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Indexed/Abstracted in: Chemical Abstracts, CINAHL, Current Contents/Clinical Medicine, EMBASE, PubMed/MEDLINE, Science Citation Index Expanded (SciSearch), Scopus
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Asal MOGHADDASZADEH, Veronica JAMNIK, Angelo N. BELCASTRO
Pediatric Exercise Science Laboratory and Muscle Health Research Centre, School of Kinesiology and Health Science, Faculty of Health, York University, Toronto, ON, Canada
BACKGROUND: Emerging evidence suggests that oxygen consumption (VO2) for self-paced physical activity (PA) is underestimated when applying laboratory-based treadmill (TM)-derived regression equations. This study examines the accelerometer (ACC) characteristics for paced TM PA and self-paced children’s PA to ascertain if the predictable regulated patterns of paced PA are implicated in the inferior estimates of VO2.
METHODS: Children’s (9.3±1.2 yrs) (n=21) VO2 (portable oxygen analyzer) and PA (accelerometry) were measured for paced treadmill PA (4-10km/h). Active playing of children’s games in a camp setting was used for self-paced PA. Treadmill and self-paced PA were compared by linear regression and Bland-Altman analysis. Relative contribution of each axes (% axis difference) for paced and self-paced PA were assessed (n=21).
RESULTS: The VO2 responses during paced treadmill exercise was linear with accelerometer quantified PA (for vertical axis r=0.95±0.03 and for vector magnitude (VM) r=0.95±0.05) (p>0.05). During self-paced PA, the VO2 responses for ACC quantified PA were not linear (for vertical axis r=0.20±0.11 and for VM r=0.25±0.09) over the same range of ACC PA (0-1500 counts/10sec). VO2 estimates for self-paced PA (using TM-derived equations) were underestimated (p<0.05) across the range of intensities, which increased as the intensity of PA increased (> 6 METs). Comparing paced versus self-paced PA the % axis dominance (i.e., difference between the highest and lowest axis) contribution to PA was 41±14% for paced and 3±2% for self-paced PA (p<0.05).
CONCLUSIONS: This study reveals that the inferior estimates of VO2 for self-paced PA (using-derived linear equations) is attributable to the presence of a dominant axis with paced TM PA, which inflates the calculation of VM and the predicted VO2 for self-paced PA where no % axis difference exists.