Veteran male athletes who have spent years training at high intensity may be at greater risk of serious heart problems while exercising, new University of Leeds research shows.
Published today and funded by the British Heart Foundation, the study shows that male endurance athletes aged over 50 may be more likely to experience abnormal heart rhythms during training if they already have scarring in their heart.
Nine in 10 sudden cardiac deaths during sport occur in older male athletes.
The researchers' aim was to establish whether doing more exercise could cause a potentially fatal abnormal heart rhythm called ventricular tachycardia in this group of athletes.
They found that the athletes who experienced these rhythms were not exercising more or at greater intensity – but three quarters of them had heart scarring.
The team says this shows that exercise itself is not dangerous - but the findings suggest that the presence of scar tissue in the heart increases the risk of potentially dangerous heart problems during physical activity.
Importantly, the researchers were only aware that these athletes had heart scarring because of their participation in the study – highlighting the importance of regular heart health checks for veteran male endurance athletes to ensure they are not at risk of complications while training.
Scarring may be caused by heart attacks, disease, and exertion from lots of high intensity exercise over many years.
Lead author Dr Wasim Javed, Research Fellow in the University of Leeds' School of Medicine and Specialist Registrar at Leeds Teaching Hospitals NHS Trust, said: "Our study shows that exercise was only associated with a risk of developing abnormal heart rhythms in those who were already high risk due to heart scarring.
"Athletes who developed abnormal heart rhythms were not exercising more or harder than athletes without abnormal heart rhythms. This suggests that exercise itself is not the cause, but could act as a trigger for dangerous heart rhythms in those athletes already with an underlying heart issue.
"Exercise is safe and has immense benefits – but athletes in this group should have regular health checks to make sure they stay healthy."
The paper is a follow up to the team's VENTOUX study , published earlier this year, which showed that older male endurance athletes who had spent decades training and competing were more likely than non-athletes to have scarring in their hearts. This scarring was closely linked to the abnormal heart rhythms detected by participants' implantable loop recorders, which are small devices inserted under the skin.
The new trial aimed to investigate whether abnormal heart rhythms were affected by exercise, and when this occurred.
The 106 participants were healthy male endurance athletes aged over 50, doing more than 10 hours' of running or cycling every week for at least the past 15 years.
The researchers tracked participants' physical activity using wearable tech, such as smart watches and heart rate monitors, to log all their training activity. The researchers then compared the data from the trackers and the implantable loop recorders to exactly match participants' heart rhythms with their physical activity.
Over the two years of the study, around one in four participants experienced ventricular tachycardia during or just after exercising. The majority experienced non-sustained ventricular tachycardia, which is shorter and usually less dangerous - but may serve as a warning sign for longer, more dangerous events.
However, three in four of the athletes who had these episodes had heart scarring.
There were three longer and potentially more serious episodes of sustained ventricular tachycardia. These occurred during exercise, and all were in athletes with heart scarring.
The researchers say their findings support the use of wearable tech for any athlete who wants to monitor their heart rate for unusual activity. Anyone noticing an over-elevated heart rate while feeling unwell should reduce their intensity or seek medical attention.
Dr Javed said: "The three athletes who experienced dangerous heart rhythms had sudden spikes on their heart rate monitors, which confirmed to them that something wasn't right. Athletes can look out for this when training, along with any symptoms, and seek help or avoid pushing themselves if this happens."
The team says theirs is the first study to use long-term wearable tech data with heart rhythm data. They say future studies on athletes and exercise should involve wearable tech, because it accurately records activity levels, whereas simply asking athletes about how much exercise they do is likely to give inaccurate results. They hope their study can pave the way for future research on different groups, such as women or younger athletes.
Further information
The study is funded by the British Heart Foundation and is published on Monday 12 January 2026 in the European Journal of Preventative Cardiology.
