Gabriel Reichert Blume1, Adam B. Salmon2, Hanyu Liang2, Elizabeth Fernandez2, Nicolas Musi2, Peter J. Hornsby2, Michael P. Massett3, and Heather L. Vellers1

1University of Oklahoma, Norman, OK; 2University of Texas Health Science Center at San Antonio, San Antonio, TX; 3Texas Tech University, Lubbock TX

PURPOSE: The purpose of this study was to characterize endurance trainability in the agenetically heterogenous HET3 aging mouse model by assessing change in exercise capacity after completing a standardized treadmill training protocol. Secondarily, we also aimed to assess the association between exercise capacity changes with body composition measures in response to the training. METHODS: 40-week-old male mice were randomly assigned to endurance training (ET, n = 23) or sedentary control (SED, n = 20) groups. Both groups underwent a graded treadmill exercise capacity test before and after four weeks of exercise training. ET mice trained five days per week for four weeks at 65% of the maximal work output calculated in joules (J = kg*gravity*vertical speed*time). Additionally, we analyzed training-induced changes in body composition (total body weight, lean mass, and fat mass). An independent sample t-test was employed to compare changes in total work and linear regression analysis to assess the association between post-training exercise work and body composition measures (body weight, fat mass, and lean mass) and exercise work (alpha level = 0.05). RESULTS:While the mean change in exercise capacity was significantly greater in ET versus SED mice (ET: 483.3 ± 48.8 joules, SED: 194.7 ± 52.0 joules; p = 0.0003), there was considerable variance in change within each group (Range: ET = 74.4 – 925.4 joules; SED = 85.1 – 432.0 joules). In the ET mice, change in exercise capacity was positively correlated with post-training body weight (37.3 ± 1.3 gms, p = 0.004) and the change in body weight (-9.5 ± 1.8 gms, p = 0.01) but no other pre- or post-training body composition factors. There were no associations between body composition measures and exercise capacity in the untrained animals. CONCLUSION: While the standardized treadmill training protocol increased exercise capacity in HET3 ET mice, these changes were variable. Interestingly, greater declines in body weight with training were associated with lower exercise capacity measures that were not linked to pre-training body weight, possibly suggesting food consumption and/or spontaneous cage activity may have influenced results. Taken together, the variable responses in endurance trainability and factors contributing to change in body weight may be, at least partially, explained by their heterogeneous nature.

ACKNOWLEDGMENTS: San Antonio Nathan Shock Center New Investigator Award Funding

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