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COMPARISON OF SELF-REPORTED PHYSICAL ACTIVITY WITH OBJECTIVELY MEASURED PHYSICAL ACTIVITY IN UNDERGRADUATE STUDENTS

Abstract

The short-form of the International Physical Activity Questionnaire (IPAQ) is widely used to assess physical activity (PA), however, research suggests the validity of this instrument is inconsistent across studies. PURPOSE: To investigate differences between estimates of sedentary behavior and PA from the IPAQ and accelerometry in undergraduate students. METHODS: 56 students (mean ± SD: age 20.6 ± 1.4 y; BMI 24.4 ± 3.6 kg/m2; and VO2peak 45.7 ± 7.7 mL/kg/min) participated in the study. Step counts and time spent in sedentary behavior, light, moderate, and vigorous PA were measured by an Actigraph GT3X+ for 7 days during waking hours. Following accelerometer wear, students self-reported their time spent sitting and in PA with the IPAQ. Partial correlations were used to assess associations among time spent sitting and in PA between the IPAQ and accelerometer while controlling for age, sex, and accelerometer wear time. The agreement between methods was assessed via Bland-Altman plots using 95% limits of agreement. The ability of the IPAQ to correctly classify students as meeting the PA guidelines was analyzed with McNemar’s test. RESULTS: IPAQ sitting time was associated with accelerometer sedentary time (r=0.38, p<0.01). IPAQ walking time was associated with accelerometer light PA (r=0.33, p=0.02) but not step counts (r=0.20, p=0.16). Although IPAQ moderate (r=0.34, p=0.02) and vigorous PA (r=0.47, p<0.01) were associated with accelerometer values, minutes spent in moderate-to-vigorous PA were underestimated by the IPAQ (409.1 ± 50.1 vs. 520.4 ± 29.6 min/week, respectively). Bland-Altman plots revealed acceptable agreement between methods. However, bias was evident for all PA intensities, with students tending to under-report moderate and over-report vigorous PA. Proportional bias existed for vigorous PA, indicating as the amount of vigorous PA increased, so did the error between methods. The IPAQ indicated that 71% of participants met PA guidelines compared with 55% for the accelerometer (p=0.09). CONCLUSION: Researchers should exercise caution when interpreting PA assessed via the IPAQ in undergraduate students. Although correlations appear acceptable, large amounts of bias may be present. However, The IPAQ may be a viable tool for assessing whether students meet current PA guidelines.

Funded by CTR-IN NIH NIGMS #1U54GM104944-01A1

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