Abstract
Simulations using a computer model of the skeletal muscle bioenergetic system demonstrate that the slowed V̇O2 on-kinetics of the second step in two-step incremental exercise (exercise initiated from elevated baseline metabolic rate) can be accounted for by a decrease in the stimulation of oxidative phosphorylation (OXPHOS) and/or increase in the stimulation of glycolysis through each-step activation (ESA) in working skeletal muscle. This effect can be caused by either a recruitment of more glycolytic type IIa, IIx and IIb fibers or metabolic regulation in already recruited fibers, or both. The elevated-glycolysis-stimulation mechanism predicts that the end-second-step pH in two-step-incremental exercise is lower than the end-exercise pH in constant-power exercise with the same work intensity (power output). The lowered-OXPHOS-stimulation mechanism predicts higher end-exercise ADP and Pi, and lower PCr in the second step of two-step-incremental than in constant-power exercise. These predictions/mechanisms can be verified or falsified in the experimental way. Data Availability StatementThere are no additional data available.
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