Study finds swimming beats running for better heart health

By Stephen Beech

Swimming beats running for strengthening the heart, according to new research.

Training in water promotes "more robust and healthy" cardiac adaptations, according to the Brazilian study.

Research involving mice showed that swimming is more effective than running in promoting healthy heart growth and improving the strength with which the heart muscle, or myocardium, contracts.

Study coordinator Professor Andrey Jorge Serra said: “Swimming and running are two excellent ways to improve cardiorespiratory health and protect the heart muscle, but we wanted to know if one could be even more beneficial than the other.

"We found that, although both increase respiratory capacity, swimming goes a step further by combining functional and molecular adaptations that make the heart stronger and more efficient."

The findings, published in the journal Scientific Reports, show that swimming promotes greater modulation of microRNAs that control various heart adaptations — including cardiac cell growth, the formation of new blood vessels and protection against cell death — compared to running training.

The researchers explained that microRNAs are molecules that regulate the expression of messenger RNAs, which are responsible for protein synthesis.

Dr. Serra, from the Federal University of São Paulo (UNIFESP), said: "Although several studies had already examined the expression of microRNAs regulated by aerobic training in general, little was known about expression patterns when swimming and running were compared in the same experimental setting.

"Therefore, this study reveals that there’s a distinction in cardiovascular effects between these two modalities."

Mice underwent an eight-week training protocol consisting of daily 60-minute sessions five days a week for the study.

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The rodents were divided into three groups: one that did not train, one that only ran, and one that only swam.

Since running and swimming are very different forms of exercise, the comparison between the training regimes was not based on the speed the animals reached but rather on the relative intensity of the effort, as measured by maximum oxygen consumption (VO₂ max) – an indicator that assesses the body’s ability to capture, transport, and utilize oxygen during physical activity.

The results showed that running and swimming improved physical fitness similarly: between the first and last training sessions, VO₂ max increased by more than 5%.

But only swimming promoted significant structural changes in the heart, such as increases in cardiac and left ventricular mass.

Running did not show relevant differences compared to the sedentary animals.

Serra said: “People’s choice of sport depends largely on personal preference, aptitude, and enjoyment.

"But our results show that swimming may have a special impact in situations involving myocardial recovery, cardiac rehabilitation, and above all, scientific research.

"This is also relevant because studies on aerobic exercise often use running and swimming interchangeably, and we now know that the effects aren’t the same."

Before and after the training period, the research team administered a series of tests to evaluate various aspects of cardiac health, including cardiorespiratory capacity, fitness, and the structure and function of the heart and myocardium.

The study also analyzed the gene expression and protein pathways involved in physiological cardiac hypertrophy and the mechanisms involved in identifying regulatory microRNAs.

Serra added: “Although we don’t yet know why this change occurs at the molecular level, of the microRNA, we were able to delve deeply into and investigate the molecular pathways that control physiological hypertrophy."