Stacy A. Clemes and Stuart J.H. Biddle
Pedometers are increasingly being used to measure physical activity in children and adolescents. This review provides an overview of common measurement issues relating to their use.
Studies addressing the following measurement issues in children/adolescents (aged 3−18 years) were included: pedometer validity and reliability, monitoring period, wear time, reactivity, and data treatment and reporting. Pedometer surveillance studies in children/adolescents (aged: 4−18 years) were also included to enable common measurement protocols to be highlighted.
In children > 5 years, pedometers provide a valid and reliable, objective measure of ambulatory activity. Further evidence is required on pedometer validity in preschool children. Across all ages, optimal monitoring frames to detect habitual activity have yet to be determined; most surveillance studies use 7 days. It is recommended that standardized wear time criteria are established for different age groups, and that wear times are reported. As activity varies between weekdays and weekend days, researchers interested in habitual activity should include both types of day in surveillance studies. There is conflicting evidence on the presence of reactivity to pedometers.
Pedometers are a suitable tool to objectively assess ambulatory activity in children (> 5 years) and adolescents. This review provides recommendations to enhance the standardization of measurement protocols.
Stacy A. Clemes, Sarah L. Hamilton and Paula L. Griffiths
This study investigated whether pedometer-determined activity varies between summer and winter in normal-weight and overweight adults.
Forty-five normal-weight (58% female, age = 39.1 ± 12.4 years, BMI = 22.2 ± 2.1 kg/m2) and 51 overweight (49% female, age = 42.1 ± 12.5 years, BMI = 29.3 ± 4.5 kg/m2) participants completed a within-subject biseasonal pedometer study. All participants completed 2 4-week monitoring periods; 1 period in the summer and 1 period the following winter. Changes in step counts across seasons were calculated and compared for the 2 BMI groups.
Both BMI groups reported significant summer to winter reductions in step counts, with the magnitude of change being significantly greater in the normal-weight group (−1737 ± 2201 versus −781 ± 1673 steps/day, P = .02). Winter step counts did not differ significantly between the 2 groups (9250 ± 2845 versus 8974 ± 2709 steps/day, P = .63), whereas the normal-weight group reported a significantly higher mean daily step count in the summer (10986 ± 2858 versus 9755 ± 2874 steps/day, P = .04).
Both normal-weight and overweight individuals experienced a reduction in step counts between summer and winter; however, normal-weight individuals appear more susceptible to winter decreases in ambulatory activity, with the greatest seasonal change occurring on Sundays. Effective physical activity policies should be seasonally tailored to provide opportunities to encourage individuals to be more active during the winter, particularly on weekends.
Stacy A. Clemes, Beverley M. David, Yi Zhao, Xu Han and Wendy Brown
In light of evidence linking sedentary behaviors to health outcomes, there have been calls for the measurement of sedentary behavior in surveillance studies. This study examined the convergent validity of 2 self-report measures of sitting time and accelerometer-determined sedentary time (minutes/day of <100 counts/minute).
44 adults wore an ActiGraph accelerometer for 7 days, during which they also recorded daily sitting time in a diary, in response to a single-item question. After 7 days, participants completed a new domain-specific questionnaire to assess usual weekday and weekend-day sitting time. Total sitting times recorded from the self-report measures were compared with accelerometer-determined sedentary time.
Total sitting time calculated from the domain-specific questionnaire did not differ significantly from accelerometer-determined sedentary time on weekdays (mean difference [±SE] = –14 ± 28 mins/day) and weekend days (–4 ± 45 mins/day, both P > .05). Sitting time was significantly underestimated using the single-item specific-day question on weekdays (–173 ± 18 mins/day) and weekend days (–219 ± 23 mins/day, both P < .001).
When assessed via self-report, the estimation of total sitting time is improved by summing sitting times reported across different domains. The continued improvement of self-report measures of sitting time will be important if we are to further our understanding of the links between sedentary behavior and health.