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Accelerometry is frequently used to assess physical activity in children. The number of articles in this area has increased dramatically in the last 10 years. The aim of this article is to provide a contemporary overview of accelerometry research in children. Specifically, the review addresses the choice of monitor, choice of epoch, when and for how long activity should be measured, the lack of consensus over how to define a complete day of activity data, issues of compliance, methods for the calibration of activity output, and the richness of data available from accelerometry.

In this insightful article, Eisenmann and Wickel (6) bring together diverse areas of animal and human research to address the issue of the existence of an “activity stat,” or biological basis for activity, outlining the evidence accumulated in this area since Rowland’s excellent commentary in 1998 (10). As the authors state, there has been progress in this area over the last 10 years, however there are still a limited number of studies that specifically address the possible existence of an activity stat in children, whether the strength of this varies by age, sex or culture, the degree of influence of environmental and social factors on this set-point and therefore the crucial question—if activity level is under central control are activity interventions doomed to failure?

This study assessed the nature of the perceived exertion response to treadmill running in 14 healthy 7–8 year-old children, using the Eston-Parfitt (E-P) Ratings of Perceived Exertion (RPE) scale and a marble dropping task. For the E-P scale and the marble dropping task, the relationships between the RPE and work rate were best described as linear (R ² = .96) and curvilinear (R ² = .94), respectively. This study further suggests that individual respiratory-metabolic cues (oxygen uptake: O₂, heart rate: HR, ventilation: V̇_E) may significantly influence the overall RPE to varying degrees in young children. The E-P scale provides an intuitively meaningful and valid means of quantifying the overall perception of exertion in young, healthy children during treadmill running. The marble dropping task is a useful secondary measure of perceived exertion, which provides further insight into the nature of the perceived exertion response to exercise in young children.

This study aimed to determine the relationship between bone mineral content, habitual physical activity, and calcium intake in children. Fifty-seven children, aged 8–11 years, wore pedometers for seven days to assess activity. Calcium intake was estimated by a 4-day food diary. Bone mineral content (BMC) and areal density (BMD) were measured at the total proximal femur and femoral neck using dual energy X-ray absorptiometry. Regression analysis was used to assess contributions of physical activity and calcium intake to BMC, residualized for bone area and body mass. Physical activity explained 11.6% of the variance in residualized BMC at the proximal femur and 14.3% at the femoral neck (p < 0.05). Calcium intake added to the variance explained at the proximal femur only (9.8%, p < 0.05). This study provides evidence for an association between BMC and habitual physical activity.

This study compared the accuracy of heart rate monitoring, pedometry, and uniaxial and triaxial aecelerometry for estimating oxygen consumption during a range of activities in Hong Kong Chinese boys. Twenty-one boys, aged 8–10 years, walked and ran on a treadmill, played catch, played hopscotch, and sat and crayoned. Heart rate, uniaxial and triaxial accelerometry counts, pedometry counts, and scaled oxygen uptake (SVO₂) were measured. All measures correlated significantly with VO₂ scaled to body mass^−0.75 (SVO₂). The best predictor of SVO₂ was triaxial accelerometry (R² = 0.89). Correlations in this study were comparable with those in a previous study that used identical methods on 30 UK boys and girls. These results provide further confirmation that triaxial accelerometry provides the best assessment of energy expenditure and that pedometry offers potential for large population studies.

The aim of this study was to investigate the relationship between habitual physical activity and body fatness in Hong Kong Chinese children. Fifty children aged 8–11 yrs wore a uniaxial accelerometer for 7 days to determine physical activity levels. The sum of seven skinfolds was used to estimate body fatness. Activity counts summed over 1 day (299384 – 140427, mean – SD) were similar to activity counts recorded in previous studies. Activity correlated significantly negatively with sum of skinfolds in boys (r = –.50, N = 24, P < .05) but not girls. In conclusion this study supports a negative relationship between physical activity and body fatness in Hong Kong Chinese boys.