A Unified Framework for Exercise-Induced Mitochondrial Adaptation Modeling

Thesis Abstract

Mitochondrial adaptation to exercise exhibits complex, non-linear dynamics that are not fully captured by existing isolated models of energy metabolism, signaling cascades, or mitochondrial biogenesis; this fragmentation limits predictive capability for individual responses to training and hampers the translation of mechanistic insights into personalized prescriptions. The study aims to develop a unified framework that integrates mechanistic signaling pathways, energetic state variables, and mitochondrial biogenesis processes to model exercise-induced mitochondrial adaptation across diverse populations. Specific objectives are (1) to synthesize theoretical constructs from the mitochondrial biogenesis paradigm (e.g., PGC-1? signaling, AMPK, mTOR axes) with models of substrate utilization and reactive oxygen species signaling; (2) to construct a dynamical systems model that links acute exercise stimuli to longer-term mitochondrial content, functional capacity, and quality control processes; (3) to calibrate and validate the framework against longitudinal data from controlled exercise interventions; and (4) to evaluate the framework’s predictive performance for individual variations in mitochondrial adaptations under different training modalities. A mixed-methods, longitudinal design will be employed. The quantitative component will recruit 240 adults aged 18–45 across three cohorts (sedentary, recreationally active, and endurance-trained) who will undergo 12 weeks of structured endurance training with a subset performing concurrent resistance work. Blood and skeletal muscle biopsies will be collected at baseline, weeks 4, 8, and 12 to measure mitochondrial DNA copy number, citrate synthase activity, OXPHOS complex expression, PGC-1? and downstream targets, and markers of mitophagy (PINK1/Parkin). Peripheral blood transcriptomics and metabolomics will be used to capture systemic signaling and substrate flux. Endurance capacity will be assessed via VO2max, while mitochondrial function will be evaluated using high-resolution respirometry on muscle samples. Instrument validity will be established through prior calibration with pilot data; reliability will be ensured via standardized sampling protocols and triplicate assays. Data will be analyzed with a combination of structural equation modeling to test causal pathways among signaling, biogenesis, and function, and nonlinear mixed-effects models to capture individual trajectories. Model specification will incorporate theoretical constructs from the AMPK-PGC-1? axis, mitochondrial biogenesis theory, and the mitochondrial quality control framework, drawing on existing literature and empirical data to parameterize plausible interactions and feedback loops. The study expects to demonstrate that a unified dynamical framework can accurately reproduce observed patterns of mitochondrial content and function over the training period, including interindividual variability linked to baseline fitness, sex, and genetic polymorphisms (e.g., variants in PPARGC1A). It is anticipated that the model will reveal key leverage points—such as thresholds in AMPK activation and PGC-1? coactivator engagement—where training dose, intensity, and modality most effectively drive mitochondrial adaptations. The integration of omics-derived biomarkers with physiological measures is expected to improve prediction of responders versus non-responders to endurance training and to identify mediating pathways for the observed heterogeneity. This research contributes new theoretical and methodological advances by delivering a parsimonious, testable framework that fuses signaling biology with systems-level energetics to explain exercise-induced mitochondrial adaptation. It offers a robust tool for forecasting mitochondrial responses to specific training prescriptions and for personalizing exercise programs to optimize mitochondrial health and metabolic efficiency. The findings will have implications for clinical populations with impaired mitochondrial function, informing rehabilitation and prevention strategies. Practical recommendations will include guidelines for tailoring training dose and modality to individual mitochondrial response profiles. Limitations include potential cohort effects and the invasiveness of muscle biopsies, which will be mitigated by stringent ethical safeguards and by incorporating noninvasive surrogates where feasible. Overall, the study aims to provide a comprehensive, scalable model that advances understanding of how exercise orchestrates mitochondrial adaptation and supports precision exercise physiology.