The term “physical activity” refers to any bodily movement produced by skeletal muscles that requires more energy expenditure than that in the resting state. “Exercise”, such as sports and fitness, is a subcategory of physical activity that is performed in a planned and regular manner to maintain and promote health and physical strength. Individuals who engage in more physical activity and exercise have a lower risk of developing and suffering from cardiovascular disease, type 2 diabetes, breast and colon cancer, locomotive syndrome, depression, and dementia than do those who engage in less physical activity and exercise. The World Health Organization (WHO) has identified physical inactivity as the fourth risk factor for mortality worldwide, following high blood pressure, tobacco use, and high blood glucose [1]. It has been estimated that between four and five million deaths could be prevented each year if the global population was more active. Given the importance of physical activity to public health and the limited availability of national guidelines on physical activity for health in low- and middle-income countries, the WHO published the 2010 Global Recommendations on Physical Activity for Health to promote physical activity and prevent noncommunicable disease [2], which have been updated as the 2020 WHO Guidelines on Physical Activity and Sedentary Behavior [3]. In the 2020 WHO guidelines, it is recommended that adults (aged 18–64 years) or older adults (aged 65 years and older) should perform at least 150–300 min of moderate-intensity aerobic physical activity or at least 75–150 min of vigorous-intensity aerobic physical activity, or an equivalent combination of moderate- and vigorous-intensity activities, throughout the week for substantial health benefits. Those recommended aerobic physical activities are equivalent to doing about 500–1000 metabolic equivalent of tasks (METs)-minutes a week. In addition, it is recommended that adults and older adults should perform muscle-strengthening activities at moderate or greater intensity that involve all major muscle groups on two or more days a week for additional health benefits. A meta-analysis has shown that individuals who perform both aerobic physical activity and muscle-strengthening activity have a 40–46% lower risk of all-cause mortality and cardiovascular disease (CVD) mortality than do individuals who report no activity, whereas aerobic activity alone or muscle-strengthening activity alone is associated with an 18–29% lower risk of all-cause mortality and CVD mortality than the risk with no activity [4]. These findings suggest that combining aerobic physical activity and muscle-strengthening activity is more effective than aerobic physical activity alone or muscle-strengthening activity alone for reducing the risk of all-cause mortality and CVD mortality (Fig. 1).

Combining muscle-strengthening activities with aerobic physical activity may have additional benefits on all-cause mortality and cardiovascular disease (CVD) mortality in patients with hypertension

Exercise therapy is strongly recommended for patients with hypertension, primarily because of its blood pressure-lowering effects. The average reduction in systolic blood pressure resulting from aerobic exercise is about 5–8 mmHg in patients with hypertension [5]. Systolic blood pressure is also reduced by muscle-strengthening activity (resistance exercise training) by 4–5 mmHg in patients with hypertension [5]. Although evidence is insufficient, it has been shown that the combination of aerobic physical activity and muscle-strengthening activity may be superior to aerobic physical activity alone or muscle-strengthening activity alone for lowering blood pressure in patients with hypertension [6]. Both aerobic physical activity alone and muscle-strengthening activity alone have been shown to improve mortality in patients with hypertension [7]. However, it has not been fully determined whether combining aerobic physical activity and muscle-strengthening activity is more effective than aerobic physical activity alone or muscle-strengthening activity alone for reducing the risk of all-cause mortality and CVD mortality in patients with hypertension. In the current issue of Hypertension Research, Choi et al. reported the results of a study conducted to investigate the associations of meeting both aerobic physical activity (≥500 METs-min/week) and muscle-strengthening activity (≥2 days/week) guidelines with all-cause and CVD mortality in 9413 patients with hypertension and 25,577 individuals without hypertension from the 2007–2013 Korean National Health and Nutrition Examination Survey, with mortality follow-up data through 2019 (a mean follow-up period of 9.2 years) [8]. Hypertension was defined as systolic blood pressure ≥140 mmHg or diastolic blood pressure ≥90 mmHg or self-reported use of antihypertensive medication. The authors reported that subjects with aerobic physical activity alone (hazard ratio [HR], 0.76; 95% confidence interval [CI], 0.67–0.87 for all-cause mortality; HR, 0.76; 95% CI, 0.59–0.99 for CVD mortality) and those with a combination of aerobic physical activity and muscle-strengthening activity (HR, 0.60; 95% CI, 0.48–0.76 for all-cause mortality; HR, 0.57; 95% CI, 0.35–0.92 for CVD mortality) had significantly lower risks of all-cause mortality and CVD mortality than did those with neither aerobic physical activity nor muscle-strengthening activity in patients with hypertension and that there was no significant association of muscle-strengthening activity alone with all-cause mortality or CVD mortality in patients with hypertension. Similar trends were observed in patients with hypertension regardless of antihypertensive medication use. Among individuals without hypertension, only those with a combination of aerobic physical activity and muscle-strengthening activity had a significantly lower risk of CVD mortality (HR, 0.48; 95% CI, 0.24–0.97) than the risk for those with neither aerobic physical activity nor muscle-strengthening activity alone. These findings suggest that, although no head-to-head comparison was performed, combining aerobic physical activity with muscle-strengthening activity, rather than aerobic physical activity alone, further reduces the risk of all-cause mortality and CVD mortality in patients with hypertension regardless of antihypertensive medication use and that the prognostic benefit of exercise is greater in patients with hypertension than in those without hypertension.

It has been postulated that muscle-strengthening activity may exert beneficial effects on all-cause and CVD mortality by improving both traditional and nontraditional CVD risk factors [9]. Resistance training has been shown to improve not only blood pressure but also other traditional CVD risk factors, including glycemia, lipids, and body composition. Resistance training can prevent the onset of diabetes and reduce fasting plasma glucose levels. In addition, resistance training has modest but favorable effects on total cholesterol, high-density lipoprotein cholesterol, and triglyceride levels. Although resistance training alone is unlikely to result in clinically significant weight loss, it is associated with increased lean body mass, decreased body fat percentage, and decreased total fat mass, which can lead to an increase in the resting metabolic rate and, consequently, reduce weight gain over time. Resistance training has also been shown to improve nontraditional CVD risk factors; it improves cardiorespiratory fitness, endothelial function, and sleep quality and reduces symptoms of depression and anxiety [9]. Greater skeletal muscle mass in older adults is independently associated with better physical performance, mobility, and the prevention of injurious falls, which are a leading cause of chronic disability and loss of independence. Therefore, resistance training is particularly important and recommended for older adults to maintain greater skeletal muscle mass, mitigate age-related declines in physical performance, and prolong functional independence. These beneficial effects of muscle-strengthening activities may provide additional benefits for all-cause and CVD mortality in patients with hypertension.

In the study conducted by Choi et al., the assessment of muscle-strengthening activity was based only on frequency, without information on intensity or duration. It is important to note that evidence for benefits of higher levels of muscle-strengthening activity is sparse and, therefore, limits conclusions regarding the benefits or risks of high volumes of muscle-strengthening activity. Observational studies have shown that the dose-response associations of resistance training with mortality and CVD are curvilinear, with the maximal benefit occurring at 30–60 min per week, suggesting that excessive muscle-strengthening activity is not necessary to gain the health benefits of muscle-strengthening activities [4]. In addition, muscle-strengthening activities may be safe for adults who can perform aerobic physical activity in terms of cardiovascular complications [10]. Together, muscle-strengthening activities in addition to aerobic physical activity are strongly recommended for patients with hypertension because of their prognostic benefits and safety. Muscle-strengthening physical activities at least two days a week, in addition to aerobic physical activity, may further keep the doctor away in patients with hypertension.