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Cardio Can Be Risky With This Heart Condition — What About Strength Training?
Exercise is one of the best things we can do for our heart. But for people with certain heart conditions, more exercise, especially more intense exercise, isn't always better.
That's the case with arrhythmogenic cardiomyopathy (ACM), an inherited disease of the heart muscle that can cause dangerous abnormal heart rhythms and raise the risk of sudden cardiac death. People with ACM or genetic variants that put them at risk are generally advised to limit high-intensity aerobic exercise and competitive sports.
But "exercise" covers a huge range of activities. Going for a long run places very different demands on your heart than doing a set of squats or lifting weights.
Most of what we know about exercise and ACM comes from research on endurance activities like running and cycling. Strength training, however, has been much less studied.
Researchers compared cardio & strength training
For the study1, published in JACC: Clinical Electrophysiology, researchers looked at 355 adults who either had ACM or carried a genetic variant that put them at risk for developing it. They asked participants about their exercise habits going all the way back to age 10, then grouped them based on the types of activities they typically did.
Endurance athletes did at least four hours of vigorous cardio per week, including running, cycling, or swimming. Strength athletes did at least two hours of activities like weightlifting, climbing, or martial arts each week. There were also groups for people who did both types of exercise and those who didn't meet either threshold.
From there, researchers looked at whether the type of exercise someone did was associated with their risk of experiencing a ventricular arrhythmia, a potentially dangerous abnormal heart rhythm that starts in the heart's lower chambers. They included serious events such as a sustained rapid heartbeat, cardiac arrest, or an abnormal rhythm that required treatment from an implanted heart device.
Strength training wasn't linked to higher arrhythmia risk
The researchers saw a clear difference depending on the type of exercise people did.
Endurance athletes were 58% more likely to experience a serious abnormal heart rhythm than people who strength trained or were sedentary. Strength training, on the other hand, wasn't linked to a higher risk compared with being sedentary.
People who did both cardio and strength training didn't have a higher risk than those who only did endurance exercise, either. That suggests the strength training itself wasn't adding additional risk.
So why might running or cycling affect the heart differently than lifting weights? During vigorous endurance exercise, the heart has to pump a large amount of blood continuously, sometimes for hours. For someone with ACM, that repeated demand can put extra stress on already vulnerable heart muscle cells.
Strength training challenges the cardiovascular system differently and doesn't require the heart to handle that same sustained increase in blood flow. Researchers think this could help explain why they didn't see the same association with abnormal heart rhythms, though more research is needed to understand which types and intensities of strength training are safest.
What this means for exercising with ACM
This isn't a green light for everyone with ACM to start lifting heavy weights. Only 7% of the people in the study were classified as strength athletes, so researchers were working with a relatively small group. The study was also observational and relied on people remembering their exercise habits over many years.
What it does suggest is that we may not need to think about every form of challenging exercise in the same way.
That's especially relevant for people with ACM who enjoy being active. Instead of simply being told to avoid intense exercise, future recommendations could become more specific about which types of movement are more or less likely to stress the heart.
For now, anyone with ACM or a genetic risk for the condition should talk with their cardiologist before changing their exercise routine. But this research gives patients and doctors more information to work with when deciding what staying active can safely look like.
The takeaway
Living with a heart condition can make exercise feel complicated. You want to protect your heart, but physical activity is also an important part of supporting your health and, for many people, something they genuinely enjoy.
This study suggests that for people with ACM, the conversation may be less about whether they can exercise and more about what kind of exercise makes sense for them.
There's still more to learn about exactly how much strength training is safe and how hard people with ACM should push themselves. But having another potential way to stay strong and active gives doctors and patients a more useful place to start that conversation.