Despite very low levels of physical activity in this population of young women, the total EE from the ST and LT questionnaires correlated reasonably well with the Caltrac confirming that the questionnaires can assess physical activity levels in even a sedentary urban population. The MOSPA questionnaire is easy to administer and gives a valid measure of activity levels overall, however, questionnaire items to detect work related activities overestimated activity and some low EE activities by women such as caring for self and others are not picked up by the questionnaire.
The absolute EE values, using both the questionnaires as well as the Caltrac, were very low. This is similar to levels of physical activity in Filipino youth where the mean EE as measured by the Caltrac was 271 kcal ± 105.4 kcal/day [16
]. In a cross sectional survey conducted in urban India, 49.5% of the population did not engage in any leisure time physical activity as assessed by an interview and another 5.7% performed physical activity irregularly, indicating that the level of leisure time related physical activity is very low in urban, populations in the region [17
]. Leisure activity represented a small portion of the activity in our sample as well.
Certain limitations to our validation study need to be recognized. The women studied were on average 16 weeks pregnant which may limit the ability to generalize these results. However, the ST questionnaire reflects their actual activities at the time of the Caltrac measure and the LT questionnaire reflected their usual activities in the last year.
The mean EE, based on LT and ST questionnaires is higher than that from the Caltrac accelerometer; several studies have reported similar findings when using Caltrac accelerometers [8
]. This may be because uni-axial Caltrac cannot measure movement in the horizontal plane or because of overestimation of activity on the questionnaire by the subject or the assumptions of the MET scores used to assess total EE. This overestimation seems to be pronounced for the work related activities in this questionnaire.
In the only other study to date validating the MOSPA questionnaire, the criterion measures used were BMI, body composition, and peak oxygen uptake values on an exercise test [18
]. The subjects of their study were physical activity instructors or former athletes. A positive correlation of r = 0.53 was observed between the questionnaire and lean body mass. In contrast, our study indicated there were no significant correlations between LT and body composition measures. We speculate that the reason for this lack of correlation is that our study population, as a whole, was not active enough to develop differences in body composition related to activity. Another reason could be an alteration in body composition due to pregnancy but this is unlikely to be substantial given their early stage in pregnancy. The lack of association with biological parameters in our study is unlikely due to a lack of statistical power as our sample size offered power of 0.80 to detect a significant correlation of r = 0.38 as statistically significant.
In a study examining the construct validity of a physical activity questionnaire in the Netherlands, work related activities, sports activities and leisure time activities (other than sports) were the three loading factors for habitual physical activity assessment [19
]. In contrast, studies done in South East Asia suggest that often the major contributor to EE are everyday tasks and walking to work/school rather than the leisure time activity, observed in the West [16
]. Our study also confirms this finding, as there was a 30% difference based on the Caltrac values between those working outside the home vs. not employed, but the values for EE were low in both groups. One of the probable reasons the questionnaire EE under reported activity for women involved in household work is its inability to assess particular elements such as care giving activities for the elderly and/or child care. Similar findings have also been reported in a Canadian Aboriginal population study where housework was the principal physical activity reported [20
In a review of seven different types of self-reported activity measures used in industrialized countries, it was observed that questionnaires that recalled activity for a shorter duration, such as past week, had validity correlations of 0.5 with Caltrac accelerometers compared to correlations ranging between 0.14 and 0.36 for longer term, physical activity questionnaires [8
]. Although our findings follow the same pattern, the correlations found among our sample of Pakistani women were higher than the correlations reported in the literature on adult participants. Although the correlation of the ST physical activity questionnaire is higher than the LT questionnaire, we do not suggest the use of the ST questionnaire to measure physical activity because of a lack of consistency in activity over weeks, variations due to seasonality, acute illness or other reasons for variability over time as have been reported by others [21
Comparing our findings to other reports of physical activity questionnaires which were validated using accelerometers in developing countries, we found similar correlations. The IPAQ [10
] conducted in 14 countries including 2 developing countries, South Africa and Guatemala reported correlations of 0.46 and 0.61 respectively in these two countries for their urban population and these were far higher correlations than in the industrialized nations participating in the study. Similarly in a validation study in sub-Saharan Africa [9
] correlations of 0.60 and 0.74 for females and males respectively were observed in a very active population.
The last item in the MOSPA LT questionnaire is a global question asking subjects to categorize themselves into 4 categories. We feel that the subjects are quite cognizant of their generally low levels of physical activity as they accurately classified themselves as being sedentary. The difference in Caltrac values between the two lowest levels of activity was significant. Such self-reporting scales are not, however, always successful.
We have shown that overall EE levels related to physical activity are very low in our study population which could be a significant predictor of rising chronic disease prevalence in the region. We have demonstrated that MOSPA physical activity questionnaire is able to assess physical activity levels adequately in a sedentary population. As the questionnaire tends to overestimate activity related to work, and not capture some household movement, some refinements in this assessment measure may enhance the precision of the questionnaire.