Background/Objective This study aimed to assess the validity and reliability of the My Jump® 2 app for measuring vertical jump height on sand. We hypothesized that the app would demonstrate good reliability (ICC > 0.75) and acceptable agreement (bias < 2 cm, CCC = 0.95) with 2D video analysis. Methods Twenty-six male beach volleyball players performed four types of vertical jumps (CMJ, SJ, AJ, BJ) on sand. Jump height was measured using the My Jump® 2 app and 2D video analysis (Kinovea). Reliability was assessed with ICC(2,1), SEM, and MDC95. Validity was assessed using Pearson correlation, Lin`s Concordance Correlation Coefficient (CCC), Bland-Altman analysis (bias and 95 % limits of agreement), and linear regression to evaluate proportional bias and standard error of estimate (SEE). Results ICCs ranged from 0.447 to 0.594. SEM varied from 4.68 to 8.39 cm and MDC95 ranged from 12.98 to 23.24 cm. Pearson correlations were high (r = 0.713-0.832), but CCC values indicated only moderate agreement (CCC = 0.487-0.632). The My Jump® 2 app consistently overestimated jump height, with bias ranging from 5.38 to 6.91 cm. Limits of agreement ranged from -11.33 to 22.08 cm. Linear regressions revealed proportional bias in all jump types. Conclusion My Jump® 2 showed good reliability but limited agreement with the reference method on sand. While the app may be suitable for monitoring performance trends, its absolute accuracy is compromised under these conditions and should be interpreted with caution.
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