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Au Bich Thuy, Leigh Blizzard, Michael Schmidt, Costan Magnussen, Emily Hansen and Terence Dwyer

Background:

Pedometer measurement of physical activity (PA) has been shown to be reliable and valid in industrialized populations, but its applicability in economically developing Vietnam remains untested. This study assessed the feasibility, stability and validity of pedometer estimates of PA in Vietnam.

Methods:

250 adults from a population-based survey were randomly selected to wear Yamax pedometers and record activities for 7 consecutive days. Stability and concurrent validity were assessed using intraclass correlation coefficients (ICC) and Spearman correlation coefficients.

Results:

Overall, 97.6% of participants provided at least 1 day of usable recordings, and 76.2% wore pedometers for all 7 days. Only 5.2% of the sample participants were involved in work activities not measurable by pedometer. The number of steps increased with hours of wear. There was no significant difference between weekday and weekend in number of steps, and at least 3 days of recordings were required (ICC of the 3 days of recordings: men 0.96, women 0.97). Steps per hour were moderately correlated (men r = .42, women r = .26) with record estimates of total PA.

Conclusions:

It is feasible to use pedometers to estimate PA in Vietnam. The measure should involve at least 3 days of recording irrespective of day of the week.

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Au Bich Thuy, Leigh Blizzard, Michael Schmidt, Pham Hung Luc, Costan Magnussen and Terence Dwyer

Background:

The Global Physical Activity Questionnaire (GPAQ) was developed as an improvement of the International Physical Activity Questionnaire (IPAQ) for use in cross-cultural settings. This study compared the reliability and validity of GPAQ and IPAQ in Vietnam.

Methods:

251 adults were randomly selected from a population-based survey (n = 1978) of noncommunicable disease risk factors. GPAQ and IPAQ were administered on 2 occasions. Participants wore pedometers and logged their physical activity (PA) for 7 consecutive days.

Results:

Test-retest correlations of GPAQ measurements differed for participants (n = 153) with stable work patterns (work PA r = .43, total PA r = .39) and those (n = 98) with unstable work patterns (work PA r = −0.02, total PA r = −0.05). IPAQ measurements did not differ in this way. GPAQ reliability was poorer for transport (GPAQ r = .25, IPAQ r = .60) and for leisure (GPAQ r = .21, IPAQ r = .45) PA. GPAQ estimates of total PA for participants with stable work patterns were moderately correlated with IPAQ total PA (r = .32), steps per day (r = .39), and PA log (r = .31).

Conclusions:

The modifications made when designing GPAQ improved its reliability for persons with stable work patterns, but at the expense of poorer reliability for persons with more variable PA. GPAQ did not have superior validity to IPAQ.

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Terence Dwyer, James F. Sallis, Leigh Blizzard, Ross Lazarus and Kimberlie Dean

The objective of this study was to examine the association of scholastic performance with physical activity and fitness of children. To do so, school ratings of scholastic ability on a five-point scale for a nationally representative sample of 7,961 Australian schoolchildren aged 7–15 years were compared with physical activity and fitness measurements. Consistently across age and sex groups, the ratings were significantly correlated with questionnaire measures of physical activity and with performance on the 1.6-kilometer run, sit-ups and push-ups challenges, 50-meter sprint, and standing long jump. There were no significant associations for physical work capacity at a heart rate of 170 (PWC170). The results are concordant with the hypothesis that physical activity enhances academic performance, but the cross-sectional nature of the observations limits causal inference, and the disparity for PWC170 gives reason to question whether the associations were due to measurement bias or residual confounding.