Document Type

Thesis

Date of Degree Completion

Spring 2026

Degree Name

Master of Science (MS)

Department

Health Sciences

Committee Chair

Kelly Pritchett

Second Committee Member

Sarah Oppelt

Third Committee Member

Jared M. Dickinson

Abstract

Metabolic Associated Fatty Liver Disease (MAFLD) is characterized by abnormal liver fat accumulation in conjunction with metabolic syndromes. MAFLD affects 33% of individuals worldwide, though little is known about how increased liver fat impacts physiological responses to exercise. This study aimed to analyze the relationship between liver composition and metabolic flexibility during a graded exercise test.  Body composition was analyzed via dual-energy X-ray absorptiometry. Liver ultrasound was evaluated for echogenicity, where elevated mean gray volume (MGV) indicates abnormal liver tissue. Rates of fat (FATox) and carbohydrate (CHOox) oxidation (g/min), respiratory exchange ratio (RER), and blood lactate concentrations ([LA-], mmol/L) were assessed during a graded exercise test on a cycle ergometer.  24 healthy males (n=11) and females (n=13) completed this study. MGV was inversely associated with FATox and positively associated with RER at rest (r=-0.43; r=0.49), 50 W (r=-0.40; r=0.49), 70 W (r=-0.35; r=0.41), 90 W (r=-0.41; r=0.45), and 110 W (r=-0.36; r=0.44).MGV and [LA-] were positively correlated at 70 W (r=0.39), 90 W (r=0.39), and 110 W (r=0.39). Additionally, mean values of FATox and [LA-] presented an inverse linear relationship (r=-0.99), and a nonlinear inverse relationship (r=-0.54, β=-0.95) when data was grouped across time and participants. In this study, elevated liver echogenicity was associated with reduced FATox and greater reliance on carbohydrates during exercise. Similar to previous literature, FATox and [LA-] were inversely correlated, thus validating [LA-] as a marker of metabolic flexibility. These results may help inform future exercise research design for MAFLD.

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