Sensitivity of V̇O2max, critical power and V̇O2 on-kinetics to O2 concentration/delivery and other factors in skeletal muscle

Abstract

Relative sensitivities of the maximal oxygen uptake (V̇O2max), critical power (CP) and transition time of the primary phase II of the V̇O2 on-kinetics (t0.63) to selected factors in skeletal muscle are simulated using a computer model of the skeletal muscle bioenergetic system. In normoxia, V̇O2max is significantly positively sensitive to peak Pi (Pipeak, Pi at which exercise is terminated because of fatigue), OXPHOS (oxidative phosphorylation) activity (kOX) and ESA (each-step-activation) intensity (AOXmax), and negatively sensitive to the accessible phosphate (and total creatine) pool (Pacc). CP is additionally moderately positively sensitive to critical Pi (Picrit, Pi at which the additional ATP usage appears) and negatively sensitive to the additional ATP usage activity (kadd). t0.63 is significantly positively sensitive to Pacc and negatively to kOX and AOXmax. The positive sensitivity of V̇O2max and CP, and negative sensitivity of t0.63 to O2 concentration/delivery is low at normoxic and hyperoxic O2 levels, but increases significantly at severely hypoxic O2 levels.