Is the Agility Test-Derived Change-of-Direction Deficit a Valid Indicator of Time Loss During Directional Change?

Purpose The change of direction (COD) deficit isolates time loss from directional changes, but the validity of deriving it from an agility test is unknown. This study examined the validity of the COD deficit calculated using an agility test in young male soccer players. Methods Data from 47 valid participants (16.8 ± 0.6 years; 172.8 ± 6.3 cm; 61.0 ± 6.5 kg) were analyzed. In addition to linear sprint time, the total and sectional times of the Reactive Shuttle Test (RST), an agility test, and the proagility test (PAT), a COD test, were measured. The RST-COD and PAT-COD deficits were calculated by subtracting the corresponding linear sprint times from the RST and PAT times. Results The RST-COD deficit was significantly correlated with the PAT-COD deficit (Spearman’s rank correlation coefficient, r s = 0.717); however, it did not meet the predetermined criterion for validity ( r s ≥ 0.750). The regression intercept (0.2131) was significantly greater than zero. The correlation of movement velocity in Section 1 ( r s = 0.532) was lower than that in Section 2 ( r s = 0.739) and 3 ( r s = 0.647). Conclusion These findings suggest that the COD deficit derived from the agility test may not be a valid indicator, potentially owing to individual variability in movement velocity immediately after the start of the test.