Background: This investigation aimed to analyze the agreement between the GT3X accelerometer and the ActivPAL inclinometer for estimating and detecting changes in sedentary behavior of different contexts among adolescents. Methods: Secondary data from an intervention using standing desks in the classroom conducted within 2 sixth-grade classes (intervention [n = 22] and control [n = 27]) were used. The intervention took place over 16 weeks, with activity assessments (ActivPAL and GT3X) being performed 7 days before and in the last week of the intervention. Baseline information from both groups was considered for cross-sectional analysis (209 valid days), while data from 20 participants (intervention group) were used for longitudinal analysis. Results: The authors observed that GT3X overestimated sedentary time at school (16.8%), after school (13.5%), and during weekends (7.3%) compared with ActivPAL (P < .05). Outside the school (after school [r = −.188] and on weekends [r = −.260]), there was a trend to higher overestimation among adolescents with less sedentary behavior. Longitudinally, the GT3X was unable to detect changes resulting from an intervention in school hours (ActivPAL = −34.7 min·9 h−1 vs GT3X = +6.7 min·9 h−1; P < .05). Conclusions: The authors conclude that GT3X (cut-point of <100 counts·min−1) overestimated sedentary time of free-living activities and did not detect changes resulting from a classroom standing desk intervention in adolescents.
Danilo R. Silva, Cláudia S. Minderico, Pedro B. Júdice, André O. Werneck, David Ohara, Edilson S. Cyrino and Luís B. Sardinha
Xavier Melo, Helena Santa-Clara, Nuno M. Pimenta, Sandra Silva Martins, Cláudia S. Minderico, Bo Fernhall and Luís B. Sardinha
It is unclear how sedentary behavior (SED), physical activity (PA), and cardiorespiratory fitness (CRF) influence vascular structure in children of varying body size. This study examined whether associations between SED, PA, and CRF with intima-media thickness (IMT) added to that of abdominal fatness and IMT. Differences in physiological measures among waist circumference (WC) percentiles were tested.
We assessed IMT of the carotid artery in 265 children aged 11 to 13 years (135 girls). Measures included IMT assessed with high-resolution ultrasonography, WC, body fat mass (BFM) from DXA, and CRF determined using a maximal cycle test. SED and PA were assessed by accelerometry. Association between IMT and CRF adjusted for PA variables, and body composition phenotypes were tested with multiple linear regression analysis.
CRF was related to IMT independently of moderate to vigorous PA (MVPA) and SED (P < .05). When WC was added to the model CRF was no longer associated with IMT (P > .05). Children in the higher WC group had increased mean values of BMI, BFM, WC, and IMT and lower MVPA and CRF (P < .05).
Full modeling of SED, MVPA, CRF, and WC revealed that regional adiposity appears to have the biggest role in arterial structure of children.