Are all MVPA minutes equal? Associations between MVPA characteristics, independent of duration, and childhood adiposity

The Effects of the LiiNK Intervention on Physical Activity and Obesity Rates among Children

BACKGROUND

Obesity and inactivity among children are at an all-time high and have been steadily increasing in prevalence over the last thirty years. The school environment provides the ideal setting for reaching a large number of children across diverse populations in order to reverse these trends. However, there are many inconsistent results yielded by school-based physical activity interventions due to implementation length, time for activities, and the use of structured physical activities. The LiiNK Project® is a whole-child intervention addressing these gaps by providing children 45-60 min of recess (unstructured, outdoor play) in their schools daily, while the control children are allowed to engage in recess for 30 min daily. The purpose of this study was to compare the physical activity intensity and obesity rates of third- and fourth-grade children participating in the LiiNK intervention, which provides 60 min of recess for third graders and 45 min for fourth graders, to those in a control group allowed 30 min of daily recess.

METHODS

The children were 8-10 years old (M = 9.2; 52% females and 48% males). The intervention children comprised 90 third graders and 100 fourth graders, and the control children comprised 101 third graders and 92 fourth graders. Physical activity levels were monitored using accelerometers to assess sedentary, light, and moderate-to-vigorous physical activity (MVPA). Obesity rates were evaluated using bio-electrical impedance analysis (BIA), in which body fat percentage is calculated based on normative values using age and sex in the equation.

RESULTS

The third-grade intervention children engaged in 13 more MVPA minutes and took 900 more steps daily than their control counterparts, and also presented a greater proportion of overweight children transitioning to a healthy weight status from the fall to the spring semester. Conversely, the fourth-grade control children increased their activity by 500 steps and 15 more MVPA minutes daily. Despite this, the intervention children overall demonstrated a reduction in body fat percentage, while the control children demonstrated an increase in body fat percentage.

CONCLUSIONS

Ultimately, 60 min of unstructured, outdoor play in schools provides children the best opportunity to engage in MVPA, which may positively impact body fat percentages, offering a potential strategy for combatting childhood obesity in school settings.

Effects of exercise timing on metabolic health

The increasing prevalence of metabolic syndrome is associated with major health and socioeconomic consequences. Currently, physical exercise, together with dietary interventions, is the mainstay of the treatment of obesity and related metabolic complications. Although exercise training includes different modalities, with variable intensity, duration, volume, or frequency, which may have a distinct impact on several characteristics related to metabolic syndrome, the potential effects of exercise timing on metabolic health are yet to be fully elucidated. Remarkably, promising results with regard to this topic have been reported in the last few years. Similar to other time-based interventions, including nutritional therapy or drug administration, time-of-day-based exercise may become a useful approach for the management of metabolic disorders. In this article, we review the role of exercise timing in metabolic health and discuss the potential mechanisms that could drive the metabolic-related benefits of physical exercise performed in a time-dependent manner.

iEngage: A digital health education program designed to enhance physical activity in young adolescents

iEngage is a modular health education and behavioural change program designed to help adolescents increase moderate to vigorous physical activity (MVPA). The program is delivered through the iEngage app which integrates activity trackers data (Misfit Ray^©) within 10 interactive learning modules. Key features include guidance to set goals, self-monitor and assess achievements, and experiential learning via the connected activity trackers which allows for continuous steps recording during the program. iEngage was implemented in two schools over 5 weeks with 10–12 years old adolescents (n = 57) and PA outcomes compared to control group (n = 26). Results show that adolescents successfully set goals and self-assessed achievements during the program, progressing toward higher physical activity (PA) levels as shown by the 30% increase in daily steps through the program (+ 2647 steps/day, P < .001) with boys increasing goals and achievements faster than girls. The consistency in days totalling at least 11,000 steps/day increased from 35% at the start to 48% at the end of the program. The increase in PA is confirmed through the assessment of MVPA during schooldays pre- and post- program via research grade wrist accelerometers in both iEngage and control participants. Contrasting with the control group, MVPA was increased in the week following the program (~+5 min/day, P = .023) in short bouts, particularly during lunch time, recess and after school. This study shows that a digital program integrating activity trackers data, health education, goals setting and self-monitoring of PA, helped young adolescents enhance PA goals, improve achievements and increase MVPA.

Physical activity and adiposity in preschool children: The Barwon Infant Study

BACKGROUND

The association between physical activity and adiposity in preschool-aged children is unclear.

OBJECTIVE

To assess the cross-sectional association between objectively measured physical activity and body fat in preschool-aged children.

METHODS

In the preschool review in an Australian birth cohort study (n = 1074), mean duration and time accumulated in ≥1-min bouts of physical activity at light-intensity (LPA), moderate- to vigorous-intensity (MVPA) and light- to vigorous-intensity (LMVPA) were computed from accelerometer (ActiGraph GT3X+) data. Percent body fat was assessed by bioelectrical impedance. Associations between physical activity and percent body fat were examined by multiple regression, adjusted for accelerometer wear time, MVPA (in analyses of LPA), maternal body mass index (BMI) and maternal education.

RESULTS

A total of 450 participants (n = 450) had valid data. There was evidence of associations between physical activity and adiposity: each additional hour of LVPA was associated with 0.6% (CI₉₅ -0.2%, 1.3%) higher body fat; ≥1-min bouts of LPA was associated with 1.0% (CI₉₅ 0.1%, 1.9%) higher body fat; each additional hour of MVPA was associated with -0.8% (CI₉₅ -1.6%, -0.1%) less body fat; and ≥1-min bouts of MVPA was associated with -1.3% (CI₉₅ -2.5%, -0.1%) body fat.

CONCLUSIONS

Among a cohort of preschool-aged children, there was evidence that more intensive physical activity assessed by an accelerometer is associated with reduced body fat.