Agility is a key component of physical fitness in adolescents. However, the measurement of this variable is usually complex, requiring high cost instruments and complex software. To test the validity and reliability of a novel iPhone app (Lap Tracker Auto-timer) to measure agility performance among adolescents. Twenty-four physically active adolescents (15.7 ± 2.3 years old) participated in two testing sessions (separated by 7 days). They performed three 4 x 10 m agility test trials measured by Photocell or the iPhone app. The correlation analysis revealed high validity (r = .92; 95% confidence interval [CI] = .88 – .95), with a standard error of the estimate of 0.56 s (p < 0.001). The coefficient of variation (CV; 0.09) and intraclass correlation coefficient (ICC; .93; 95% CI = .85 – .97) showed an acceptable reliability. This study demonstrated that the iPhone App Lap Tracker Auto-timer could be a valid, reliable and low-cost tool to evaluate agility performance in adolescents. However, more studies are required to guarantee the utility of this app.

中文翻译：

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一种新颖的移动应用程序测量身体活跃青年群体的敏捷性表现的有效性和可靠性

敏捷性是青少年身体健康的关键组成部分。然而，这个变量的测量通常很复杂，需要高成本的仪器和复杂的软件。测试一款新颖的 iPhone 应用程序（Lap Tracker Auto-timer）的有效性和可靠性，以测量青少年的敏捷性表现。24 名身体活跃的青少年（15.7 ± 2.3 岁）参加了两次测试（相隔 7 天）。他们进行了三个由 Photocell 或 iPhone 应用程序测量的 4 x 10 m 敏捷性测试试验。相关分析显示高有效性（r = .92；95% 置信区间 [CI] = .88 – .95），估计标准误差为 0.56 秒（p < 0.001）。变异系数 (CV; 0.09) 和组内相关系数 (ICC; .93; 95% CI = .85 – .97) 显示出可接受的可靠性。这项研究表明，iPhone App Lap Tracker Auto-timer 可以成为评估青少年敏捷性表现的有效、可靠且低成本的工具。然而，需要更多的研究来保证这个应用程序的实用性。