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Clark Cotton


Our world has an increasing demand for finding different exercise and diet combinations that lead to greater aerobic performance. Previous studies show that independently, endurance training and high-fat diets increase aerobic muscle fibers and fatigue resistance of muscle. My experiment tested whether the combination of high-fat diet and endurance training would produce greater increases in aerobic muscle fibers and fatigue resistance than either treatment alone. I predicted that there would be an increased proportion of type I and type IIa, oxidative fibers, in addition to an increase time for muscle to fatigue and a decrease in lactic acid concentrations after exercise. Mice were broken into four groups. One experimental group was a control, one ate a high-fat diet, one followed an exercise regime, and one group did both. Weights and lactic acid levels were monitored throughout the experiment. The tibialis anterior muscle was analyzed with in vitro tests and microscopic analysis. All mice experienced weight gain, but it was most pronounced in the two high-fat groups. In vitro properties, such as contraction time and time to fatigue, showed no significant difference between groups. There were also no significant changes in fiber type ratios. Conversely, fiber cross-sectional area significantly decreased for groups undergoing the exercise regime. Lactic acid concentrations following standardized exercise decreased significantly for the High-Fat & Exercise group after the 28-day experiment but were unchanged for all other groups. The lower lactic acid levels could have been the result of a decrease in fiber area and an increase in capillarization of the tissue. This would have increased the oxidative capacity of the cells, reducing the need for anaerobic respiration. The timeframe, sample size (N=32) and exercise intensity appeared insufficient to induce significantly noticeable changes in muscle function, fiber type, and lactic acid dynamics.