Year of Award


Document Type


Degree Type

Master of Science (MS)

Degree Name

Health and Human Performance (Exercise Science Option)

Department or School/College

Department of Health and Human Performance

Committee Chair

Steven E. Gaskill

Committee Co-chair

Carla Cox

Commitee Members

James Laskin


maximal oxygen consumption, RER, training, ventilatory threshold


University of Montana


Lieberg, Erika M., M.S., May 2007 Health and Human Performance Variability of substrate utilization during exercise relative to VO2vt and VO2max Chairperson: Steven E. Gaskill PURPOSE: The purpose of this study was to determine to the stability of ventilatory threshold (VT) as a set point for prescription of exercise intensity. METHODS: Fifty-eight healthy adults (males n = 28, females n = 30) performed VO2max and steady state testing. The VO2max test used a treadmill ramp protocol to determine VO2max and VO2vt. The results were used to determine workload exercise relative to VO2vt and VO2max (70% VO2vt ? 40% VO2max, 90% VO2vt ? 50% VO2max, 125% VO2vt ? 65% VO2max). During the steady state test, subjects walked for 4 minutes at each of the workloads associated with the six exercise intensities. These stages were sequentially completed in the order of increasing intensity. Ventilation (VE), respiratory gas-exchange ratio (RER), VO2, and VCO2 were measured continuously and heart rate and rate of perceived exertion (RPE) were collected each minute. RESULTS: The mean overall variance of RER at the %VO2vt intensities was significantly less than at the %VO2max intensities (%VO2vt = 0.030±0.025, %VO2max = 0.041±0.029, p<0.001). The mean RER variance was not different between genders relative to %VO2vt (p>0.05). For males and females, the variance in RER was significantly less when evaluated at 70% and 90% of VO2vt than at 40% and 50% of VO2max respectively (p<0.001). When the RER mean variance values were compared at the 125%VO2vt vs. 65%VO2max, RER variance values within subjects (males, females and overall) were not different (p>0.05). Similar patterns in RER variance were seen when compared by body mass index (BMI) or fitness. CONCLUSIONS: Using % VO2vt is a viable method to prescribe exercise intensity during research and/or training, with overall lower RER variance, especially when the intensity of exercise is below the ventilatory threshold.



© Copyright 2007 Erika Marie Lieberg