Practical considerations

The effort of physical activity diaries and logs limit the length of time they can be used. They are typically undertaken between 1 and 7 days. This short time frame may have implications for systematic and random variation in physical activity. If the objective of the assessment is to measure habitual activity a longer time frame is needed. It has been suggested that 1.8 to 2.0 weeks of diaries are required to attain a reliability of 0.8 (Baranowski and de Moor, 2000) but this length of time is too long to be feasible. Researchers should think about possible differences between weekdays and weekend activity in their population when deciding how many and which days to assess.

To enhance compliance contacting individuals (e.g. phone, email, SMS) throughout the measurement period may be helpful.
If using a pre-defined list of activities ensure the activities are appropriate to the population being studied.
Clear instructions (ideally face-to-face) must be provided on this method, particularly if prospective recording of activity is required. The diary or log should be well formatted and easy to complete. Think about the best size if this has to be carried around during the day.
Research assistants who will be assigning MET values to diary data should be trained and assessed first to ensure inter-rater agreement and high objectivity. If strict protocols are followed the need for double entry of data may be obviated (Masse et al, 2002).