Objective To examine the test-retest reliability and concurrent validity (with T-test and Lane test) of the Shuffle-Change of Direction (SCOD) test and the Shuffle-Shuttle Test (SST) using a smartphone-based timing application. Methods Forty-four elite collegiate basketball players (20 males, 24 females; age: 20.30±1.19 years; training experience >= 3 years) completed the SCOD (left and right), SST, T-test, and Lane test in Session 1, and repeated the SCOD and SST in Session 2. Timing was performed via the CODTimer app. Reliability was assessed using the intraclass correlation coefficient (ICC2,1), coefficient of variation (CV), standard error of measurement (SEM), minimal detectable change (MDC), and Bland-Altman analysis. Results Total-sample test-retest reliability was good-to-excellent (single-measures ICC2,1=0.81-0.91, CV=2.43%-4.08%, SEM=0.04-0.65s, MDC=0.12-1.80s; mean bias: -0.062 to -0.009s, all p>0.05). After controlling for sex, the SST remained significantly correlated with the T-test (partial r=0.43, p=0.004) and Lane test (partial r=0.44, p=0.003). Most sex-adjusted SCOD correlations were non-significant, except the left SCOD with the Lane test (partial r=0.32, p=0.03). Conclusion Both tests are reliable using a smartphone app. The SCOD assesses side-specific shuffle performance, whereas the SST provides a reliable assessment of sustained multi-directional shuffle performance. The concurrent validity of the SCOD remains insufficiently established.
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