The aim of the study was to analyse the VO₂ on-kinetics belonging to the work rates within the lower district of extreme exercise domain. Maximal O₂ utilisation and peak power outputs of eight well-trained cyclists were revealed by multisession trails. Critical threshold (CT) as the lower boundary of severe domain and aerobic limit power (ALP) as the upper boundary of severe domain were determined by multisession constant-load exercises. VO₂ on-kinetics over time were best fitted by multicomponent exponential models described by an initial concave-up response known as cardio-dynamic phase ($\tau$ = 18.2 ± 2.88 s; a = 1.56 ± 0.39 L·min^―1) before a primary concave-up phase ($\tau$ = 35.4 ± 12.4 s; a = 1.53 ± 0.36 L·min^―1), and then a slow component in two of the participants ($\tau$ = 80.8 ± 37 s; a = 0.47 ± 0.05 L·min^―1) or without a slow component in six of the participants during exercises performed at 50 W above the CT (R²≥0.96; SEE ≤ 0.24; p < 0.001). However, VO₂ on-kinetics over time belonging to exercises performed at 50 W above the ALP were best fitted by sigmoidal model (R²≥0.98; SEE ≤ 0.14; p < 0.001) in comparison with linear (R² = 0.37−0.66; SEE = 0.46−0.64; p < 0.01), or exponential functions (p> 0.05). Indeed, during those exercises, a short period of convex-up response ($\tau$ = 16.8 ± 3.1 s; a = 1.72 ± 0.39 L·min^―1) was determined just before a concave-up primary phase in VO₂ over time ($\tau$ = 24.6 ± 5.86 s; a = 1.31 ± 0.20 L·min^―1). It was shown that multicomponent exponential trend in VO₂ transformed into a sigmoidal shape, once the work rate exceeded the upper boundary of severe exercise domain.

该研究的目的是分析属于极限运动域较低区域内的工作速率的 VO ₂运动动力学。八名训练有素的自行车手的最大 O ₂利用率和峰值功率输出通过多路段路径显示。临界阈值（CT）作为严重域的下限，有氧极限功率（ALP）作为严重域的上限，通过多阶段恒负荷练习确定。随着时间的推移，VO ₂ on-动力学最适合多分量指数模型，该模型由称为心动力阶段的初始上凹响应描述。$\tau$= 18.2 ± 2.88 秒；a = 1.56 ± 0.39 L·min ^―1 ) 在初级上凹阶段 ($\tau$= 35.4 ± 12.4 秒；a = 1.53 ± 0.36 L·min ^―1），然后是两个参与者的缓慢分量（$\tau$= 80.8 ± 37 秒；a = 0.47 ± 0.05 L·min ^―1 ) 或 6 名参与者在 CT 上方 50 W 下进行锻炼时没有慢速分量（R ² ≥0.96；SEE ≤ 0.24；p < 0.001）。然而，与线性模型（R ² = 0.37-0.66 ）相比，属于在 ALP 以上 50 W 下进行的运动的VO ₂随时间变化的动力学最适合 Sigmoidal 模型（R ² ≥0.98；SEE ≤ 0.14；p < 0.001）; SEE = 0.46−0.64; p < 0.01)，或指数函数 (p> 0.05)。确实，在这些练习中，会有短暂的上凸反应（$\tau$= 16.8 ± 3.1 秒；a = 1.72 ± 0.39 L·min ^―1 ) 是在 VO ₂随时间推移的上凹初级相之前确定的（$\tau$= 24.6 ± 5.86 秒；a = 1.31 ± 0.20 L·min ^―1 )。结果表明，一旦工作速率超过剧烈运动域的上限，VO _{2 的}多分量指数趋势转变为S形。