Ever since the very first marathoner collapsed as he reached Athens in ancient Greece, humans have been questioning the sanity of running 26.2 miles. Fast forward to today, and that anxiety still persists. Whether it’s a concerned family member asking if an athlete’s heart is overstressed or a runner’s own inner voice questioning their choices at mile 18, worry may be hiding in the back of a marathoner’s mind.
A False Alarm
Critics who raise concerns about the toll of extreme endurance running may cite study findings that show maximizing miles can increase the following risks:
- Heart tissue scarring (myocardial fibrosis)
- Irregular heart rhythms (atrial fibrillation)
- Temporary elevation of heart damage biomarkers
- Hidden plaque buildup in the heart's arteries (coronary artery calcium or CAC) that often leads to heart attacks
While it may look alarming on paper – and it's true that studies often find higher rates of this plaque buildup in marathoners compared to non-runners – there’s a big caveat. Headlines that warn about heart plaque in marathon runners can be missing crucial context, spreading unnecessary fear and discouraging people who want to start training.
What MHIF Research Reveals
The Minneapolis Heart Institute Foundation (MHIF) wanted to see if running long distances really does add up to more plaque in the arteries. To find out, we analyzed more than 5,000 individuals who had their CAC scores checked at our clinic. People who had participated in at least six marathons were 42% more likely to have detectable plaque than non-runners. That may sound like a red flag. Yet their overall health revealed a completely different picture: the marathoners had lower body mass indexes (BMIs), lower blood pressure, healthier cholesterol levels, and lower rates of diabetes than the non-marathoners.
Plaque’s Critical Difference
Seeing a higher likelihood of plaque in marathon runners could raise concern, but there is an important structural difference in how that plaque behaves. Plaques found in in endurance-trained runners tend to be smaller and more calcium-dense (hard plaques). In contrast, non-runners are more likely to have larger, softer plaques, which are more likely to rupture and cause heart attacks. In addition, endurance training is consistently associated with a lower risk of heart attacks, lower cardiovascular mortality rates and a reduction in cardiovascular risk factors.
The Real Takeaway for Runners
Ultimately, while the legend of the first marathon might make endurance running seem risky, modern science tells a much more encouraging story. Digging deeper into plaque structure and the overall health of runners themselves alleviates any false fears surrounding heart health in marathoners. When you look at the full picture, the verdict from our research is clear: the cardiovascular benefits of long-distance running far outweigh the theoretical risks. Continue lacing up those shoes; marathon training remains an excellent way to protect the heart, boost fitness and improve quality of life.
