Exercise Keeps Athletic Heart Supple, Strong, Healthy: JACC Deep Dive

An international group of sports cardiology and physiology experts are shining a light on the importance of physical activity for the prevention and treatment of cardiovascular disease, including heart failure with preserved ejection fraction (HFpEF), and on the positive cardiac remodeling that typifies the athlete’s heart.

As part of a series published online September 5, 2022, in the Journal of the American College Cardiology, the experts turn their attention to not only the optimal mode, dose, duration, and intensity of exercise to reduce CVD, but also the management of athletes diagnosed with hypertrophic cardiomyopathy (HCM) and other inherited disorders. In addition, they highlight a range of current controversies and challenges in dealing with the athlete’s heart. 

Jason Kovacic, MBBS, PhD (Victor Chang Cardiac Research Institute, Darlinghurst, Australia), senior author on all four papers, said sports cardiology is a rapidly evolving specialty of mounting interest to physicians and athletes alike. That said, it’s not just the domain of competitors participating in high-level sports.

“It even transcends cardiology,” Kovacic told TCTMD. “In a way, there’s not a single one of us that isn’t interested in learning about this. Whether it’s for your patients or for yourself, it’s relevant.”

For physicians, physical activity is one of the only tools capable of positively affecting every cardiovascular risk factor, including obesity, hypertension, hypercholesterolemia, and diabetes, among others. “You name it, exercise has beneficial effects,” said Kovacic. “There is no other tool in our armamentarium as physicians that is so broadly beneficial to so many people.”

How Much Exercise? Can You Do Too Much?

At its most basic level, exercise training improves cardiorespiratory fitness (CRF), which is known to be a better predictor of prognosis than physical activity levels alone. Low CRF is a strong, independent risk factor for both CVD and all-cause mortality.

The most recent World Health Organization (WHO) guidelines recommend adults perform at least 150 to 300 minutes of moderate-intensity aerobic exercise (about 64% to 76% maximum heart rate or 5 to 6 on a 10-point scale) or 75 to 150 minutes of vigorous-intensity aerobic exercise per week (77% to 93% maximum heart rate or 7 to 8 on a 10-point scale). Data have shown that adhering to these WHO recommendations is associated with a 23% to 40% reduction in CVD and a 27% to 31% reduction in all-cause mortality.

“Cardiovascular disease is the number-one killer around the world,” said Kovacic. “Exercise is one of the cornerstones of mitigating that problem. All physicians need to be doing their part to underscore the importance of exercise to all of our patients. For most, it’s 30 minutes, five times per week, of moderate-intensity exercise. That could be brisk walking, mowing the lawn, vacuuming, ballroom dancing. That type of activity five times a week has a huge impact on reducing the risk of cardiovascular disease.”  

As part of the review, Kovacic and colleagues highlight the cardiac changes that occur as a result of exercise, namely the adaptive increases in cardiac chamber size and wall thickness, as well as the accompanying increases in contractile function. On average, athletes have excellent long-term health outcomes and survival, which the researchers attribute to the heart’s structural and functional remodeling. These changes, they note, are “rarely” associated with adverse clinical effects, but the experts do explore the relationship between high volumes of physical activity—such as the levels seen in elite endurance athletes—and atrial fibrillation (AF) and other arrhythmias.

All physicians need to be doing their part to underscore the importance of exercise to all of our patients. Jason Kovacic

“Can you do too much exercise?” said Kovacic. “Perhaps. It’s still a point of discussion, and it’s something that’s being worked out.” Still, in framing the question, he emphasized that the benefits of exercise are overwhelming, and that the vast majority of people needn’t worry about any potential downside. “For 99.9% of the population, exercise is a good thing,” he said.

The researchers note there is some debate whether higher volumes of exercise lead to even greater reductions in CVD or mortality, but there is evidence showing that doing as much as 10 times the recommended amount—levels seen in training endurance athletes—leads to CVD and survival benefits that outweigh any risks, such as the risk of sudden cardiac death.

Beyond primary prevention, the focused deep dive also looks at exercise as a secondary preventive therapy, pointing out that its benefits are on top of medication. In CAD patients, for example, exercise-based rehabilitation can reduce all-cause mortality anywhere from 36% to 63%. In a supervised setting, structured exercise training can begin as soon as 7 to 10 days after ACS treated with PCI. They also point out that exercise generally benefits patients with HFpEF, PAD, and AF, among other conditions. Exercise prescriptions, such as the duration and intensity, vary in these populations, but the benefits have been shown to clearly outweigh any associated risks.

Exercise and HFpEF

In one of the papers, Kovacic, along with lead author Andre La Gerche, MBBS, PhD (Baker Heart and Diabetes Institute, Melbourne, Australia), explore the association between physical activity, CRF, and cardiac function. In fact, they argue that lack of exercise is a major risk factor for HFpEF in some patients.

As they point out, physical activity results in athletic cardiac remodeling typified by an increase in cardiac mass, stroke volume, cardiac output, and peak oxygen consumption, but they posit that the reverse is true as well. For example, in those who are physically inactive, there is cardiac atrophy, reduced output, and reduced heart chamber size.

The researchers suggest that these smaller hearts are problematic as they limit an individual’s ability to meet metabolic demand and place patients at an increased of HF. 

“In people who don’t exercise, they do tend to have those small, stiff hearts, and they’re predisposed HFpEF,” said Kovacic. “By exercising throughout life, it does appear you can keep the heart supple and maintain a positive response in terms of diastolic function. As you get older, the age-related negative changes are counterbalanced by having that heart in a good place to start. People who are sedentary do tend to have other comorbidities—obesity, hypertension—and these obviously compound HFpEF as well.”

Right now, there hasn’t been a lot of research into HFpEF patients with exercise programs, but the data suggest that exercise throughout the lifetime is likely better to prevent HFpEF later in life rather than as a treatment once the disease manifests, said Kovacic. Still, there are some data showing that exercise programs can modestly improve peak oxygen consumption and quality of life by increasing the ability to perform self-care tasks and other functions. It’s unknown if exercise programs can reduce HF hospitalizations or morbidity/mortality, though. 

Loosening the Grip on HCM Patients

When it comes to sports participation following a diagnosis of HCM, the researchers point out that it was historically not recommended because of concerns about sudden cardiac death. Those notions are changing, however.

“The field has undergone a sea change over the past couple of years,” said Kovacic. “It has reached a tipping point where there is some momentum now underpinning our thinking that we were probably too restrictive over the last few decades in our approach to athletes with HCM and other genetic diseases. That’s borne out by a number of emerging studies, such as ICD registries and other data, suggesting that sports participation isn’t as dangerous as we perhaps first thought. A significant proportion of those patients probably can safely engage in exercise, even some in competitive sports.” 

One consequence of restricting people with HCM from sports/physical activity is that it has led to a sedentary lifestyle for many. In fact, data show that just a little more than half of HCM patients meet the minimal physical activity recommendations and 70% are obese. This only further contributes to larger left ventricular mass, obstructive physiology, heart failure, and AF in this population.  

Today, both the European Society of Cardiology (ESC) and American College of Cardiology/American Heart Association (ACC/AHA) guidelines state that participation in high-intensity sports competition “may be considered” after a comprehensive evaluation by expert physicians such as sports cardiologists. Such patients are those without markers of increased risk, such as cardiac symptoms or history of cardiac arrest or unexplained syncope. Low-to-moderate intensity competition and/or exercise is also generally endorsed by both the ESC and ACC/AHA. 

The decision to participate in sports with HCM should be based on a discussion between physician and patient about the risks and benefits. Consensus statements from experts no longer provide a binary yes/no approach to participation but are instead relying on input from the athlete and family. There is an increasing recognition about the upside of sports—quality of life, emotional well-being, decreased stress, and physical benefits—so the decision to participate should be made in the context of the risks alongside the patient’s values and preferences, according to the experts. 

“It’s not for a physician to say you’re done, you can’t compete,” said Kovacic. “It’s not for us to dictate people’s lives for them. It needs to be a shared decision-making process where there’s a discussion between the athlete, the team, the club, the physician, the family. It’s a whole team that comes to a decision that is going to work for that patient.”