Preface
Exercise professionals need to have extensive knowledge and technical skills in order to work safely and effectively. Historically, individuals working in exercise settings, such as health and fitness clubs, were not necessarily required to have specialized education and training in exercise science. However, survey research indicates that a bachelor’s degree in exercise science and certification from the American College of Sports Medicine (ACSM) or National Strength and Conditioning Association (NSCA) are strong predictors of a personal trainer’s knowledge (Malek et al. 2002). To carry the U.S. Bureau of Labor and Statistics’ job title of “exercise physiologist,” one must have earned the minimum of a bachelor’s degree (Simpson 2015). There is also a growing trend within health care facilities to require their exercise physiologists to hold a master’s degree (Collora 2017); this corroborates Wagner’s (2014) finding that a master’s degree is commonly held by exercise physiologists working in clinical settings (69% of 140 survey respondents).
A global survey of fitness trends for 2018 revealed that “educated, certified, and experienced fitness professionals” is ranked number 6 in importance, and this has been a top 10 concern since the annual survey began more than a decade ago (Thompson 2017). These findings suggest that formal education and certification by professional organizations should be required for personal fitness trainers and exercise science professionals. Their knowledge and skills are instrumental in preparticipation screening, cardiorespiratory fitness testing, muscular fitness testing, flexibility assessment, results interpretation, and scientifically sound exercise prescription design. To promote exercise science as a profession, issues surrounding accreditation, certification, national boards, and licensure need to be understood and addressed.
ACCREDITATION
Organizations and programs are awarded accreditation by meeting or exceeding standards established
by an independent third-party accrediting agency. Although no single accrediting agency exists for health and fitness and clinical exercise science programs, exercise science professionals seem to agree that some form of regulation is needed.
Independent third-party accrediting agencies such as the Commission on Accreditation of Allied Health Education Programs (CAAHEP) and the National Commission for Certifying Agencies (NCCA) may serve this purpose. The CAAHEP accredits academic programs—graduate programs in exercise physiology, baccalaureate programs in exercise science, and certificate and associate degree programs for personal fitness trainers. Also, the American Society of Exercise Physiologists (ASEP) has developed standards for the profession of exercise physiology as well as accreditation standards for universities and colleges offering academic degrees in exercise science (ASEP 2018). The NCCA accredits certification programs; many organizations that provide professional credentialing or licensing exams in the allied health professions are accredited through the NCCA (ACSM 2004).
CERTIFICATION
Fitness and exercise science professionals obtain certification by passing examinations developed by professional organizations. These organizations typically offer education and training programs, administer their own examinations (written and practical), and issue certifications to individuals passing the examinations. These certifications are generally issued for a 2 to 3 yr period; certification is maintained by taking continuing education courses and earning continuing education credits. Some certification programs are accredited by third-party agencies like the NCCA.
More than 75 organizations offer over 250 certifications for exercise science and fitness professionals (Cohen 2004; Pierce and Herman 2004). Given that there is no governing entity to oversee the development of certification examinations and
eligibility requirements, inequalities exist among the certifications available to exercise science professionals. Some certification programs are more rigorous than others, having stringent eligibility requirements; others may or may not be accredited by a third-party accrediting agency like the NCCA. To address the inequality among certification programs, the NCCA formally reviews applications for the accreditation of certification programs. In 2004, the International Health, Racquet, and Sportsclub Association (IHRSA) recommended that all health clubs belonging to their organization hire only personal fitness trainers certified by an NCCA-accredited organization or agency. Wagner (2014) reported results from a survey of 589 exercise physiologists and indicated that 69% of the respondents held one certification while 28% held two or more. Nevertheless, not all exercise science and fitness certifications are equal. This leads to confusion for the consumer in terms of knowing who is and who is not highly trained and qualified as an exercise professional. It also complicates selecting the most appropriate certification for yourself. Some agencies sponsor certification programs primarily for financial gain, while others certify professionals in order to promote exercise science as a profession.
Table 1 lists some of the organizations that offer certifications accredited by the NCCA. Additionally, the Coalition for the Registration of Exercise Professionals (CREP), a not-for-profit corporation composed of organizations that offer NCCA-accred-
ited exercise certifications, established a registry of professionals in the United States certified by any of six organizations (www.usreps.org). This website is a convenient means for locating professionals by location, certification, or name. Registries are also available for the United Kingdom (www.exerciseregister.org), Europe (www.europeactive.eu/why-ereps), and New Zealand (www.reps.org.nz).
NATIONAL BOARDS
Some professional organizations in the fitness industry believe there should be alternatives to accreditation of certification programs by the NCCA or other third-party agencies. In the United States, one such alternative was the establishment of National Board examinations for fitness professionals. Unlike the multitude of certification examinations developed by individual organizations and agencies, National Boards are standardized tests to assess the knowledge, skill, and competence of professionals. Most medical and allied health professions utilize National Boards.
In 2003, the National Board of Fitness Examiners (NBFE) was founded as a nonprofit organization with the twin purposes of defining scopes of practice for all fitness professionals and determining standards of practice for various fitness professionals, including floor instructors, group exercise instructors, personal fitness trainers, specialists in youth and senior fitness, and medical exercise specialists.
Table 1 Selected Organizations Associated With National Commission for Certifying Agencies (NCCA) and National Board of Fitness Examiners (NBFE)
NCCA affiliates
American Council on Exercise (ACE)
American College of Sports Medicine (ACSM)
Cooper Institute for Aerobics Research
National Exercise and Sports Trainers Association (NESTA)
National Exercise Trainers Association (NETA)
National Federation of Professional Trainers (NFPT)
National Strength and Conditioning Association (NSCA)
International Fitness Professionals Association (IFPA)
National Council on Strength and Fitness (NCSF)
National Academy of Sports Medicine (NASM)
NBFE affiliates
Aerobics and Fitness Association of America (AFAA)
American Aerobic Association International/International Sports Medicine Association (AAAI/ISMA)
International Sports Sciences Association (ISSA)
National Association for Fitness Certification (NAFC)
National Council for Certified Personal Trainers (NCCPT)
National Exercise and Sports Trainers Association (NESTA)
National Gym Association (NGA)
National Personal Training Institute (NPTI)
National Strength Professionals Association (NSPA)
The NBFE established national standards of excellence that certifying organizations and colleges or universities may adopt. The written portion of the National Boards for personal fitness trainers is now offered through the NBFE (for additional information, visit www.NBFE.org). The practical portion of this exam is still being developed and validated under the supervision of the National Board of Medical Examiners (NBME). The NBME and the NBFE are engaged in preliminary discussions and planning that will allow certification organizations to assist in the delivery of practical exams for personal trainers.
To be eligible to sit for the National Boards, personal fitness trainers must successfully complete a personal training certification program from an approved NBFE affiliate. Affiliate status is available to qualified groups from the areas of medicine, certification organizations, fitness professionals, health clubs, and higher education. In the future, the NBFE’s National Boards may be used by certifying organizations, colleges and universities, and U.S. state licensing programs to test the knowledge, skill, and competence of fitness professionals (American Fitness Professionals and Associates 2004). Table 1 lists some of the organizations offering personal training certifications affiliated with the NBFE.
LICENSURE
Although many practitioners in the fitness and exercise science fields agree that certification ensures professional competency, other professionals believe that licensure is better suited for protecting consumers and for enhancing the credibility and professionalism of exercise science and fitness professionals (Eickhoff-Shemek and Herbert 2007). For the first time in the 12 yr history of the worldwide survey of fitness trends, licensure for fitness professionals broke into the top 20 trends (number 16 for 2018) (Thompson 2017). In the United States, licensure is decided at the state level; therefore, requirements may vary from state to state. Louisiana was the first state to pass a law requiring licensure of all clinical exercise physiologists (Herbert 1995). Licensure of clinical exercise physiologists has also been considered in Maryland, Massachusetts, Michigan, North Carolina, Texas, and Utah (Clinical Exercise Physiology Association, 2013). Several states including Georgia, Maryland, Massachusetts, New Jersey,
Nevada, Oregon, and the District of Columbia have considered licensure for personal trainers (Eickhoff-Shemek and Herbert 2008b; Herbert 2004; Thompson 2017).
To promote exercise science and exercise physiology as a profession, the ASEP is working with exercise professionals throughout the United States to develop uniform state licensure requirements for exercise physiologists. Licensure would place exercise physiologists and personal trainers on a par with other allied health professionals (e.g., nurses, nutritionists, physical therapists, and occupational therapists) who are required to have licenses to practice. Licensed fitness professionals may be more likely to obtain referrals from health care professionals and to receive reimbursement for services from third parties (e.g., insurance companies).
Along with advantages, added responsibilities and disadvantages are associated with state licensure. Licensure may limit the scope of practice and services that exercise professionals are currently able to provide to the public. For example, Louisiana licensure law requires clinical exercise physiologists to work under the direction of a licensed physician. Also, the costs of licensure, continuing education for licensure, and professional liability insurance may be more expensive compared with the cost of certifications. Professionals moving from state to state may be required to obtain another license because each state could require different credentials for licensure (Eickhoff-Shemek and Herbert 2008a, 2008b).
STATUTORY CERTIFICATION
Instead of licensure, some American states use statutory certification for allied health professionals. Statutory certification regulates what titles professionals can use and the qualifications needed to obtain these titles. Only certified professionals with the required credentials are allowed to use the specific title (e.g., certified nutritionist). Other professionals without the necessary credentials can still practice in the state but must use a different title. This approach could be promoted by the fitness and exercise professions to prevent the use of titles, such as personal trainer or exercise physiologist, by indi-
viduals having no formal education or professional certifications.
All these approaches demonstrate the pressing need to get a handle on certifications for exercise professionals so we can gain control of who is practicing in our field. This will ensure the safety of exercise program participants and enable individuals working in the fitness field to be recognized as exercise science professionals. Until these issues are resolved and a list of accredited certification agencies and organizations is finalized, you should select a professional certification that matches your level of education and career goals. For more information about certification programs, visit the websites of those professional certifying organizations.
Many advantages are associated with obtaining either state licensure or certification with professional organizations. You will have a better chance of finding a job in the health and fitness field because many employers are now hiring only professionally
certified health and fitness instructors. Certification by reputable professional organizations upgrades the quality of the typical person working in the field and assures employers and their clientele that employees have mastered the knowledge and skills needed to be competent exercise science professionals. Hence, the likelihood of lawsuits resulting from negligence or incompetence may be lessened. Also, certification and licensure help validate exercise specialists as health professionals who are equally deserving of the respect afforded to professionals in other allied health professions. Individuals holding a Registered Clinical Exercise Physiologist (RCEP) or Certified Clinical Exercise Physiologist (CEP) certification now have a National Provider Identifier code that may be used for service reimbursement from insurance companies. For more information on this development, visit the website of the Clinical Exercise Physiology Association (www.acsm-cepa.org).
Chapter 1 Physical Activity, Health, and Chronic Disease
KEY QUESTIONS
u Are adults in the United States and other countries getting enough physical activity?
u How does physical inactivity differ from sedentarism?
u What diseases are associated with a sedentary lifestyle, and what are the major risk factors for these diseases?
u What are the benefits of regular physical activity in terms of disease prevention and healthy aging?
Although physical activity plays an important role in preventing chronic diseases and reducing the hazardous effects of extended periods of sitting time, an alarming percentage of adults in the United States report no physical activity during leisure time. One of the national health objectives for the year 2020 is to increase to 47.9% the proportion of people aged 18 yr and older who regularly (preferably daily) engage in moderate physical activity at least 30 min per day (U.S. Department of Health and Human Services 2010). According to a U.S. national survey, in 2014 only a small percentage (21.5%) of adults over the age of 18 met the 2008 federal physical activity guidelines for adults in terms of both aerobic and muscle strengthening activities. Slightly more than half (53.2%) met either the aerobic activity or the muscle-strengthening guidelines, but not both (Centers for Disease Control and Prevention 2015a). Generally, women (50%) are less likely to meet the full aerobic and muscle-strengthening recommendations than men (43.4%), and older (≥65 yr) adults are less likely (58.7%) to meet them than younger (18-24 yr) adults (40.8%) (Centers for Disease Control and Prevention 2015a).
u How does physical activity improve health?
u How much physical activity is needed for improved health benefits?
u What kinds of physical activities are suitable for typical people, and how often should they exercise?
Physical inactivity, the failure to meet the recommended physical activity guidelines, is not just a problem in the United States; it is a global issue and the fourth leading cause of global mortality (World Health Organization 2010). Cardiovascular diseases, diabetes, obesity, chronic respiratory disorders, and cancers as a group of noncommunicable diseases (NCDs) are the leading causes of death worldwide. These chronic conditions are heavily influenced by poor lifestyle factors including physical inactivity and unhealthy diet (World Medical Association 2017). NCDs accounted for approximately 52% of worldwide deaths occurring before age 70 in 2012 (World Health Organization 2016d). Physical inactivity became a targeted priority of the World Health Organization’s Global Action Plan for 2013-2020 (World Health Organization 2013); a global goal was set to reduce physical inactivity levels by 10% by the year 2025 (Sallis et al. 2016). Results from survey data collected from 146 countries representing all income levels estimated that 23% of the global adult (≥15 yr) population was physically inactive in 2016. However, an 8% decrease in physical inactivity between 2012 and
USING TECHNOLOGY TO INCREASE PHYSICAL ACTIVITY AT WORK
Active workstations (e.g., treadmill desks or pedal desks) and adjustable-height work surfaces that allow employees to stand (sit-stand desks) are becoming more commonplace. They provide a means to reduce prolonged periods of sitting. Some employees have their own active workstations, while others have access to one located in a common area. A recent review of studies about active workstations (Cao et al. 2016) indicates that the calories burned may increase two- to fourfold for employees who change from sitting in a chair (~70-90 kcal·h−1) to active workstations. Additionally, daily step counts and physical activity (min/ day) increase dramatically for those using active workstations during the workday. Crandall and colleagues (2016) found that using sit-stand workstations reduces sitting time by approximately 85 min/day. They also reported that employees using a shared treadmill desk accumulate slightly fewer than 9,000 steps·day−1 while at work. Ongoing longitudinal research in this area may identify long-term effects of using active workstations on employee health. Currently, these effects are not well documented.
2016 may be less reflective of changes in activity levels than in updated physical activity recommendations (150 min of moderate-intensity activity or 75 min of vigorous-intensity activity per week, or combination thereof). The current recommendations changed the frequency of exercise bouts from 5 days per week (moderate-intensity) or 3 days per week (vigorous-intensity) to weekly totals of minutes. The prevalence of physical inactivity ranges from approximately 38% in the eastern Mediterranean countries to a low of 14.8% in southeast Asia; by World Bank income classification, the low- and lower-middle-income countries were more physically active than their upper-middle- and high-income counterparts (Sallis et al. 2016). In England and Scotland, more than 65% of men and at least 50% of women met the government’s physical activity guidelines in 2012 (British Heart Foundation 2015a). However, only 18% of Canadian adults responding to the 2014-2015 Canadian Health Measures Survey met the recommendation of 150 minutes of moderate-to-vigorous intensity activity in bouts lasting at least 10 minutes (Statistics Canada 2017). Thus, as an exercise specialist, you face the challenge of educating and motivating your clients to incorporate physical activity as a regular part of their lifestyles and to reduce the amount of time spent being seated (Benatti and Ried-Larsen 2015; Bergouignan et al. 2016; Levine 2015; Same et al. 2016).
This chapter deals with the physical activity trends, risk factors associated with chronic noncommunicable diseases, the role of regular exercise and physical activity in disease prevention and health, physical activity guidelines and recommendations
for improved health, and the importance of including exercise and physical activity as one of the vital signs (i.e. heart rate, blood pressure, etc.) monitored during annual visits to the doctor. For definitions of terminology used in this chapter, see the glossary.
PHYSICAL ACTIVITY, HEALTH, AND DISEASE: AN OVERVIEW
Technological advances affecting nearly every facet of life have substantially lessened work-related physical activity as well as the energy expenditure required for performing activities of daily living like cleaning the house, washing clothes and dishes, mowing the lawn, and traveling to work. What would have once required an hour of physical work now can be accomplished in just a few seconds by pushing a button or setting a dial. Survey results from 23 low-income and 25 upper-middle-income countries suggest that access to modern technological conveniences underlies an inverse relationship between both education level and financial assets with the prevalence of physical inactivity (Allen et al. 2017). The unfortunate fact is, however, that many individuals do not engage in physical activity during their leisure time and sit too much at work and after hours.
Although the human body is designed for movement and strenuous physical activity, exercise is not part of the average person’s lifestyle. Industrialization and urbanization have led to increased
sedentarism and sedentary behaviors (performing activities of ≤1.5 METs while in a sitting or reclining posture) (Benatti and Ried-Larsen 2015; Sedentary Behaviour Research Network 2012). One cannot expect the human body to function optimally and to remain healthy for extended periods if it is abused or is not used as intended.
Physical inactivity is recognized as a major contributor to the physical and economic burden of disease nationally and globally. The identification of physical inactivity as the fourth leading risk factor for mortality supports what experts noted nearly a decade ago—physical inactivity may well be the most important public health problem in the 21st century (Blair 2009). To highlight this, a global action plan was developed to increase the number of people meeting the recommended weekly amount of physical activity by 10% (World Health Organization 2013). The World Health Organization (2014) reported that physical inactivity causes an estimated 3.2 million deaths annually. Data from large cohort studies conducted around the world were pooled and analyzed; resulting estimations revealed that between 6% and 10% of coronary heart disease, type
Cardiomyopathy Over fat Coronary heart disease
2 diabetes, and breast and colon cancers are due to physical inactivity (Lee et al. 2012). As a risk factor, physical inactivity is basically equivalent to the combined risk of smoking and obesity. Sedentarism has repeatedly been identified as an independent risk factor associated with an increased risk for all-cause mortality and metabolic and heart disorders (Benatti and Ried-Larsen 2015). Individuals who do not exercise regularly and sit too much are at greater risk for developing chronic noncommunicable diseases such as those in figure 1.1.
For years, exercise scientists as well as health and fitness professionals have maintained that regular physical activity is the best defense against the development of many diseases, disorders, and illnesses. The importance of regular physical activity in maintaining a high quality of life and in preventing disease and premature death received recognition as a national health objective in the first U.S. surgeon general’s report on physical activity and health (U.S. Department of Health and Human Services 1996). This report identified physical inactivity as a serious nationwide health problem, provided clearcut scientific evidence linking physical activity to
Congestive heart failure
Hypertension
Low back pain Osteoarthritis Bone fractures and connective tissue
numerous health benefits, presented demographic data describing physical activity patterns and trends in the U.S. population, and made physical activity recommendations for improved health. In 1995, the CDC and the American College of Sports Medicine (ACSM) recommended that every U.S. adult should accumulate 30 min or more of moderate-intensity physical activity on most, preferably all, days of the week (Pate et al. 1995). This recommendation has since been adopted by many international organizations.
Since 1995, new scientific evidence increased our understanding of the benefits of physical activity for improved health and quality of life. In light of these findings, the American Heart Association (AHA) and the ACSM updated physical activity recommendations for healthy adults and older adults (Haskell et al. 2007; Nelson et al. 2007). These recommendations address how much and what type of physical activity are needed to promote health and reduce the risk of chronic disease in adults. Table 1.1 summarizes the ACSM and AHA physical activity recommendations for adults.
The recommended amounts of physical activity are in addition to routine activities of daily living (ADLs) such as housework, cooking, shopping, and walking around the home or from the parking lot.
The intensity of exercise is expressed as a metabolic equivalent of task (MET). An MET is the ratio of the person’s working (exercising) metabolic rate to the resting metabolic rate, with 1 MET defined as the energy cost of sitting quietly. Moderate-intensity aerobic activity (3.0-6.0 METs or 5 or 6 on a 10-point perceived exertion scale) is operationally defined as activity that noticeably increases heart rate and lasts more than 10 min (e.g., brisk walking at 3.0-4.0 mph [4.8-6.4 km·hr−1]). Vigorous-intensity activity (>6.0 METs or 7 or 8 on a 10-point perceived exertion scale) causes rapid breathing and increases heart rate substantially (e.g., jogging or running at 4.5 mph [7.2 km·hr−1] or higher). For adults (18-65 yr) and older adults (>65 yr), the ACSM recommends a minimum of 150 min of moderate-intensity aerobic activity per week or 75 min of vigorous-intensity aerobic exercise per week. It is also recommended that these totals be spread over the course of a week to avoid injury). They also recommend moderate- to high-intensity (8- to 12-repetition maximum [RM] for adults and 10-RM to 15-RM for older adults) resistance training for a minimum of 2 nonconsecutive days per week. Balance and flexibility exercises are also suggested for older adults.
Table 1.2 summarizes the physical activity guidelines (U.S. Department of Health and Human
1
(5 or 6 on 10 pt. scale)
(7 or 8 on 10 pt. scale)
to 15-RM; 8-10 exercises for major muscle groups; Moderate intensity (5 or 6 on 10 pt. scale)
Vigorous intensity (7 or 8 on 10 pt. scale) 2 nonconsecutive days
dation
For flexibility at least 2 days/wk for at least 10 min each day; include balance exercises for those at risk for falls
aCombinations of moderate and vigorous intensity may be performed to meet recommendation (e.g., jogging 20 min on 2 days and brisk walking on 2 other days).
b Multiple bouts of moderate-intensity activity, each lasting at least 10 min, can be accumulated to
Table 1.1
ACSM/AHA Physical Activity Recommendations
for Americans
All adults should stretch to maintain flexibility for regular physical activity (PA) and activities of daily living (ADLs).
Older adults should stretch to maintain flexibility for regular PA and ADLs. ≥ 3 days/wk balance
(1.1-2.9 METs) to
METs)
(3.0-5.9 METs)
min/wk
min/wk or
( ≥ 6.0 METs)
(RPE = 3 or 4) to moderate (RPE = 5 or 6) 5 days/wk 1 Light (RPE = 3 or 4) to moderate (RPE = 5 or 6) 2 or 3 days/ wk
min/wk
( ≥ 6.0 METs) Older adults ≥ 65 yr Inactive
(RPE = 5 or 6) ≥ 3 days/wk
min/wk
min/wk or
1 Moderate (RPE = 5 or 6) to high (RPE = 7 or 8) 8-RM to 12-RM ≥ 2 days/wk, nonconsecutive days 75-150 min/wk Vigorous (RPE = 7 or 8)
* Intensity is expressed in METs and repetition maximums (RM) for adults; for older adults, intensity is expressed as a rating of perceived exertion (RPE; 0-10 scale) and RM.
HEALTH BENEFITS OF PHYSICAL ACTIVITY
Lower risk of
• dying prematurely;
• coronary artery disease;
• stroke;
• type 2 diabetes and metabolic syndrome;
• high blood pressure;
• adverse blood lipid profile;
• colon, breast, lung, and endometrial cancers; and
• hip fractures.
Data from U.S. Department of Health and Human Services 2008.
Services 2008) for children and adolescents (6-17 yr), adults (18-64 yr), and older adults (≥65 yr). The key message in these guidelines is that for substantial health benefits, adults should engage in aerobic exercise at least 150 min/wk at a moderate intensity or 75 min/wk at a vigorous intensity or an equivalent combination thereof. In addition, adults of all ages should do muscle-strengthening activities at least 2 days/wk. In addition to stretching to support physical activity and activities of daily living, those who are at risk for falling should also perform balance exercises. Children should do at least 60 min of physical activity every day. Most of the 60 min per day should be either moderate or vigorous aerobic activity and should include vigorous aerobic activities at least 3 days/wk. Part of the 60 min or more of daily physical activity should be muscle-strengthening activities (at least 3 days/wk) and bone-strengthening activities (at least 3 days/wk).
The term exercise deficit disorder (EDD) has been used to identify children who do not attain at least 60 min of moderate- to vigorous-intensity physical activity (MVPA) on a daily basis (Faigenbaum and Myer 2011). Children with EDD are at an increased risk for developing harmful health effects in their adolescent and adult years due to a physically inactive lifestyle (Stracciolini, Myer, and Faigenbaum 2013). For example, results from a study that monitored children for 14 yr revealed that those who maintained their active childhood MVPA levels through adolescence were less likely
Reduction of
• abdominal obesity and
• feelings of depression and anxiety.
Helps in
• weight loss, weight maintenance, and prevention of weight gain;
• prevention of falls and improved functional health for older adults;
• improved cognitive function;
• increased bone density; and
• improved quality of sleep.
to become obese as young adults (Kwon et al. 2015).
Exercising 150 min/wk equates to expending approximately 1,000 kcal·wk−1. Results from a meta-analysis (Sattelmair et al. 2011) indicated that individuals meeting the 2008 physical activity guidelines decrease their risk for coronary heart disease by 14% compared with those reporting no leisure-time physical activity (LTPA). Participating in regular physical activity and exercise on a daily basis provides numerous preventative benefits for no fewer than 25 chronic medical conditions (Warburton and Breden 2016) such as cardiovascular disease, hypertension, diabetes, stroke, dementia, and several types of cancer. Disease risk is further reduced when moderate-intensity physical activity (150-180 min/wk) is performed throughout the week (i.e., 30 min/day on 5 days/wk) and in bouts lasting at least 10 min as opposed to in one single session (Kesäniemi et al. 2010).
Sattelmair and colleagues (2011) reported that 300 min/wk of moderate-intensity physical activity results in a 20% reduction in the risk for coronary heart disease (CHD). Furthermore, a review of studies on asymptomatic adults (19-65 yr) revealed that 90 min of vigorous-intensity physical activity accumulated throughout the week (90 min/wk) in increments of no fewer than 10 min reduces the risk of all-cause mortality by 30%, as well as the risk for cardiovascular disease (CVD), hypertension, stroke, type 2 diabetes, and breast and colon cancer (Kesäniemi et al. 2010).
In 2009, an international consensus conference was convened to review Canada’s Physical Activity Guide to Healthy Active Living (Health Canada 2003). The consensus panel recommended that asymptomatic Canadian adults (19-65 yr) accumulate 150 min/wk of moderate-intensity physical activity or 90 min/wk of vigorous-intensity activity as a primary prevention against cardiovascular disease, stroke, hypertension, colon cancer, breast cancer, type 2 diabetes, and osteoporosis. They also recommended multiple exercise sessions in a week, with each session lasting a minimum of 10 min (Kesäniemi et al. 2010). In addition to the aerobic exercise, they recommended strength activities (2-4 days/wk) and flexibility activities (4-7 days/wk). The duration of the activity depends on the intensity or effort: Perform light activities (e.g., walking, video gaming that promotes light effort, gardening, carrying small children, or hairstyling) for 60 min, moderate activities (e.g., brisk walking, swimming, vacuuming, moving furniture, or chopping wood) for 30 to 60 min, and vigorous activities (e.g., jogging, hockey, wheelchair basketball, felling large trees, or rollerblading) for 20 to 30 min.
Improvements in health benefits depend on the volume (i.e., combination of frequency, intensity, and duration) of physical activity. This is known as the dose-response relationship (Loprinzi 2015). Because of the dose-response relationship between physical activity and health, even a low level of
MVPA each week is better than none; doses less than one-half of the recommended guidelines may lead to notable health benefits for those with elevated risks for chronic conditions and premature mortality (Warburton and Breden 2016). Exceeding the minimum recommended MVPA dose by a factor of 5 (i.e., 750 min/wk or ≥10,000 MVPA MET-min/mo) may confer the greatest reduction in all-cause mortality risk; no additional mortality-related benefit is associated with a dose 10 times higher than recommended (Arem et al. 2015; Loprinzi 2015). MVPA MET-min/mo is easily computed by multiplying the respective MET level for the specific activities (see appendix E.3) by the number of minutes one engages in those MVPA activities within a month.
Figure 1.2 illustrates the general dose-response relationship between the volume of physical activity participation and selected health benefits (e.g., muscular strength and aerobic fitness) that do not require a minimal threshold intensity for improvement. The volume of physical activity participation needed for the same degree of relative improvement (%) varies among health benefit indicators. For example, to improve triglycerides from 0% to 40% requires 250 kcal·wk−1 of physical activity compared with 1,800 kcal·wk−1 for the same relative improvement (0%40%) in high-density lipoprotein (HDL; see figure 1.2). It appears that aerobic-style activities that can be maintained for longer periods (e.g., bicycling, dancing, jogging) are positively related to beneficial
1.2 Dose-response relationship for health benefits and volume of physical activity.
FIGURE
Courtesy of N. Gledhill and V. Jamnik of York University School of Kinesiology and Health Science.
changes in HDL (Loprinzi 2015). Jogging at a slow or average pace ≤3 days/wk for a total of 60 to 150 min/wk confers a favorable increase in heart function and a similar decrease in mortality, whereas decades-long strenuous endurance training routines (≥12 METs) in preparation for extreme endurance competitions may actually damage the cardiovascular system (Schnohr et al. 2015). Therefore, too much physical activity, defined as engaging in 5 hr of structured high-intensity activity per week, may be associated with negative health consequences or overuse injuries.
Although no specific dose of sedentary behavior has been found, a direct linear relationship between total daily time in sedentary behavior and negative health indicators associated with metabolic syndrome (high triglycerides, high fasting blood glucose, and low HDL-C) has been reported (Gennuso et al. 2015). Each 60 min increase in daily time spent being sedentary is associated with a 9% increase in the odds of satisfying the criteria for metabolic syndrome (Gennuso et al. 2015).
Although the physical activity guideline—a minimum of 150 min of moderate- to vigorous-intensity
aerobic activity weekly, preferably performed on a daily basis—reduces disease risk, additional physical activity is needed to mitigate weight gain over time (Moholdt et al. 2014). Levine (2015) describes how standing and walking double the energy expended as compared with sitting; he also illustrates how office workers can expend approximately 1,000 kcal·day−1 and increase time spent being active by incorporating walking meetings and short activity breaks in the typical business day. In 2002, the Institute of Medicine (IOM) recommended 60 min of daily moderate-intensity physical activity. In the IOM report, the expert panel stated that 30 min of daily physical activity is insufficient to maintain a healthy body weight and to fully reap its associated health benefits. The IOM recommendation addresses the amount of physical activity necessary to maintain a healthy body weight and to prevent unhealthful weight gain (Brooks et al. 2004). The IOM recommendation of 60 min of daily physical activity is consistent with recommendations for preventing weight gain made by other organizations (i.e., Health Canada, International Association for the Study of Obesity, and World Health Organization) (Brooks et al. 2004).
EXAMPLES OF MODERATE-INTENSITY AND VIGOROUS-INTENSITY AEROBIC ACTIVITIES
This list provides several examples of moderate- and vigorous-intensity aerobic activities. Some activities can be performed at varied intensities. This list is not all-inclusive; examples are provided to help people make choices. For a detailed list of energy expenditures (METs) for conditioning exercises, sports, and recreational activities, see appendix E.3 and http://links.lww.com/MSS/A82. Generally, light activity is defined as <3.0 METs, moderate activity as 3.0 to 6.0 METs, and vigorous activity as >6.0 METs.
Moderate Intensity
• Walking briskly (3.0 mph [4.8 km·hr−1] or faster, but not race walking)
• Skateboarding (noncompetitive)
• Water aerobics and water calisthenics
• Bicycling slower than 10 mph (16 km·hr−1)
• Tennis (doubles)
• Ethnic and cultural dancing (e.g., Middle Eastern, salsa, merengue, swing)
• General gardening
• Yoga (e.g., hatha, power)
Data from http://links.lww.com/MSS/A82 (accessed June 28, 2018).
Vigorous Intensity
• Race walking, jogging, running, or vigorous lap swimming
• Tennis (singles)
• Dancing (e.g., folk, line, competitive ballroom)
• Bicycling 10 mph (16 km·hr−1) or faster
• Jumping rope
• Backpacking
• Circuit training (resistance based with some aerobics and minimal rest intervals)
The bottom line is that 150 min/wk of moderate-intensity physical activity provides substantial health benefits but may be insufficient to prevent weight gain for many individuals. It is a good initial goal and a sufficient amount of activity to move individuals from a sedentary to low physical activity level (Brooks et al. 2004). As individuals adopt regular physical activity and improve their lifestyle and fitness, they should increase the duration of daily physical activity to a level (60 min) that prevents short-term weight gain and provides additional health benefits. Progression to daily engagement in physical activity, inclusive of resistance training, for 60 to 90 min is important for long-term weight maintenance after weight loss (Bray et al. 2016; Ryan and Heaner 2014). Although there appears to be little overall effect on long-term weight loss based
on exercise type (aerobic vs. resistance) or intensity (lower vs. higher), the reduced time requirement for equivalent energy expenditure of high-intensity exercise as compared with low-intensity exercise may increase exercise adherence and, hence, weight maintenance (Bray et al. 2016).
The Exercise and Physical Activity Pyramid illustrates a balanced plan of physical activity and exercise to promote health and to improve physical fitness (see figure 1.3). Encourage your clients to engage in physical activities around the home and workplace on a daily basis to establish a foundation (base of pyramid) for an active lifestyle. Strategies for increasing energy expenditure in the workplace are built on encouraging active breaks from sitting in order to move around (e.g., step in place, walk laps around the office, perform light calisthenics,
Balance activities
• 3 or more days a week, for prevention of falls
• Tai chi, yoga, Pilates, and dance improve balance
Resistance exercise
• 2 or more days a week
• 8-12 repetitions
• 8-10 exercises
• Rest at least one day between workouts
Activities of daily living
Sports and recreational activities
• 2-3 days a week
• Intersperse days of training with a variety of sport and recreational activities
• Follow safety rules for each activity
• Wear protective equipment
Flexibility exercise
• 2 or more days a week, preferably daily
• 10 min duration minimum
• 3-4 repetitions
• Hold each stretch 10-30 sec
Aerobic exercise
• 30 min, moderate-intensity (3-6 METs), 5 days a week or
• 20 min, vigorous-intensity (>6 METs), 3 days a week
• Try to be active for at least 30 min every day
FIGURE 1.3 The Exercise and Physical Activity Pyramid.
• Activity can be continuous or in multiple segments of at least 10 min
• Daily physical activity is the base for physical fitness
Adapted by permission from “Exercise and Activity Pyramid,” Metropolitan Life Insurance Company, 1995. E7227/Gibson/F01.03/589292/mh-R1
walk down the hall to a colleague’s office instead of calling or e-mailing to deliver a message, climb a flight of stairs to get a drink of water or use the restroom). Your clients should perform aerobic activities a minimum of 3 days/wk; they should do weight-resistance exercises and flexibility or balance exercises at least 2 days/wk. Recreational sport activities (middle levels of pyramid) are recommended to add variety to the exercise plan. High-intensity training and competitive sport (top of pyramid) require a solid fitness base and proper preparation to prevent injury; most adults should engage in these activities sparingly.
CARDIOVASCULAR DISEASE
Cardiovascular disease (CVD) is projected to cause more than 26 million deaths by 2030 (World Health Organization 2011b). CVD caused 17.9 million deaths (46% of the deaths attributed to all noncommunicable diseases) worldwide in 2015. Of the deaths due to CVD in 2015, the combination of stroke and ischemic heart disease accounted for the great majority (85%) (GBD 2015 Mortality and Causes of Death Collaborators 2016). More than 75% of cardiovascular deaths occurred in low- and middle-income countries (World Health Organization 2016a). CVD is the principal cause of premature death in Europe, accounting for a nearly equal percentage of all deaths before age 75 in women (36%) and men (35%). Interestingly, however, CVD was surpassed by cancer as the leading cause of death in several Western European countries (Townsend et al. 2016). CVD is also a leading cause of disease burden in developing low- and middle-income countries; deaths due to CVD range from a low of 10% in sub-Saharan Africa to 58% in Eastern Europe (Wagner and Brath 2012).
In a 2015 report by the CDC identifying the underlying causes of death in the United States between 1999 and 2003, diseases of the heart and blood vessels claimed the lives of about 610,000 people (Centers for Disease Control and Prevention 2015a). CVD accounted for 25% of all deaths (one out of every four) in the United States. Extrapolating to 2014 levels, the CDC estimated that more than 92 million Americans have some form of CVD such
as hypertension (~86 million), CHD (27.6 million), or stroke (7.2 million) (American Heart Association 2017). Among American adults 20 yr of age or older, the estimated age-adjusted prevalence of coronary heart disease is higher for black men and women compared with Hispanic and white men and women (American Heart Association 2017).
One myth about CVD is that it is much more prevalent in men than in women. Between 2011 and 2014, the prevalence of CVD in adult women (35.9%) and men (37.7%) in the United States was similar (American Heart Association 2017). Nearly 399,000 females died from CVD in 2014 in the United States. Another misconception about CVD is that it afflicts only the older population. Although it is true that older people are at greater risk, more than 50% of the people in the United States with CVD are younger than 60 yr (American Heart Association 2017), and CVD ranks as the second-leading cause of death for children under age 15 (American Heart Association 2012).
The prevalence of American adults with CHD was 45.1% in 2014 (American Heart Association 2017). In Europe, CHD accounts for more than 1.7 million deaths, with nearly 19% of those occurring in adults below the age of 65 (Townsend et al. 2016). Coronary heart disease (CHD) is caused by a lack of blood supply to the heart muscle (myocardial ischemia) resulting from a progressive degenerative disorder known as atherosclerosis. Atherosclerosis is an inflammatory process involving a buildup of low-density lipoprotein (LDL) cholesterol, scavenger cells (monocytes), necrotic debris, smooth muscle cells, and fibrous tissue. This is how plaques form in the intima, or inner lining, of the mediumand large-sized arteries throughout the cardiovascular system. As more lipids and cells gather in the plaques, they bulge into the arterial lumen (Barquera et al. 2015). In the heart, these bulging plaques restrict blood flow to the myocardium and may produce angina pectoris, which is a temporary sensation of tightening and heavy pressure in the chest and shoulder region. A myocardial infarction, or heart attack, can occur if a blood clot (thrombus) or ruptured plaque obstructs the coronary blood flow. In this case, blood flow through the coronary arteries is usually reduced by more than 80%. The portion of the myocardium supplied by the obstructed artery may die and eventually be replaced with scar tissue.
CARDIOVASCULAR DISEASE RISK FACTORS
Epidemiological research indicates that many factors are associated with the risk of CVD. The greater the number and severity of risk factors, the greater the probability of CVD. The positive risk factors for CVD are
• age,
• family history,
• hypercholesterolemia,
• hypertension,
• tobacco use,
• diabetes mellitus or prediabetes,
• overweight and obesity, and
• physical inactivity.
An increased level (≥60 mg·dl−1) of high-density lipoprotein cholesterol, or HDL-cholesterol (HDLC), in the blood decreases CVD risk. If the HDL-C is high, you should subtract one risk factor from the sum of the positive factors when assessing your client’s CVD risk.
PHYSICAL ACTIVITY AND CORONARY HEART DISEASE
Approximately 12% of CHD deaths in the United States can be attributed to a lack of physical activity (American Heart Association 2017). As cited in American Heart Association (2017), the percentage of physically inactive people worldwide in 2012 (35%) surpassed the percentage of those who smoked (26%); however, Sallis and colleagues (2016), reported the global percentage of physically inactive adults to be closer to 23%. As an exercise scientist, you must educate your clients about the benefits of physical activity and regular exercise for preventing CHD. Physically active people have lower incidences of myocardial infarction and mortality from CHD and tend to develop CHD at a later age compared with their sedentary or less active counterparts (American Heart Association 2017). Leading a physically active lifestyle and sitting less than 4 hr a day may reduce cardiovascular disease mortality rates by 23% to 74% (Ekelund et al. 2016). Alternatively, in their analysis of multiple studies investigating
sedentary behavior and incidence of CVD, Biswas and associates (2015) reported an increase in odds ranging from 6% to more than doubled. Physical activity, just like sedentary behavior and cardiorespiratory fitness levels, exerts its effect independently of other risk factors related to premature death from CHD and all causes (Bouchard, Blair, and Katzmarzyk 2015). Another conclusion about the independent effect of sedentary behavior (Carter et al. 2017) is that evidence increasingly points to the likely link between sedentarism and its ability to further exacerbate the traditional, modifiable CV risk factors (Benatti and Ried-Larsen 2015; Bergouignan et al. 2016; Same et al. 2016). Also, in a meta-analysis of studies dealing with the dose-response effects of physical activity and cardiorespiratory fitness on CVD and CHD risk, Williams (2001) reported that cardiorespiratory fitness and physical activity have significantly different relationships to CVD and CHD risk. Although physical fitness and physical activity each lower the risk of developing CVD and CHD, the reduction in relative risk was almost twice as great for cardiorespiratory fitness as for physical activity. These findings suggest that in addition to physical activity level, low cardiorespiratory fitness level should be considered a potential risk factor for CHD (U.S. Department of Health and Human Services 2008).
HYPERTENSION
Hypertension, or high blood pressure, is a chronic, persistent elevation of blood pressure. Individuals with this diagnosis are often prescribed antihypertensive medicine. Elevated blood pressure is the term used to identify systolic blood pressure (SBP) values between 120 and 129 mmHg, even if diastolic blood pressure (DBP) is lower than 80 mmHg. Stage 1 hypertension describes a value of 130 to 139 mmHg for SBP or a DBP value of 80 to 89 mmHg; stage 2 hypertension denotes SBP values ≥140 mmHg or DBP values ≥ 90 mmHg (Whelton et al. 2017). An expanded link exists between hypertension and several forms of CVD (Rapsomaniki et al. 2014). The World Health Organization (2011b) identified hypertension as the leading cardiovascular risk factor, attributing 13% of deaths worldwide to high blood pressure. If not kept in check, hypertension becomes a primary risk factor for stroke, heart
attacks, heart and kidney failure, dementia, and blindness (World Health Organization 2014). In the United States, hypertension attributes to about 40% of all adult deaths from CVD (Yang et al. 2012).
In 2014, about 22% of the global adult population (≥18 yr of age) had hypertension (World Health Organization 2014). As of 2015, hypertension is more prevalent in low-income countries in sub-Saharan Africa and south Asia than in high-income countries; however, elevated blood pressure continues to be problematic in Eastern and Central Europe (NCD Risk Factor Collaboration 2017). With an estimated 1.4 billion adult diagnoses worldwide, hypertension is touted as being the leading preventable cause of death before age 70. Its prevalence is lower in high-income countries (28.5%) as compared with low- and middle-income countries (31.5%), which reflects differences in awareness levels as well as treatment and control of the condition (Mills et al. 2016). Nearly one out of every three adults has blood pressure values in the elevated rage (Centers for Disease Control and Prevention 2016). In the United Kingdom, approximately 14% of adults are hypertensive, with Northern Ireland having a lower prevalence compared with England and Scotland (British Heart Foundation 2015b). In comparison, the prevalence of hypertension is estimated to be higher for adults in Latin America and the Caribbean (~39%) than for the Pacific and East Asian region (~36%), Europe and Central Asia (~32%), South Asia (~29%), and Africa (~27%) (Sarki et al. 2015).
In the United States, more men than women are hypertensive prior to age 65; after that the percentage of hypertensive women surpasses that of their male counterparts (American Heart Association 2017). Up to age 45 yr, the percentage of American men with hypertension (11%-23%) is slightly higher than that of women (8%-23%). Between ages 45 and 54 yr, the prevalence of hypertension is similar for men (36.1%) and women (33.2%). Likewise, for those between 55 and 64 yr, men have a slightly higher (57.6%) prevalence of hypertension than do women (~55.5%). After age 65, the percentage of women (65.8%) with high blood pressure is somewhat higher than that of men (63.6%). Women with hypertension
have a 3.5 times greater risk of developing CHD than do women who have normal blood pressure (normotensive). Also, the prevalence of high blood pressure for blacks in the United States (45.5%) is among the highest in the world and is substantially greater than that of American Indians or Alaskan Natives, Asians or Pacific Islanders, Hispanics, and whites in the United States (American Heart Association 2017). Table 1.3 summarizes the risk factors associated with developing hypertension.
For individuals with elevated blood pressure values, healthy lifestyle changes and periodic BP reassessments are recommended as part of the treatment plan. For people whose blood pressure is in the stage 1 range, their risk for stroke and CVD within the next 10 yr should be assessed using the atherosclerotic cardiovascular disease risk calculator (http://static.heart.org/riskcalc/app/index.html#!/ baseline-risk) (Whelton et al. 2017). Sharman, La Gerche, and Coombes (2015) combined data from studies investigating the effect of exercise on blood pressure values in people diagnosed with hypertension. They indicate that while both aerobic and resistance training can reduce blood pressure, aerobic training is the preferred method. Their study also reports on the combination of exercise and antihypertensive medications, with a cautionary note about monitoring postexercise blood pressure responses. Regular physical activity prevents hypertension and lowers blood pressure in younger and older adults who have normal, elevated, stage 1, or stage 2 values. Compared with normotensive individuals, training-induced changes in resting systolic and diastolic blood pressures (5-7 mmHg) are greater for hypertensive individuals who participate in endurance exercise. However, even modest reductions in blood pressure (2-3 mmHg) by endurance or resistance exercise training decrease CHD risk by 5% to 9%, stroke risk by 8% to 14%, and all-cause mortality by 4% in the general population (Pescatello et al. 2004). See Exercise Prescription for Individuals with Hypertension for an exercise prescription that the ACSM endorses to lower blood pressure in adults with hypertension.
(reflects income and education levels). a Males (M) at higher risk than females (F) up to age 55 yr.
b Menopausal females at higher risk than males.
EXERCISE PRESCRIPTION FOR INDIVIDUALS WITH HYPERTENSION
Mode: Primarily endurance activities supplemented by resistance exercises
Intensity: Moderate-intensity endurance (40%60% V O2R),* rate of perceived exertion of 12-13, and resistance training (60%-80% 1-RM)
Duration: 30 min or more of continuous or accumulated aerobic physical activity per day, and a minimum of two sets (8-12 reps) of resistance training exercises for each major muscle group
Frequency: Most, preferably all, days of the week for aerobic exercise; 2 or 3 days/wk for resistance training
*V O2R is the difference between the maximum and the resting rate of oxygen consumption. See the V O2 Reserve (MET) Method section in chapter 5 for more information. Based on American College of Sports Medicine 2018.
HYPERCHOLESTEROLEMIA AND DYSLIPIDEMIA
Hypercholesterolemia, an elevation of total cholesterol (TC) in the blood, is associated with increased risk for CVD. Hypercholesterolemia is also referred to as hyperlipidemia, which is an increase in blood lipid levels; dyslipidemia refers to an abnormal blood lipid profile. Approximately 18% of strokes and 56% of heart attacks are caused by high blood cholesterol (World Health Organization 2002a). Between 2011 and 2014, the number of adults (≥20 yr of age) having a TC value ≥240 mg∙dl–1 fell for all racial and ethnic subgroups; however, this decrease may be due to an increase in medication prescriptions instead of exercise or diet (American Heart Association 2017). Results from the longitudinal, biracial CARDIA study (Schneider et al. 2016) indicate that although TC dropped initially, values stabilized and appear to be reversing toward the end of the 25 yr observation period.
More than 94.6 million Americans age 20 yr and older have total blood cholesterol levels of
200 mg·dl–1 or higher. According to data gathered between 2011 and 2014, 28.5 million American adults (≥20 yr) have TC levels classified as high risk (>240 mg·dl–1); more women (16.4 million) than men (10.6 million) have TC levels equaling or exceeding 240 mg·dl–1 (American Heart Association 2017). Of note, the prevalence of TC, when adjusted for age, decreased in the 2013-2014 period as compared with the 2011-2012 period for both men and women across the four major racial and ethnic groups; the one exception is a 2.6% increased prevalence for non-Hispanic Asian males. Compared with Western countries, the average TC levels for adults in China, Japan, and Indonesia are uniformly lower (190-207 mg·dl–1) (American Heart Association 2001). Risk factors for hypercholesterolemia are identified in table 1.3.
LDLS, HDLS, AND TC
Cholesterol is a waxy, fatlike substance found in all animal products (meats, dairy products, and eggs). The body can make cholesterol in the liver and absorb it from the diet. Cholesterol is essential to the body, and it is used to build cell membranes, produce sex hormones, and form bile acids necessary for fat digestion. Lipoproteins are an essential part of the complex transport system that exchanges lipids among the liver, intestine, and peripheral tissues. Lipoproteins are classified by the thickness of the protein shell that surrounds the cholesterol. The four main classes of lipoproteins are chylomicron, derived from the intestinal absorption of triglycerides (TG); very low-density lipoprotein (VLDL), made in the liver for the transport of triglycerides; low-density lipoprotein (LDL), a product of VLDL metabolism that serves as the primary transporter of cholesterol; and high-density lipoprotein (HDL), involved in the reverse transport of cholesterol to the liver. The molecules of LDL are larger than those of HDL and therefore precipitate in the plasma and are actively transported into the vascular walls. Excess LDL-cholesterol (LDL-C) stimulates the formation of plaque in the intima of the coronary arteries. Plaque formation reduces the cross-sectional area and obstructs blood flow in these arteries, eventually producing a myocardial infarction. Therefore, LDL-C values less than 100 mg·dl−1 are considered optimal for reducing CVD
and CHD risk (National Cholesterol Education Program 2001). The prevalence of borderline high levels (≥130 mg·dl−1 to <160 mg·dl−1) of LDL-C is nearly identical for adult women (31%) and adult men (32.5%) in the United States (Roger et al. 2012).
The smaller HDL molecules are suspended in the plasma and protect the body by picking up excess cholesterol from the arterial walls and delivering it to the liver, where it is metabolized. HDL-cholesterol (HDL-C) values less than 40 mg·dl−1 are associated with a higher risk of CHD. Based on data collected between 2011 and 2014, 19% of men and women in the United States who are older than 20 yr have low (<40 mg·dl−1) HDL-C levels (Zwald et al. 2017).
Individuals with low HDL-C or high TC levels (dyslipidemia) have a greater risk of heart attack. Those with lower HDL-C (<37 mg·dl−1) are at higher risk regardless of their TC level. This emphasizes the importance of screening for both TC and HDL-C in adults.
PHYSICAL ACTIVITY AND LIPID PROFILES
Regular physical activity, especially habitual MVPA aerobic exercise, positively affects lipid metabolism and lipid profiles (Lin, Zhang, et al. 2015). Cross-sectional comparisons of lipid profiles in physically active and sedentary women and men suggest that physical fitness is inversely related to TC and the TC/HDL-C ratio (Despres and Lamarche 1994; Shoenhair and Wells 1995).
Data from 160 randomized controlled trials were pooled to examine the effects of aerobic exercise on cardiometabolic biomarkers such as lipids and lipoproteins in a large number of adults. Results show that compared with control groups, adults in moderate-intensity and vigorous-intensity aerobic exercise interventions, respectively, reduce TC (4.3 and 3.87 mg·dl−1), LDL-C (3.09 and 4.64 mg·dl−1), VLDL-C (1.93 and 7.35 mg·dl−1), and TG (5.31 and 5.31 mg·dl−1) and increase HDL-C (1.16 and 2.71 mg·dl−1) (Lin, Zhang, et al. 2015). However, Lin and colleagues found no differences across exercise-intensity subgroups, which lends support to the premise that moderate- and vigorous-intensity exercise training confer similar favorable results for cardiometabolic health. A 1% reduction in TC has been shown to reduce the risk for CHD by 2%;
likewise, a 1% reduction in HDL-C increases CHD risk by 2% to 3% (Gordon et al. 1989). However, for individuals with hyperlipidemia, lifestyle changes (e.g., healthy diet) or pharmacologic interventions (e.g., statins), in addition to aerobic exercise, may be necessary for optimizing lipid and lipoprotein profiles (Kelley and Kelley 2006).
Increases in HDL-C in response to aerobic exercise appear to be related to the training dose (interaction of the intensity, frequency, and duration of each exercise session and the length of the training period), and they are less dramatic in women than in men. Across adult age ranges, those who met (17.7%) the physical activity guidelines (≥150 min of MVPA per week) had higher HDL-C levels than did those American adults (21.0%) who did not meet the meet the guidelines. Interestingly, the prevalence of low HDL-C values decreased with increasing age for adults meeting the physical activity guidelines; for those ≥60 yr old, only 12.6% of the active seniors had low HDL-C values compared with approximately 19% for the younger age groups (Zwald et al. 2017). Based on results from a longitudinal study of biracial adults, a high level of aerobic fitness as a young adult in combination with a continued physically active lifestyle confers favorable results for blood lipid levels in the middle-age adult years (Sarzynski et al. 2015).
The research on the effect of resistance training on cholesterol levels continues to remain inconclusive. Ribeiro and associates (2016) reported improvements in HDL-C for the older, physically independent women (67.6 ± 5.1 yr) randomly assigned to 8 wk of traditional (three sets of 8-RM to 12-RM) or 8 wk of pyramid (12-RM/10-RM/8-RM) styles of resistance training. After a 12 wk washout period, the women switched training styles. There were numerous favorable responses, including increases in HDL-C, by the end of each 8 wk period; however, there were no differences between training styles. Similarly, 12 wk of a nonlinear resistance training program designed to increase strength significantly improved HDL-C and other variables compared with the normally active controls in a sample of adults (18-60 yr) living with HIV and taking prescribed highly active antiretroviral medications (Zanetti et al. 2016). Conversely, 16 wk of combined aerobic (30 min) and resistance (27 min) training produced no significant improvements in HDL-C
in postmenopausal women as compared with those in the aerobic training (52 min) group (Rossi et al. 2016). It is possible that the resistance training portion of their combined group (three or four sets of 12-RM to 15-RM) may not have provided the exercise intensity needed to invoke significant changes in HDL-C in their postmenopausal sample.
TOBACCO
Although tobacco usage (e.g., cigarettes and cigars) is declining in the United States and other countries, there continues to be a steep increase worldwide (American Heart Association 2017). Ng and colleagues (2014) attribute the increase in the number of smokers to the world’s population growth. The World Health Organization (2011) estimates there are approximately 1 billion smokers in the global population. According to age-standardized results for smoking prevalence (Ng et al. 2014), between 16.5% and 19.7% of men in the United States, Canada, Brazil, and Australia smoke, while 34.7% to 61.1% of men in Russia, China, Eastern Europe, Egypt, and Turkey smoke. The lowest prevalence (0.5%-2.6%) of female smokers is found in Africa, China, and the Persian Gulf, whereas the prevalence exceeds 25% in Austria, Chile, France, and Hungary. Of the 187 countries included in the study, the age-adjusted prevalence of men who smoke daily exceeds that of their female counterparts in all but one country: Sweden. Although the prevalence of tobacco usage is lower for women than men across the majority of the predominant race and ethnic groups in the United States, the prevalence is slightly higher for Native American and Alaskan Indian women and nearly equal for non-Hispanic white women compared with their respective male counterparts (American Heart Association 2017).
Approximately 13.7% of American women and 16.7% of American men currently smoke (American Heart Association 2017). Smoking cessation strategies in Canada, Iceland, Mexico, and Norway have cut smoking rates in half since 1980 (Ng et al. 2014) and may provide invaluable assistance for curbing tobacco use in other countries. In a study of school-aged adolescents (average age 15 yr) representing 50 schools in six European cities (Lorant et al. 2015), 17.4% of the 11,000 participants self-reported being a smoker. Even if people abstain
from smoking tobacco, the risk of death from CHD increases by 30% in those exposed to environmental tobacco smoke at home or at work (American Heart Association 2004).
Smoking is one of the largest preventable causes of disease and premature death. Nearly 33% of CHD deaths are due to first- and secondhand exposure to smoke (American Heart Association 2017). Cigarette smoking is linked to CHD, stroke, and chronic obstructive pulmonary disease. It causes cancer of the lungs, larynx, esophagus, mouth, and bladder and is also associated with no fewer than eleven cancers (Carter et al. 2015). Compared with nonsmokers, smokers have more than twice the risk of heart attack and die, on average, at least 10 yr earlier (American Heart Association 2017). As mentioned previously, cigarette smoking is a major cause of stroke. It also multiplies the effect of CHD risk factors such as elevated blood lipid levels, diabetes mellitus, and untreated hypertension. Some researchers who study adults ≥55 yr of age are encouraging further investigations of the possible associations between smoking and deaths resulting from infections, respiratory diseases, prostate and breast cancer, intestinal ischemia, kidney failure, and hypertensive heart disease. The relative risk of dying from these conditions drops with each year subsequent to quitting (Carter et al. 2015). Additionally, although not well studied at this time, the inhaled vapors from electronic cigarettes deliver nicotine and other substances for which the health risks are not yet known.
When individuals stop smoking, their risk of CHD declines rapidly, regardless of how long or how much they have smoked. Although health benefits associated with smoking cessation happen within weeks or months, the relative risk of a former smoker dying from CHD approximates that of a nonsmoker within 10 yr of quitting (American Heart Association 2017).
DIABETES MELLITUS
Diabetes is a global epidemic with rising prevalence rates, especially in the low- and middle-income countries. Consequently, there is a commitment by world leaders to reduce, by one-third, the rates of premature mortality from diabetes and the other priority NCDs by 2030 (World Health Organiza-
tion 2016b). As of 2014, an estimated 422 million adults (8.5%) worldwide have the disease (World Health Organization 2016b). Factors linked to this epidemic include urbanization, aging, physical inactivity, unhealthy diet, and obesity (Wagner and Brath 2012). At least 43% of the deaths attributable to elevated blood glucose levels occur in people younger than 70 yr of age (World Health Organization 2016b). Diabetes is a major contributor toward the development of CHD, stroke, specific cancers, kidney failure, and cognitive disability (World Health Organization 2016b). This increased risk of CHD and stroke is higher for women than men with diabetes for a variety of reasons: higher-level CVD risk factors and obesity at time of diagnosis, longer exposure to an elevated risk profile when in the prediabetic stage, and relative undertreatment following diagnosis (Peters, Huxley, and Woodward 2014). In the United States, diabetes was the seventh leading cause of death in 2010 (American Diabetes Association 2017).
In 2012, 29 million adults in the United States had type 2 diabetes, while 86 million ≥20 yr of age were identified as having prediabetes (American Diabetes Association 2017). In China and India, there are 138 million people with diabetes (Danaei et al. 2011). Danaei and colleagues (2011) also estimated that approximately 42 million people with diabetes are from Brazil, Indonesia, Japan, Mexico, and Pakistan. Furthermore, in 2008, they reported the highest prevalence of diabetes was found in countries located in Oceania, northern Africa, the Middle East, and the Caribbean. Conversely, the lowest prevalence of diabetes was in southeast Asia, east Africa, and Andean Latin America (Danaei et al. 2011).
The prevalence of diabetes for adults (≥20 yr) in the United States was 12.3%; 1.7 million people in this age group were diagnosed with diabetes for the first time in 2012 (Centers for Disease Control and Prevention 2014). Compared with white adults in the United States, the prevalence of diabetes and impaired blood glucose levels for blacks (13.2%), Hispanics (12.8%), and American Indians/Alaska Natives (15.9%) is higher (Centers for Disease Control and Prevention 2014). The age-adjusted prevalence of diabetes for American Indians and Alaska Native adults is region dependent; American Indians in southern Arizona have a prevalence of diabetes
(24.1%) that is four times that of Alaska Natives (Centers for Disease Control and Prevention 2014).
Prediabetes, in addition to being a positive risk factor for CVD, is a medical condition identified by fasting blood glucose or glycated hemoglobin ( HbA1c) levels that are above normal values but lower than the threshold for a diagnosis of diabetes. HbA1c is an indicator of the average blood glucose over the past 2 to 3 mo (Centers for Disease Control and Prevention 2014). Fortunately for the 86 million American adults (Centers for Disease Control and Prevention 2014) and others worldwide, prediabetes appears to respond favorably to weight loss, dietary changes, and increases in physical activity. The age-adjusted percentage of prediabetes in U.S. adults during the period 2009 to 2012 was nearly identical for non-Hispanic whites, non-Hispanic blacks, and Hispanics (35%, 39%, and 38%, respectively) (Centers for Disease Control and Prevention 2014). Type 1 diabetes, formerly referred to as insulin-dependent diabetes mellitus (IDDM), usually occurs in children and adolescents but can develop at any age. Type 2 diabetes, previously known as non-insulin-dependent diabetes mellitus (NIDDM), is more common and no longer occurs primarily in middle-aged and elderly adults; 90% to 95% of individuals diagnosed with diabetes mellitus have type 2 diabetes (Centers for Disease Control and Prevention 2014). Risk factors for developing diabetes are presented in table 1.3. Type 1 diabetes may be caused by autoimmune, genetic, or environmental factors, but the specific cause is unknown. Unfortunately, although clinical trials are under way, there is currently no known way to prevent type 1 diabetes (World Health Organization 2016b). Healthy nutrition and increased physical activity, however, can reduce the risk of type 2 diabetes by as much as 67% in high-risk individuals (Sanz, Gautier, and Hanaire 2010). Regular physical activity, as part of a modest weight loss intervention, has reduced the risk of developing type 2 diabetes by a maximum of 58% for those in the high-risk category (Colberg et al. 2010). Too much body fat is recognized as the dominant risk factor for type 2 diabetes. Elevated waist circumferences and BMI values also increase the risk, but the associated risk varies by geographic region (World Health Organization 2016b).
The effect of exercise alone as an intervention for people with type 2 diabetes is not well known beyond
