Evaluating the task-specific nature of inter-limb asymmetry across change-of-direction and curve sprint tests in youth soccer players

Background Although inter-limb asymmetry is widely investigated, its task-specific nature during multidirectional speed tests remains unclear. The aim of this study was to evaluate the task-specific nature of asymmetry by examining the directional and ordinal consistencies across three common running-based field tests (5-0-5 agility test, 90° change of direction [COD] test, and curve sprint test [CST]). Methods Forty-four elite male youth soccer players (age: 17.7 ± 0.8 years) performed the 5-0-5, 90° COD, and CST on both legs. Inter-limb asymmetry was calculated using performance differentials with limb dominance determined based on the faster limb. Cohen's Kappa ( k ) and Spearman's rank-order correlation (rho) were used to assess the directional and ordinal agreement between the tests. Results Mean asymmetry magnitudes were relatively small (CST: 3.45 ± 2.63%; 5-0-5 and 90° COD: 2.62 ± 2.27%). A perfect directional ( k = 1.00, p < 0.001) and ordinal (rho=1.000, p < 0.001) agreement was found between the 5-0-5 and 90° COD tasks. In contrast, no significant agreements were observed between the CST and 5-0-5 and 90° COD tests ( k = 0.05, p = 0.70). Notably, 51.2% of the players exhibited a total shift in the direction of limb dominance when transitioning from the sharp cuts (i.e., 5-0-5 and 90° COD) to the curve sprint. Conclusion Inter-limb asymmetry is a highly task-specific trait. Linear-based COD tests (5-0-5 and 90° COD) provide similar information regarding asymmetry profiling. However, curve sprinting presents a distinctly independent asymmetry profile. In addition to COD tasks, practitioners may incorporate the CST as a separate assessment tool to profile asymmetry, given its task-specific nature.