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The heart is a muscle, and like any other muscle, it adapts to repetitive loads.
How the heart changes
In individuals who train for endurance regularly, the left ventricle dilates and the muscle wall thickens moderately. As a result, stroke volume — the amount of blood pumped per beat — increases significantly.
Because the body requires a certain blood flow at rest, the heart needs fewer beats when it pumps more blood per beat. This is why the resting heart rate of endurance athletes is often 40–50 beats per minute, compared to 60–80 in sedentary individuals.
It is necessary to distinguish this physiological adaptation from pathological hypertrophy caused by hypertension: the morphology, diastolic function, and potential for recovery are quite different.
Blood vessels
The layer of cells lining the blood vessels — the endothelium — secretes nitric oxide to dilate vessels. Fast blood flow during exercise creates shear stress on the vessel walls, stimulating this very process.
Regular exercise improves endothelial function, and this is considered one of the central mechanisms explaining why physical activity lowers blood pressure: meta-analyses show a reduction of about 5–8 mmHg in systolic blood pressure in people with hypertension — equivalent to some monotherapies.
VO₂max: a powerful predictor
VO₂max is the maximum amount of oxygen the body can use per minute. In large cohort studies, this is one of the strongest predictors of all-cause mortality — stronger than smoking, hypertension, or diabetes in some analyses.
The good news: the greatest risk reduction occurs when moving from "completely sedentary" to "mildly active." Going from 0 to 90 minutes per week significantly reduces risk; going from 300 to 400 minutes provides much smaller additional benefits.
Current recommendations
WHO recommends that adults:
- 150–300 minutes of moderate-intensity physical activity per week, or 75–150 minutes of vigorous-intensity activity
- Plus muscle-strengthening activities involving major muscle groups at least 2 days/week
- Reduce sedentary time — interrupt it by standing up and walking for a few minutes
People with cardiovascular disease, uncontrolled hypertension, or those who have been sedentary for a long time should consult their doctor before starting a high-intensity program.
This article provides scientific information for reference purposes and does not replace medical advice, diagnosis, or treatment from healthcare professionals. If you have specific health concerns, please consult your doctor.
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References
- [1]WHO guidelines on physical activity and sedentary behaviour — World Health Organization (2020)
- [2]Exercise and cardiovascular health: mechanisms and clinical implications — Circulation Research (2019)
Tvanbr / Wikimedia Commons — public domain
