Doctoral Dissertations

Date of Award

5-2025

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Kinesiology

Major Professor

Kelley Strohacker

Committee Members

Jannika M. John, Jedediah E. Blanton, Dawn P. Coe

Abstract

Flexible Nonlinear Periodization (FNLP) is a person-adaptive exercise model, but its psychobehavioral components remain underdeveloped, as research has primarily focused on performance outcomes in controlled settings, neglecting fidelity and social validity. Purpose: Assess FNLP enactment and fidelity using ecological momentary assessment (EMA; Aim 1), explore perceptions of social validity regarding FNLP-based program development and exercise (Aim 2), and understand participants’ exercise-related decision-making under FNLP based exercise (Aim 3). Methods: Following an explanatory sequential multiphase mixed-method design, 24 participants (67% female, 34 ± 10 years, 79% White) co-produced a personalized FNLP-based exercise plan and implemented it over 14 days. Each session, participants self-reported readiness, situational motives, and session choices via EMA, followed by post-session affective and perceptual ratings. For Aim 1, fidelity was assessed using within-person Spearman rank correlations to examine the correspondence between readiness, fatigue ratings, and session demand. For Aim 2, semi-structured interviews were conducted at the end of the trial to capture participants’ perceptions of FNLP’s goals, procedures, and outcomes. For Aim 3, timelines of participants’ EMA data were visually presented during interviews to facilitate discussions on lived experiences and decision-making processes underlying session choices. Qualitative data was analyzed using a reflexive thematic analysis. Results: Physical, cognitive, and emotional readiness were positively associated with session demand in 83%, 67%, and 75% of participants, respectively (ρ’s 0.10 to 0.84). Physical and cognitive fatigue were inversely related to session demand in 75% and 63% of participants (ρ’s -0.14 to -0.94). Thematic analysis highlighted that participants valued FNLP’s flexibility, autonomy, and personalization but faced challenges overcoming rigid exercise beliefs and balancing structure with adaptability. The approach fostered reflection, enhanced motivation, and encouraged exercise instigation, though refinements and support are needed. Participants’ exercise decisions under FNLP were shaped by readiness, fatigue, personal motives, and external constraints. While some choices aligned with FNLP principles, others reflected habitual routines, social influences, or emotional coping strategies. Conclusion: FNLP was supported by participants in terms of its goals, procedures, and effects, supporting its utility as a model for promoting autonomous exercise engagement while balancing structure and flexibility. Evidence of fidelity, including explanations for deviations, were demonstrated. Longer term research is warranted to further refine FNLP procedures, enhance guidance, and support decision-making.

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