Swimming and jogging have long been considered two of the most effective forms of aerobic exercise for maintaining cardiovascular health. However, a new study suggests that swimming may offer even greater benefits by triggering stronger structural and molecular adaptations in the heart.
Researchers at the Federal University of São Paulo (UNIFESP) in Brazil compared the effects of swimming and running in an animal model and found that, although both forms of exercise produced similar improvements in physical fitness, swimming promoted greater cardiac growth and more favorable molecular changes linked to heart health.
Greater cardiac adaptation
The findings, published in Scientific Reports, showed that swimming was more effective than jogging at enhancing the heart muscle’s contractile strength and stimulating healthy cardiac remodeling.
“Swimming and running are both excellent ways to improve cardiorespiratory fitness and protect the heart muscle. However, we wanted to determine whether one exercise offered additional advantages. While both improved aerobic capacity, swimming went a step further by inducing functional and molecular adaptations that made the heart stronger and more efficient,” said Professor Andrei Jorge Serra, who led the study.
The role of microRNAs
One of the study’s key findings was that swimming produced more pronounced changes in microRNAs small RNA molecules that regulate gene expression and, consequently, protein production.
These molecular changes were associated with:
- growth of cardiac muscle cells,
- formation of new blood vessels (angiogenesis),
- protection against cell death,
- improved cardiac contractility,
- reduced oxidative stress.
According to the researchers, these adaptations were consistently more pronounced in the swimming group than in the running group.
The study
The study involved mice that completed an eight-week exercise program consisting of 60-minute sessions, five days per week. The animals were divided into three groups: a sedentary control group, a running group, and a swimming group.
To ensure a fair comparison, the researchers matched exercise intensity using maximal oxygen uptake (VO₂ max), a standard indicator of the body’s ability to take in and utilize oxygen during exercise.
Both exercise groups increased their VO₂ max by more than 5%, indicating similar improvements in aerobic fitness. However, only the swimming group showed significant increases in total heart mass and left ventricular mass. No comparable structural changes were observed in the running group compared with the sedentary animals.
What the findings mean
The researchers believe the results highlight that different types of aerobic exercise do not affect the heart in exactly the same way. Although personal preference remains an important factor when choosing a sport, swimming may offer unique advantages for cardiac rehabilitation and for understanding the biological mechanisms that protect the heart.
The team also examined gene expression and protein signaling pathways involved in physiological cardiac hypertrophy the healthy enlargement of the heart that occurs as an adaptation to exercise rather than as a sign of disease. While the precise molecular mechanisms remain under investigation, the findings provide new insights into how different forms of aerobic exercise shape heart function and cardiovascular resilience.