INTRODUCTION

The literature shows irrefutable evidence that document the health benefits of physical activity (PA). The common message within health promotion settings is to be physically active. Physical inactivity and sedentary behavior correlate with numerous chronic diseases as well as premature all‐cause mortality. Several public health organizations as well as the World Health Organization (WHO) provide recommendations for the amount (frequency, intensity, duration) and types of PA for people in all age groups and those living with chronic conditions or disability.

In this chapter, we will discuss the estimations of physical activity/inactivity worldwide, the health effects of PA, and the current PA recommendations.

PHYSICAL ACTIVITY AND INACTIVITY ESTIMATIONS WORLDWIDE

There is increasing evidence of poor PA worldwide.

The estimates on insufficient PA in 2010 using data from 146 countries was 23.3%, with higher levels among women and older age groups. Pooled data from 358 surveys across 168 countries, including 1.9 million participants, showed that in 2016, the global age‐standardized prevalence of insufficient PA increased to 27.5%, with a difference between sexes of more than 8 percentage points (i.e., 23.4% in men versus 31.7% in women) (Guthold, Stevens, Riley, & Bull, 2018). This practically means that more than one in four adults globally are physically inactive. This increase in physical inactivity correlates with technology advances including increased television viewing as well as computer, mobile device, and video game use (Anderson & Durstine, 2019).

Physical inactivity prevalence seems to increase with age: 25% of young adults aged 18 to 44 years, 33% of middle‐aged adults aged 45 to 64 years, 36% of older adults aged 65 to 74 years, and 53% of the elderly aged ≥75 years are considered inactive (Anderson & Durstine, 2019).

The definition of physical inactivity has changed through the years, from failing to meet the previous recommendations—30 min of moderate‐intensity PA at least 5 days per week, 20 min of vigorous PA at least 3 days per week, or a combination of walking, moderate‐intensity, and vigorous‐intensity activities to total 600 MET minutes per week (Pate et al., 1995)—to the current recommendations (US Department of Agriculture and US Department of Health and Human Services 2018; World Health Organization, 2020; World Health Organization, 2010)— at least 150 min of moderate‐to‐vigorous‐intensity physical activity per week regardless of over how many days activity is accumulated. This has led to an artificial decline in the global prevalence of physical inactivity, although estimates, as mentioned previously are high (Ding Ding et al., 2020).

According to a 2010 WHO report (World Health Organization, 2010), insufficient PA is considered the fourth leading risk factor for mortality, leading to 3.2 million deaths and 32.1 million disability‐adjusted life years (DALYs) (about 2.1% of global DALYs) annually. Individuals that are physically inactive have a 20% to 30% increased risk of all‐cause mortality compared to those with at least 30 minutes of moderate‐intensity PA most days of the week (World Health Organization, 2010).

There is a strong link between physical inactivity and major non‐communicable diseases (NCDs). In high‐income countries with a high prevalence of insufficient PA levels, high prevalence rates of NCDs also occur. Physical inactivity is directly responsible for 6% of the global burden of coronary heart disease (CHD), 7% of type 2 diabetes (T2D), and 10% of breast cancer. For instance, if a patient with T2D increases sedentary time by just 60min/day, independently of moderate‐to‐vigorous PA (MVPA), all‐cause mortality will increase by 13% (Loprinzi & Sng, 2016). Similarly, patients with symptomatic chronic heart failure (HF), who are physically inactive have a greater risk of all‐cause death and cardiac death (Doukky et al., 2016). Other health problems associated with physical inactivity are impaired circulation, osteoporosis, arthritis and/or other skeletal disabilities, diminished self‐concept, a greater dependence on others for daily living, reduced opportunity and ability for normal social interactions, and an overall diminished quality of life (Anderson & Durstine, 2019).

Due to the strong association of physical inactivity with NCDs, member states of the WHO agreed to a 10% relative reduction in the prevalence of insufficient PA by 2025 as one of the nine global goals for the prevention and treatment of NCDs (Figure 6.1) (World Health Organization, 2021).

SEDENTARY BEHAVIOR

In 2012, the Sedentary Behavior Research Network proposed (González, Fuentes, & Márquez, 2017) a definition of sedentary behavior as waking behavior with an energy expenditure of ≤1.5 METs. The term ‘sedentary’ comes from the Latin ‘sedere’ (to sit). Sedentary behavior, therefore, typically refers to sitting, lying, and reclining behaviors during waking hours rather than a simple absence of MVPA. The term ‘physical inactivity’ as already mentioned, describes the insufficient amounts of PA that are performed, that is, failing to meet specified PA guidelines (González et al., 2017).

US adults seem to spent 54.9% of their waking time, or 7.7 hours/day, in sedentary behaviors, while older adults aged ≥60 years spent about 60% of their waking time sedentary (Matthews et al., 2008). Accordingly, in Europe, an average of 40% of leisure time is spent watching TV. However, sufficient levels of MVPA does not automatically mean low levels of sedentary time and vice versa. Moreover, the inverse health effects of sedentary behaviors tend to persist, with some attenuation, after considering MVPA (Patterson et al., 2018).

There is strong evidence of a positive relationship between sedentary behavior and all‐cause mortality, fatal and non‐fatal cardiovascular disease (CVD), T2D (Wilmot et al., 2012), and metabolic syndrome (MetS). In addition, there is moderate evidence for incidence rates of ovarian, colon, and endometrial cancers with sedentary behavior (i.e., overall sitting time, sitting outside of work, and TV viewing).

PREMATURE ALL‐CAUSE MORTALITY

The first epidemiological data that demonstrated a clear dose‐response relationship between PA and lower risk for all‐cause mortality was from the Harvard alumni study (Paffenbarger Jr, Hyde, Wing, & Hsieh, 1986). The study showed that all‐cause mortality was lower among active individuals compared to less active participants; large risk reductions were found with relatively small changes in PA behavior (Paffenbarger Jr et al., 1986).

Since then, numerous meta‐analyses and systematic reviews of epidemiological and interventional studies (Ekelund et al., 2016; Kraus et al., 2019; Ramakrishnan et al., 2021) have verified these early data.

More recently, a prospective study by Dohm and colleagues (Dohrn, Kwak, Oja, Sjöström, & Hagströmer, 2018) followed up with 851 women and men for 14.2 years (standard deviation of 1.9) during which time 79 deaths occurred (24 deaths from CVD, 27 from cancer, and 28 from other causes). Researchers showed that replacing 30 minutes/day of sedentary time with light‐intensity PA was linked to a significant reduction in all‐cause and CVD mortality risk. Replacing only 10 minutes of sedentary time with MVPA was associated with a reduction in CVD mortality risk. These results clearly suggest that replacing sedentary behavior with PA for the same amount of time could also impact all‐cause mortality.

Any PA rather than none, is also beneficial for all‐cause mortality, which may help those struggling to follow the guidelines to engage more with PA. In a systematic review and harmonized meta‐analysis of eight observational studies (n = 36 383; mean age 62.6 years; 72.8% women), with a median follow‐up of 5.8 years and 2149 (5.9%) deaths, Ekelund and colleagues (Ekelund et al., 2019) showed that any PA, regardless of intensity, and less time spent sedentary, were associated with a lower risk for premature mortality in a non‐linear dose‐response.

In conclusion, it seems that PA decreases remarkably the risk for premature all‐cause mortality, even with relatively small participation.

HEALTH IMPACT OF PHYSICAL ACTIVITY

Routine PA is an effective method for the primary and secondary prevention of more than 25 chronic medical conditions and premature mortality (D. E. R. Warburton & Bredin, 2017). In particular, there is an inverse relationship between routine PA and CVD/coronary artery disease (CAD), hypertension, stroke, osteoporosis, T2D, MetS, obesity, and 13 types of cancers (breast, bladder, rectal, head and neck, colon, myeloma, myeloid leukemia, endometrial, gastric cardia, kidney, lung, liver, and esophageal adenocarcinoma) (Liguori & Medicine, 2020) (Figure 6.2). Data from interventional studies, large‐scale population‐based, and observational studies show strong evidence of a dose‐response inverse relationship between these conditions and PA.

Of note, the greatest health benefits are observed in individuals who are physically inactive and become more physically active (D. E. Warburton, Nicol, & Bredin, 2006; D. E. R. Warburton & Bredin, 2019) (Figure 6.3) (D. E. Warburton & Bredin, 2016).

Moreover, the domain of PA seems to positively affect health. In a prospective cohort study including participants from 17 countries (Lear et al., 2017), both leisure‐time and non‐leisure‐time PA were protective of mortality and CVD in low‐, middle‐, and high‐income countries. Furthermore, occupational PA is protective of several NCDs, including some cancers. In an umbrella review of 23 health outcomes across 158 observational studies (Cillekens et al., 2020), those engaging in high versus low occupational PA had better health effects, considering multiple cancer outcomes (i.e., colon and prostate), ischemic stroke, CHD, and mental health (i.e., mental well‐being and life satisfaction) (Cillekens et al., 2020). However, high occupational PA was associated with unfavorable health outcomes for all‐cause mortality in men, mental ill health (i.e., depression and anxiety), osteoarthritis, and sleep quality and duration, suggesting a potential paradox. This observation received some criticism. The misclassification of occupational activities using simple questionnaires as well as incomplete adjustments for covariates, e.g., cigarette smoking and socio‐economic status, may explain the observed paradox (Ding Ding et al., 2020).

In older adults, increased PA is linked to improved functional health, performance capabilities, mental health, sleep, and quality of life (autonomy and vitality) (D. Ding et al., 2020). Moreover, age‐related losses of bone mineral density in women as well as hip fracture risk and falls are reduced (Chodzko‐Zajko et al., 2009). PA is suggested to both prevent and improve cognitive function in terms of preventing and lowering both age‐related cognitive decline and the risk for neurological disorders, such as Alzheimer’s disease (Gheysen et al., 2018) (More will be discussed in Unit 3).

The mechanisms by which routine PA is thought to be effective in primary and secondary prevention strategies of chronic diseases include (Rhodes, Janssen, Bredin, Warburton, & Bauman, 2017):

• improved cardio‐respiratory and health‐related physical fitness,
  
• better exercise toleration and functional status,
  
• improved body composition (e.g., strategies against obesity, reduced central obesity, weight management),
  
• improved lipid profiles (e.g., reduced triglycerides, higher high‐density lipoprotein (HDL) ‐cholesterol, lower low density lipoprotein (LDL)‐to‐HDL ratios, improved glucose parameters (e.g., glucose homeostasis, insulin resistance, insulin sensitivity),
  
• improved blood pressure,
  
• improved autonomic tone,

  

  

  
  
• better blood coagulation,
  
• improved coronary blood flow,
  
• augmented cardiac function,
  
• improved endothelial function,
  
• less systemic inflammation, and
  
• improved psychological well‐being (e.g., improvements in stress, anxiety, and depression).

PHYSICAL ACTIVITY GUIDELINES

The 2020 WHO Guidelines on Physical Activity and Sedentary Behavior (Bull et al., 2020) provide recommendations on the amount (frequency, intensity, duration) and types of PA for children, adolescents, adults, and older adults as well as pregnant and postpartum women and people living with chronic conditions or disability (Figure 6.4) (World Health Organization, 2020).

These guidelines (Table 6.1) (Bull et al., 2020) include some major developments compared to previous published guidelines. They address, for the first time, the health impact of sedentary behavior, support the evidence for additional health benefits (e.g., improved cognitive health, health‐related quality of life, mental health, and sleep) apart from previously known health effects on specific conditions, provide recommendations for specific groups, i.e., pregnant and postpartum women and people living with chronic conditions or disability, while clearly supporting the notion that “any physical activity is better than none” (D. Ding et al., 2020).

Previously published PA guidelines (Figure 6.5) focused mainly on continuous vigorous aerobic exercise to improve performance or cardiac rehabilitation. The American College of Sports Medicine (ACSM) has published guidelines for PA since 1975. Through the years, the PA recommendations of the ACSM were focused on how much exercise someone following the recommendations should do, suggesting that a PA level that does not meet these specific criteria is of limited or no value.

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