predisposing them rather than succumbing to the stress of exercise with a normal heart. We also know that the incidence of deaths is higher during marathons than half marathons (although still quite low in both), suggesting the same as this study.
Anyone who runs will tell you a marathon is harder than a half marathon. This should have no real impact on clinical practice as we’ve known it before.
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