ABSTRACT
Introduction/Purpose: Recess represents a prime opportunity for physical activity during the school day. However, evidence is mixed with regard to factors associated with activity during recess. Methods: Data were collected as a part of the Texas Initiative for Children's Activity and Nutrition (I-CAN!) program from 14 elementary schools and 1,049 4th-grade students. Percent of time in moderate-to-vigorous physical activity (MVPA) and sedentary behavior during recess was measured using GT3X+ accelerometers. Students' demographics, aerobic fitness, and body mass index (BMI) were collected from school records and FITNESSGRAM® data. Aspects of the playground environment supporting activity (e.g. soccer goals) or sedentary behavior (e.g. benches) were calculated following the procedures of the System for Observing Play and Leisure Activity in Youth (SOPLAY), with recess spatial area calculated via the polygon measurement tool in Google™ Earth Pro software. Recess time was collected from school data. Weather during recess was determined using time-stamped archived weather data from Weather Underground. Two-level, linear mixed model regression examined associations between individual- and school-level characteristics and percent time in MVPA. Results: At the student-level, boys were more active than girls (effect size (ES)=0.50) and percent time in MVPA was directly associated with aerobic fitness (ES=0.35). At the school-level, recess infrastructure was associated with percent time in MVPA (ES=1.45), except for factors related to sedentary behavior, which were indirectly associated with percent time in MVPA (ES=-1.98). Patterns for sedentary behavior mirrored these effects. Conclusions: This is one of the few studies to test the associations of fitness and sedentary upgrades to play areas with MVPA and sedentary behavior. The results suggest that recess is most likely to support MVPA in boys and those who are already most fit (i.e., those who would not be the target of intervention). This is not surprising because the focus of recess is on free choice of play, and thus recess might be supported more for social and emotional benefits than the impact on physical activity.
ABSTRACT
BACKGROUND: Our goal was to investigate the role of physical exercise to protect brain health as we age, including the potential to mitigate Alzheimer's-related pathology. We assessed the effect of 52 weeks of a supervised aerobic exercise program on amyloid accumulation, cognitive performance, and brain volume in cognitively normal older adults with elevated and sub-threshold levels of cerebral amyloid as measured by amyloid PET imaging. METHODS AND FINDINGS: This 52-week randomized controlled trial compared the effects of 150 minutes per week of aerobic exercise vs. education control intervention. A total of 117 underactive older adults (mean age 72.9 [7.7]) without evidence of cognitive impairment, with elevated (n = 79) or subthreshold (n = 38) levels of cerebral amyloid were randomized, and 110 participants completed the study. Exercise was conducted with supervision and monitoring by trained exercise specialists. We conducted 18F-AV45 PET imaging of cerebral amyloid and anatomical MRI for whole brain and hippocampal volume at baseline and Week 52 follow-up to index brain health. Neuropsychological tests were conducted at baseline, Week 26, and Week 52 to assess executive function, verbal memory, and visuospatial cognitive domains. Cardiorespiratory fitness testing was performed at baseline and Week 52 to assess response to exercise. The aerobic exercise group significantly improved cardiorespiratory fitness (11% vs. 1% in the control group) but there were no differences in change measures of amyloid, brain volume, or cognitive performance compared to control. CONCLUSIONS: Aerobic exercise was not associated with reduced amyloid accumulation in cognitively normal older adults with cerebral amyloid. In spite of strong systemic cardiorespiratory effects of the intervention, the observed lack of cognitive or brain structure benefits suggests brain benefits of exercise reported in other studies are likely to be related to non-amyloid effects. TRIAL REGISTRATION: NCT02000583; ClinicalTrials.gov.
