Computer simulations, using the "P_i double-threshold" mechanism of muscle fatigue postulated previously (the first threshold initiating progressive reduction in work efficiency and the second threshold resulting in exercise intolerance), demonstrated that several parameters of the skeletal muscle bioenergetic system can affect the maximum oxygen consumption (V̇O_2max), critical power (CP) and oxygen consumption (V̇O₂) on-kinetics in skeletal muscle. Simulations and experimental observations together demonstrate that endurance exercise training increases oxidative phosphorylation (OXPHOS) activity and/or each-step activation (ESA) intensity, the latter especially in the early stages of training. Here, new computer simulations demonstrate that an endurance training-induced increase in OXPHOS activity and decrease in peak P_i (Pi_peak), at which exercise is terminated because of exercise intolerance, result in increased V̇O_2max and CP, speeding of the primary phase II of V̇O₂ on-kinetics and decrease of the V̇O₂ slow component magnitude, consistent with their observed behavior in vivo. It is possible, but remains unknown, whether there is a contribution to this behavior of an increase in the critical P_i (Pi_crit), above which the additional ATP usage underlying the slow component begins, and decrease in the activity of the additional ATP usage (k_add). Thus, we offer a mechanism, involving P_i accumulation, Pi_crit and Pi_peak, of the training-induced adaptations in V̇O_2max, CP, and the primary and slow component phases of V̇O₂ on-kinetics that was absent in the literature.

中文翻译：

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决定训练引起的骨骼肌 V̇O2max、临界功率和 V̇O2 动态变化的因素

计算机模拟，使用先前假设的肌肉疲劳的“P _i双阈值”机制（第一个阈值导致工作效率逐渐降低，第二个阈值导致运动不耐受），证明骨骼肌生物能量系统的几个参数可以影响最大耗氧量 (V̇O _2max )、临界功率 (CP) 和耗氧量 (V̇O ₂) 骨骼肌中的动力学。模拟和实验观察共同表明，耐力运动训练增加了氧化磷酸化 (OXPHOS) 活动和/或每步激活 (ESA) 强度，后者尤其是在训练的早期阶段。在这里，新的计算机模拟表明，耐力训练引起的 OXPHOS 活动增加和峰值 P _i (Pi _peak ) 降低，在该峰值处，由于运动不耐受而终止运动，导致 V̇O _2max和 CP 增加，初级阶段加速V̇O ₂开启动力学的II 和 V̇O _2的降低缓慢的分量幅度，与他们在体内观察到的行为一致。_{临界 Pi (} Pi _crit )的增加是否对这种行为有贡献，但仍然未知，在此之上，慢组件下的额外 ATP 使用开始，以及额外 ATP 的活性降低用法（k_加）。因此，我们提供了一种机制，涉及 P _i积累、Pi _crit和 Pi _peak，用于训练诱导的 V̇O _{2max 、CP 适应，以及 V̇O 2}动力学的初级和慢分量阶段，这在文献中是不存在的。