New Research Suggests Swimming Triggers Superior Cardiac Muscle Adaptations Compared to Running

New research shows swimming drives stronger heart muscle growth and better pumping efficiency than running by activating unique molecular pathways.

By: AXL Media

Published: May 1, 2026, 11:26 AM EDT

Source: Information for this report was sourced from Earth.com

The Biological Distinction Between Aquatic and Land Cardio

Cardiovascular health has long been associated with any form of sustained aerobic activity, yet new data indicates that the medium in which one exercises may dictate the heart's physical evolution. Led by Professor Andrey Jorge Serra at the Federal University of São Paulo, a research team conducted a controlled comparison between running and swimming to observe their respective impacts on heart muscle efficiency. While both modalities significantly improved respiratory capacity and general endurance, swimming was found to go a step further by inducing specific functional adaptations that land-based running did not replicate under the same experimental conditions.

Structural Remodeling of the Left Ventricle

The most prominent physical finding of the study was the noticeable enlargement of the heart in the swimming group. Unlike the runners, the swimmers exhibited a significant increase in heart mass relative to total body weight. Specifically, the left ventricle—the chamber responsible for pumping oxygenated blood to the rest of the body—became both thicker and wider. This structural growth, known as physiological hypertrophy, was supported at the cellular level by larger heart muscle cells with more complex internal structures. In contrast, the hearts of those in the running group remained structurally similar to the sedentary control group despite their improved fitness levels.

Enhanced Contractile Force and Pumping Efficiency

Beyond mere size, the study measured the mechanical performance of the heart tissue, finding that swimming produced a heart that was objectively stronger. The cardiac muscles from the swimming group generated more force and demonstrated a faster rate of both contraction and relaxation. This dual improvement suggests that the heart becomes more efficient at handling blood volume, a critical factor in long-term cardiovascular resilience. While running did provide marginal improvements in the speed of contraction, it failed to match the robust increase in total pumping power observed in the aquatic subjects.