Degree Name
PhD (Doctor of Philosophy)
Program
Sport Physiology and Performance
Date of Award
12-2026
Committee Chair or Co-Chairs
Marco Duca
Committee Members
Michael H. Stone, Satoshi Mizuguchi
Abstract
This study was a characterization of longitudinal changes in body composition and vastus lateralis muscle morphology across an 11-week off-season, block-periodized resistance training program in NCAA Division I sprinters and jumpers. Eighteen athletes (12 women, 6 men) were assessed at four time points: baseline and after the strength-endurance, basic strength, and strength-power phases. Skeletal muscle mass and fat mass were estimated using multi-frequency segmental bioelectrical impedance analysis. B-mode ultrasonography quantified vastus lateralis muscle thickness and pennation angle at proximal, middle, and distal sites, and a representative-site model compared muscle thickness across the middle vastus lateralis, biceps femoris long head, lateral gastrocnemius, and soleus. Data were analyzed with linear mixed-effects models. Skeletal muscle mass initially increased and was above baseline at the end of every subsequent phase (peak change +0.88 kg, d = 0.67 [0.36, 0.97]), whereas fat mass increased more gradually and reached significance only at the end of the final, strength-power oriented, phase (+0.77 kg, d = 0.41 [0.12, 0.70]). Vastus lateralis muscle thickness followed a curvilinear trajectory, with significant linear and quadratic components, peaking after the basic strength phase and stabilizing thereafter; this pattern did not differ across measurement sites. Pennation angle did not change at any site. In the representative-site model, muscle thickness increased linearly when averaged across muscles (d = 0.44 [0.15, 0.73]) with no muscle-by-phase interaction, and the pooled increase appeared, descriptively, to be concentrated in the directly loaded thigh muscles. These changes are consistent with the early structural component of the phase-potentiation model and occurred without measurable change in fascicle orientation. Because bioelectrical impedance estimates of muscle mass are indirect, body-composition values should be interpreted as systemic markers rather than direct measures of contractile tissue. The findings provide an empirical reference for interpreting routine body-composition and ultrasound monitoring in trained track and field athletes.
Document Type
Dissertation - embargo
Recommended Citation
Dennis, Joshua, "Body Composition and Skeletal Muscle Morphological Adaptations to Block-Periodized Resistance Training in Division I Track and Field Athletes" (2026). Electronic Theses and Dissertations. Paper 4765. https://dc.etsu.edu/etd/4765
Copyright
Copyright by the authors.
