Individual Physical Activity



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f The original depiction of this relationship is in a book edited by Dr. Tom Rowland (Rowland TW. Aerobic fitness. In T. W. Rowland, ed. Developmental Exercise Physiology. 2nd edition. Champaign, IL: Human Kinetics, 2005. P. 89-108.). The concepts have been adapted and used in different ways in this Guide to characterize the relationships among the measures and the distinctions among the three main classes of assessments.

g Figure 5B has been developed by David Berrigan and Richard Troiano for the purposes of this User Guide.

h Records or logs of physical activity can sometimes include diaries depending on the definition but are often placed into a separate category of self-reports ( just as we did in this Guide). These include recording the frequency and/or duration of activities as they occur and providing comprehensive characterization of physical activity patterns. However, these are likely the least feasible method within self-reports as they place a great burden on individuals being assessed.

i Quantitative histories are typically long questionnaires (e.g., 50 items) that are designed to assess lifetime or long-term (e.g., over the previous year) physical activity patterns. These can provide a comprehensive characterization of physical activity and capture important dimensions such as duration and frequency. However, they are likely to have a considerable amount of error when compared to other categories of self- reports.

j These are very brief questionnaires (typically composed by a single item) that are designed to assess general physical activity levels and are often used to determine whether individuals meet or not a specific physical activity threshold, such as recommended guidelines. These types of self-reports provide limited characterization of physical activity levels as they do not ask about type, context, or patterns of physical activity.

k The majority of work on accelerometry-based monitors has been conducted using waist/hip worn devices. However, investigators have moved toward using wrist-worn monitors. This transition has been fueled by the progression in consumer-based monitors as well as by evidence that compliance is enhanced when participants are asked to wear monitors on the wrist (more like a watch).

l New pattern recognition approaches have shown promise in detecting underlying movement patterns and classifying type of activities performed, but accurate detection of the diverse range of activities performed under free-living conditions remains elusive.

m Calibration equations are generally based on the assumption that heart rate is linearly related to energy expenditure. This assumption is particularly true for moderate- to vigorous-intensity activities. However, the assumption might not hold across sedentary and light-intensity activities.

n The portable systems use the same principles as metabolic carts but require participants to wear a backpack-type harness that holds two light-weight sensors (O2 and CO2) and transmission modules secured to the body that enable estimates of oxygen consumption and carbon dioxide production to be sent to and displayed on a laptop computer.

o Ecological momentary assessment techniques provide a way to capture context of behavior. Using text messages and smartphone prompts, it is possible to capture information about the type, intensity, purpose, or setting of activity. Ecological momentary assessment offers many advantages for physical activity research but it has a number of logistical and assessment challenges. (See references 69-71).