Addressing the pandemic of physical inactivity is an important public health priority with targeted efforts needed across all populations (1,2). The national Diabetes Prevention Program (DPP) (3) and subsequent translation studies have demonstrated the efficacy of behavioral lifestyle interventions in reducing the risk and burden of diabetes and other chronic diseases. Accordingly, behavioral lifestyle interventions that include physical activity promotion have expanded beyond the realm of structured, medically supervised settings and into a variety of diverse community settings. However, the translation from the clinical setting into that of the community poses new challenges. Appropriate guidelines for physical activity preparticipation screening are important for community translation prevention efforts to help mitigate the risks associated with increased physical activity, structured exercise, or both, and to help identify individuals who may be at risk for exertion-related sudden cardiac death and/or acute myocardial infarction.
Lifestyle interventions that include the goal to increase physical activity have been shown to reduce risk factors for metabolic and cardiovascular disease (CVD) and to decrease the incidence of diabetes (4–6). The multicentered DPP (3) was a landmark study in that it validated the use of lifestyle interventions in disease prevention, demonstrating that a behavioral lifestyle program aimed at modest weight loss and regular physical activity significantly reduced the risk of type 2 diabetes by 58% in “at risk” overweight participants. The structured lifestyle intervention included a weight loss goal of >7% and a physical activity goal of >150 min·wk−1 of moderate physical activity with most participants performing brisk walking.
Translational research efforts have since focused on adapting the DPP lifestyle intervention into diverse settings such as local community centers (7–10), YMCAs (11–13), churches (14), worksite (15), military, and health care settings (16–18). Both systematic reviews and meta-analysis on these pragmatic translation efforts have been promising (19–22). As a result, the call to disseminate and implement DPP-based behavioral lifestyle intervention programs in real-world settings is high (23,24). Accordingly, the Centers for Disease Control (CDC) has led an initiative where programs that are based on the DPP and meet the standards of recognition can apply for accreditation through the “CDC Diabetes Prevention Recognition Program” (25,26). Addressing the issue of preparticipation CVD screening for physical activity as part of these behavioral lifestyle programs is important in their implementation. However, the CDC Standards of Practice are not clear on this matter and simply state that “it is the organization’s responsibility to have procedures in place to assure safety” (27). Although several of the CDC recognized diabetes prevention programs currently mandate physician approval before participation in physical activity, the logistics of this requirement can impose barriers to participation in terms of feasibility, efficiency, and cost.
The American College of Sports Medicine (ACSM), which is the preeminent professional organization for exercise science within health and medical fields, has invariably provided guidance on exercise screening for individuals planning to initiate a moderate- to vigorous-intensity physical activity program that applies to varied settings and contexts. Recently, the ACSM released new guidelines (28) that included substantive modifications for preparticipation CVD screening for physical activity. These updated recommendations represent a substantial paradigm shift from past iterations toward a more liberal approach that results in fewer individuals needing to seek medical clearance before starting a physical activity program. This shift has significant implications for those promoting physical activity within the community setting. The objectives of this commentary are to review the new recommendations within the context of community-based diabetes prevention programs and to discuss the implications for those providers implementing and leading community-based physical activity interventions.
Out with the Old
Historically, the ACSM guidelines (29) recommended that preparticipation screening for exercise be largely based on risk stratification for CVD (i.e., low, moderate, and high). This classification was rather conservative because it was based on the presence or absence of traditional coronary risk factors such as age, physical inactivity, obesity, family history, dyslipidemia, hypertension, prediabetes, and smoking status. For adults who were categorized as moderate or high risk, it was recommended that most undergo a medical exam, exercise test, and/or obtain medical clearance before participating in moderate- to vigorous-intensity physical activity. The new ACSM guidelines no longer include cardiovascular risk factor profiling as part of the exercise preparticipation algorithm, which is a considerable change from past approaches to screening. Several important considerations provided the impetus for this change in approach (30).
Given the high prevalence of CVD risk factors in adults, the old approach proved to be too inclusive. For example, a relevant study (31) examined a nationally representative sample of 6785 adults ≥40 yr old in the 2001 to 2004 National Health and Nutrition Examination Survey database. The investigators calculated the proportion of adult participants who would receive a recommendation for physician consultation before starting an exercise program based on the American Heart Association/ACSM preparticipation questionnaire. Interestingly, the investigators reported that approximately 95% would be advised to consult a physician before exercising based on these conventional screening guidelines. This also proves to be particularly true for behavioral lifestyle programs based on the DPP aimed at reducing risk because these programs tend to target overweight individuals at risk for diabetes and/or metabolic syndrome. In applying the former guidelines, essentially all participants were required to obtain medical clearance and/or undergo peak or symptom-limited exercise testing before initiating a moderate-intensity exercise program such as brisk walking.
In addition to the high prevalence of CVD risk factors, the low frequency of fatal and nonfatal exercise-related cardiac events is another reason for the shift in approach (32–36). In the DPP, although there were some small differences in the incidence of musculoskeletal symptoms, there were no differences between the lifestyle group and the other groups in terms of adverse cardiovascular events related to hospitalizations or deaths (3). In considering screening for CVD and the safety of physical activity, it is important to put the risk of activity interventions into perspective.
Clearly, for the general population, the benefits of physical activity not only outweigh the acute risks (37), but regular participation in moderate- to vigorous-intensity physical activity is associated with a decrease in the risk of an exercise-related acute myocardial infarction (38–40). However, there is an increased relative risk of sudden cardiac death during vigorous-intensity exercise in habitually sedentary individuals with occult or known CVD, particularly when the activity bout is sudden and unaccustomed. Although the relative risk of cardiovascular events is higher for sudden vigorous physical activity, the absolute risk of these events is extremely low, and most community physical activity programs like those based on the DPP do not encourage vigorous-intensity activity.
A recent study (41) prospectively evaluated sudden cardiac arrest during sports in middle-aged adults over a 10-yr period. The investigators reported that the burden of sports-associated sudden cardiac arrest was relatively low when compared with the overall rate in the community. They also found that a substantial proportion of individuals who experienced sudden cardiac arrest reported having had symptoms in the days or weeks before the event, a finding also reported by others (42). However, this study was conducted in middle-aged adults participating in recreational sports, a cohort that does not necessarily reflect the population participating in lifestyle interventions where the primary form of activity is moderate-intensity walking.
Community-based lifestyle prevention programs, like those based on the DPP, tend to mitigate risk by recommending a “start low and go slow” approach with moderate-intensity physical activity as the goal behavior. The incidence of acute cardiovascular events in individuals during light- to moderate-intensity exercise, such as those prescribed in these community-based interventions, appears to be extremely low (30,42), making it a high-benefit, lower-risk activity.
The unknown effectiveness of preexercise medical evaluation is another reason for the shift in approach. Little data is available to substantiate routine screening recommendations or that physician clearance before participation in a physical activity program improves safety (31,40). How to accurately identify asymptomatic individuals at risk for an exercise-related acute cardiovascular event, even if a preliminary medical examination is undertaken, remains unclear. The use of graded exercise testing to identify unknown CVD in asymptomatic individuals is controversial (40). It has become increasingly apparent that exercise testing is a poor predictor of future cardiovascular events as most acute coronary events evolve from vulnerable plaque rupture in previously nonobstructive coronary lesions (40,43). Accordingly, it appears impractical to use exercise testing to prevent acute cardiovascular events in asymptomatic exercisers (34). Furthermore, unnecessary referrals for diagnostic testing can lead to high rates of false-positives in some populations, which can result in additional costly noninvasive and invasive testing.
Lastly, the requirement for medical clearance before initiating a physical activity program is another potential barrier for many who want to become more physically active. Many programs that require a preparticipation form to be completed by a medical provider place the burden of this administrative task on the participant. If the provider in turn requires a physical examination and/or exercise testing before completing the form, the individual may have to coordinate time off work, child care, and transportation to a medical visit at which he or she may be responsible for a copayment and related costs. Because habitually sedentary individuals often perceive numerous barriers to the initiation and maintenance of a physical activity program (44), decreasing the need for medical clearance may help to eliminate another barrier. Furthermore, many community interventions attempt to reach traditionally underserved populations who may lack access to primary care providers or other medical services. Even for those in underserved communities who have access to care, the above-referenced logistical barriers may be more challenging, and individuals may experience additional impediments (e.g., language) when interacting with the health care system. In situations where obtaining clearance for physical activity may be unrealistic, the reach of programs, particularly in underserved communities in greatest need, is significantly compromised. In addition, as practitioners work to extend the reach of physical activity interventions using innovative technology-based modes of delivery (45), the requirement for medical clearance by a physician may not be feasible.
In with the New
The new ACSM guidelines (28) on exercise preparticipation screening are based on the participant’s current level of physical activity; known cardiovascular, metabolic, or renal disease; presence of signs and/or symptoms suggestive of CVD; and the anticipated exercise intensity (Table 1). These characteristics have been identified as important modulators of exercise-related acute cardiovascular events (30).
Current Level of Exercise
Consideration of the individual’s current level of physical activity is new to the updated guidelines. To be considered as currently physically active, individuals should be performing planned, structured exercise for at least 30 min per session at a moderate or vigorous exercise intensity, at least 3 d·wk−1, for a minimum of 3 months or longer (28). To clarify, physical activity has been defined as “any bodily movement produced by skeletal muscles that results in energy expenditure” and is positively correlated with physical fitness, whereas exercise is defined as a “subset of physical activity defined as planned, structured, and repetitive bodily movement done to improve or maintain one or more components of physical fitness” (46).
Identifying individuals with known diseases that can increase the risk of a cardiovascular event is the next step in the new ACSM preexercise screening guidelines. Individuals with “known disease” are defined as those diagnosed with any of the following: diabetes, renal disease, atherosclerotic CVD (e.g., previous myocardial infarction, coronary artery bypass surgery, percutaneous coronary revascularization, pacemaker, valve disease, heart failure, or structural heart disease), or combinations thereof. Individuals with pulmonary disease are no longer automatically required to seek medical clearance before physical activity.
Signs and Symptoms
Within the guidelines (28), all individuals should be screened for resting and/or exertional signs and/or symptoms suggestive of CVD (see Table 2). If participants are symptomatic, they should be instructed to seek medical clearance before engaging in physical activity. After medical clearance, light- to moderate-intensity physical activity is initially recommended, and individuals may gradually progress as tolerated.
With this information in place, the latest ACSM guidelines now suggest that medical clearance be reserved for inactive, asymptomatic individuals who have known cardiovascular, metabolic, or renal disease. For all other asymptomatic individuals (i.e., the vast majority of participants in diabetes prevention and other community-based lifestyle intervention programs), routine medical clearance is no longer recommended. For those who desire to initially perform vigorous rather than moderate-intensity physical activity, the guidelines now suggest that inactive or moderately active individuals with known disease seek medical clearance before starting such a program. Regardless, for those who are inactive, the guidelines recommend that exercise programs start at a low to moderate intensity and, if desired, gradually progress to a vigorous-intensity over time, provided they remain asymptomatic—or again, individuals should be instructed to “start low and progress slow.” This is referred to as the “progressive transitional phase.” ACSM also suggests the preparticipation health screening may, in some cases, be completed by using the updated PAR-Q+ (47). However, concerns over the recommendation that most participants with hypertension would need to seek medical clearance, as well as the high level of literacy required to use the questionnaire, limit enthusiasm for its widespread adoption (28).
IMPLICATIONS FOR THE PROVIDER IN THE COMMUNITY SETTING
Because the new guidelines greatly limit the need for medical clearance in the community setting, it is important that health care practitioners such as health coaches delivering diabetes prevention programs have an understanding of this new approach. The reduced need for medical clearance will now put the impetus on these community coaches and interventionists to be especially vigilant about screening for, and educating participants on, warning signs and symptoms suggestive of CVD. This is of particular importance when laypersons or peer coaches are engaged in the delivery of such programs. Identifying individuals who are defined as inactive and have known disease will be important, as well as having an understanding of the level of exercise intensity (Table 2).
In recommending moderate-intensity physical activity, community-based diabetes prevention programs should work to mitigate cardiovascular risk by recommending a “start low and go slow” approach. This approach will also likely diminish risks associated with musculoskeletal injuries when initiating an exercise program. Although a moderate-intensity exercise program can reduce musculoskeletal injury, some participants may experience an increase in musculoskeletal pain such as back, hip or knee pain, and/or plantar fasciitis. Such musculoskeletal adverse events are much more common than cardiovascular events. A “start low and go slow” approach reduces the risk for both musculoskeletal and cardiovascular events for people initiating a moderate-intensity exercise program such as brisk walking; this is discussed as part of the safety education in diabetes prevention programs recognized by the CDC.
The educational component of diabetes prevention programs should also include clear instruction on warning signs and symptoms of coronary disease and when to cease exercise and contact a health care provider or to seek medical attention. Education on the presence of symptoms, especially with increasing exercise intensity or when performing a new activity, should be carefully reviewed with participants. Given that this new screening paradigm eliminates risk stratification based on conventional risk factors, it would also be imperative for providers/health coaches in the community setting to continue to stress the importance of general risk factor profiling and management, including regular medical appointments and blood pressure, cholesterol, and glucose checks. Furthermore, it is important to recognize that guidelines are recommendations and not requirements, and are not a substitute for common sense approaches and good clinical judgment.
It is not possible to eliminate all risk from physical activity. Given the level of physical activity recommended in these lifestyle intervention efforts is identical with the national public health recommendations (37) (i.e., 150 min or more of moderate-intensity activity per week), the risks are quite rare but still exist. Understanding that lifestyle intervention programs in the community take place in a wide variety of settings and contexts, it is important that all programs consider their unique situation and implement appropriate preparticipation screening and ongoing participant safety procedures (e.g., regular emergency drills, cardiopulmonary resuscitation certified staff, hotline to emergency medical responders, and the immediate availability of an automated external defibrillator).
Community-based lifestyle interventions, like those based on the DPP, that aim to increase physical activity within the community setting have great potential to improve participant health outcomes. Evidence for the need for routine medical clearance or, for that matter, exercise testing before participating in low- to moderate-intensity activity is weak, particularly in asymptomatic individuals. Recognizing that physical activity interventions can be conducted in many contexts and locations, a paradigm shift from preparticipation exercise medical clearance by a health care provider to one that considers the current level of physical activity, medical history, desired exercise intensity, and the presence of signs and/or symptoms of CVD likely represents a more realistic and cost-effective approach. This shift in approach should help reduce barriers to participation in physical activity interventions within the community setting, and subsequently result in increased activity levels and improved health outcomes among those individuals who stand to benefit the most.
This commentary was not funded. The authors have no conflicts to declare. Results of the present commentary do not constitute endorsement by the ACSM.
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