It’s no secret that regular exercise affects the mind and body in a plethora of beneficial ways. Most people are encouraged to exercise throughout the week to fend off heart disease, type-two diabetes, and other health complications. One of the most popular forms of exercise is cardio. Cardio exercises are often easily practiced and extremely heart-healthy, making them ideal for anyone looking to get or stay in shape. However, all cardio exercises aren’t quite the same. Two of the most popular aerobic exercises, running and swimming, can have substantially different impacts on your health. So, how does running compare to swimming when it comes to your health? Each offers surprisingly different results when it comes to strengthening essential sections of your heart.

The long-term effects of exercise

Science has already proved, time and time again, that regular exercise alters the body in remarkable ways. Aerobic exercises, in particular, are beneficial for one of your most essential organs: your heart. They quite literally alter its functioning. When you run, swim, or engage in another form of cardio, your muscles require more oxygen to perform without giving out. The heart pumps oxygen-rich blood from the lungs into your heart’s left ventricle during any normal workout. The heart then sends this blood to the muscles throughout your body. Aerobic exercises require a much more extreme and rapid version of this process. Since your muscles require more oxygen during cardio workouts, the heart is forced to pump oxygen-rich blood more rapidly throughout the body. This forces the left ventricle to work even harder to keep up with the pumping process. Over time, this chamber of the heart becomes stronger and more resilient, protecting the essential organ from a number of diseases and conditions. Any form of exercise can result in a strengthening of the left ventricle over time, specifically when it comes to cardio. However, a new study has revealed that even closely-related cardio workouts can have staggeringly different effects on the heart.

Comparing the hearts of both athletes

Running and swimming have some obvious performance differences: land v. water, exposure v. immersion, and breathing v. breath-holding. While these two exercises haven’t often been studied together, a group of experts took an interest in how the differences between the two exercises affect the hearts of runners versus swimmers. After all, the amount of blood pumped from the lungs into the heart has a major impact on how the heart alters and develops during exercise. In November of 2018, a study comparing the left ventricular in runners and swimmers emerged in Frontiers in Physiology. The study was the brainchild of a number of institutions, including the University of Guelph in Canada, who aspired to accurately map the function and structure of the hearts of both types of athletes. In order to do so, they drew on data from expert athletes in both sports, arguing that they would be the best participants to showcase the long-term effects of each individual exercise technique on the heart.

When comparing the hearts of each type of exerciser, they observed 16 professional runners and 16 professional swimmers. They invited them to come to their lab after not exercising for 12 hours. There, they were asked to lie still and allow the researchers to examine a variety of physical factors regarding their hearts. Besides studying their blood pressure and heart rates, they also used echocardiograms (echos) to dig into the functioning of their hearts. They found a number of significant similarities between the structures and functioning of the runners and swimmers hearts, including low heart rates and strong left ventricles. Both the heart rates of the runners and swimmers hovered around 50 b.p.m., and, thanks to their extensive aerobic exercise practices, their left ventricles were much heartier than any sedentary adult. However, it was the subtle differences between the two athletes hearts that had researchers lifting their eyebrows.

The subtle yet significant differences

Across the course of the study, researchers noted that there was a clear difference in functioning in the left ventricle between swimmers and runners. While they both boasted extremely healthy and resilient left ventricles, the performance of each type of heart during the blood-pumping process varied. The study seemed to show that runners’ hearts pumped blood more quickly and easily than swimmers’ hearts, if only by a slight degree. During the study, the runners’ hearts pumping process seemed to be more fluid, with their ventricles filling up earlier and becoming untwisted with less effort. Still, while this may suggest that runners’ hearts are stronger than swimmers’ hearts, it isn’t necessarily indicative of better heart functioning.

Posture plays a role in this doubt. Runners exercise in a vertical position, and therefore, are battling with gravity to pump blood back up to their hearts. Swimmers don’t face the same challenge. Athletes hearts adapt to their sports, so swimmers’ hearts don’t need to develop to handle the physical roadblocks of a runner. The study’s findings shed light on how the human body subtly adapts over time to manage the strain of the exercises we perform. It suggests a remarkable correlation between the type of workouts we perform and how our organs develop over time. Since this is the first study of its kind, more research will need to be conducted to confirm their findings. However, while the study’s findings certainly could be expanded on (such as observing athlete’s hearts during strenuous exercise sessions), the results are still telling of how runners’ and swimmers’ hearts function differently.