Design and evaluation of a computer-based 24-Hour physical activity recall (cpar24) instrument

Background: widespread access to the internet and an increasing number of internet users offers the opportunity of using web-based recalls to collect detailed physical activity data in epidemiologic studies. objective: the aim of this investigation was to evaluate the validity and reliability of a computer-based 24-hour physical activity recall (cpar24) instrument with respect to the recalled 24-h period. methods: a random sample of 67 german residents aged 22 to 70 years was instructed to wear an actigraph gt3x+ accelerometer for 3 days. accelerometer counts per min were used to classify activities as sedentary (<100 counts per min),light (100-1951 counts per min),and moderate to vigorous (≥1952 counts per min). on day 3,participants were also requested to specify the type,intensity,timing,and context of all activities performed during day 2 using the cpar24. using metabolic equivalent of task (met),the cpar24 activities were classified as sedentary (<1.5 met),light (1.5-2.9 met),and moderate to vigorous (≥3.0 met). the cpar24 was administered twice at a 3-h interval. the spearman correlation coefficient (r) was used as primary measure of concurrent validity and test-retest reliability. results: as compared with accelerometry,the cpar24 underestimated light activity by -123 min (median difference,p difference <.001) and overestimated moderate to vigorous activity by 89 min (p difference <.001). by comparison,time spent sedentary assessed by the 2 methods was similar (median difference=+7 min,p difference=.39). there was modest agreement between the cpar24 and accelerometry regarding sedentary (r=.54),light (r=.46),and moderate to vigorous (r=.50) activities. reliability analyses revealed modest to high intraclass correlation coefficients for sedentary (r=.75),light (r=.65),and moderate to vigorous (r=.92) activities and no statistically significant differences between replicate cpar24 measurements (median difference for sedentary activities=+10 min,for light activities=-5 min,for moderate to vigorous activities=0 min,all p difference ≥.60). conclusion: these data show that the cpar24 is a valid and reproducible web-based measure of physical activity in adults. © serials publications pvt. ltd.