It is generally accepted that being physically active has many health benefits. The WHO issued recommendations for various age groups in 2010, based on scientific evidence on health benefits. How active people are, can be measured in various ways such as questionnaires or accelerometry. Activities can be classified by their intensity using MET (Metabolic Equivalent of Task)-values as a reference.

About physical activity 

Physical activity generally refers to all energy expended by movement. Major contributors are everyday activities such as walking, cycling, housework and shopping. Exercise, on the other hand, is a planned attempt to improve fitness and/or health such as active hobbies and sports.

Physical activity can be classified to be of moderate or vigorous intensity. Moderate intensity refers to activities performed at 3.0–5.9 times the intensity of rest, vigorous intensity to 6.0 or more (see table 1 for examples).1 Aerobic activity or endurance activity includes those activities that improve cardio respiratory fitness such as running, jumping rope and swimming.2

Table 1: Examples of moderate and vigorous physical activity1

Moderate–intensity

Physical Activity

(Approximately 3-6 METs)

Requires a moderate amount of effort and noticeably accelerates the heart rate.

Vigorous–intensity

Physical Activity

(Approximately >6 METs)

Requires a large amount of effort and causes rapid breathing and a substantial increase in heart rate.

Examples of moderate-intensity exercise include:

  • Brisk walking
  • Dancing
  • Gardening
  • Housework and domestic chores
  • Traditional hunting and gathering
  • Active involvement in games and sports with children / walking domestic animals
  • General building tasks (e.g. roofing, thatching, painting)
  • Carrying / moving moderate loads (<20 kg)
Examples of vigorous-intensity exercise include:

  • Running
  • Walking / climbing briskly up a hill
  • Fast cycling
  • Aerobics
  • Fast swimming
  • Competitive sports and games (e.g. traditional games, football, volleyball, hockey, basketball)
  • Heavy shoveling or digging ditches
  • Carrying / moving heavy loads (>20 kg)

Recommendations

In 2010, the WHO issued recommendations for physical activity for different age groups (table 2), based on scientific evidence on health benefits.3  While this recommendation covers the majority of people, various groups are not yet included such as children under 5 years, pregnant women and people with disabilities. Also the amount physical activity needed for weight loss or weight management and treatment of chronic diseases is still to be explored. An emerging topic of interest is the extent to which sedentary behavior contributes to disease risk profile.3

A study assessing physical activity levels in 122 countries found that globally, about one-third of adults are physically inactive. Inactivity levels were higher in high-income countries, with proportions ranging from 17% in southeast Asia to about 43% in the Americas and the eastern Mediterranean. Four-fifths of adolescents did not reach public health guidelines for recommended levels of physical activity.4

Table 2: WHO-recommendations for physical activity3

Age (years) Minutes Intensity physical activity
5-17 ≥ 60 per day moderate to vigorous
18-64 ≥ 150 or
≥ 75 or
an equivalent combination andon 2 or more days
moderate (aerobic)

vigorous

moderate and vigorous

muscle-strengthening activities

≥ 65* ≥ 150 or
≥ 75 or
an equivalent combination andon 2 or more days
moderate (aerobic)

vigorous

moderate and vigorous

muscle-strengthening activities

* Adults with poor mobility should perform physical activity to enhance balance and prevent falls on 3 or more days per week. Furthermore, when they cannot do the recommended amounts of physical activity due to health conditions, they should be as physically active as their abilities and conditions allow.

Measuring physical activity

In large surveys, physical activity is usually assessed by self-reporting through questionnaires or diaries. Recently, objective assessment of movement through accelerometry has been used in larger nationally representative samples in the USA and UK.2  Other methods include pedometry, heart rate monitoring, observation, or measuring energy expenditure through the doubly labeled water method or indirect calorimetry. The choice of method to measure physical activity depends on the research question.5  The doubly labeled water method is considered the gold standard.6

Different activities are being classified by their intensity by using the Metabolic Equivalent of Task (MET) as a reference. One MET is the rate of energy expenditure while sitting at rest, reflecting an oxygen uptake of 3.5 milliliters per kilogram of body weight per minute. To quantify the energy cost of a wide variety of activities and to enhance the comparability of results across studies, the Compendium of Physical Activities (2011) provides 821 codes for specific activities and their MET values.7

The WHO’s stepwise approach to chronic disease risk factor surveillance provides a good framework and practical ways to initiate physical activity surveillance, particularly in countries of low and middle income.4

References

  1. World Health Organization. Global Strategy on Diet, Physical Activity and Health. 2014 [cited 2014 June 6]; Available from: http://www.who.int/.
  2. ILSI Europe, Healthy Lifestyles: Diet, Physical Activity and Health. . ILSI Europe Concise Monograph, 2012: p. 1-52.
  3. World Health Organization, Global recommendations on physical activity for health. 2010.
  4. P.C. Hallal et al., Global physical activity levels: Surveillance progress, pitfalls and prospects. Lancet, 2012. 380: p. 247-257.
  5. Medical Research Council. Physical activity assessment – Methods. 2014 [cited 2014 16 May]; Available from: http://dapa-toolkit.mrc.ac.uk/.
  6. P.C. Hallal PC et al., Energy Expenditure Compared to Physical Activity Measured by Accelerometry and Self-Report in Adolescents: A Validation Study PlosOne, 2013. 8(11): p. e77036.
  7. B.E. Ainsworth et al., Compendium of Physical Activities: a second update of codes and MET values. Med Sci Sports Exerc, 2011. 3(8): p. 1575-81.