Exercise as Medicine, 16 Feb 2016
It is known to mankind that industrial and technological advancements have made a tremendous contribution on our daily living. It saves us from ancient work such as hunting, walking to collect water and physical commuting (locomotion). In comparison to primitive civilizations which used to require large amount of energy to perform daily tasks, the modern society requires less total energy expenditure. That means, this low energy requirement in the modern society is attributable to trends in automation, transportation, media (TV, computers, smartphones, etc), social and environmental changes. Despite the changes in physical pattern which are clearly altered in comparison to our descendants, we still presenting the same genetic makeup of our ancestors.
Today, modern society in general has lesser energy expenditure (physical inactivity) and positive energy availability (excessive consumption of calories). This physical inactivity has been associated with mortality and according to the World health Organization, it is the fourth leading risk factor (Figure 1) for global mortality (6% of deaths globally).
Unfortunately, physical inactivity is rising in many countries with major implications for the general health of people worldwide. Physical inactivity is the results in the so-called “disuse syndrome” (i.e., premature aging, obesity, cardiovascular vulnerability, musculoskeletal fragility, and depression). For example, workers that spent too much time seated (bus driver, office workers, phone operators, etc) are likely to experience twice the cardiovascular diseases (CVD) mortality than the comparatively more physically active workers (post mail, builders, bike delivery couriers, etc). Remarkably, studies also have shown that individuals in active jobs that acquired cardiovascular diseases, are likely to develop the disease at later ages and much less severe in comparison to sedentary jobs.
In addition, inactivity is also associated with combination of risk factors such as cardiovascular disease, diabetes, cancer, high blood pressure, raised blood sugar and overweight. According to the World Health Organization, more than 60% of the global population has not enough regular physical activity to prevent risk factors associated with diseases.
Conversely, participation in regular physical activity can decrease the risk of death by 40% for the following conditions; coronary heart disease and stroke, diabetes, hypertension, colon cancer, breast cancer and depression. Some studies have shown that 80 years old seniors that maintain physical activity demonstrate lower risk of death in comparison to inactive individuals in their 60s.
Regular physical activity may decrease the risk of the following risk factors:
Figure 2: The association with physical activity and possible decrease on the percentile of risk factors.
Besides, adults with better muscle strength have a 20% lower risk of mortality (33% lower risk of cancer specific mortality) than adults with low muscle strength. In a study by Ruiz et al. (2008) including over 8000 participants followed for approximately 18 years to assess the influence of muscle strength and cardiorespiratory fitness on healthy ageing. The subjects were separated by vital status and by thirds of muscular strength and the combined effects of muscular strength and cardiorespiratory fitness with all-cause mortality revealed that death rate in men with high levels of both muscular strength and cardiorespiratory fitness was 60% lower in comparison to the death rate in the group of unfit men with the lowest levels of muscular strength. That means, the result suggests that individuals with higher muscular strength and cardio-respiratory fitness are likely to have longer life expectancy.
Figure 3: Subjects separated by thirds of muscular and cardiorespiratory fitness categories. Death rate was inversely related to muscular strength and high cardiorespiratory fitness. Adapted from (Ruiz et al., 2008).
Another study by Haskell, Blair and Hill (2009), have demonstrated that individuals with low cardiorespiratory fitness accounted for about 16% of all deaths in both women and men, which were substantially higher in comparison to other risk factor such as obesity, smoking, hypertension, high cholesterol and diabetes. Figure 4 presents the attributable fraction, which is an estimate of the number of deaths in a group that would have been avoided if a specific risk factor had been absent. For example, if physical inactive individuals become physical active getting 30 minutes of walking on at least 5 days of the week.
Figure 4: Attributable fractions (%) for all-cause mortality in 40,842 (3333 deaths) men and 12,943 (491 deaths). The cardiorespiratory fitness was evaluated by maximal exercise test on a treadmill. Adapted from (Haskell et al., 2009).
Professor Steven Blair, an epidemiologist professor of the University of South Carolina, raises the point of how many times have you included the risk factors described on figure 3, as typical physician examination is 10–50 times more likely to measure cholesterol, blood pressure, and BMI than to measure fitness. A stress test would be a much better choice, but unfortunately because of cost, duration and insurance policy, this type of test is usually neglected. Other options such as the Balke test or the VO2Max test, are quick, affordable and reliable. Surprisingly, cardiorespiratory fitness appears to be of such importance that it has shown to decrease the risk of mortality even in obese individuals (Figure 5).
Figure 5: Hazard ratios for total mortality according to levels of physical activity and BMI (<30 vs >30 kg/ m2 ). Adapted from (Hu et al., 2005).
What to do to increase life expetancy
One way to evaluate the daily requirements of physical activity is the utilisation of Metabolic Equivalent. Metabolic Equivalent (MET) is defined as the resting metabolic rate which is the amount of oxygen consumed at rest (3.5mlO2/kg/min). That means, 2 METS is the result of an increase in the metabolic rate of twice the resting metabolism (7mlO2/kg/min). The work by Kokkinos and Myers (2010), demonstrate that relative risk for mortality decreases for individuals with high exercise capacity (METS).
Figure 6: Mortality risk according to METS exercises capacity. A reduction in mortality rate are noticeable at >4 METs and decreases exponentially. Adapted from (Kokkinos & Myers, 2010).
Below is a sample of a few activities and the energy cost in METS. A more comprehensive review of METS activities can be found here.
The exercise guidelines recommendations of the major health institutions worldwide are pretty much similar. Below is a summary of the recommendation points of the American Heart Association, American College of Sport Medicine, National Health Service - UK, Australian Government – Department of Health.
Cardiorespiratory Exercise – 150 minutes of moderate intensity exercise, could be performed at moderate intensity for 20-30 minutes 5 times per week or 20- 25 minutes vigorous intensity three times per week (Total of 75 minutes).
Resistance Exercise - Adults should train each major muscle group two or three days each week of moderate- to high-intensity resistance training for additional health benefits. It is recommended a light intensity for older person or sedentary adults starting exercise. Two to four sets of each exercise and repetitions ranging between 8 to 20 repetitions (lower for gains in strength, power or hypertrophy and higher for muscular endurance) with a 48 hours rest between resistance training sessions.
Flexibility Exercise - Two or three session per week should be dedicated to flexibility with exercises held for 20-60 seconds between two to four times.
Neuromotor Exercise - These exercises are fundamental to improve balance, coordination, gait and agility. A proprioceptive training is recommended as part of a comprehensive exercise program and may have the potential to minimise falls, improve balance and coordination and general skills. This type of training should be integrated in an exercise program for two or three days per week with a 20 to-30 minutes per day.
American Heart Association: http://www.heart.org
Australian Government – Department of Health: http://www.health.gov.au/
Blair, S. N. (2009). Physical Inactivity: The Biggest Public Health Problem of the 21st Century. British Journal of Sport Medicine, 43, 1–3.
Haskell, W. L., Blair, S. N., & Hill, J. O. (2009). Physical activity: Health outcomes and importance for public health policy. Preventive Medicine, 49, 280–282.
Hu, G., Tuomilehto, J., Silventoinen, K., Barengo, N. C., Peltonen, M., & Jousilahti, P. (2005). The effects of physical activity and body mass index on cardiovascular, cancer and all-cause mortality among 47 212 middle-aged Finnish men and women. International Journal of Obesity (2005), 29(8), 894–902.
Kokkinos, P., & Myers, J. (2010). Exercise and Physical Activity: Clinical Outcomes and Applications. Circulation, 122(16), 1637–1648.
Kokkinos, P., Sheriff, H., & Kheirbek, R. (2011). Physical Inactivity and Mortality Risk. Cardiology Research and Practice, 2011, 924945.
Lee, I.-M., Shiroma, E. J., Lobelo, F., Puska, P., Blair, S. N., & Katzmarzyk, P. T. (2012). Impact of Physical Inactivity on the World’s Major Non-Communicable Diseases. Lancet, 380(9838), 219–229.
Matheson, G. O., Klügl, M., Engebretsen, L., Bendiksen, F., Blair, S. N., Börjesson, M., … Ljungqvist, A. (2013). Prevention and management of non-communicable disease: the IOC consensus statement, Lausanne 2013. British Journal of Sports Medicine, 47(16), 1003–11.
National Health Service: http://www.nhs.uk/NHSEngland/thenhs/about/Pages/overview.aspx
Ruiz, J. R., Sui, X., Lobelo, F., Morrow, J. R., Jackson, A. W., Sjostrom, M., & Blair, S. N. (2008). Association between muscular strength and mortality in men: prospective cohort study. BMJ, 337(jul01 2), a439–a439.
World Health Organization: http://www.who.int/en/