David Bellar, Valeriu Tomescu, Lawrence W. Judge

There are many tests available to coaches and practitioners who seek to identify a point during exercise when excess lactate is being produced or hyperventilation stimulated as a result of metabolic acidosis. This investigation sought to determine the relationship between performance and the first occurrence of excess CO2 production because of increased ventilatory buffering. For this investigation, 2 separate studies were conducted, each examined the predictive value of the 2 standard ventilatory threshold (VT) assessments (V-Slope and examination of ventilatory equilvalents) and the point of equivalence in change (PEC) against performance in an endurance race. The PEC was determined by examining the third-order trend for V[Combining Dot Above]CO2 and V[Combining Dot Above]O2 and determining where the change by time was equivalent (ΔV[Combining Dot Above]O2/ΔV[Combining Dot Above]O2 = 1). The first study examined the assessments of PEC vs. VT in a population of 10-km race competitors (study 1) and the second a population of National Collegiate Athletic Association Division 1 crosscountry runners (study 2). Partial correlations (controlled for weight) were used to assess the relationships with performance. In study 1, the partial correlations revealed that the PEC had the highest correlation to race performance (r = 0.961, p < 0.001) compared with the other techniques (V-slope r = 0.890, p < 0.001, ventilatory equivalents r = 0.733, p = 0.01). Analyses of difference in strength of correlations within study 1 demonstrated differences between PEC and mean race speed as compared with V-slope or ventilatory equivalents and mean race speed. In study 2, a similar trend was observed (PEC r = 0.863, p = 0.001, V-slope (r = 0.828, p = 0.002, ventilatory equivalents r = 0.750, p = 0.008). The results of this study suggest that determination of PEC is more related to 10-km race performance than 2 well-established methods for VT determination.