Assessing SB as a sum of behaviours and using a previous day recall were the most promising features of existing tools .
Accuracy was poor for all existing tools , with underestimation and overestimation of SB .
There was a lack of evidence about sensitivity to change .
OBJECTIVE Sedentary behaviour ( SB ) has distinct deleterious health outcomes , yet there is no consensus on best practice for measurement .
This study aim ed to identify the optimal self-report tool for population surveillance of SB , using a systematic framework .
Validity and repeatability of the EPIC-Norfolk Physical Activity Questionnaire.
BACKGROUND Physical activity is an important lifestyle which is often poorly assessed in epidemiological studies . The European Prospect i ve Investigation into Cancer Study -Norfolk cohort ( EPIC-Norfolk ) , a large population -based cohort study , has developed a comprehensive question naire to assess activity in different domains of life aim ed at assessing total energy expenditure . We report the repeatability of this instrument and its validity against repeated objective measures of fitness and energy expenditure undertaken throughout the time frame of reference of the question naire . METHODS The validity of the instrument was measured in 173 individuals r and omly selected from a continuing population -based cohort study .  Energy expenditure was assessed by four separate episodes of 4-day heart-rate monitoring , a method previously vali date d against whole body calorimetry and doubly-labelled water . Cardio-respiratory fitness was assessed by four repeated measures of sub-maximum oxygen uptake . At the end of the 12-month period , participants completed the physical activity question naire that assesses past-year activity at home , work and in recreation . Repeatability was assessed in a separate group of 399 r and omly selected participants in EPIC who completed the physical activity question naire twice with a 3-month interval . RESULTS The age- and sex-adjusted correlation between the objective measure of daytime energy expenditure and the sum of recreational and occupational reported physical activity ( in MET h per week ) was 0.28 ( P < 0.001 ) . The reported time spent in vigorous activity was correlated with cardio-respiratory fitness ( 0.16 , P < 0.05 ) and with the proportion of time when energy expenditure was more than five times basal ( 0.17 , P < 0.05 ) . The repeatability of the sum of recreational and occupational reported activity was high , r = 0.73 . CONCLUSIONS The indices of physical activity derived from this question naire have levels of validity and repeatability comparable to other physical activity instruments that are used in large epidemiological studies and which have undergone such intense development and testing
Assessing SB as a sum of behaviours and using a previous day recall were the most promising features of existing tools .
Accuracy was poor for all existing tools , with underestimation and overestimation of SB .
There was a lack of evidence about sensitivity to change .
OBJECTIVE Sedentary behaviour ( SB ) has distinct deleterious health outcomes , yet there is no consensus on best practice for measurement .
This study aim ed to identify the optimal self-report tool for population surveillance of SB , using a systematic framework .