What aspect does the effectiveness part of the APEASE criteria model primarily focus on?

The effectiveness part of the APEASE criteria model focuses primarily on the impact of the intervention on participant behavior. In the context of sports nutrition and coaching, an intervention's effectiveness is measured by how well it achieves the desired outcomes related to participants' behaviors, such as dietary choices, exercise habits, or adherence to nutrition plans. This aspect emphasizes not only the success in changing behaviors but also the sustainability of those changes over time. It is crucial for a program to demonstrate that it can positively influence participants in a way that leads to lasting improvements in their health and performance.

Other aspects like resources, enjoyment, or duration are important to consider in the overall planning and implementation of an intervention but do not directly define its effectiveness in terms of behavior change.