How often do you exercise weekly, and how long are your sessions? And how intense are these activities? If you’re wondering this, you’re not alone. Many of us are not sure whether we get enough exercise in our daily lives. To properly assess and measure your physical activity, it’s important to know the components that make up any type of activity: frequency, duration, and intensity. With this knowledge, it will be easier to be aware of when you are physically active, how often, and for how long, and thus keep track of your current physical activity.
Frequency
Frequency refers to the number of physical activity units per week for the same type of activity. Exercise units of the same activity type (e.g., activities that stress the cardiovascular system) can be added together. The goal is to add up activities that act on the same system and cause the same changes in the body to adapt to a particular load. This includes, for example, increased oxygen uptake and better blood flow to the heart during endurance training or the build-up of muscle mass during strength training.The following examples of activities or exercise units and the systems they affect can help classify them:
- Endurance-oriented movements such as running, jogging, and cycling affect the cardiovascular system.
- Muscle-strengthening movements such as weight training or weight lifting affect the musculoskeletal system.
- Exercises promoting flexibility, such as yoga or Pilates, work on the musculoskeletal system and flexibility.
- Activities such as swimming, water aerobics, dancing, aerobics, and Zumba work on the whole body.
It’s important to note that most activities don’t just affect one specific system but can affect different systems simultaneously. For example, running can work both the cardiovascular and musculoskeletal systems. For instance, if you go cycling twice a week and do yoga once a week, you complete a total of two units of endurance-oriented exercise and one unit of flexibility training (= weekly volume).
Duration
The duration of a physical activity is determined by the time of exertion for a single activity. This can be expressed in:
- Hours, minutes, or seconds (e.g., 30 minutes of cycling)
- Meters (e.g., 400 meters of jogging)
- Number of repetitions (e.g., 12 knee bends)
Advice: To gain a better overview of the duration of activities over the course of a week, it is recommended to record the units in meters or repetition count and then convert them into an approximate time (in hours, minutes, or seconds). For example, if you jog a total of 2000 meters, you could also record the time it takes (e.g., 12 minutes).
Intensity
The intensity of physical activity refers to the level of effort required to perform a particular exercise. This level of effort is measured in metabolic equivalent tasks (METs). This intensity measure compares oxygen uptake at rest with oxygen uptake during exercise. One MET corresponds to a turnover of:
- 3.5 milliliters (ml) of oxygen per kilogram of body weight (kg) per minute (min) for men
- 3.15 ml of oxygen per kilogram per minute for women
The metabolic equivalent indicates the power (= calorie consumption) of activities as a multiple of the resting metabolic rate. One MET corresponds to the physical energy turnover of about one kilocalorie (kcal) per kilogram of body weight per hour at rest. Physical activities are divided into moderate and higher intensity:
- In moderate intensity activities, people can still talk while moving. Examples include brisk walking, gardening, hiking, Nordic walking, or dancing. These activities are described as having 3 to 5.9 METs.
- Activities of higher intensity include running, cross-country skiing, bicycling, hiking, or cardiovascular exercise, during which only short exchanges of words are possible. They are described as having 6 METs or higher.
Since resting metabolic rate varies from person to person, the MET value also varies depending on the individual. For example, if a person walks for one hour (which is equivalent to 3 METs), they will burn 3 kcal multiplied by 70 (kg). So at the end of this walk, the person will have burned a total of 210 kcal.
Note: What really matters for your health is the total amount of energy you burn through exercise. Therefore, even low-intensity exercise can be very beneficial as long as it is done frequently and over a long period.
Here, you learned about the different components of physical activity. Why don’t you take a rough estimate of how often, for how long, and at what intensity you’re physically active, and compare those figures with the physical activity guidelines for your age group!
You can find further information on this topic here:
Ainsworth, B. E., Haskell, W. L., Herrmann, S. D., Meckes, N., Bassett, D. R., Jr., Tudor-Locke, C., Greer, J. L., Vezina, J., Whitt-Glover, M. C., & Leon, A. S. (2011). Compendium of Physical Activities: A second update of codes and MET values. Medicine & Science in Sports & Exercise, 43(8), 1575–1581. https://doi.org/10.1249/MSS.0b013e31821ece12
Barisic, A., Leatherdale, S. T., & Kreiger, N. (2011). Importance of frequency, intensity, time and type (FITT) in physical activity assessment for epidemiological research. Canadian Journal of Public Health, 102(3), 174–175. https://doi.org/10.1007/BF03404889
Deutsche Gesellschaft für Sportmedizin und Prävention e. V. (n. d.). Trainingsempfehlungen mit dem Rezept für Bewegung. https://www.dgsp.de/seite/389565/trainingsempfehlungen-mit-dem-rezept-für-bewegung.html
Kozey, S. L., Lyden, K., Howe, C. A., Staudenmayer, J. W., & Freedson, P. S. (2010). Accelerometer output and MET values of common physical activities. Medicine & Science in Sports & Exercise, 42(9), 1776–1784. https://doi.org/10.1249/MSS.0b013e3181d479f2