Measuring Physical Activity

1. Measuring Physical Activity

2. What we need to know… • Methods of measuring physical activity • Subjective measures • Objective measures

3. Why Measure Physical Activity? • Document the frequency and distribution of physical activity in defined population groups. • Monitor the achievement of physical activity guidelines and population trends • Study the relationship between physical activity and health conditions e.g. cardiovascular disease, diabetes etc • Determine the amount of physical activity required to influence specific health issues • Identify the biological, psychological and environmental factors that influence physical activity • Evaluate intervention programs

4. Subjective Measures • These measures rely on the person recalling the activity which they perform. • Recall instruments require the subjects to remember which physical activity they engaged in over a period of time e.g. day, week, month

5. Self Report Measures • Most common measure of physical activity • Self administered recalls • Diaries-excellent tool if participants follow instructions correctly • Questionnaires

6. Advantages • Can be administered quickly and easily for large groups • Cost-effective for large scale studies • Usually low participant burden • Easy to complete • Can provide detailed information i.e. how the subject was feeling, location, other participants.

7. Disadvantages • Not suitable for children under 10 and older adults due to cognitive limitations to recall • Reliability and subjects may over or under record their data to make them look like they are doing more or less of what the self-report is asking.

8. Objective Measures • Assessment using either direct observation or a device such as a pedometer, heart rate monitor etc. • Removes the disadvantages of subjective measures

9. Direct Observation • Watching peoples behaviours within specific settings, whilst recordings specific activities or intensity etc • Provides detailed, accurate information about several dimensions of physical activity • Time sampling technique involves documenting data for a set period of time e.g. 2 min followed by a 30 sec break • Most commonly used to assess children

10. Advantages • Can capture excellent quantitative and qualitative information • Allows for specific physical activity to be observed • Allows for the collection of contextual information (environmental situation) • Software programs are now available to simplify data collection • Useful in a variety of community and school based settings

11. Disadvantages • Difficult to use with large populations • Time consuming and labour intensive • Presence of observer may bias behaviour • Training is required for the observer

12. SOPLAY • System for Observing Play and Leisure Activity in Youth • Designed to assess the physical activity of groups of people • Can be used to assess the number of students and their physical activity levels during play and leisure activity levels during play and leisure activities in a specified activity area (target area)

13. Heart Rate Monitors • Records beats per minute (bpm) and has been used as an indirect measure of physical activity • Influences which can effect heart rate and limit the accuracy as a tool include: environmental conditions (temperature and humidity), hydration, emotional state, age, gender, body size and cardiorespiratory fitness level • Linear relationship between heart rate (HR) and oxygen consumption (VO2) as physical activity intensity increases

14. Advantages • Valid in laboratory and field based settings • Provides a good description of several dimensions of physical activity among adults • Quick and easy data collection

15. Disadvantages • Expensive for use with large numbers of participants • Some discomfort with wearing heart rate monitors for extended periods • Useful only for aerobic activities • Influenced by other factors e.g. stress, and fitness levels • Changes in heart rate lag behind changes in physical activity, which can underestimate children’s physical activity and mask the sporadic nature of their movements

16. Pedometers • Determine the number of steps a person takes, and the distance covered • Some models can estimate distance, energy expenditure, and total minutes moving • Worn on the hip and respond to vertical forces, with the impact of the foot strike • 10,000 steps per day is the recommended for health benefits

17. Advantages • Inexpensive • Small and lightweight • Easy to use with large groups • Useful in detecting change in daily average steps taken between pre and post tests, or to identify changes in rank among groups • Objective measurement of the most common physical activity behaviour (walking) • Appropriate for use in a range of settings (school, work and community) • Provide immediate feedback and have the potential to promote behaviour change

18. Accelerometers • Motion sensors, are small and lightweight devices, generally worn on the hip • Measure motion both in single or multiple planes outside of the ‘normal’ human motion (e.g. sitting in a moving car) electronically • Measure in real time, which allows each minute of monitoring to be sorted by intensity

19. Advantages • Small, lightweight and non invasive • Objective measure of body movement (acceleration) • Good alternative to self reporting activity by children • Can be used in laboratory or field settings • Assesses intensity, frequency and duration • Records in real time • Can store date for several weeks

20. Disadvantages • Expensive for large groups • Cannot be worn during aquatic based activities • Underestimates movement during bike riding, rollerblading, or activities which are predominately upper body