Preventing lower limb injuries in women's football: Influence of the Stop X prevention programme on jump performance and isokinetics in professional and young elite-level female football - a prospective observational cohort study.

BACKGROUND: Lower limb injuries, particularly anterior cruciate ligament (ACL) and thigh injuries, are highly prevalent in women's football, often resulting from sudden changes in direction and poor landing mechanics. Neuromuscular training is critical to address these injury risk factors. This study evaluated the adaptions observed during implementation of the Stop X programme, a specialised neuromuscular training developed by the German Knee Society, on jump performance and isokinetic strength in elite female players. METHODS: In this prospective observational cohort study, 147 female players (Professional: n = 55, U20: n = 34, U17: n = 58) were monitored during 2022-2024 seasons. Stop X was integrated into the team warm-up (5-6 sessions/week, 15-20 min). Pre-season and in-season assessments included countermovement jump (CMJ), single-leg drop jump (SLDJ), and isokinetic strength testing (60°/s). Non-contact injuries were documented by the medical staff. Statistical analysis compared longitudinal performance changes and baseline values between injured and uninjured players. RESULTS: Significant inseason improvements were observed in CMJ and SLDJ performance, with youth elite players (U17/U20) showing the most pronounced gains in reactive strength index (RSI) and jump height. In the U20 group, non-dominant leg propulsive force increased significantly (p = 0.04). Regarding isokinetic strength, tests revealed a significant inseason decline in the functional H/Q ratio (60°/s) for both the dominant (preseason: 0.79 ± 0.15 vs. inseason: 0.75 ± 0.13; p = 0.004) and non-dominant leg (preseason: 0.80 ± 0.14 vs. inseason: 0.76 ± 0.14; p = 0.005), while the conventional H/Q ratio showed no significant changes. Furthermore, matched non-contact injured players exhibited significantly lower in-season conventional H/Q ratios in the dominant leg compared to uninjured players (0.54 vs. 0.59, p = 0.03). ACL-injured players also showed a trend toward increased knee valgus in pre-injury tests (p = 0.06). CONCLUSION: Improvements in jump performance and propulsive forces were observed during the implementation of Stop X, providing a crucial performance-based incentive for coach and player compliance. However, the significant in-season decline in functional H/Q ratios indicates the need to refine prevention programmes by integrating more female-centric hamstring exercises alongside jumping and landing technique drills. During the implementation period, a low overall number of injuries was recorded; future randomised controlled trials with precise exposure tracking are warranted to investigate definitive injury reduction rates.