Award Date


Degree Type


Degree Name

Master of Science in Exercise Physiology


Kinesiology and Nutrition Sciences

First Committee Member

John Young, Chair

Second Committee Member

Lawrence Golding

Third Committee Member

Richard Tandy

Graduate Faculty Representative

Timothy Bungum

Number of Pages



The “crossover” concept is a means of understanding fuel utilization over a range of exercise intensities. According to this concept, certain biochemical adaptations occur in a fit individual allowing for an increase in lipid oxidation. The present study examined whether there was a relationship between fitness level, gender, and the percentage of maximum aerobic capacity (VO2 max) at crossover. Twenty-five subjects age 18-40 participated in this study. Subjects were divided in half based on their fitness level. After completing a graded exercise test to exhaustion, the crossover point for each subject was determined relative to their VO2 max. A 2x2 factorial ANOVA was used to assess whether the percentage of VO2 max at crossover could be predicted from fitness level (top half and bottom half of sample), gender, and the interaction between fitness level and gender. No significant interaction between fitness level and gender was found (F=1.064, p=.314). The lack of significance shows that beyond certain intensities, gender and fitness no longer have an effect on the percentage of VO2 max at crossover. It is reasonable to assume that at lower intensities fat oxidation is affected by fitness level and gender, but at higher intensities the sympathetic nervous system causes an increase in glycogen available for use with a reduced dependence on fatty acid oxidation. Further research is needed to determine the effects of gender and fitness level on percentage of VO2 max in non-healthy adult populations and to explain the large amount of variability in crossover from one subject to the next.


Crossover; Exercise; Fat Oxidation; Fatty acids — Oxidation; Physical fitness; Substrate Utilization; Sympathetic Nervous System


Exercise Science | Kinesiology

File Format


Degree Grantor

University of Nevada, Las Vegas




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