We investigated the ability of energy expenditure, movement sensing, and muscle activity to discriminate sedentary and non-sedentary activities in children. Thirty-five 7–11-year-old children participated in the study. Simultaneous assessment of oxygen uptake (V̇O 2 ), triaxial accelerometry, and thigh muscle electromyography (EMG) were performed during eight different sedentary and non-sedentary activities including lying down, sitting-, standing-, and walking-related activities, which were performed in a random order. Mean values of V̇O 2 , accelerometry, and EMG from the concurrent 2 min epochs during each activity were computed. Resting energy expenditure (REE) was measured during 30 min supine rest. Directly measured metabolic equivalent of tasks (METs, V̇O 2 in activities/V̇O 2 in REE) were calculated for each activity. Mean amplitude deviation (MAD) was computed for accelerometry. EMG was normalized for mean muscle activity during self-paced walking. The classification accuracy of METs, MAD, and EMG to discriminate sedentary activities from physical activities was investigated by receiver operating characteristic curves and optimal cut-offs based on maximal sensitivity and specificity. Mean (SD) REE was 5.0 ± 0.8 ml/kg/min. MET, MAD, and EMG values ranged from 1.0 to 4.9, 0.0020 to 0.4146 g, and 4.3 to 133.9% during lying down and walking at 6 km/h, respectively. Optimal cut-offs to discriminate sedentary activities from non-sedentary activities were 1.3 for METs (sensitivity = 82%, specificity = 88%), 0.0033 g for MAD (sensitivity = 80%, specificity = 91%), and 11.9% for EMG (sensitivity = 79%, specificity = 92%). In conclusion, this study provides applicable thresholds to differentiate sitting and standing and sedentary and non-sedentary activities based on METs, MAD, and EMG in young children.

there are no practical and valid methods for the assessment of individualised physical activity (PA) intensity in observational studies. Therefore, we investigated the validity of commonly used metabolic equivalent of tasks (METs) and predetermined PA intensity classification methods against individualised PA intensity classification in 35 children 7-11-years-of-age. Then, we studied validity of mean amplitude deviation (MAD) measured by accelerometry during self-paced walking and running in assessment of individualised PA intensity. Individualised moderate PA (MPA) was defined as V̇o 2 ≥ 40% of V̇o 2reserve and V̇o 2 < ventilatory threshold (Vt) and vigorous pA (VpA) as V̇o 2 ≥ VT. We classified > 3-6 (or alternatively > 4-7) METs as MPA and > 6 (> 7) METs as VPA. Task intensities were classified according to previous calibration studies. MET-categories correctly identified 25.9-83.3% of light PA, 85.9-90.3% of MPA, and 56.7-82.2% of VPA. Task-specific categories correctly classified 53.7% of light PA, 90.6% of MPA, and 57.8% of VPA. MAD during self-paced walking discriminated MVPA from light PA (sensitivity = 67.4, specificity = 88.0) and MAD during self-paced running discriminated VPA from MPA (sensitivity = 78.8, specificity = 79.3). In conclusion, commonly used methods may misclassify PA intensity in children. MAD during self-paced running may provide a novel and practical method for determining individualised VpA intensity in children. Free-living physical activity (PA) has been inversely associated with cardiometabolic risk in children 1. Moreover, higher PA intensity may confer greater cardiometabolic health benefits than lower PA intensity 2-4. Therefore, accurate assessment of PA intensity is important for informing health-related PA recommendations and in research on dose-response relationships. Nowadays, volume and intensity of PA in observational studies are typically assessed using accelerometers 5,6. However, previous studies have used fixed acceleration magnitude cutoffs to define different PA intensities without accounting for individual variation in exercise capacity 6. The continuing use of fixed cutoffs may have obscured our understanding on the prevalence of children accumulating recommended 60 min of daily moderate-to-vigorous PA (MVPA) and the role of PA intensity in health outcomes among youth 7,8 .

We investigated direct and indirect cross-sectional associations of physical activity, fundamental motor skills, executive functions, and early numeracy in preschoolers. The participants were 214 preschoolers aged three to five years. Time spent in moderate and vigorous physical activity was measured by hip-worn accelerometers and fundamental motor skills using the tasks assessing locomotor, object control, and stability skills. Inhibition/switching and working memory/updating, as components of executive functions, were assessed by computerised tests and a standardised test was used to assess early numeracy. Path analyses were used to examine direct and indirect associations between the constructs. Our results showed that stability skills were indirectly positively associated with early numeracy through inhibition/switching (β = 0.07, p < 0.05, 95% CI [0.02, 0.14]) and locomotor skills through working memory/updating (β = 0.13, p = 0.001, 95% CI [0.06, 0.20]). Vigorous physical activity was positively associated with early numeracy through locomotor skills and working memory/updating (β = 0.04, p = 0.01, 95% CI [0.01, 0.07]) and negatively associated with early numeracy through inhibition/switching (β = −0.06, p < 0.05, 95% CI [−0.11, −0.02]). Highlights. Locomotor skills are positively associated with early numeracy through working memory/ updating. . Stability skills are positively associated with early numeracy through inhibition/switching. . Vigorous physical activity is indirectly associated with early numeracy: Positively through locomotor skills and working memory/updating and negatively through inhibition/switching.

Commercial indoor activity parks provide children with a variety of entertaining physical activities. This study examined whether visiting SuperPark affects total daily sitting and physical activity time. The participants (8 girls and 7 boys, aged 10.3 ± 1.9 years, height 144.5 ± 11.8 cm, body mass index (BMI) 19.3 ± 3.0 kg/m2) wore a thigh-worn accelerometer during a normal week and were provided free tickets to visit SuperPark on at least one day. On average, the children spent 3.3 ± 1.2 h in SuperPark. During the visits the children had 0.9 h less sitting (0.7 ± 0.3 h, p = 0.000) and 0.9 h more moderate-to-vigorous physical activity (MVPA; 1.4 ± 0.6 h, p = 0.002) as compared to the reference periods on days without a SuperPark visit (1.6 ± 0.3 h sitting and 0.5 ± 0.4 h MVPA). During the days when visiting SuperPark, sitting time decreased 1.0 h (5.8 ± 0.9 h, p = 0.008) and MVPA increased 0.8 h (3.0 ± 1.0 h, p = 0.017) as compared to the reference days (6.8 ± 1.1 h sitting and 2.2 ± 0.8 h MVPA). The effects were more pronounced during weekdays than weekends. The children spent more than three hours in SuperPark on one visit, of which almost a half was MVPA. During the whole day, one hour of sitting was replaced with MVPA, suggesting that visiting SuperPark has the potential to improve health. Whether children continue visiting SuperPark and gain health benefits merits investigation.