Background Anterior cruciate ligament (ACL) injury prevention programs have shown mixed results, which may be in part due to suboptimal training components.

Objective Determine effects of a prevention program with external and internal focus of attention on (potential) biomechanical risk factors for ACL injury.

Design Pretest-posttest control group.

Setting Laboratory and field.

Participants 31 elite female soccer players participated. Exclusion criteria included previous ACL injury or current lower extremity injury.

Intervention Two teams performed warm-up programs, including strength, agility, balance, plyometric, core and speed exercises twice a week for 12 weeks. One team received instructions to focus attention internally toward movements of the body (INT); another team received instructions to focus attention externally near the body (EXT). The control group (CON) performed their regular warming-up without specific instructions.

Main outcome measurements Normalized external knee and ankle joint moments and joint angles on a two-legged jump-landing-rebound task.

Results Results of 3x2 repeated measures ANOVA revealed significant group x time interaction for peak knee extension moment (F (2,23)=4.09, P=.03), the EXT group decreased more (–0.90±0.16 to −0.73±0.15 Nm/kg*m) than the CON group (P<.05). Regarding knee flexion angle at peak varus-valgus, a significant interaction was observed (F (2,26)=3.95, P=.03), the INT group increased more (61.58±11.14 to 69.07±1.53°) than the EXT group (P=.08). Differences between groups were found for peak varus-valgus moment (F (2,26)=4.81, P=.02) and ankle flexion-extension moment (F (2,26)=6.40, P<.01). No significant main effects for time were displayed.

Conclusions External or internal focused instructions could be beneficial in improving landing technique, which is promising as an external focus of attention requires less time from coaches and has therefore great potential in ACL injury prevention.