Jenna L. Carducci1, Matthew J. Garver1, Whitley J. Stone1, Meera Penumetcha1, Dustin W. Davis1, Adam R. McMillin1, Josie N. Hair1, Nicolas M. Philipp1, Jordan R. Elledge1, Emily B. Sheck1, & Katherine M. Scherry1

1University of Central Missouri, Warrensburg, Missouri

Exercise programs are more favorable when individualized to particular needs and preferences. Controlling training and exercise characteristics such as time of day and glucose provision may enhance subsequent performance. PURPOSE: The purpose of this research was to investigate maximal VO2 at extreme ends of the day following a standardized glucose provision. METHODS: Thirteen participants (Females: 8, Males: 5, Age: 20.7 ± 1.4 yrs., BMI: 24.9 ± 3.0 kg/m2) volunteered to complete two maximal VO2 tests, one between 06:00-09:00 and the other between 21:00-24:00. A familiarization trial was utilized to mitigate a learning effect and determine the speed that elicited a perceived effort of 12-13 on the Borg 6-20 RPE scale when steady-stated. Considering body mass and activity level, a standardized test meal of approximately 80% carbohydrates, 3% fat, and 17% protein was provided 2 hours prior to testing. For the maximal testing, treadmill speed was maintained at the predetermined intensity, and grade was increased 2% every 2 minutes until volitional fatigue. Maximal VO2 was determined via a metabolic cart using a 15-breath moving average. RESULTS: The maximal tests lasted 10.13 ± 2.15 minutes. There was no statistical difference (p < .05) found for morning vs. evening tests for maximal VO2 (47.0 ± 7.0 vs. 47.3 ± 8.0 ml/kg/min). CONCLUSION: The glucose provision prior to exercise was intended to standardize nutrient intake prior to completing the maximal VO2 tests. The results of this study align with the available literature suggesting that maximal VO2 does not significantly differ between morning and evening exercise tests. Exercising at extreme ends of the day may not result in a significant difference in maximal VO2 among a group of younger, recreationally active adults provided a high-glucose test meal.

ACKNOWLEDGEMENTS: This research was funded by the Graduate Student Research Fund from the University of Central Missouri.

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