Determination of ventilatory threshold through quadratic regression analysis

Gregg, JS, Wyatt, FB, and Kilgore, JL. Determination of ventilatory threshold through quadratic regression analysis. J Strength Cond Res 24(9): 2512-2515, 2010--Ventilatory threshold ([V.sub.T]) has been used to measure physiological occurrences in athletes through models via gas analysis with limited accuracy. The purpose of this study is to establish a mathematical model to more accurately detect the ventilatory threshold using the ventilatory equivalent of carbon dioxide ([V.sub.E]/[??]C[O.sub.2]) and the ventilatory equivalent of oxygen ([V.sub.E]/[??][O.sub.2]). The methodology is primarily a mathematical analysis of data. The raw data used were archived from the cardiorespiratory laboratory in the Department of Kinesiology at Midwestern State University. Procedures for archived data collection included breath-by-breath gas analysis averaged every 20 seconds (ParVoMedics[TM], TrueMax 2400). A ramp protocol on a Velotron[TM] bicycle ergometer was used with increased work at 25 W x [min.sup.1] beginning with 150 W, until volitional fatigue. The subjects consisted of 27 healthy, trained cyclists with age ranging from 18 to 50 years. All subjects signed a university approved informed consent before testing. Graphic scatterplots and statistical regression analyses were performed to establish the crossover and subsequent dissociation of [[??].sub.E]/[??][O.sub.2] to [[??].sub.E]/[??]c[o.sub.2], A polynomial trend line along the scatterplots for [[??].sub.E]/[??][o.sub.2] and VE/[??]C[O.sub.2] was used because of the high correlation coefficient, the coefficient of determination, and trend line. The equations derived from the scatterplots and trend lines were quadratic in nature because they have a polynomial degree of 2. A graphing calculator in conjunction with a spreadsheet was used to find the exact point of intersection of the 2 trend lines. After the quadratic regression analysis, the exact point of [[??].sub.E]/[??][O.sub.2] and [[??].sub.E]/[??]C[O.sub.2] crossover was established as the [V.sub.T]. This application will allow investigators to more accurately determine the VT in subsequent research. KEY WORDS metabolic, polynomial trend line, mathematical model