• What is assessed?
• How is the assessment conducted
• When is this method used?
• How are estimates of physical activity derived?
• Strengths and limitations
• Populations
• Further considerations
• Resources required
• Instrument library
• References

Direct observation provides detailed information about frequency, duration and intensity of bouts of activity occurring during the period of observation. This method exceeds most methods in its capacity to capture the type and context of physical activity, including components such as where and with whom it occurs. Direct observation can be tailored to fit the needs of the specific research question and in particular the behavioural and contextual variables of interest. The dimensions of physical activity assessed by direct observation are described in Table P.3.17.

Table P.3.17 The dimensions which can be assessed by direct observation.

Direct observation requires recording of the dimensions of physical activity by an (ideally independent) observer in real-time. Systems of direct observation vary by the characteristics set out below.

Time frame and setting

The time frame and setting of direct observation are constrained by the necessity for the observer to be present at the time of monitoring. This requirement means that this method is generally used in more controlled settings, such as schools or care homes, although some instruments are designed for coding activity in diverse settings.

It follows that observation periods are typically relatively short, as observation for long periods is burdensome for the participants and researcher alike, and could also be intrusive. Costs of data collection and analyses for long periods of observation must also be considered. Direct observation is therefore not typically suitable for recording total daily physical activity. Although individual observation periods may be of limited duration, it is possible to conduct multiple assessments in order to account for some of the intra-individual variation in behaviours and the effect of factors such as season, weather, and time of day.

These limitations mean that it is more suitable for research questions focusing on particular time periods and settings, for example, examining the number of minutes of MVPA recorded by school children during recess.

Observation sampling frequency

Sampling can be continuous or interval based:

1. Continuous sampling involves noting the start and end times of all behaviours during the specified period. This provides the most detailed information but is the most labour intensive and difficult system to implement, especially when multiple dimensions of behaviour are to be recorded.
2. Interval sampling involves periods of observation interspersed with time for noting information about the dimensions of interest. The two periods are normally of the same duration, e.g.5 seconds of observation followed by 5 seconds of recording.

Categorisation of behaviour

The dimensions of physical activity recorded by direct observation vary by system and should be selected to suit the requirements of the research question. Some instruments record intensity category (e.g. sedentary, light, moderate, vigorous), while others record aspects of posture (e.g. sitting, lying, standing) or type (e.g. walking, running) of activity. Some instruments are even more detailed, and many record aspects of the context in which activity occurs.

Electronic vs. paper-pencil

Typically an observer will watch the participant(s) using a specific observational system and record a rating of physical activity into a laptop computer or by pencil into a coding form. A number of systems are available and have been comprehensively reviewed (McKenzie, 2002; Oliver et al., 2007). Electronic systems allow more rapid entry through key strokes or mouse clicks, with time stamps added automatically. Key advantages of electronic direct observation include:

1. Immediate data entry, avoiding coding errors and missing data
2. Possibility of direct scoring, reporting and interpreting of results
3. Reduction of research time and cost
4. Codes for different observation instruments can be loaded on the same device
5. Automated time stamp and duration calculation

1. Direct observation has been used mainly in child populations and many of the instruments have been developed especially for this purpose
2. Direct observation can typically only measure physical activity in controlled environments such as school break times
3. Direct observation has also been used as a criterion method to assess physical activity; it is a strong method for assessing type
4. Since this method can effectively record context and type dimensions of activity, it is useful for research examining the psychosocial and physical environmental aspects of physical activity (Trost, 2007).

Physical activity estimates are dependent upon instrument used, but can include:

1. Duration and timing of physical activity occurring of different types (e.g. walking, running, jumping) or in different social contexts (e.g. by self, with others etc.)
2. Duration and timing of estimated intensity of physical activity, based on multiple indicators such as amount of movement, speed, breathlessness, sweating, facial expressions, etc.
3. Total physical activity energy expenditure

Interpretation of observational data is aided by additional information, such as:

1. Demographic data (e.g. age, sex)
2. Anthropometric data (e.g. body mass)
3. Energy cost tables by activity type (needed for energy expenditure calculations)

It is usual for MET values to be assigned based on the type and/or intensity data reported during observation. MET scores for each interval of observation can then be summed, either in total to provide total energy expenditure or grouped according to dimensions such as intensity category, type, or context to identify relative contributions. Since timing of activity is recorded, they can also be used to describe change in energy expenditure during the observation period. Research assistants who will be assigning MET values should be trained and assessed first to ensure inter-rater agreement and high objectivity.

This approach assumes the following:

1. MET values of activities do not vary within and between individuals, beyond that of the coding system
2. MET values recorded during direct observation in a subsample are generalisable to the sample of the current investigation; this is particularly important if using direct observation to calibrate body-worn devices that are then used during free-living

Considerable time and effort is required to conduct observation studies but advances in technology have increased the potential of this method to assess physical activity but mostly in controlled settings. An overview of the characteristics of direct observation is outlined in Table P.3.18.

Strengths

1. Observational procedures are flexible and allow researchers to record factors related to physical activity such as:
1. behavioural cues
2. environmental conditions
3. the presence of significant others
4. availability of toys and equipment (Trost, 2007)
2. Observation can be used as a process or an outcome measure, hence is valuable to researchers and those undertaking interventions or practitioners

Limitations

1. The method is highly burdensome for observers, is labour intensive and expensive
2. Observers must be well trained
3. The data coding is laborious if using paper and pen
4. Observation can only be undertaken in controlled settings and therefore can only measure physical activity in one domain at a time
5. The presence of an observer may lead to a reactivity effect leading to a change in usual behaviour. Repeated measures may reduce the potential effect of reactivity (Trost, 2007)

Table P.3.18 Characteristics of direct observation.

Considerations relating to the use of direct observation for assessing physical activity are summarised by population in Table P.3.19.

Table P.3.19 Physical activity assessment by direct observation in different populations.

Given the number of observational systems available, one of these should be used and adapted as required rather than a new one developed. Advances in technology have resulted in several bespoke software packages to collect, handle, analyse and present observational data. PDAs are particularly suited to field work and real time recording of physical activity. It is also possible to collect contextual data with these packages.

1. Highly trained observers
2. Observational system – software packages have largely reduced pen and paper methods
3. PDAs or laptops for use in the field

A list of specific direct observation instruments is being developed for this section. In the meantime, please refer to the overall instrument library page by clicking here to open in a new page.

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