A model for identifying intensity zones above critical velocity

Bergstrom, HC, Housh, TJ, Cochrane-Snyman, KC, Jenkins, NDM, Byrd, MT, Switalla, JR, Schmidt, RJ, and Johnson, GO. A model for identifying intensity zones above critical velocity. J Strength Cond Res 31(12): 3260–3265, 2017—The purpose of this study was to describe the V^_ O₂ responses relative to V^_ O₂peak at 4 different intensities within the severe domain and, based on the V^_ O₂ responses, identify intensity zones above critical velocity (CV). Twelve runners (mean 6 SD age = 23.2 6 3.0 years) performed an incremental treadmill test (I_TT) to exhaustion to determine the V^_ O₂peak and velocity associated with V^_ O₂peak (vV^_ O₂peak). Critical velocity was determined from 4 exhaustive, constant velocity, randomly ordered treadmill runs (V₁, V₂, V₃, and V₄; V₁ = highest, V₄ = lowest). The V^_ O₂ responses were recorded during each of the constant velocity runs. Mean differences among V^_ O₂peak values from the I_TT and the highest value recorded during the constant velocity runs were examined. The V^_ O₂ values at exhaustion for V₁ (3.32 6 0.10 L$min2¹, p = 0.15) and V₂ (3.27 6 0.91 L$min2¹, p = 0.13) were not significantly different from V^_ O₂peak (3.39 6 0.96 L$min2¹) from the I_TT. The V^_ O₂ values at exhaustion for V₃ (3.18 6 0.88 L$min2¹; p = 0.007) and V₄ (3.09 6 0.86 L$min2¹; p = 0.003), however, were significantly less than the V^_ O₂peak from the I_TT. There were intensity-dependent V^_ O₂ responses above CV. Based on these findings, we have hypothesized 3 intensity zones (first severe intensity zone [SIZ₁], second severe intensity zone [SIZ₂], and extreme intensity zone [EIZ]) within the severe and extreme domains, which are characterized by specific V^_ O₂ responses and may be used to design programs that maximize aerobic performance adaptations.