COVID-19: Return to sport or strenuous activity following infection

INTRODUCTION — The coronavirus disease 2019 (COVID-19) pandemic has had an unprecedented impact on physical activity and sport, affecting professional, elite, collegiate, tactical, occupational, and recreational athletes [1-3]. Sports participation was widely curtailed in 2020 to reduce viral spread, while tactical and occupational endeavors have required special precautions and modifications.

Illness from COVID-19 can cause a range of medical complications with potential intermediate and long-term consequences. For athletes preparing to return to play, residual effects of illness can complicate medical clearance, protocols for returning to play or activity, and monitoring [2,4].

The primary purpose of this topic is to provide guidance about individual return to play or strenuous activity following infection with COVID-19, with a focus on older adolescent (eg, high school) athletes, recreational and elite adult athletes, tactical personnel, and heavy occupational laborers. How sports leagues and teams should address the COVID-19 pandemic, including team return to play, is not discussed.

Issues pertaining to children and to general recovery from COVID-19 in adults are discussed separately, as are details about the evaluation and management of specific medical conditions associated with COVID-19 illness (eg, myocarditis, pulmonary embolus, residual pulmonary injury). A small sample of the many UpToDate topics addressing COVID-19 related illness includes the following: (see "COVID-19: Clinical features" and "COVID-19: Clinical manifestations and diagnosis in children" and "COVID-19: Infection prevention for persons with SARS-CoV-2 infection" and "COVID-19: Vaccines").

COVID-19 CLINICAL COURSE AND SEQUELAE IN ATHLETES — Our understanding of COVID-19-related illness continues to evolve. While many athletes develop only mild symptoms or remain asymptomatic, others experience persistent symptoms following acute illness [5]. For both athletes and non-athletes, recovery varies widely depending upon on the extent and severity of the acute illness, premorbid conditions, and other factors. These issues are discussed in detail separately. (See "COVID-19: Evaluation and management of adults with persistent symptoms following acute illness ("Long COVID")".)

Impact of physical fitness on clinical course — Although the clinical course of COVID-19 illness varies among athletes, (just as it does among non-athletes), on average, physical fitness appears to mitigate the severity of COVID-19 illness, while physical inactivity is associated with more severe disease and worse outcomes [6-10]. The effect of physical inactivity upon the course and severity of COVID-19 illness is discussed separately. (See "COVID-19: Clinical features", section on 'Risk factors for severe illness'.)

As examples, in a retrospective study of 246 patients (59±12 years, 42 percent male, 75 percent Black) diagnosed with severe acute respiratory syndrome secondary to COVID-19 illness, hospitalization was found to be inversely related to aerobic fitness [6]. Baseline fitness in peak metabolic equivalents, based on exercise stress testing results obtained within the prior four years, were significantly lower among patients who were hospitalized (6.7±2.8) compared with those not hospitalized (8±2.4) (unadjusted odds ratio [OR] 0.83; 95% CI 0.74-0.92; OR adjusted for major risk factors 0.87; 95% CI 0.76-0.99). In a retrospective, nationwide study of over 65,000 people participating in a physical activity rewards program, those with high physical activity levels (>150 minutes/week) suffered substantially lower morbidity and mortality from complications of COVID-19 infection than those with low physical activity levels (<60 minutes/week) [8]. High physical activity was associated with lower rates of hospitalization (risk ratio [RR] 0.66; 95% CI 0.63-0.70), intensive care unit (ICU) admission (RR 0.59; 95% CI 0.52-0.66), mechanical ventilation (RR 0.55; 95% CI 0.47-0.64), and death (RR 0.58, 95% CI 0.50-0.68).

Given evidence that greater physical fitness may mitigate the severity of disease among those who become infected with COVID-19, several researchers and other authorities have called for practical recommendations to promote physical fitness during the pandemic [11-14].

Pandemic effect on detraining — A concern among recreational and elite athletes during the COVID-19 pandemic is the impact of detraining. Several studies report that community lockdowns to prevent viral spread have had adverse effects on physical fitness. As an example, a retrospective study of Spanish students enrolled in 16 universities, and involving a total of 13,754 valid survey responses, described reduced moderate (-29.5 percent) and vigorous (-18.3 percent) physical activity during confinement and increased sedentary time (+52.7 percent) [15]. Multiple small, observational cohort studies report comparable declines in fitness among adolescents [16-19]. A small case-control study of children reported a substantial decline in the mean maximum oxygen uptake in a post-COVID-19 cohort compared with pre-pandemic controls (39.1 versus 44.7) [16]. Detraining is an important consideration for clinicians to address when providing guidance about return to play [20]. (See 'Return to activity progression' below.)

Cardiovascular complications in athletes — The possible cardiovascular sequelae of COVID-19 illness present challenges for clinicians caring for athletes preparing to return to play. One concern is myocarditis or other myocardial injury, which in rare cases may develop without symptoms and can be exacerbated by exercise during recovery, possibly precipitating sudden cardiac arrest. Cardiovascular disease, including myocarditis, associated with COVID-19 illness is discussed in detail separately. (See "COVID-19: Cardiac manifestations in adults".)

Our understanding of the epidemiology of subclinical myocarditis in asymptomatic athletes with COVID-19 and among athletes with mild or moderate disease continues to evolve. Overall, the risk appears to be extremely low. Even among young athletes with persistent or exertional symptoms following infection with COVID-19, the prevalence of significant cardiac complications remains low [21].

While several small studies in athlete populations have reported signs consistent with myocarditis using cardiac magnetic resonance imaging (CMR), other larger studies report a very low incidence among asymptomatic athletes and those with mild disease, including adolescents, and question the utility of using CMR as part of any initial evaluation [22-30]. Of note, while CMR findings can help to establish the diagnosis of myocarditis, sensitivity is variable and time dependent (eg, studies performed late after symptom onset are less likely to show signs of disease), and abnormalities are nonspecific. (See "Clinical manifestations and diagnosis of myocarditis in adults".)

In an observational study of 789 professional athletes who tested positive for COVID-19, five (0.6 percent) demonstrated evidence of inflammatory heart disease (myocarditis or pericarditis) on CMR [31]. All five athletes had manifested symptoms and signs that exceeded mild illness. Among the more than 19,000 collegiate athletes followed as part of a prospective, multicenter observational study, 3018 tested positive for COVID-19 and underwent cardiac evaluation [27]. Possible cardiac injury was noted in 21 (0.7 percent) of the infected athletes, including 15 (0.5 percent) who underwent CMR based on findings from preliminary testing (electrocardiogram [ECG], serum troponin, and/or transthoracic echocardiography). During a subsequent one-year period of surveillance, only one adverse cardiac event occurred, most likely unrelated to COVID-19 infection [32].

Other medical complications — Recovering athletes are susceptible to a number of other COVID-19-related complications, including general fatigue, cognitive dysfunction, and coagulopathy (eg, deep vein thrombosis, pulmonary embolism). However, there is no clinical information specific to athletes addressing these concerns. (See "COVID-19: Evaluation and management of adults with persistent symptoms following acute illness ("Long COVID")".)

Several authors have raised concern about the impact of neurologic and neuromuscular complications on return to play. Athletes recovering from COVID-19 illness may suffer from fatigue, impaired neuromuscular function, and reduced muscle strength, leading to poor performance [33,34]. (See 'Return to activity progression' below.)

SCHEDULES AND GUIDANCE FOR RETURN TO ACTIVITY AND FULL PLAY — In the attached graphics, we provide a flow chart that outlines a symptom-based approach to medical clearance for return to play (RTP) following COVID-19 illness (algorithm 1 and table 1) and a table describing the stages through which an athlete should progress for return to play (table 2). These guides can be applied to recreational, occupational, tactical (eg, military), and elite athletes. General guidance about rest and quarantine following exposure or infection with COVID-19 is provided separately (algorithm 2). (See "COVID-19: Infection prevention for persons with SARS-CoV-2 infection", section on 'Discontinuation of precautions'.)

COVID-19 illness poses special challenges for determining how athletes can return to intense exercise and full play safely once they are medically cleared to begin exercising [35]. The process can be complex and requires that clinicians consider the following:

●Safety of the athlete

●Potential risks to the safety of other participants

●Functional capabilities of the athlete (ie, baseline and current fitness)

●Functional demands of the athlete's sport or occupation (eg, military, first responder)

●Legal and regulatory requirements (eg, federal or local government, sport governing body)

While there are no evidence-based guidelines to assist decision-making about RTP of the athlete recovering from COVID-19, several authorities recommend refraining from exercise during the acute illness [2,4,36-38]. The duration of subsequent abstention from exercise varies depending on individual factors including illness severity and the presence of cardiopulmonary symptoms [29,39]. We concur with the general guidance provided by groups including the American Medical Society for Sports Medicine and the American College of Cardiology as follows:

●Asymptomatic athlete: three days abstinence following positive test

●Mild illness: three days abstinence from symptom onset

●Moderate illness or cardiopulmonary symptoms: minimum five days abstinence; evaluation prior to return (note that this period has been reduced from 10 days in previous recommendations)

A clinical evaluation is necessary for all athletes recovering from moderate or severe illness or those who experienced cardiopulmonary symptoms prior to returning to exercise. In addition, the athlete should be symptom free and off all symptom-related treatment before beginning a structured return to activity. As loss of taste or smell may persist beyond the recommended period of exercise abstinence, but we do not consider these symptoms when making RTP decisions.

The period of inactivity before an athlete can begin exercising causes a degree of detraining and increases the risk for potential injury, particularly if the athlete resumes exercise too aggressively [20]. The National Collegiate Athletic Association (NCAA) of the United States has identified this period as one of special vulnerability. Caution is needed as athletes begin training and sports participation. While monitoring athlete progress, the clinician should pay close attention to training intensity and volume, making adjustments as necessary. (See 'Return to activity progression' below.)

In 2019, the National Strength and Conditioning Association (NSCA) and Collegiate Strength and Conditioning Coaches Association (CSCCa) of the United States published guidelines recommending modifications to training schedules to allow for acclimatization and to increase safety [20]. These are discussed in more detail below. (See 'Strength training' below.)

MEDICAL CLEARANCE IN ATHLETES — The safety and ideal timing for resuming intense exercise after COVID-19 infection is unknown, and no evidence-based guidelines for return to play are available to help clinicians. Several consensus statements based on expert opinion and data from athlete registries promote risk stratification based on the severity of the athlete's illness and other relevant factors [27,29,31,39-41].

The severity of illness from COVID-19 varies widely with potential effects on many organ systems. Athletes who suffered more severe illness or have major underlying morbidities will likely require additional testing and specialist consultation before they can resume intense training.

Categories of COVID-19 illness severity are described in the table (table 1). The following flow chart outlines a symptom-based approach to medical clearance for return to play following COVID-19 illness (algorithm 1). Information about several complications of COVID-19 illness of particular relevance to medical clearance for athletes is provided below.

Cardiovascular evaluation

Myocardial injury — Myocarditis is a major cause of sudden cardiac death in young athletes, shown by postmortem analysis to be present in 8 to 12 percent of such cases [42]. Although most COVID-19-related myocardial injury occurs in hospitalized patients, there are multiple case reports of myocarditis or presumed myocarditis developing in ambulatory patients. Myocarditis following infection with COVID-19 appears to disproportionately affect males under 20 years of age, with a rate of 450 per million, about twice that reported in young females [43]. Overall, myocarditis remains a rare but serious complication of COVID-19 infection and vaccination. Thus, detection of occult myocarditis or other myocardial injury is a concern when evaluating the cardiovascular system of athletes following COVID-19 illness.

Myocarditis in the general population, its role in cardiac arrest among athletes, and its association with COVID-19 illness and vaccination are discussed separately, as outlined below. The evaluation and RTP of athletes recovering from COVID-19 illness in whom myocarditis is a concern is discussed here.

●Sudden cardiac arrest in athletes (see "Athletes: Overview of sudden cardiac death risk and sport participation" and "Screening to prevent sudden cardiac death in competitive athletes")

●Myocarditis in general population (see "Clinical manifestations and diagnosis of myocarditis in adults" and "Myocarditis: Causes and pathogenesis")

●Myocarditis and COVID-19 illness and vaccination (see "COVID-19: Cardiac manifestations in adults", section on 'Myocardial injury' and "COVID-19: Vaccines", section on 'Myocarditis')

Myocarditis may rarely be present without symptoms or examination findings. When present, clinical findings may include:

●Third heart sound (suggests volume overload but may be normal)

●Mitral or tricuspid regurgitation (suggests chamber dilation; rare in acute presentations)

●Elevated jugular venous pressure; lower extremity edema (suggest fluid overload)

Examination findings in athletes can be difficult to interpret because an athletic heart may normally exhibit a flow murmur or even a third heart sound in those younger than 40. (See "Heart failure: Clinical manifestations and diagnosis in adults", section on 'Physical examination' and "Auscultation of heart sounds".)

We concur with expert consensus documents that recommend further cardiac evaluation of athletes recovering from severe cases of COVID-19 illness and those with symptoms (eg, chest pain, fatigue, palpitations) or signs consistent with myocarditis [39,41]. Cardiac screening is not necessary for athletes recovering from moderate illness without cardiopulmonary symptoms.

The initial assessment for this population consists of a triad of cardiac testing: electrocardiogram (ECG), cardiac biomarkers (eg, high-sensitivity troponin), and an echocardiogram. Some guidelines also recommend ambulatory cardiac rhythm monitoring or exercise stress testing, but none recommends cardiac magnetic resonance imaging (CMR) as part of the initial evaluation. Because intense exercise within 48 hours of testing can cause a false-positive result, blood for measuring cardiac biomarkers should not be drawn within this window, and clinicians should confirm this prior to testing. Any finding suggestive of cardiac injury should prompt strict limits on activity (no more than a brisk walk) and referral to a cardiologist with experience assessing athlete's heart and myocarditis. (See "Clinical manifestations and diagnosis of myocarditis in adults".)

More extensive evaluation for myocarditis typically involves CMR, which can identify a number of signs suggestive of the disease. However, healthy athletes exhibit similar findings to COVID-19 patients, particularly late gadolinium enhancement (LGE), making it challenging to distinguish between exercise-induced cardiac remodeling (athlete's heart) and pathologic change [26]. Thus, many experts think that CMR should not be used for preliminary assessment and should be performed only when thought necessary by an experienced cardiologist after initial evaluation is completed [44]. Indications for CMR may include:

●Symptoms that limit exercise capacity and have no alternative explanation

●Sustained troponin elevation (ie, two samples >99^th percentile)

●Findings on ECG or echocardiogram consistent with myocarditis

Athletes with pre-existing cardiovascular abnormalities should be assessed using the same tiered risk stratification based on COVID-19 severity described above. Given the challenges of COVID-19 illness and occult myocarditis, we maintain a low threshold for cardiology referral, particularly for athletes with prior myocarditis (unrelated to COVID-19), hypertrophic cardiomyopathy, or ventricular arrhythmias other than rare premature ventricular contractions (burden <1 percent). (See "Hypertrophic cardiomyopathy: Clinical manifestations, diagnosis, and evaluation" and "Athletes with arrhythmias: Electrocardiographic abnormalities and conduction disturbances" and "Athletes with arrhythmias: Clinical manifestations and diagnostic evaluation".)

Antihypertensive medications — Because severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contains a spike protein that binds to the angiotensin-converting enzyme (ACE)-2 receptor enabling entry into host cells, early reports expressed concerns that patients taking medications that inhibit the renin-angiotensin-aldosterone system would develop more severe COVID-19 illness. However, among 12,594 patients tested for COVID-19, neither positive tests nor severity of disease were increased in patients taking such medications [45]. Athletes taking renin-angiotensin-aldosterone inhibitors for hypertension should continue their medication and only cease if adverse events (eg, hypokalemia, hypotension, angioedema) occur. (See "Hypertension in athletes".)

Pulmonary evaluation

General approach and guidance — The lungs are the organ system most affected by COVID-19, and patients who develop acute respiratory distress syndrome secondary to COVID-19 infection are at substantial risk of death. Survivors of such severe disease often manifest persistent pulmonary injury, and even among those with less severe pulmonary disease, recovery can be prolonged. Clinicians should perform a careful lung examination in athletes preparing for return to play following COVID-19 illness. Certain examination findings should prompt further evaluation, including egophony (suggests consolidation), dullness to percussion (suggests pleural effusion), and crackles (consistent with pulmonary edema or fibrosis). The pulmonary manifestations of COVID-19 and follow-up for patients with pneumonia are discussed in detail separately. (See "COVID-19: Management in hospitalized adults" and "COVID-19: Evaluation and management of adults with persistent symptoms following acute illness ("Long COVID")".)

Although persistent dyspnea is a common complaint among patients recovering from COVID-19 pulmonary infection, such symptoms may represent cardiac complications. Clinicians should perform a careful assessment of the cardiovascular system before ascribing dyspnea solely to pulmonary complications. (See 'Persistent dyspnea' below.)

Patients hospitalized with respiratory failure due to COVID-19 pneumonia should not resume exercise until given permission by their pulmonologist or another clinician with appropriate expertise. Respiratory failure is defined as an acute hypoxemic condition requiring advanced support (eg, high-flow nasal cannula, noninvasive positive-pressure ventilation, invasive mechanical ventilation, or extracorporeal life support).

At four to six weeks following discharge, patients recovering from severe or critical pulmonary illness should be evaluated in person or via telemedicine to determine their functional recovery and their risk for pulmonary embolism and other complications.

At 12 weeks following discharge, all patients recovering from COVID-19 pneumonia that manifested as a consolidation on plain chest radiograph or that required supplemental oxygen or hospitalization should be re-evaluated, including a repeat chest radiograph. For those without symptomatic improvement or with persistent abnormalities on chest radiograph, we recommend pulmonary referral for further testing and functional assessment before exercise is permitted. Depending upon the history and patient characteristics, follow-up may include formal testing (eg, pulmonary function tests), advanced imaging (eg, high-resolution computed tomography [CT], CT angiography), functional assessment (eg, six-minute walk, one-minute sit to stand, Kasch pulse recovery, Get Up and Go for older patients), or some combination. For elite athletes, cardiopulmonary exercise testing may be performed. Evaluation of patients following COVID-19 illness is discussed in detail separately. (See "COVID-19: Evaluation and management of adults with persistent symptoms following acute illness ("Long COVID")".)

Once symptoms have resolved and patients are able to perform activities of daily living without breathlessness, they may begin a gradual, closely monitored return to activity as described below. (See 'Return to activity progression' below.)

Persistent dyspnea — According to the World Health Organization (WHO), the median time for clinical recovery following infection with COVID-19 is two weeks for mild cases and three to six weeks for severe illness [46]. For athletes who continue to experience activity-limiting dyspnea, we perform an initial evaluation for myocarditis as described above with ECG, cardiac biomarkers, and an echocardiogram. If the results of the initial evaluation suggest possible myocarditis or other cardiac injury, we refer to a cardiologist with appropriate expertise. (See 'Cardiovascular evaluation' above.)

If the initial evaluation shows no evidence of myocardial injury but dyspnea persists, we extend activity limitations and reassess the athlete at four to six weeks from symptom onset for ambulatory patients and at four to six weeks after discharge for athletes who were hospitalized.

Should dyspnea persist at the first follow-up appointment, additional workup is performed focusing on the cardiovascular and pulmonary systems. Depending on clinical suspicion, this may consist of cardiology referral and imaging with CMR for suspected myocarditis and pulmonary referral and imaging with CT pulmonary angiogram for pulmonary embolus or thrombosis. More extensive pulmonary function testing is deferred until after 12 weeks following discharge [47]. The evaluation of patients with persistent symptoms following COVID-19 illness and after the initial evaluation is discussed in detail separately. (See "COVID-19: Evaluation and management of adults with persistent symptoms following acute illness ("Long COVID")".)

Residual pulmonary injury is to be expected following infection with COVID-19. In prior epidemics, such as severe acute respiratory syndrome (SARS) and influenza A (H1N1), a substantial number of patients developed persistent dyspnea, pulmonary function deficits, and decreased health-related quality of life (HRQoL). In a study of 110 survivors of SARS re-evaluated at six months, 30 percent had abnormal chest radiographs, and 26.5 percent had abnormal pulmonary function test (PFT) values [48]. Those with intensive care unit admission had significantly lower PFT values, and lower PFT values correlated with lower HRQoL scores. Acute respiratory distress syndrome associated with H1N1 was associated with similar outcomes. In one study, 40 percent of patients requiring intensive care unit admission had persistent dyspnea on exertion at one year [49]. (See "Severe acute respiratory syndrome (SARS)" and "Influenza: Epidemiology and pathogenesis".)

Asthma — Resolution of adult-onset asthma is rare (3 percent), but most patients respond to long-term bronchodilation therapy and achieve a well-controlled (34 percent) or partially controlled (36 percent) state [50]. Patients who develop asthma or those whose asthma is worsened by COVID-19 illness may require long-term bronchodilation therapy and may benefit from serial assessment with PFTs. (See "Asthma in adolescents and adults: Evaluation and diagnosis", section on 'Clinical features'.)

Renal evaluation — Kidney injury associated with COVID-19 infection is discussed in detail separately. (See "COVID-19: Issues related to acute kidney injury, glomerular disease, and hypertension".)

The patient recovering from COVID-19-related acute kidney injury should avoid nephrotoxic medications and maintain proper hydration. Patients with hypertension should follow the medical regimen and follow-up schedule prescribed. Assuming renal function was normal at baseline, it should have returned to normal before the patient resumes exercise. In most cases, kidney injury sustained from acute COVID-19 disease resolves without complication. Should kidney injury persist, nephrology consultation should be obtained before any return to strenuous exercise.

Post-acute sequelae of SARS-CoV-2 — Post-acute sequelae of severe acute respiratory syndrome coronavirus 2 (PASC; "long COVID") is discussed in detail separately. (See "COVID-19: Evaluation and management of adults with persistent symptoms following acute illness ("Long COVID")".)

RETURN TO ACTIVITY PROGRESSION — No evidence-based guidelines are available to assist clinicians working with athletes embarking upon a return to play following infection with COVID-19. Our guidance about important issues confronting clinicians is provided in the discussions below, and stages for return to play are summarized in the following table (table 2). Other useful resources include the following:

●A document from the Scotland Institute of Sport and English Institute of Sport incorporates information from several excellent resources and provides sound guidance [4].

●Based on their experience with COVID-19 in New York City, clinicians from the Hospital for Special Surgery have published general considerations and recommendations for recreational athletes returning to activity [2].

Monitoring — Little evidence is available to guide appropriate monitoring during an athlete's return to activity and return to play. Two types of monitoring are necessary. The first type involves watching for signs of potentially dangerous complications of COVID-19-related illness (eg, myocarditis, pulmonary embolism). Some refer to these as "red-flag" symptoms or warning signs. The second type of monitoring involves regular assessment of how the athlete is responding to increases in activity to ensure that the pace at which they are progressing is appropriate.

In their return to activity flowchart, the Australasian College of Sport and Exercise Physicians identifies "red-flag" symptoms that warrant urgent attention by a clinician and possible referral to a cardiologist or a pulmonologist [51]. The symptoms and signs identified include:

●Chest pain or palpitations

●Breathlessness out of proportion to that expected during recovery from exercise

●Findings associated with thrombosis or pulmonary embolism (eg, swollen leg, tachycardia, or dyspnea at rest)

Particularly early during the return to play process, clinicians and athletes should remain alert for such symptoms and signs.

While monitoring athlete recovery during the stages of return to play, clinicians should remain flexible and adjust the time interval between follow-up visits and the progression in activity based on the individual athlete's history, goals, and response to current activity levels. We concur with guidance about return to play provided by the Scottish and English Institutes of Sport [4]. Their recommendations include the following:

●Monitor symptoms throughout all stages of return to play.

●Pay close attention to fatigue, quality of sleep, muscle soreness, and psychological stress.

●Morning resting heart rate is a simple, useful gauge of recovery. An increase in the morning resting heart rate of more than 10 beats per minute is generally considered a sign of overtraining and accumulated fatigue [52,53].

●Standardized scales (eg, rate of perceived exertion [RPE]) can be used to assess athlete recovery and readiness to progress.

●Athletes should move back one stage should fatigue appear excessive or other symptom measures be prolonged or concerning. Renewed progression to the next stage should not begin until after a minimum of 24 hours rest without symptoms.

In addition to monitoring symptoms, clinicians may use any of several validated tools to follow athlete recovery and assess accumulated fatigue. As examples, the RPE scale and the Injury-Psychological Readiness to Return to Sport (IPRRS) scale may be used to monitor training loads. (See "Overtraining syndrome in athletes".)

Stages of return to play and their duration — The stages for returning to full sport participation can be summarized as follows [54,55]:

●Stage I – Recovery and rest

●Stage II – Light activity

●Stage III – Moderate activity

●Stage IV – Intense activity

●Stage V – Normal training and full play

A table describing each of these stages in greater detail is provided (table 2).

There is no clear consensus about the appropriate duration of each stage in an athlete's progression to full sport. Multiple authors and organizations recommend that Stage I be at least 10 days in duration. Before proceeding to Stage II, the athlete must remain symptom free for seven days, be able to perform all activities of daily living, and be off all medications directed at controlling symptoms. Exceptions to the medication requirement include over-the-counter medications used rarely for mild ailments (eg, acetaminophen for a minor headache) and medications taken regularly for chronic conditions (eg, albuterol inhaler for asthma), provided there is no acute exacerbation of illness requiring increased use.

Clinicians must exercise judgment and maintain close communication with athletes as they move from Stage II through subsequent stages. We suggest a minimum of one to two days per stage, but this can be modified depending upon the patient's age, severity of COVID-19 illness, comorbidities, and activity goals. As examples, for otherwise healthy athletes under age 25 who experienced only mild symptoms, one day per stage may be all that is necessary. Conversely, for athletes over age 40 with a significant comorbidity (eg, type 1 diabetes mellitus) recovering from severe illness (eg, intensive care unit admission) and hoping to return to demanding activity (eg, iron man competition, Masters judo), many weeks per stage may be required. The pace at which athletes progress within and between stages will vary widely; individuals must complete each stage comfortably prior to progressing to the next stage.

As an additional resource, the United States Department of Defense guidelines for return to activity outline a range of minimum times in each stage that depend upon an initial risk stratification [56]. This stratification is based in part upon the patient's duration of symptoms during their illness and whether hospitalization was required. As an example, the minimum duration for all Stage II and beyond is five days for those who were hospitalized and required supplemental oxygen.

Special considerations

Children and adolescents — We concur with the guidance provided by the American Academy of Pediatrics (AAP) to assist in the management of return to sport for children and adolescents recovering from COVID-19 illness [40]. The AAP advises that children younger than 12 years may progress back to sports and physical education classes according to their own tolerance while following all necessary infection control guidelines. Children and adolescents 12 years of age and older recovering from moderate or severe disease require a thorough, in-person evaluation before they can begin any return to sport. The necessary evaluation will vary depending on the severity of illness and clinical findings at the time of assessment. The approach is described in the AAP guidelines and summarized in the algorithm (algorithm 3).

For children and adolescents 12 years and older recovering from mild illness, a graduated return to play may begin once the child has been cleared by an appropriate clinician (this may be done via a telemedicine visit or phone call), the required quarantine period has passed, and the child exhibits no cardiorespiratory symptoms when performing normal activities of daily living. Return to sport should progress gradually over a few days but may take longer depending on the severity of symptoms (generally mild in children) and other factors. (See "COVID-19: Management in children".)

A sample program for a 12-year-old child recovering from mild illness who has completed any necessary isolation period might be:

●Day one: Light sports practice (eg, light running, ball drills, playing catch or kicking ball while running at easy pace).

●Day two: Normal sports practice (eg, regular running, ball drills, controlled intra-squad scrimmage); no match play.

●Day three: Normal sports practice; may begin match play if ready.

During the return to play and after, the AAP further recommends that children and their parents and caregivers should watch closely for concerning symptoms, such as chest pain, shortness of breath out of proportion for an upper respiratory tract infection, new-onset palpitations, or syncope during or after exercise. If any of these occur, the child should stop all sports and be reassessed by their clinician. Depending on the symptoms and the results of the initial re-evaluation, a pediatric cardiology or other specialty consultation may be needed.

Adjusting exercise prescription variables — A graduated return to exercise in a patient recovering from COVID-19 should follow established principles for exercise prescription. These principles are discussed separately. (See "Exercise prescription and guidance for adults".)

The basic exercise prescription consists of four variables (FITT):

●F – Frequency: Number of days each week

●I – Intensity: Low, moderate, or greater

●T – Time: Minutes per session for endurance exercise

●T – Type: Endurance, strength, mobility, or some combination

This scheme should be used at each stage of the return to play progression from stages II through V (table 2).

While there are no evidence-based guidelines for prescribing exercise in patients recovering from COVID-19, we suggest that clinicians should increase exercise frequency first, then duration, and finally intensity. Each parameter should be increased gradually. As a general rule of thumb for patients recovering from COVID-19-related illness, we suggest increasing training intensity or volume no more than 10 percent per week or every three to five training sessions. As with all aspects of the return to play protocol, this general approach should be modified based on the athlete's age, severity of COVID-19 illness, and comorbidities. Appropriate monitoring is needed throughout the process. (See 'Monitoring' above.)

Strength training — The detraining associated with COVID-19 increases the risk of injury for athletes when they begin preparations for return to play. To minimize such risk for athletes resuming strength training, we suggest following the recommendations in guidelines published by the National Strength and Conditioning Association (NSCA) and the Collegiate Strength and Conditioning Coaches Association (CSCCa) of the United States [20]. These guidelines, based on expert opinion, apply to the two-to-four-week period immediately following inactivity and are intended to minimize injury risk and allow for appropriate acclimatization and include the following:

●Training volume/workload – The first recommendation is the 50/30/20/10 percent training adjustment, which refers to the percent reduction in weekly total lifting volume or workload, using totals performed prior to COVID-19 illness as a baseline. In other words, during the first week back to weight training, the volume or total workload is reduced by at least 50 percent, during the second week by at least 30 percent, etc. The training volume or workload is calculated using sets, repetitions, and weights.

Intensity, generally determined by the percent of the one repetition maximum (1RM) being lifted, should be modified appropriately. A lower percentage of the 1RM should be used initially and the percentage increased gradually over subsequent weeks. The interested reader is referred to the NCSA and CSCCa document for detailed guidance.

●Work-rest ratio – The second recommendation addresses work-rest cycles to allow for adequate recovery. The guidelines recommend that, in the first week back, the minimum work-to-rest ratio be 1:4 (ie, one minute or one set of work followed by four minutes of rest). The minimum ratio is 1:3 in the second week, and then 1:2 for the remaining two weeks.

Mental health considerations — Clinicians should be alert for signs of mental health problems among the athletes they are helping to return to play following illness with COVID-19, particularly those with known risk factors (eg, history of depression). The loss of opportunities to participate and compete in sport due to the COVID-19 pandemic has caused psychological stress for many athletes. Such stress has been exacerbated by declines in physical fitness and diminished opportunities to socialize with teammates [57-62]. As an example, in a survey study of 692 South African elite and semi-elite athletes performed in the spring of 2020, 79 percent reported disturbed sleep, and 52 percent reported feeling depressed [63]. A detailed narrative review of mental health management of elite athletes describes the challenges of providing care virtually, particularly psychotherapy and medication prescribing, and provides recommendations [59].

Wearing a mask during exercise — Research is needed to clarify the effects of mask-wearing during intense training and competition, particularly during high heat and humidity. Wearing face masks during combative sports (eg, wrestling, boxing, mixed martial arts) is discouraged because of the risk of blocking the athlete's vision, thereby placing them at risk of injury. During periods when infection rates are high, appropriate precautions, including mask wearing, should be taken. These interventions are discussed separately. (See "COVID-19: Epidemiology, virology, and prevention".)

When infection rates are not high, we believe it is reasonable to discuss the risks and benefits of masking and then engage in shared decision-making with athletes and team members. Evidence suggests that wearing a mask (particularly FFP2/N95 type) during intense exercise consistently causes a subjective sense of discomfort, particularly at peak exertion.

To minimize the risk of transmission during a staged return to exercise, mask use is recommended for indoor or close-quarter exercise during the post-COVID-19 infectious stage, days 5 to 10 following infection. (See "COVID-19: Infection prevention for persons with SARS-CoV-2 infection".)

Data regarding the effect of wearing a mask on exercise performance is heterogenous, showing no or only modest impact on physiologic parameters and overall performance but a consistent increase in subjective measures of discomfort. As examples:

●A 2021 systematic review and meta-analysis of 22 studies (1573 participants) found a small increase in end-tidal carbon dioxide (mean difference 3.3, 95% CI 1.0-5.6) and heart rate (mean difference 2 beats per minute, 95% CI 0-4) without an impact on exercise performance [64]. An increase was noted in subjective parameters of dyspnea and ratings of perceived exertion.

●A 2023 systematic review and meta-analysis of 45 studies (1264 participants) found that masks had a moderate impact on pulmonary function, gas exchange, and subjective discomfort [65]. Only FFP2 and N95 type masks caused a small decrease in exercise performance.

These reviews suggest that mask use during strenuous exercise can have a modest impact on performance without causing significant deviations in physiologic parameters. However, the impact on elite performance may be significant and necessitate changes in training regimens.

Vaccination and return to activity — Athletes should follow standard vaccination guidelines. No training modifications are needed (eg, athletes need not avoid training the day they receive the vaccination). There is no evidence-based guidance about vaccination against COVID-19 specifically for athletes, although several publications provide general guidance [66-68]. (See "COVID-19: Vaccines".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: COVID-19 – Index of guideline topics" and "Society guideline links: COVID-19 – Exercise and sports medicine".)

SUMMARY AND RECOMMENDATIONS

●Coronavirus disease 2019 (COVID-19) illness in athletes – Athletes and heavy laborers recovering from COVID-19-related illness may be susceptible to a range of complications that may prevent or hinder their return to strenuous activity. Potential complications may include general fatigue, myocarditis, pulmonary injury, coagulopathy, pulmonary embolism, and cognitive dysfunction. Occult myocarditis is of special concern as it may first present with cardiac arrest during activity. (See 'COVID-19 clinical course and sequelae in athletes' above.)

General follow-up and management of patients after recovery from COVID-19 illness is discussed in detail in other UpToDate topics. (See "COVID-19: Management in hospitalized adults" and "COVID-19: Evaluation and management of adults with persistent symptoms following acute illness ("Long COVID")".)

●Approach to medical clearance and return to play -The safety and ideal timing for resuming intense exercise after COVID-19 infection is unknown. Clinical decisions about return to play must account for the severity of illness, age, comorbidities, degree of detraining, and activity goals. Athletes who suffered more severe illness or have high-risk morbidities (eg, hypertrophic cardiomyopathy, coagulopathy) likely require additional testing and specialist consultation before they can resume intense training. (See 'Medical clearance in athletes' above.)

Our suggested approach to initial medical evaluation and return to play is outlined in the following resources:

•A table defines the categories of COVID-19 illness severity for return to play (table 1).

•A flow chart outlines our approach to medical clearance for adults and older adolescents returning to play following COVID-19 illness based on the severity of illness and presence of high-risk comorbidities (algorithm 1). (See 'Medical clearance in athletes' above.)

•A table describes the stages of return to play and what level of activity is permitted at each stage (table 2). (See 'Return to activity progression' above.)

●Cardiovascular evaluation – We recommend that athletes recovering from moderate or severe cases of COVID-19 illness or whose symptoms persist beyond the expected period be evaluated for myocardial injury. Initial assessment for this population consists of an electrocardiogram (ECG), cardiac biomarkers (ideally high-sensitivity troponin), and an echocardiogram. Any finding suggestive of myocarditis or other myocardial injury should prompt strict limits on activity (no more than a brisk walk) and referral to a cardiologist with experience assessing athlete's heart and myocarditis. (See 'Cardiovascular evaluation' above.)

●Pulmonary evaluation – Patients hospitalized with respiratory failure due to COVID-19 pneumonia should not resume exercise until given permission by their pulmonologist or another clinician with appropriate expertise. Respiratory failure is defined as an acute hypoxemic condition requiring advanced support (eg, high-flow nasal cannula, noninvasive positive-pressure ventilation, invasive mechanical ventilation, or extracorporeal life support). (See 'Pulmonary evaluation' above.)

At 12 weeks after discharge, all patients recovering from COVID-19 pneumonia that manifested as a consolidation on plain chest radiograph or that required supplemental oxygen or hospitalization should be re-evaluated with a chest radiograph. Those with persistent symptoms need further evaluation as described above. Persistent dyspnea is common among patients recovering from COVID-19 pulmonary infection but may also be due to cardiac or vascular complications (eg, myocarditis, pulmonary embolism). Those who are symptom free and able to perform activities of daily living without breathlessness may begin a gradual, closely monitored return to activity. (See "COVID-19: Evaluation and management of adults with persistent symptoms following acute illness ("Long COVID")" and 'Return to activity progression' above.)

●Returning to activity and full play

•Monitoring return to play – Patients cleared to begin return to play require close monitoring of two kinds. The first involves watching for signs of potentially dangerous complications of COVID-19 illness (eg, myocarditis, pulmonary embolism), especially early in the process of return to play. The second involves regular assessment throughout the return to play process of the athlete’s response to increases in activity to ensure safety and appropriate progress. For the latter, close attention should be paid to fatigue, sleep quality, muscle soreness, and psychological stress. (See 'Monitoring' above.)

•Stages for return to play – Athletes returning to play after COVID-19 illness progress through five stages (table 2). Clinicians must exercise judgment and maintain close communication with athletes as they move from Stage II through all subsequent stages. We suggest a minimum of one to two days per stage, but this can and should be modified depending upon the patient's age, severity of COVID-19 illness, comorbidities, and activity goals. (See 'Stages of return to play and their duration' above.)

•Children and adolescents returning to play – Children younger than 12 years may progress back to sports and physical education classes according to their own tolerance. For children and adolescents 12 years and older, a gradual return to play may begin once the child has been examined and cleared by an appropriate clinician, the required quarantine period has passed, and the child exhibits no cardiorespiratory symptoms when performing normal activities of daily living. Return to sport should progress gradually over at least three days but may take longer. (See 'Children and adolescents' above.)

•Other considerations – Other aspects of return to play following COVID-19 illness including how to modify aerobic and resistance exercise, awareness of mental health issues, and how wearing a mask affects exercise tolerance are discussed in the text. (See 'Special considerations' above.)