Due to Covid-19 restrictions, handball training was only performed about 2 months at the start of the season, and intervention and evaluation could not be conducted as planned.

Evidence-based injury prevention training is highly effective in reducing sport-related musculoskeletal injuries in youth. However, this training has so far had limited public health impact because it is not widely or properly implemented or sustained. In this single case study with youth teams from two handball clubs in Southern Sweden, the aim is to test the I-PROTECT model, featuring injury prevention training and an associated implementation plan. The main hypothesis is that the intervention will result in higher motivational and volitional levels in relation to injury prevention training.

This is a pilot study included in the "Implementing injury Prevention training ROutines in TEams and Clubs in youth Team handball (I-PROTECT)" project (Ageberg et al, 2019, 2020). The overall aim of I-PROTECT is to achieve wide-spread, sustained and high-fidelity use of evidence-based injury prevention training in youth handball through behavior change at multiple levels within the sports delivery system (individual and organizational levels). The I-PROTECT model is evidence-based, theory-informed, and context-specific injury prevention training specifically tailored for youth handball players, incorporating physical and psychological components and an associated implementation strategy. The process of developing the I-PROTECT model has been described (Ageberg et al 2020). The current study is a prospective single case study for initial testing and evaluation of the I-PROTECT model (i.e., before the model is implemented in a larger scale study). The reporting will adhere to the SCRIBE guidelines. All youth teams in the two clubs with representatives of the stakeholder group overseeing the I-PROTECT project will use the I-PROTECT model for one handball season. The Health Action Process Approach (HAPA) theory will be used to evaluate behavior change among players, coaches and club administrators. The Reach, Effectiveness, Adoption, Implementation, and Maintenance Sport Setting Matrix (RE-AIM SSM) framework will be used to guide the evaluation of implementation outcomes of the I-PROTECT model among all stakeholders (players, coaches, club administrators, caregivers).

The main hypothesis is that the intervention increases scores in HAPA questions in coaches from pre- to post intervention by at least 30%, indicating higher motivational and volitional levels in relation to injury prevention training post intervention (end of season) compared to pre-intervention (baseline). A preliminary sample size calculation indicates that 42 coaches are needed to detect a clinically relevant change in behavior of at least 30% (baseline vs post intervention) with 80% power at the 5% significance level. Secondary outcomes will be: i) HAPA questions among players and club administrators; ii) RE-AIM SSM questions, descriptive data, and/or mobile application data among all stakeholders (players, coaches, club administrators, caregivers). Interviews (e.g., focus groups) with end-users will be conducted to enable an in-depth understanding of the feasibility, acceptability and usability of the program, including its packaging. An "exit strategy" will be employed to refine the model, address any potential barriers for implementation and sustainability, and embed the I-PROTECT model into the organizations that have participated in the study.

Due to pandemic restrictions, handball training was only performed as usual about 2 months at the start of the season, and evaluation of the I-PROTECT-model could not be conducted as planned. Nineteen teams with their coaches, players, and caregivers included (approx. 700 participants in total). The following data was collected:

• Main outcome: HAPA questions for coaches at baseline and at end-of-season
• Secondary outcomes: HAPA and RE-AIM questions caregivers at baseline

Stakeholders (players, coaches, caregivers, club administrators) of all youth teams (13-17 years) in two community handball clubs will be eligible for participation.

Inclusion Criteria:

• Players: ages 13-17 years and training ≥2 times/week in a team
• Coaches: leading ≥1 training session/week
• Caregivers: directly associated with the eligible players
• Club administrators: engagement in the issues of sports injury, coach education - or policy development for youth players

Exclusion Criteria

• Employed/paid players
• Stakeholder other than the groups listed in inclusion criteria

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