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Before The Start: Adrenaline, Nervous System And Heart Rate Trigger
You have probably felt that intense surge of adrenaline before the start of a major race. The gun sounds, the legs start spinning, and almost immediately, the heart races. It beats faster due to excitement, nervousness, and, above all, physical exertion.
This feeling of “heart racing” is common among runners. However, although it seems dramatic, it is part of a natural physiological response.
When you get nervous, the amygdala sends a signal to the hypothalamus, the “command center” of the brain, according to Harvard Health. Then the hypothalamus activates the fight-or-flight response. As a result, the adrenal glands release epinephrine (adrenaline).
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As epinephrine circulates through the bloodstream, the heart speeds up. Heart rate increases, blood pressure rises, and breathing becomes faster. Still, as cardiologist Gregory Katz from NYU Langone Health explains, this pre-race increase typically poses no risk for healthy individuals.
The information was released by “Outside RUN,” based on interviews with cardiologists and scientific studies published in Missouri Medicine (2012) and JAMA Cardiology.
During The 42.195 Km: Cardiac Output Can Increase Up To Eight Times
As soon as the race begins, the heart takes on an expanded role. Now, in addition to keeping the body functioning, it needs to supply enough oxygen and nutrients to the muscles over the 42.195 km.
For this, it beats faster and pumps more blood with each contraction. This combined effect can elevate total cardiac output by up to eight times.
According to Eamon Y. Duffy, assistant professor of medicine at Columbia University and founding director of the Columbia Runners Heart Clinic, the runner typically maintains between 70% and 90% of their maximum heart rate for three, four, or five hours.
Additionally, as the force of contraction increases, blood pressure also changes. However, the extent of this variation depends on age, training level, and individual factors.
Cardiovascular Drift: Why Heart Rate Increases Even When Maintaining Rhythm
As the kilometers progress, many athletes experience what is called cardiovascular drift.
That is, even while maintaining the same pace, heart rate gradually rises. This happens because the body tries to preserve cardiac output while experiencing mild dehydration over the course of the race.
Therefore, even if the runner feels comfortable, it is unlikely that heart rate will decrease during the marathon.
In the final kilometers, there may be a further increase in heart rate. As the finish line approaches, both accumulated physical effort and mental pressure raise adrenaline levels once again.
Troponin And Marathon: What Scientific Studies Say
One of the most debated points involves troponin. Some runners show elevated levels of this enzyme in the blood after the marathon.
Troponin usually indicates stress or injury to the heart muscle. Therefore, elevated levels typically raise suspicion of a heart attack.
In 2012, an article published in Missouri Medicine suggested that long-distance running could harm the heart. However, more recent research has provided a different perspective.
A study published in JAMA Cardiology followed runners for more than 10 years after a marathon. Researchers observed that although troponin often rises immediately after the race, the heart recovers within a few days.
According to Duffy, in a heart attack, cell death occurs due to lack of oxygen. In the marathon, the scenario is different. Cells work under high stress, but do not necessarily experience cell death. In this process, muscle proteins may temporarily “leak” — and one of them is troponin.
Recovery After The Marathon: Rest Is Part Of Training
As soon as the runner stops running, heart rate begins to gradually decrease. However, each person has a different baseline level of fitness.
In the days and weeks that follow, the heart needs to recover just like the legs do. After all, a marathon represents immense physiological stress.
The effort affects the heart, the brain, the lungs, and the muscles. Therefore, experts recommend a few days — or even weeks — of rest after completing 42.195 km.
In summary, although running a marathon imposes acute stress on the heart, scientific evidence suggests that it can recover adequately.
Thus, for the vast majority of well-trained runners, the marathon is safe and can strengthen cardiovascular health.
After understanding what happens to your heart when running 42.195 km, do you approach the next marathon with more confidence or still feel apprehensive?
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