Physical Activity and Outcome Measures

Introduction[edit | edit source]

Pedometer Omron

For clinical and research purposes, measuring physical activity is vital for studying and evaluating its health benefits. Being a variable with many dimensions (frequency, intensity, mode, duration, volume, context), there is no standardised outcome measure for physical activity, hence, the choice of assessment/proxy measure of physical activity is dependent on which dimension is being studied.

Measures[edit | edit source]

Physical activity can be measured across all age groups and health spectrum, with choice of tool dependent on the type of activity being examined:

  • Preschool children (2-5 years)
  • Children (6-12 years)
  • Adolescents (13-17 years)
  • Adults (18-64 years)
  • Older adults (65+)

Physical activity can be measured using different techniques[1] such as:

Method of measurement Unit of measurement
Self-report Bouts of physical actvity
Activity monitors/motion sensors Movement counts
Heart rate Beats per minute
Pedometers Step counts
Direct observation Activity rating
Indirect calorimetry Oxygen consumption
Doubly labelled water Carbon dioxide production

Self-report Techniques[edit | edit source]

The self-report approach to measuring physical activity is one that is commonly used because of its affordability, low respondent burden and ability to capture large population in a shorter time frame[2]. It relies on the ability of participants to recall their physical activity in retrospect, and can be documented by use of a questionnaire, either self-administered or interview-administered[3] or by daily logs and diaries[4].

Self-report physical activity instruments can be further classified into:

Physical Activity Records & Diaries[edit | edit source]

PA diary

While logs involve the participants documenting the amount of time spent in broad categories of activity (sitting, standing, walking), records/diary require the participant to record the individual sessions of activity as they occur prospectively[5]. Examples include: Physical activity log book[6] and Bouchard’s activity diary[7].

Global Self-report[edit | edit source]

When the objective of the researcher or clinician is to stratify an individual’s level of physical activity as either high or low using generic terms, self-report assessments are usually used[8]. This involves using an instrument that contains one to four items to identify the physical activity pattern of the individual, in a specific domain over a specific period of time[9]. eg Global physical activity questionnaire (GPAQ)

Recall Questionnaires[edit | edit source]

In surveillance studies, the physical activity patterns of participants are quantified using short and easy instruments that contain less than 15 items[3]. Data from these questions can further be described and individuals classified into broad categories.  

Quantitive History Questionnaire[edit | edit source]

When the objective of the researcher is to capture the physical activity patterns of participants over multiple domains, a more detailed approach of assessment such as the quantitative history questionnaire is used. This usually entails more questions over multiple segments designed to provide comprehensive information on the physical activity patterns over a period of time such as a day, week, month or year[6] [5].

Objective Monitors[edit | edit source]

Heart rate monitor

The use of monitoring devices such as accelerometers, pedometers and heart rate monitors in measuring physical activity have been made possible through recent advances in technology[10]. When worn, intensity of body acceleration is measured using an electronic component embedded within the device[11], which usually has the capacity to store and record these data over a period of time. See also Physical Activity and Technology

The different types of objective monitors are further discussed below:

Pedometers[edit | edit source]

Since walking has been shown to provide substantial health benefits[12] and is a known form of physical activity commonly employed by people, measuring walking-based activity is made possible by the use of pedometers which are usually worn on the waist, or the wrist, ankle, shoe, and counts the number of steps taken by the individual over a period of time.[13] A 2017 study found that accuracy of waist pedometers was higher than those worn on the wrist.[14] Pedometers are fairly inexpensive, but more advanced versions with added features may cost higher. Available types include Kenz Lifecorder, New-Lifestyles NL-2000 (piezoelectric), and Yamax Digi-Walkers SW-200 and SW-70.

Accelerometers[edit | edit source]

Accelerometers are often used in research to obtain more detailed information about physical activity and to help to address the limitations of self‐report methods.[15] Uniaxial and multi axial measurements across one to three orthogonal planes of movement can be obtained by the use of accelerometers[16][10], which is a more advanced and slightly more expensive electronic device than the pedometer[16] with an added advantage of being able to distinguish between walking and running by the wearer.[17] Information on the amount, frequency and duration of physical activity can be obtained with the aid of accelerometers. Accelerometers are portable, noninvasive and provide quality information on human movement[18]. Available types include GT3x Actigraph and Activpal monitor.

Heart Rate Monitor[edit | edit source]

Heart rate monitor

Heat rate monitors, usually worn on the chest or wrist, have an electrocardiogram (ECG) transmitter that sends signals to the receiver which calculates average heart rate within 5 to 15 seconds intervals and displays it as beats per minute[1]. Although more expensive than pedometers and accelerometers, data obtained from heart rate monitors can be transferred to a computer, are useful in calculating energy expenditure and physical activity for observational and intervention studies[19]. Available types include Fitbit Surge fitness superwatch, Timex personal trainer, Polar FT7, Garmin vivofit.  

Direct Observation[edit | edit source]

Obtaining accurate information on the frequency, duration, intensity and type of physical activity carried out by an individual is only possible through systematic observation[10]. In direct observation, the physical activity levels are assessed in specific settings[20] such as playground, classes etc. and can be done by a trained observer or videotaping[1]. Several instruments such as System for Observing Fitness Instruction Time (SOFIT), Fargo Activity Timesampling Survey (FATS) and Children’s Activity Rating Scale (CARS) have been specifically designed to capture different dimensions of interest depending on the behavioural category of interest[21]. The results obtained can be useful in assessing and designing intervention programs for a target group[22].

Evidence[edit | edit source]

Reliability[edit | edit source]

Self-report measure[23] ICC 0.67 (95% CI 0.54-0.77)

ICC 0.70 (95% CI 0.66-0.83)

ICC 0.52 (95% CI 0.33-0.66)

Accelerometry-based activity monitors[18] 0.62 – 0.80
Heart rate monitor[24] 0,993
Pedometer[25] ICC 0.71 (95% CI 0.47-0.86)

Validity[edit | edit source]

Self-report instruments[26] (0.50-0.60)
Accelerometry- based activity monitors[27] 0.9
Heart rate monitor[28] 0.81
Pedometer[29] 0.60

Responsiveness[edit | edit source]

The ability of physical activity outcome measures to respond to changes in physical activity intensity is important when selecting the appropriate tool for the intended objective. From several studies, accelerometers have been shown to have high responsiveness e.g. Actical (1.2-4.7) and Actigraph (1.1-3.3)[30].

References[edit | edit source]

  1. 1.0 1.1 1.2 Welk, G. J. (2002). Introduction to physical activity research. In G. J. Welk (Ed.), Physical Activity Assessments in Health Related Research (pp. 3–18). Champaign IL: Human Kinetics.
  2. Siegel, D. (2005). A Self-Report Measure of Physical Activity. Journal of Physical Education, Recreation & Dance (JOPERD), 76(7), 11.
  3. 3.0 3.1 Matthews, C. (2002). Use of self-report instruments to assess physical activity. In G. J. Welk (Ed.), Physical activity assessments for health-related research (2002nd ed., pp. 107–23). Champaign, IL: Human Kinetics.
  4. Sylvia, L. G., Bernstein, E. E., Hubbard, J. L., Keating, L., & Anderson, E. J. (2014). Practical guide to measuring physical activity. Journal of the Academy of Nutrition and Dietetics, 114(2), 199–208.
  5. 5.0 5.1 Strath, S. J., Kaminsky, L. A., Ainsworth, B. E., Ekelund, U., Freedson, P. S., Gary, R. A., Swartz, A. M. (2013). Guide to the assessment of physical activity: Clinical and research applications: A scientific statement from the American Heart association. Circulation, 128(20), 2259–2279
  6. 6.0 6.1 Ainsworth, B. E., Haskell, W. I. L., Whitt, M. C., Irwin, M. L., Swartz, A. M., Strath, S. J., Leon, A. S. (2000). Compendium of physical activities: an update of activity codes and MET intensities. Medicine and Science in Sports and Exercise, 32(9 Suppl), S498–S504
  7. Wickel, E. E., Welk, G. J., & Eisenmann, J. C. (2006). Concurrent validation of the Bouchard diary with an accelerometry-based monitor. Medicine and Science in Sports and Exercise, 38(2), 373–379
  8. Biddle, S. J. H., Gorely, T., Pearson, N., & Bull, F. C. (2011). An assessment of self-reported physical activity instruments in young people for population surveillance: Project ALPHA. The International Journal of Behavioral Nutrition and Physical Activity, 8(1), 1
  9. Steene-Johannessen, J., Anderssen, S. A., Van Der Ploeg, H. P., Hendriksen, I. J. M., Donnelly, A. E., Brage, S., & Ekelund, U. (2016). Are self-report measures able to define individuals as physically active or inactive? Medicine and Science in Sports and Exercise, 48(2)
  10. 10.0 10.1 10.2 Taylor, N. (2014). Available methods for measuring physical activity. In A. Clow & S. Edmunds (Eds.), Physical Activity and Mental Health (pp. 35–40). Champaign, IL: Human Kinetics.
  11. Graham, D. J., & Hipp, J. A. (2014). Emerging technologies to promote and evaluate physical activity: cutting-edge research and future directions. Frontiers in Public Health, 2, 66
  12. Lee, I. M., & Buchner, D. M. (2008). The importance of walking to public health. Medicine and Science in Sports and Exercise, 40(7 SUPPL.1), 512–518
  13. Bassett Jr, D., & Tudor-Locke, C. (2004). How many steps / day are enough ? Preliminary pedometer indices for public health . PubMed Commons. Sports Medicine, 34(1), 1–8
  14. Husted HM, Llewellyn TL. The Accuracy of Pedometers in Measuring Walking Steps on a Treadmill in College Students. Int J Exerc Sci. 2017;10(1):146-53.
  15. Arvidsson D, Fridolfsson J, Börjesson M. Measurement of physical activity in clinical practice using accelerometers. J Intern Med. 2019;286(2):137-53.
  16. 16.0 16.1 Corder, K., Brage, S., & Ekelund, U. (2007). Accelerometers and pedometers: methodology and clinical application. Current Opinion in Clinical Nutrition & Metabolic Care, 10(5), 597–60
  17. Physical Activity Resource Center for Public Health. Accelerometers. Available from: (last accessed 10 October 2022).
  18. 18.0 18.1 Welk, G. J. (2002b). Use of Accelerometry-Based Activity Monitors to Assess Physical Activity. In G. J. Welk (Ed.), Physical Activity Assessments in Health Related Research (pp. 125–140). Champaign, IL: Human Kinetics
  19. Janz, K. F. (2002). Use of Heart Rate Monitors to Assess Physical Activity. In G. J. Welk (Ed.), Physical Activity Assessments in Health Related Research (pp. 143–158). Champaign, IL: Human Kinetics
  20. Dugdill, L., & Stratton, G. (2007). Evaluating sport and physical activity interventions: A guide for practitioners. Salford University, 44(0), 9–10
  21. Mckenzie, T. L. (2002). Use of Direct Observation to Assess Physical Activity. In G. J. Welk (Ed.), Physical Activity Assessments in Health Related Research (pp. 179–191). Champaign, IL: Human Kinetics
  22. Bird, M. E., Datta, G. D., van Hulst, A., Kestens, Y., & Barnett, T. A. (2015). A reliability assessment of a direct-observation park evaluation tool: the Parks, activity and recreation among kids (PARK) tool. BMC Public Health, 15(1), 906
  23. Murphy, J. J., Murphy, M. H., MacDonncha, C., Murphy, N., Nevill, A. M., & Woods, C. B. (2017). Validity and Reliability of Three Self-Report Instruments for Assessing Attainment of Physical Activity Guidelines in University Students. Measurement in Physical Education and Exercise Science, 0(0), 1–8
  24. Brage, S., Brage, N., Franks, P. W., Ekelund, U., & Wareham, N. J. (2005). Reliability and validity of the combined heart rate and movement sensor Actiheart. European Journal of Clinical Nutrition, 59(4), 561–570
  25. Kooiman, T. J. M., Dontje, M. L., Sprenger, S. R., Krijnen, W. P., van der Schans, C. P., & de Groot, M. (2015). Reliability and validity of ten consumer activity trackers. BMC Sports Science, Medicine and Rehabilitation, 7, 24
  26. Sallis, J. F., & Saelens, B. E. (2000). Assessment of physical activity by self-report:  status, limitations, and future directions. Res Q Exercise Sport, 71(2), 1–14
  27. Leenders, N. Y. J. M., Nelson, T. E., & Sherman, W. M. (2003). Ability of different physical activity monitors to detect movement during treadmill walking. International Journal of Sports Medicine, 24(1), 43–50
  28. Barreira, T., Kang, M., & Caputo, J. (2009). Validation of the Actiheart monitor for the measurement of physical activity. International Journal of Exercise Science, 2, 60–71
  29. Jago, R., Watson, K., Baranowski, T., Zakeri, I., Yoo, S., Baranowski, J., & Conry, K. (2006). Pedometer reliability, validity and daily activity targets among 10- to 15-year-old boys. Journal of Sports Sciences, 24, 241–251
  30. Montoye, A. H., & Pfeiffer, K. A. (2014). Change in Physical Activity. Measurement in Physical Education and Exercise Science, 18(4), 273–285