Background: Injury prevention is highly needed in physically active populations, such as pre-service and in-service physical education teachers (PETs). As a lack of adherence to preventive strategies is problematic in injury, it seems crucial to develop and optimize interventions that correspond to the specific needs and wishes of PETs.Aim: The purpose of the present study was fourfold. Specifically, we aimed at (1) systematically optimizing an injury prevention intervention for PETs, based on teachers' qualitative evaluation of the intervention, (2) quantitatively investigating whether the appreciation of the injury prevention intervention was higher after optimization, (3) examining whether participation in the intervention resulted in positive changes in teachers' perceived utility of, and confidence to apply the proposed preventive strategies, as well as their knowledge about these strategies, and (4) describing teachers' adherence to the proposed preventive strategies while they were engaging in the intervention.Participants: Twenty PETs (13 men, Mage = 42.1 12.17 years) from nine different secondary schools in Flanders (Belgium) voluntarily participated in this study. The intervention, based on findings from the continuing professional development (CPD) literature, and the principles of the self-determination theory, took place on two different training days (Training A and Training B) and consisted of seven intrinsic injury prevention strategies.Data collection and analysis: Qualitative data on teachers' appreciation of the intervention were collected by means of focus group interviews, which were used to optimize the intervention (Aim 1). Quantitative data on teachers' appreciation were collected directly after they had engaged in the intervention and were used to compare the appreciation from the initial to more optimized versions of the trainings (Aim 2). Further, by means of repeated measures ANOVAs positive evolutions in teachers' belief in the utility of, confidence to apply and knowledge about the provided strategies across time were examined (Aim 3). Finally, teachers' adherence was evaluated by relying on weekly online registrations of minutes and types of preventive strategies teachers had practised during the past week (Aim 4).Findings: Despite the relatively high initial appreciation scores (4.2 out of 5), the optimized versions of the trainings scored better on interaction, intelligibility, innovation, practical usefulness, and recommendation (Aims 1 and 2). Significant differences were found over time in terms of within-teacher changes in perceived utility of (4.05-4.73-4.48; p<.001), confidence to apply (3.75-3.96-4.26; p<.001) and knowledge about preventive strategies (2.49-3.53-3.39; p<.001; Aim 3). Finally, prospective registrations of teachers' adherence to the proposed strategies showed a mean time of 62.1 +/- 48.6 min/week with a balanced distribution of the different strategies (Aim 4).Conclusions: The present study developed an intervention that optimally fulfils the wishes and needs of the target population, namely PETs, and can readily be implemented in PET education programmes or CPD programmes for in-service PETs. Results of this pilot study are promising because teachers displayed increases in several relevant outcomes. Various suggestions are formulated on how to increase PETs' appreciation of CPD programmes.