Exercise During COVID-19: Safe Practices to Prevent Cardiovascular Complications

Epidemiological evidence suggests exercise offers preventive as well as therapeutic health-related benefits.1-4 Exercise prevents the development of obesity and cardiovascular-related diseases such as hypertension, type 2 diabetes, and thrombosis,1, 3-4 all of which can result in a worse prognosis in a coronavirus disease 2019 setting (COVID-19).5-7 Numerous studies have confirmed the risks for severe complications from COVID-19 including acute respiratory distress syndrome, cardiogenic shock, and thromboembolic events.8 Thrombosis is currently considered a hallmark of severe COVID-19 infections,7 as COVID-19 is purported to be as much a vascular infection as it is a respiratory infection,8 further explaining why COVID-19 may increase the risk for acute coronary syndromes, ischemic strokes and pulmonary embolism. The cardiovascular sequelae from COVID-19 appear to be unique5 and not consistently established as of yet.7-12

Exercise as a Preventative Strategy for Health During COVID-19

Regular exercise has been considered a critical component of health1-4 and remains a key prevention strategy even in the midst of the pandemic. Interestingly, most individuals have changed exercise habits13 during the COVID-19 pandemic; those previously most active and those less than 40 have decreased exercise engagement, whereas those over 65 have become extra-active – 50 percent of whom are at least 70. Exercise increases immune cells,14 immediately affecting immune system function and inflammation.15 This is especially encouraging for individuals with chronic conditions, as moderate intensity exercise prior to becoming infected may reduce the severity of illness.15 Verrall16 suggests a bottom-up approach to COVID-19 prevention in which the goal is to optimize the immunity of the entire host through exercise. Although the effects of exercise in individuals with COVID-19 are not certain, the benefits of exercise on immune system function,14, 17-19 inflammation, and viral respiratory infections are well established.15

How Much Exercise is Enough?

The lack of exercise is currently a global pandemic.20-22 In the U.S., only 19% of women, 26% of men and 20% of adolescents currently meet the physical activity recommendations of 30-60 minutes of exercise 3-5 days per week at a moderate intensity, thus, the vast majority are at increased risk for chronic disease.15 Moreover, the existing evidence on the benefits of exercise with respect to the COVID-19 pandemic are compelling.15

Physical activity potentially reduces the severity of COVID-19 infections by enhancing muscle function through two biological processes that reduce the inflammation response to infection.15 Muscles comprise 30-40% of body weight and can be a powerful ally for fighting infections. Moderate-intensity activity like walking has the most impact, whereas extreme vigorous exercise like running marathons enhances oxidant production,23 temporarily reducing immune function.15 High intensity training in athletes has been associated with transient immune system changes, inflammation and subsequent muscle damage;24 whereas, regular moderate-intensity exercise training was associated with a decreased risk of respiratory infections.24 Although limited data exists regarding the prevalence, nature, and/or behavior of COVID-19-related illness in athletic individuals, elite athletes who consistently train at a high intensity are considered safe to continue this training without increasing the risk for illness, providing no sudden increase in training occurs.24

Cardiovascular Sequelae of COVID-19 and Safe Return to Exercise

Evidence-based recommendations exist for the safe return to an exercise routine after mild-to-moderate symptoms of COVID-19 in the recreational athlete. Metzl25 and colleagues advise close observation, especially in the first 3 to 6 months, although a wide range of disease expression exists. It is essential to ensure the absence of persistent cardiac complications related to COVID-19 prior to returning to exercise. According to Emery et al.,26  recreational athletes who show mild-to-moderate symptoms and lack pre-existing cardiac conditions do not need additional testing to safely exercise at a moderate intensity. Barker-Davies27 and colleagues provide more conservative restrictions of 2 to 3 weeks of rest upon symptom resolution, although if myocarditis ensues, refraining from exercise for 3 to 6 months along with follow-up exercise testing, echocardiography and heart rhythm monitoring, and blood analysis of biomarkers such as troponin I are required.

Puntmann et al.9 recently evaluated 100 patients who had recovered from COVID-19 between April and June 2020 in which cardiac involvement was found in 78% per CMR (cardiac magnetic resonance imaging). Ongoing myocardial inflammation was evident in 60 patients, independent of preexisting conditions, severity, overall course of the acute illness, and time from the original diagnosis. High-sensitivity troponin I, a reflection of subclinical myocardial damage, is detectable in 80% of the general population and predicts all-cause mortality even in those without CVD.28 Heffernan29 suggests high-sensitivity troponin I levels may be a useful marker of vulnerability to the systemic inflammatory effects and severe complications of COVID-19.

The cardiovascular effects of COVID-19 has also been evaluated in athletes. Following a mild initial presentation, a recovery period (5–7 days) often occurs, although some experience lingering tachycardia30 with deterioration to fulminant respiratory manifestations or myocarditis (inflammation of the heart).11-12 Two recently published consensus statements11, 31 provide conservative recommendations for athletes and highly active individuals to safely resume training following a COVID-19 infection. For those with mild to moderate symptoms, cessation of any exercise trainingis advised for at least 14 days from symptom resolution with a gradual return to exercise under the guidance of a medical team.11 In addition, a cardiovascular evaluation including biomarkers (troponin), and ECG, a cardiac MRI, and exercise testing is recommended before resuming training.11 Hull24 recommends rest for at least 10 days following symptom onset and an additional 7 days from symptom resolution without additional testing.

Rajpaland colleagues12 recently evaluated the hearts of 26 male and female student athletes (football, soccer, lacrosse, basketball, and track) with asymptomatic or mild COVID-19 cases using CMR. Changes consistent with myocarditis was observed in the hearts of four athletes following 11 to 53 days of quarantine, although eight of the 26 (31 percent) had subtle prior myocardial injury. While these findings are not definitive in their association with COVID-19, Rajpal11 advises athletes to be cognizant of cardiac symptoms such as, chest pain or shortness of breath.

Conclusion: Implications and Application

The long-term consequences and disease progression of COVID-19 remain a mystery, although ongoing evaluation and analysis of the cardiovascular manifestations are essential. Modest increases in exercise are feasible for most individuals and may be necessary to reduce the number of hospitalizations. The most common type of physical activity is walking; walking is free and accessible to nearly everyone and lends itself well to social distancing. Future research to evaluate exercise habits at the time of COVID-19 testing along with follow-up to determine if exercise was associated with morbidity and mortality is currently warranted.

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