Broadly measurement of sedentary behaviour is either carried out objectively by accelerometry or subjectively by self-report. Whether objectively or subjectively measured, the time frame of measurement of sedentary behaviour is defined by minutes, or hours, in a week, or day, or set period time. Papers may present data as an average or percentage and may provide total sedentary time or patterns of sedentary behaviour accumulation.
With subjective reports different domains of sedentary behaviour are considered. Study participants are often asked about total sitting time in the day, which may be the waking day, in 24hrours or between specific time frames. Alternatively, the participants may be asked about particular activities from which sedentary behaviour can be inferred by asking about the following:
- TV viewing
- Computer Use/Video Games
- Screen Time
- Telephone Use
- Sitting Socializing with Friends
- Listening to Music
The recall period across studies varies from considering the previous day to the last month, or people may be asked to consider a “typical” or “average” day. The information retrieval method of the questionnaires may be postal, telephone administered or face-to-face. Large scale surveys include questions about sedentary behaviour, such as: The Scottish Health Survey; The Australian Diabetes and Lifestyle Study; International Physical Activity Questionnaire (IPAQ short & long forms); Time Use Study; National Health and Nutrition Examination Survey; European Prospective Investigation into Cancer; Behavioral Risk Factor and many more! Sedentary behaviour questionnaire are also used in smaller scale trials.
Sedentary behaviour can also be objectively measured by use of activity monitors, such as, ActivCal & ActiGraph, where counts of <100/min are considered sedentary; or the ActivPAL which measures time by posture. The definition of what constitutes a “valid wear day” and how many valid days are required for inclusion in data sets changes from on study to the next. For example, to be included a study might require at least 4 days/7 day wear with a valid day being at least 10 hours of recording.
Activity monitor can be combined with other methods eg with interviews or body worn camera to help define the context of sedentary behaviour. This can be done with the participant or inferred in the absence of the participant. When this is done with the participant this proves to be a rich source of information on participants behavioral choices.