Caroline Angus

Physical activity levels of children living in different built environments

OBJECTIVE To review the available literature assessing differences in physical activity levels of children living in different built environments classified according to land use within developed countries. METHODS A systematic review of published literature up to March 2009. Online searches of five databases yielded 18 studies which met inclusion criteria. Studies provided data on n=129446, 5-18 years old (n=117544 from the United States). RESULTS From 13 assessments of differences in physical activity between rural and urban children one showed that rural children were significantly more active than urban children. In studies where the built environment was sub-divided further, suburban and small town children showed the highest levels of physical activity, followed by rural, then urban children. Differences in types of physical activity undertaken were evident, showing that rural children spent more time outdoors, involved in unstructured play compared with urban children. These findings were mainly restricted to children <13 years old. CONCLUSIONS The literature does not show major differences in the physical activity levels between children from rural or urban areas. Where studied, the suburban built environment appears most conducive to promoting physical activity. Further research should use at least a trilateral division of the built environment and should also account for socioeconomic status, racial factors and seasonal effects.

A randomised control trial of physical activity in a perceived environment on self-esteem and mood in UK adolescents

This study assessed whether exercising whilst viewing natural or built scenes affected self-esteem (SE) and mood in adolescents. Twenty-five adolescents participated in three exercise tests on consecutive days. A graded exercise test established the work rate equivalent to 50% heart rate reserve for use in subsequent constant load tests (CLTs). Participants undertook two 15-min CLTs in random order viewing scenes of either natural or built environments. Participants completed Rosenberg’s SE scale and the adolescent profile of mood states questionnaire pre- and post-exercise. There was a significant main effect for SE (F(1) = 6.10; P < 0.05) and mood (F(6) = 5.29; P < 0.001) due to exercise, but no effect of viewing different environmental scenes (P > 0.05). Short bouts of moderate physical activity can have a positive impact on SE and mood in adolescents. Future research should incorporate field studies to examine the psychological effects of contact with real environments.

Comparison of Local Adipose Tissue Content and SRS-Derived NIRS Muscle Oxygenation Measurements in 90 Individuals

Adipose content in the region over the vastus lateralis muscle was measured in a young (21.1 +/- 3.1 years old, mean +/- SD) population of males (n = 62) and females (n = 28). Three techniques were used: skinfold thickness, ultrasound and near infrared spectroscopy. All techniques closely correlated with each other and all showed a significantly larger adipose content in females and a limited overlap with the range of values in males. Spatially resolved near infrared spectroscopy (SRS-NIRS) was then used to measure the tissue oxygenation index (TOI) at the same site. A source-detector separation of 4 cm was used to allow for significant light penetration into muscle tissue. TOI at rest was significantly higher in the female (65.3 +/- 7.0, mean +/- SD) than the male (61.9 +/- 5.1, mean +/- SD) group. There was a strong positive correlation between adipose content and TOI in male subjects. However, no correlation was seen in the female group. The possible optical and physiological explanations for these results are discussed.

Pacing Strategy in Schoolchildren Differs with Age and Cognitive Development

PURPOSE The studys purpose was to examine differences in pacing strategy between schoolchildren of different age, gender, and stage of cognitive development. METHODS Schoolchildren (n = 106) from four age groups (5-6, 8-9, 11-12, and 14 yr) participated in this study. Each schoolchild completed four conservation tasks to evaluate his or her Piagetian stage of cognitive development. Each schoolchild then performed a best-effort running task on a 150-m running track that was video recorded to analyze pace at 5% increments. The length of the run was varied for each age group to ensure that all schoolchildren were running for approximately 4 min (5-6 yr = 450 m, 8-9 yr = 600 m, 11-12 yr = 750 m, and 14 yr = 900 m). RESULTS Differences in pacing strategy were found between schoolchildren of different age (P < 0.0001), gender (P < 0.0001), and cognitive development (P < 0.0001). Pacing differences were also found between age groups after controlling for cognitive development (P < 0.001), between cognitive abilities after controlling for age (P < 0.01), and between genders after controlling for both age (P < 0.0001) and cognitive ability (P < 0.0001). CONCLUSIONS Younger schoolchildren with less advanced cognitive development exhibited a negative pacing strategy indicating an inability to anticipate exercise demand. Older schoolchildren at a more advanced stage of cognitive development exhibited a more conservative U-shaped pacing strategy characterized by faster running speeds during the first 15% and last 20% of the run. Anticipatory pacing strategy seems to be related to both the age and cognitive development of schoolchildren.

Estimation of Lactate Threshold by Near Infrared Spectroscopy

The anaerobic or lactate threshold (LT) is defined as the point at which blood lactate levels rise significantly above basal levels and correlates with athletic performance in endurance events (Weltman, 1995). Currently gas exchange measurements of whole body VO2 and VCO2 are the best non-invasive techniques of measuring the LT (Beaver et al., 1986). Near-infrared spectroscopy (NIRS) data has shown a correlation between muscle deoxygenation and blood lactate concentration (Rundell et al., 1997) and it has recently been suggested that NIRS can be used to determine the LT (Belardinelli et al., 1995; Bhambhani et al., 1997). NIRS provides a non-invasive method for the continuous measurement of changes in muscle haemo(myo)globin oxygenation and blood volume (Chance et al, 1992; Ferrari et al., 1997; Wilson et al., 1989). By identifying particular trends in the rate and extent of muscle deoxygenation these authors have shown correlations with gas exchange methods of measuring the LT.

Blood Volume Changes are Controlled Centrally Not Locally - A Near-Infrared Spectroscopy Study of One Legged Aerobic Exercise

It is well known that blood flow increases in an exercising limb to match increases in oxygen consumption. However, it is less clear what effects occur in the opposite limb. We performed a one legged incremental cycling protocol and used near-infrared spectroscopy to measure changes in muscle blood volume and oxygenation in the exercising and non-exercising leg. As expected during exercise the exercising leg was deoxygenated relative to the non-exercising leg. However, there were similar increases in blood volume to both legs during the exercise, and during the post-exercise recovery period similar volume and oxygenation increases were seen in both legs. We conclude that blood volume increases may be signalled locally, but the effect is expressed globally. Previous studies have demonstrated a training effect in the non-exercising leg following one legged aerobic exercise. The large haemodynamic changes in the non-exercising leg observed here may be partially responsible for the cross-training effect.