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 .
Screen-Based Sedentary Behavior, Physical Activity, and Muscle Strength in the English Longitudinal Study of Ageing
Background Sarcopenia is associated with loss of independence and ill-health  in the elderly although the causes remain poorly understood . We examined the association between two screen-based leisure time sedentary activities ( daily TV viewing time and internet use ) and muscle strength . Methods and Results We studied 6228 men and women ( aged 64.9±9.1 yrs ) from wave 4 ( 2008 - 09 ) of the English Longitudinal Study of Ageing , a prospect i ve study of community dwelling older adults . Muscle strength was assessed by a h and grip test and the time required to complete five chair rises .  TV viewing and internet usage  were inversely associated with one another . Participants viewing TV ≥6hrs/d had lower grip strength ( Men , B = −1.20 kg , 95 % CI , −2.26 , −0.14 ; Women , −0.75 kg , 95 % CI , −1.48 , −0.03 ) in comparison to < 2hrs/d TV , after adjustment for age , physical activity , smoking , alcohol , chronic disease , disability , depressive symptoms , social status , and body mass index . In contrast , internet use was associated with higher grip strength ( Men , B = 2.43 kg , 95 % CI , 1.74 , 3.12 ; Women , 0.76 kg , 95 % CI , 0.32 , 1.20 ) . These associations persisted after mutual adjustment for both types of sedentary behaviour . Conclusions In older adults , the association between sedentary activities and physical function is context specific ( TV viewing vs. computer use ) . Adverse effects of TV viewing might reflect the prolonged sedentary nature of this behavior
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 .