• Zenong Yin, Justin B Moore, Maribeth H Johnson, Marlo M Vernon, and Bernard Gutin.
• Department of Health and Kinesiology, University of Texas at San Antonio, 6900 North Loop 1604 West, San Antonio, TX 78249, USA. zenong.yin@utsa.edu
• Child Obes. 2012 Feb 1;8(1):60-70.

BackgroundChildren tend to be sedentary during the after-school hours, and this has deleterious effects on their health. The objective of the present study was to determine the effects of a 3-year after-school physical activity (PA) program, without restriction of dietary energy intake, on percent body fat (%BF), cardiorespiratory fitness (CRF), and cardiometabolic markers in children.MethodsA cluster randomization design was employed. A total of 574 3rd grade children from 18 elementary schools in the southeastern United States participated. The intervention consisted of 80 minutes of age-appropriate moderate-to-vigorous PA each school day. The main outcomes of interest were %BF measured by dual-energy X-ray absorptiometry; CRF measured by heart rate in response to a submaximal step test; nonfasting total and high-density lipoprotein cholesterol (HDL-C); and resting blood pressure (BP).ResultsIntent-to-treat analyses showed significant treatment by time interactions for %BF (p = 0.009) and CRF (p = 0.0003). The change pattern of the means suggested that %BF and CRF in intervention children improved relative to control children during the school months, rebounding to the levels of control children over the summers following years 1 and 2. Year-by-year analyses of what occurred during the months when the program was offered revealed dose–response relations for %BF and CRF, such that the clearest beneficial effects were seen for those youth who attended at least 60% of the after-school sessions. No significant intervention effects were seen for cholesterol or BP.ConclusionsAn after-school PA program was effective in reducing adiposity and improving CRF, especially in the children who attended the sessions at least 3 days/week. However, the favorable effects on %BF and CRF were lost over the summer. Thus, it is critical to incorporate strategies that attract and retain the children to receive an adequate dose of PA year-round.

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