Project Title

Reversing the Athlete’s Heart: Can Detraining Promote Myocardial Recovery? 

Background

Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting millions worldwide. While regular exercise is a cornerstone of cardiovascular health, endurance athletes face a 2–5 fold higher risk of AF. This raises a critical question in sports cardiology: Should athletes with AF continue training or reduce training ("detrain") to improve their health outcomes? 

Aim

With this project we aim to investigate how reduced training-intensity (“detraining”) influences AF susceptibility and cardiac remodelling in an athletic horse model with paroxysmal AF (pAF). Furthermore, we aim to identify candidate plasma biomarkers of reverse cardiac modelling (“myocardial recovery”) in horse and human pAF athletes undergoing detraining. 

Methods

Sixteen endurance-trained racehorses with pAF will be randomised to either continued training or detraining. By combining 3D electro-anatomical mapping with cardiac biopsies, we will define how detraining affects AF triggers or alters the heart’s ability to sustain the arrhythmia. Findings will be compared with blood samples from human athletes with AF, to identify potential biomarkers. 

Preliminary results

In a small pilot study, we used mass spectrometry on equine right atrial tissue samples, comparing healthy trained racehorses (n=4) to healthy horses detrained for one year (n=2). Detrained horses showed downregulation of proteins associated with inflammation and contractility. These findings suggest that detraining may reverse hallmarks of exercise-induced cardiac remodelling.