Abstract
We investigated the associations of peak oxygen uptake (V̇O2peak), ventilatory threshold (VT), muscle strength, motor competence (MC), and adiposity with the indicators of PA intensity during different physical activities used to create absolute PA intensity cut-offs among 35 children 7–11-years-of-age. V̇O2peak was defined as the highest V̇O2 achieved in the maximal cardiopulmonary exercise test (CPET) on a cycle ergometer, self-paced running, or running on a treadmill at 8 km/h. VT was defined from the CPET data. Peak isometric knee extensor and flexor strength was assessed by a dynamometer, MC by the Körperkoordination test für Kinder tests, and body composition by the bioelectrical impedance analysis. PA intensity was assessed using V̇O2 as a % of V̇O2reserve or V̇O2 at VT, mean amplitude deviation (MAD) measured by accelerometry, metabolic equivalent of task (MET), and muscle activity measured by textile electromyography during walking or running on a treadmill at 4, 6, and 8 km/h, playing hopscotch, walking up and down the stairs, self-paced walking, and self-paced running. Children with lower V̇O2peak, V̇O2 at VT, and MC operated at higher intensity level during given physical task than their peers with higher fitness and MC when PA intensity was expressed using relative PA intensity using V̇O2 as a % of V̇O2reserve or V̇O2 at VT (p < 0.05). MAD and METs during different tasks were not able to discriminate PA intensity between children with varying levels of physical fitness or MC. Traditionally used absolute measures of PA intensity based on accelerometry or MET underestimated PA intensity in children with lower V̇O2peak, V̇O2 at VT, and MC.
Highlights
There are no previous studies investigating whether VO2peak, VO2 at ventilatory threshold (VT), motor competence (MC), muscle strength, and adiposity are associated with indicators of Physical activity (PA) intensity based on VȮ 2reserve or VȮ 2 at VT during different activities commonly used in accelerometry cut-off validation studies[5,21]
Differences in VO2 as a % of VO2reserve, VO2 as a % of VO2 at VT, mean amplitude deviation (MAD), and EMG among children divided to three equal size groups of VO2peak normalised for skeletal muscle mass (SMM), VO2 at VT normalised for SMM, MC, peak isometric strength normalised for SMM1.77, and adiposity were investigated using Kruskal–Wallis test
We found that children with lower VȮ 2peak and VȮ 2 at VT operated at higher intensity level during given physical activity than their peers with higher fitness
Summary
There are no previous studies investigating whether VO2peak, VO2 at VT, MC, muscle strength, and adiposity are associated with indicators of PA intensity based on VȮ 2reserve or VȮ 2 at VT during different activities commonly used in accelerometry cut-off validation studies[5,21]. We are not aware of previous studies in children investigating whether PA intensity assessed by accelerometry or METs during those activities can capture differences in physical fitness or adiposity.
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