Unanticipated Visual Stimulus Negatively Affects Change of Direction Performance and Biomechanical Patterns in Female Football Players

Miralles-Iborra, A, Dos´Santos, T, Elvira, JLL, Vera-Cartagena, J, Del Coso, J, and Moreno-Pérez, V. Unanticipated visual stimulus negatively affects change of direction performance and biomechanical patterns in female football players. J Strength Cond Res XX(X): 000–000, 2026—The aim of this study was to explore the effect of anticipation on performance and kinematic patterns during change of direction (COD) in female football players. Thirty-two female amateur football players (mean ± SD for age: 19.4 ± 1.4 years; height: 1.64 ± 0.10 m; body mass: 58.5 ± 9.0 kg) performed a 90° COD during unanticipated (i.e., reactive light stimulus) and anticipated conditions (i.e., preplanned). A 2-D kinematic analysis and the Cutting Movement Assessment Score (CMAS) were used to assess the movement quality of the players in both conditions. Both conditions were compared through paired t test or Wilcoxon signed-rank test and their respective effect size Cohen's d (d) and rank biserial correlation coefficient ( r b ). Players demonstrated longer COD times ( p < 0.001; d = 1.16–1.33) and higher CMAS scores ( p ≤ 0.002; r b = 0.69–0.85) during the unanticipated condition compared with anticipated condition. Several COD biomechanical patterns were modified in the unanticipated condition, such as increased lateral trunk flexion toward the stance leg ( p ≤ 0.011; d = 0.51–0.70), reduced knee frontal plane projection angle at initial contact ( p ≤ 0.002; d = −0.72 to −0.62), increased knee flexion at initial ( p = 0.008; d = 0.51) and final contact ( p = 0.001; d = 0.63), and increased lateral leg plant distance ( p ≤ 0.004; r b = 0.67–0.93). Female football players exhibited impaired performance (i.e., test time) and kinematic changes in the unanticipated COD, particularly in the frontal plane of motion, and could indicate high-risk movement patterns.