Learning the Capacity to Feel Better Through Experiment in a Box (XB): Qualitative Interpretive Description and Prototheory Development of Tuning.

Background: Experiment in a Box (XB) is a guided, time-limited framework designed to help individuals test and adapt simple eating and movement heuristics within the context of everyday life. Rather than emphasizing external performance metrics alone, XB invites participants to evaluate practices through felt experience, including whether a practice helps them feel better, worse, or the same. Although prior XB studies have shown promise for supporting health behavior change, less is known about the experiential and interpretive processes through which participants use XB to connect felt experience with action, adaptation, and continued practice. Objective: This study aimed to develop a preliminary prototheory of tuning to explain how participants used felt experience to guide eating and movement experimentation within XB. We define tuning as a dynamic, person-centered process through which individuals learn to sense, interpret, and act on bodily and contextual feedback during guided experimentation. Methods: We conducted a secondary, post hoc qualitative inquiry using interpretive description, reflexive thematic analysis, and abductive analysis. The qualitative corpus consisted of responses to 39 open-text postintervention survey questions completed across 3 survey sections. Descriptive implementation information was used to characterize participant flow and survey completion. A total of 44 participants enrolled and accessed the XB app. Of these, 12 completed the general postintervention survey, 11 completed the MOVE survey section, and 8 completed the XB app and implementation section. Self-determination theory and activity theory were used as sensitizing frameworks rather than fixed coding templates. Analysis involved iterative coding, analytic memoing, conceptual mapping, and team-based review to develop a preliminary prototheory of tuning. Results: The analysis resulted in a prototheory of tuning organized around recursive loops linking action, felt experience, interpretation, adaptation, and future action. Participants described XB as creating a low-pressure structure for trying practices, noticing bodily and experiential signals, interpreting those signals through practical health heuristics, and adapting practices to their bodies, routines, social relationships, and environments. Over time, repeated experimentation appeared to support the development of portable knowledge, skills, and practices, including movement snacks, eating heuristics, and an ongoing experimental orientation toward health behavior. Social, material, and environmental conditions shaped whether and how participants could engage in tuning, particularly across home, work, and family contexts. Conclusions: Tuning offers a preliminary conceptual lens for understanding how guided experimentation may support health behavior change by helping participants connect action, felt experience, interpretation, and adaptation. Rather than positioning behavior change as compliance with external prescriptions or metrics, the tuning prototheory foregrounds how individuals may cultivate the capacity to notice, interpret, and act on felt experience in context. Future prospective qualitative and mixed methods studies should test, refine, and potentially challenge this prototheory across more diverse populations and implementation settings.