The present study found fair and significant validity coefficients between pedometer-determined steps counts and total time spent on activity based on ATLS physical activity questionnaire. The associations were higher with ambulatory activities such as walking, jogging and running compared to non-ambulatory activities such as bicycling, martial arts, weight training and some household activities. Gender differences did not greatly affect the strength of relationship between steps counts and total time spent in physical activity. The pedometer that was utilized as a convergent measure in the current study has been extensively used in previous reports and showed a fair validity and a high reliability [19
The strength of the association observed in the present validity study is similar to the upper range of correlations that have been previously shown between self-reported physical activity questionnaires and objectively assessed activity levels in adult population [23
]. In another review paper [19
], the median correlation of pedometer counts with self-reported physical activity questionnaire was shown to be 0.33; a value that is very close in magnitude to what has been found in the present study. A similar correlation (r = 0.33–0.35) was also found between Bouchard Activity Diary and ActiGraph activity monitor in Spanish adolescents [24
]. Another validity study on Vietnamese adolescents reported an acceptable coefficient (r = 0.27) when comparing physical activity questionnaire with accelerometer measurement [25
]. Lower validity coefficients (r = 0.17–0.30) were found for the modified version of International Physical Activity Questionnaire in European adolescents [26
], as well as for the activity questionnaire for adults and adolescents (AQuAA) from The Netherlands [27
]. A recent systematic review on the validity of physical activity questionnaires for young people in the European countries reported a fair validity for the majority of these instruments [28
]. However, a somewhat higher correlation (r = 0.45) between physical activity questionnaire for Swedish adolescents and accelerometer measurement was reported elsewhere [29
In the present study, the correlation between pedometer steps counts and ATLS questionnaire was higher for the time spent on vigorous-intensity physical activity compared to moderate-intensity activity. The higher correlations with activity such as jogging and running may have greatly contributed to the strength of the association. In addition, jogging and running involve frequent stepping, activity that pedometer is built to accurately capture and record. In addition, the planned nature of the vigorous physical activity perhaps makes them easier to be recalled. Our hypothesis that the relationships between pedometer counts and the activity questionnaire would be the highest in ambulatory activity and the lowest in the non-ambulatory activity was fulfilled. Pedometer usually records ambulatory activities and may not capture all other types of physical activity. It is also worth noting that in adult studies validity coefficient for household activities tended to be lower [30
], something that is similar to what has been found in the present study.
Based on the results of the pedometer step counts reported in the present study, it appears that a large proportion of the participants were generally not active enough. Only one third of the males and about 14% of the females had pedometer count above a cut score of 10,000 steps per day. A recent study using pedometer counts suggested a zone-based hierarchy for measurement and motivational purposes in adults. The suggested cut-off range for the low active category was 5,000–7,499 steps per day [31
]. Applying such cut-off scores to our data resulted in having more than half of the males and about three quarter of the females were being classified as insufficiently active. Moreover, studies have shown that boys report more moderate-to vigorous intensity physical activity than girls [32
]. In our questionnaire findings, males reported significantly more vigorous-, but not moderate-intensity physical activity compared to females. However, the intended purpose of present study was not to focus on the gender differences in physical activity prevalence.
Comparison made between questionnaires and objective measures of physical activity such as activity monitors may under predict the questionnaire capacity to provide an accurate estimate of total physical activity. Thus, a high correlation between the questionnaire result and the motion sensor outcome should not be expected, since both measures intend to assess differing components of the activity behavior [23
]. Finally, the assessment of physical activity by the questionnaire method, though has many advantages, suffers from several limitations that must be kept in mind. These limitations include the social desirability effect of the questionnaire and the recall bias. In addition, respondents may sometimes have difficulty understanding obscure terms such as physical activity, moderate-intensity and a like. We have validated ATLS questionnaire against electronic pedometer, and although pedometer is a reliable instrument and provides an objective estimate of the level of physical activity, it is of course not the gold standard criterion for assessing habitual physical activity [7
]. Thus, pedometer, in the present study, could have underestimated the actual physical activity levels of the participants. Pedometry is not sensitive to activities like swimming, bicycling, martial arts, weight training and most household activities. This was evident by the lower correlations of pedometer steps counts with time spent on these activities that were reported in our study. Furthermore, pedometer is not capable of assessing the intensity of physical activity, as the correlation of pedometer output did not improve much when the total physical activity was calculated as MET-min per week instead of only minutes per week. The current study examined the relationship between pedometer counts and questionnaire results using Person correlation, but no absolute agreement was provided between the two instruments. Moreover, in the present study, we only collected step counts for three week days. It would have been much better had we placed the pedometer on the participants for one week, so to include weekend days too. However, that would have required more time and a much larger number of pedometers than what we had.
We can conclude that the findings of the present study provide support for the validity of the ATLS questionnaire as an instrument for the assessment of habitual physical activity among Arab adolescents with varying body mass index and irrespective of gender type. The ATLS physical activity questionnaire was designed to collect complete information on frequency, duration and intensity of light-, moderate- and vigorous-intensity physical activities, which makes it a robust instrument for capturing all youth physical activities related to transport, household, fitness and sports domains.