Athlete’s heart

In January 2014 I went for an annual checkup of blood work, urine checks and an electrocardiogram (ECG). I timed it after January 10 to let any potential “damage” from December 23 through January 1 settle down 🙂 This was also a requirement for my Medical Certificate to participate in TransGranCanaria. Entered my local test centre AVASAD with good spirits and expected everything to be OK.

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Blood work was super:

* low total cholesterol
* high good cholesterol (HDL)
* little inflammation – C-reactive protein count was low despite a strong block of training throughout January, which implies good recovery
* good hemoglobin (red blood cell) count and hematocrit percentage

Urine was all clear too. However there were some drastic changes in my ECG from 7 months of daily, yet controlled (8 to 10 hours a week of varied intensity), endurance training …

ECG false positives in athletes

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The ECG is primarily used to detect underlying cardiac conditions, especially those that can lead to sudden cardiac death (SCD) in younger athletes. However there’s a very good chance of false positives for endurance athletes, especially regular high volume training of more than 8 hours per week. Mine got flagged with as first-degree ventricular block , also a symptom of a condition known as athlete’s heart

Athletic heart syndrome

Athletic heart syndrome is a heart condition that may occur in people who exercise or train for more than an hour a day, most days of the week. Athletic heart syndrome isn’t necessarily bad for you, IF you’re an athlete. The benign structural changes to the heart needs to be checked to rule out any genetic changes that would imply a more serious condition.

The heart gets bigger and stronger with exercise, allowing it to pump more blood per beat. Thickening of the walls can also occur with intense exercise, further increasing pumping power. Common symptoms include a low resting hear rate of 35 to 50 beats per minute. Changes to the electrical system however show up on and skew ECG readings, which needs to be verified further in order to rule out life threatening conditions. It’s harmless and a testament to the body’s ability to adapt to training load.

First-degree Atrioventricular block

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In first-degree heart block, like in my ECG, the heart’s electrical signals are slowed as they move from the atria to the ventricles (the heart’s upper and lower chambers, respectively). In a normal heart rhythm, the PR interval is in the range of .12 to .20 seconds. In first degree AV block, that interval will exceed .20 seconds and can be as long as .50 seconds

Other physiological heart adaptions

Cardiac chamber enlargement and the ability to generate a larger stroke volume allows endurance-trained athletes to increase cardiac output, the ability to circulate blood throughout the body, by 5 to 6 times (!!!!). Most of these changes occur in the left ventricle.

Heart size

Muscle tissue increase in size, especially in the left ventricle which provides a more powerful contraction.

Stroke volume

If the left ventricle is larger, it can fill with more blood. If its walls are thicker, contractibility increases, with the ability to deliver more blood to the body.

Resting heart rate

An increased stroke volume equals a lower resting heart rate.

Cardiac output

A high stroke volume results in greater oxygen supply, waste removal and thus improved endurance performance.

Blood pressure

If you suffered from hypertension before commencing a training regime, it’ll normalise.

Note than none of these adaptions are permanent and the heart and circulatory system would revert back to “normal” during the course of several months.


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As a follow up exam to rule out any underlying changes not related to training, I had to go for an . The results were fine and I was cleared with a medical certificate and a license to suffer until 2015 🙂

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As a recommendation, it’s good to establish a protocol with your cardiologist and keep an eye on the progression of physiological changes at least once a year with more frequent checkups if and when required.

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