Cardiac Remodeling from Swim Aerobic Anaerobic Workouts

Swimming’s Cardiac Remodeling: A New Study Shows Aerobic and Anaerobic Workouts Shape the Heart Differently

New research from the University of Health Sciences in Istanbul provides a detailed look at how the heart physically adapts to distinct swimming exercise protocols. A study published in the Journal of Clinical Medicine in 2026 examined how healthy rats’ hearts changed after 30 days of anaerobic, aerobic, and endurance swimming, both with and without the diabetes drug empagliflozin. It shows that exercise type directs structural and electrical changes in the heart, a process known as physiological cardiac remodeling.

Echocardiograms Reveal Aerobic Exercise Drives Chamber Size Changes

Led by Dr. Sezen Yavuz, the research team at Babaeski State Hospital and collaborating institutions used transthoracic echocardiography to measure the heart’s structure before and after the 30-day regimen. They found significant differences in key structural parameters, specifically the thickness of the wall between the ventricles (IVSd), the internal diameter of the left ventricle (LVIDd), and the end-diastolic volume (EDV), which is the amount of blood in the ventricle just before it contracts.

The most pronounced structural effect involved the combination of aerobic swimming and empagliflozin. This group showed distinct differences in LVIDd and EDV compared to several exercise-only groups. In simpler terms, the aerobic-plus-drug condition was associated with a larger left ventricular chamber and a greater pre-contraction blood volume. This suggests the aerobic stimulus, potentially amplified by the drug, promoted adaptations for increased stroke volume—a hallmark of the athlete’s heart.

Electrocardiograms Show Anaerobic Exercise Alters Electrical Recovery

Beyond structure, the team analyzed the heart’s electrical activity. They measured intervals on the electrocardiogram (ECG) related to repolarization—the critical recovery phase between beats. These intervals (QT, QTc, JT, and Tpeak-Tend) differed significantly across the groups by day 30.

Anaerobic exercise alone caused the most notable shifts in QT and JT intervals compared to aerobic and endurance swimming. Since these intervals reflect the time the heart muscle cells take to reset electrically, the finding implies anaerobic training places a unique type of stress on the heart’s electrical system. Interestingly, when empagliflozin was added to the anaerobic protocol, it was associated with a lower resting heart rate. This indicates the drug may modulate the heart’s response to high-intensity, anaerobic stress.

A critical limitation is that these findings are from a controlled animal model using healthy, male Sprague-Dawley rats. Human hearts, with greater genetic and lifestyle diversity, may respond differently. The 30-day timeline also only shows early adaptive changes, not long-term outcomes.

Understanding Modality-Specific Cardiac Adaptation

This study clarifies that not all exercise reshapes the heart in the same way. The adaptations are modality-dependent. Aerobic exercise, like steady-state Zone 2 training, traditionally promotes eccentric remodeling—the heart chamber enlarges to hold and pump more blood per beat, improving efficiency. The empagliflozin combination seemed to accentuate this pattern in the echocardiogram data.

Conversely, anaerobic exercise, characterized by short, high-intensity bursts, appears to influence the heart’s electrical properties more directly. This could be related to the different ionic and metabolic demands of repeated, forceful contractions. The fact that empagliflozin lowered heart rate specifically in the anaerobic group suggests it may help stabilize autonomic nervous system drive during intense training. For more on how different training loads affect swimmers, see our analysis of low-load, high-speed training for swimmers.

The endurance protocol in this study likely represented a different, perhaps mixed, metabolic challenge, resulting in its own unique signature of change. This aligns with the principle of specific adaptation to imposed demand (SAID), applied directly to cardiac tissue. These cardiac changes contribute directly to cardiorespiratory fitness, a key pillar of health and longevity.

Practical Applications for Endurance and Metabolic Fitness

For athletes and individuals focused on endurance and metabolic fitness, this research reinforces the value of a periodized training plan that includes varied intensities. Relying solely on one type of workout may lead to an incomplete cardiac adaptation profile.

Incorporate Aerobic Base Training: The structural benefits linked to aerobic swimming support the foundational role of Zone 2 training. This builds the heart’s pumping capacity and efficiency, which is vital for endurance performance and metabolic health by improving fat oxidation and mitochondrial density.

Strategic Use of High Intensity: Anaerobic sessions have a place, but this study suggests they provoke distinct electrical and autonomic responses. These sessions should be planned carefully, with adequate recovery, to allow for positive adaptation without undue stress. Training that challenges the cardiorespiratory system also has broader benefits, such as those discussed in our article on how exercise boosts heart rate variability.

Context on Pharmacological Aids: The empagliflozin findings are intriguing but not directly actionable for healthy individuals, as this is a prescription medication for type 2 diabetes and heart failure. The study’s primary value is in showing that metabolic interventions can interact with exercise to shape cardiac adaptation, a area requiring much more human research.

Frequently Asked Questions

Does this mean I should take empagliflozin to improve my heart’s response to exercise?

No. Empagliflozin is a prescription medication with specific indications. This study was an investigational animal model, and its findings do not support using this drug for performance enhancement or cardiac remodeling in healthy people.

Which is better for my heart: aerobic or anaerobic swimming?

Neither is universally “better”; they promote different types of adaptation. Aerobic swimming appears more influential on heart chamber size and volume, while anaerobic swimming affects electrical recovery patterns. A balanced program likely provides the most comprehensive benefits.

How quickly does the heart remodel in response to swimming?

This study detected measurable changes in both structure and electrical activity after 30 days of training in rats. In humans, detectable remodeling typically requires consistent training over several months, but early functional improvements occur much sooner.

Can I apply these findings to running or cycling?

The core principle—that exercise modality directs cardiac adaptation—likely applies across endurance sports. However, the specific pattern of remodeling may differ due to factors like body posture and the muscle groups involved.

Sources:
https://pubmed.ncbi.nlm.nih.gov/42355940/
https://pubmed.ncbi.nlm.nih.gov/42100593/
https://pubmed.ncbi.nlm.nih.gov/42036656/