This cluster-randomised controlled trial aims to evaluate whether a multi-component load management intervention-incorporating real-time acute:chronic workload ratio (ACWR) feedback, automated alerts, coach education, and structured load adjustment protocols-reduces time-loss injury incidence in Chinese elite mixed-gender adolescent football players compared with routine training practices.
Background: Injury prevention in elite youth football is a public health and performance priority. Approximately two-thirds of players sustain at least one time-loss injury annually, with lower extremity injuries predominating. The acute:chronic workload ratio (ACWR) is widely used in sport science as a practical decision-support tool, yet experimental evidence for its effectiveness in reducing injury incidence remains limited and conflicting, particularly in Asian adolescent populations. Objectives: This cluster-randomised controlled trial evaluates whether a multi-component ACWR-guided load management intervention reduces time-loss injury incidence in Chinese elite youth football players compared with routine practice. Study Design: A prospective, two-arm, parallel-group, cluster-randomised controlled trial with 1:1 allocation, stratified by age group (U15/U17/U19). Participants: Twenty-eight elite youth football teams (U15-U19, n=774, 45.2% female) from 28 academies in Henan Province. Intervention: The intervention comprises real-time ACWR feedback, automated alerts for values outside the 0.8-1.3 range, coach education workshops, and structured load-adjustment protocols. Control teams follow routine practice without ACWR-derived feedback. Primary Outcome: Time-loss injury incidence rate per 1000 athlete-exposure hours. Secondary Outcomes: (1) Severe injury incidence (≥28 days lost); (2) Injury burden (days lost per 1000 h); (3) Proportion of lower-extremity injuries; (4) Proportion of non-contact injuries. Sample Size: 28 teams (14 per arm) with 774 players (median 27 per team, range 22-31), providing 80% power to detect a 25% reduction in injury incidence (IRR=0.75) with α=0.05 and ICC=0.05. Statistical Analysis: Mixed-effects Poisson regression with ICC adjustment, Fine-Gray competing risk models, shared frailty Cox models, Kaplan-Meier survival analysis, and E-value sensitivity analysis. Ethics: The study protocol was approved by the Xinyang Agriculture and Forestry University Ethics Committee (XYAFUAE2024021). Written informed consent was obtained from all participants and their parents/legal guardians.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
PREVENTION
Masking
NONE
Enrollment
847
Intervention teams implement a structured ACWR-guided load management protocol for the entire season. The protocol comprises four components: Component 1 - Load Monitoring: After each training session and match, players rate perceived exertion on the Borg CR-10 scale. Session-RPE (sRPE) is calculated as duration (minutes) × RPE score. Data are recorded using a dedicated mobile application (CoachMe v3.2). Research staff provide technical support and weekly reminders. Component 2 - Weekly ACWR Reports: The research team generates weekly ACWR reports for each player. Reports are emailed to head coaches each Monday morning, covering the preceding week's data. Component 3-Automated Alerts and Load-Adjustment Recommendations: Coaches receive automated alerts when a player's ACWR falls below 0.8 or exceeds 1.3. When ACWR \< 0.8, a progressive increase in training load (10-20% weekly) is suggested. When ACWR \> 1.3, coaches are instructed to implement a 10-20% load reduction at the next session,
Time-loss injury incidence rate per 1000 athlete-exposure hours.
Definition: Consistent with the football injury consensus statement, a time-loss injury is defined as any physical impairment sustained during structured football training or competitive matches that prevents a player from full participation in subsequent training sessions or matches. Injuries occurring outside football activities are not recorded.
Time frame: From enrolment to the end of the 10-month competitive season
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