Swimming Vs. Running — Which Is Proven To Be Better For Your Heart?
If you've ever wondered the difference between types of cardio, new research suggests it might be measurable when it comes to the strength of your heart.
A new study found that swimming may actually superior to running when it comes to building a stronger, more efficient heart.
Swimming vs running for cardio
Researchers at the Federal University of São Paulo wanted to understand why different types of cardio seem to affect the heart differently. To find out, they put rats through eight weeks of either swimming or running training, both at about 75% of their maximum aerobic capacity. This is similar to a moderately challenging workout for humans. A third group of rats remained sedentary for comparison.
Both types of exercise improved overall fitness. But differences emerged when researchers looked at what was happening inside the heart.
Only the swimming group showed increases in heart mass, larger heart muscle cells, and bigger left ventricle chambers, which is the part of your heart responsible for pumping blood to the rest of your body. This type of heart growth is called "eccentric hypertrophy." It's very healthy, and helps your heart become a more powerful, efficient pump.
While running also improved fitness, it didn't produce the same structural changes to the heart.
When researchers tested the heart muscle tissue directly, they found that swimming improved how forcefully the heart contracts and how well it relaxes between beats. Running only improved the contraction part, but relaxation is key because it allows the heart to refill with blood between beats. Better relaxation means better blood flow and a more efficient cardiovascular system overall.
What's happening at the cellular level
The researchers dug deeper to understand why swimming had an edge over running for cardiovascular fitness. They found that swimming activated a specific signaling pathway in heart cells that helps regulate healthy heart muscle growth. It also prevents the kind of harmful enlargement you'd see in heart disease.
Swimming also increased the activity of certain small molecules called microRNAs that protect the heart and regulate how heart cells grow and function.
What this means for your workout routine
Before you ditch your running shoes, it's important to remember that this study was done in rats, not humans. Animal studies help researchers understand biological mechanisms, but the results don't always translate directly to people.
That said, this research adds to a growing body of evidence that suggests swimming offers unique cardiovascular benefits. The water's buoyancy reduces stress on joints while the resistance engages your whole body. And unlike running, swimming requires you to work against resistance in all directions, which might explain why it creates a different type of demand on the heart.
If you're looking to mix up your cardio routine, adding a few swim sessions per week could be a smart move — especially if you want a low-impact option that still challenges your cardiovascular system.
The takeaway
While more human research is needed, it's definitely worth thinking about if swimming may have a spot in your fitness routine. With the warm weather coming, it's a perfect time to throw on some goggles and swim some laps.