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首页> 外文期刊>Medicine and science in sports and exercise >School-level intraclass correlation for physical activity in adolescent girls.
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School-level intraclass correlation for physical activity in adolescent girls.

机译：青春期女孩体育活动的学校级班际相关性。

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PURPOSE: The Trial for Activity in Adolescent Girls (TAAG) is a multi-center group-randomized trial to reduce the usual decline in moderate to vigorous physical activity (MVPA) among middle-school girls. In group-randomized trials, the group-level intraclass correlation (ICC) has a strong inverse relationship to power and a good estimate of ICC is needed to determine sample size. As a result, we conducted a substudy to estimate the school-level ICC for intensity-weighted minutes of MVPA measured using an accelerometer. METHODS: To estimate the ICC, each of six sites recruited two schools and randomly selected 45 eighth grade girls from each school; 80.7% participated. Each girl wore an Actigraph accelerometer for 7 d. Readings above 1500 counts per half minute were counted as MVPA. These counts were converted into metabolic equivalents (MET) and summed over 6 a.m. to midnight to provide MET-minutes per 18-h day of MVPA. Minutes of MVPA per 18-h day also were calculated ignoring the MET value. RESULTS: The unadjusted school-level ICC for minutes of MVPA was 0.0205 (95%CI: -0.0079, 0.1727) and for MET-minutes of MVPA was 0.0045 (95% CI: -0.0147, 0.1145). Adjustment for age and BMI had no measurable effect, whereas adjustment for ethnicity reduced both ICC; adjusted values were 0.0175 (95% CI: -0.0092, 0.1622) for minutes of MVPA and 0.0000 (95% CI: -0.0166, 0.0968) for MET-minutes of MVPA. This information was used to calculate the number of schools and girls needed for TAAG to have 90% power to detect a 50% reduction in the decline of MET-minutes of MVPA between sixth and eighth grade. CONCLUSIONS: The results called for 36 schools in TAAG, with 120 girls invited for measurements at each school, and a minimum participation rate of 80%.
机译：目的：青少年活动试验（TAAG）是一项多中心的小组随机试验，目的是减少初中女孩中度至剧烈运动量（MVPA）的通常下降。在小组随机试验中，小组级别的组内相关性（ICC）与功效有很强的反比关系，需要对ICC进行良好的估算才能确定样本量。结果，我们进行了一项子研究，以估计使用加速度计测量的MVPA强度加权分钟的学校水平ICC。方法：为了评估ICC，六个地点中的每个地点都招募了两所学校，并从每所学校中随机选择了45名八年级女孩。参加率80.7％。每个女孩戴着Actigraph加速度计7天。每半分钟1500计数以上的读数计为MVPA。将这些计数转换为代谢当量（MET），并在上午6点至午夜进行总计，以提供每18小时MVPA的MET分钟。忽略MET值也计算每18小时的MVPA分钟。结果：未经调整的学校水平ICC的MVPA分钟为0.0205（95％CI：-0.0079，0.1727），而MET-分钟的MVPA分钟为0.0045（95％CI：-0.0147，0.1145）。年龄和BMI的调整没有可测量的影响，而种族的调整减少了ICC。对于MVPA分钟，调整值为0.0175（95％CI：-0.0092，0.1622），对于METPA分钟为0.0000（95％CI：-0.0166，0.0968）。此信息用于计算TAAG拥有90％的能力以检测MVPA在六年级和八年级之间的MET-分钟下降减少50％所需的学校和女孩的数量。结论：结果要求TAAG有36所学校，每所学校邀请120名女孩参加测量，最低参与率为80％。

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